annotate man/cl.texi @ 4917:fce43cb76a1c

xlike cleanup, documentation -------------------- ChangeLog entries follow: -------------------- man/ChangeLog addition: 2010-02-03 Ben Wing <ben@xemacs.org> * internals/internals.texi (Top): * internals/internals.texi (Evaluation; Stack Frames; Bindings): * internals/internals.texi (Ben's README): * internals/internals.texi (Consoles; Devices; Frames; Windows): * internals/internals.texi (Window Hierarchy): * internals/internals.texi (The Window Object): * internals/internals.texi (Modules for the Basic Displayable Lisp Objects): * internals/internals.texi (Window-System Support): * internals/internals.texi (Creating a Window-System Type): * internals/internals.texi (Discussion -- Garbage Collection): Update the part at the top about how to maintain the file with more tips. Add a chapter on "window-system support" describing in a general way how the support for different window systems/device types works, including the separation between device-independent and device-dependent parts, device methods, the specific device types and the "xlike" pseudo-type. src/ChangeLog addition: 2010-02-03 Ben Wing <ben@xemacs.org> * Makefile.in.in: * Makefile.in.in (x_objs): * Makefile.in.in (gtk_gui_objs): * console-xlike-inc.h: * depend: * device-x.c: * emacs.c: * gccache-gtk.h: * gccache-gtk.h (gc_cache_lookup): * gccache-x.c: * gccache-x.c (GCCACHE_HASH): * gccache-x.h: * toolbar-gtk.c: * toolbar-gtk.c (gtk_initialize_frame_toolbars): * toolbar-x.c: * toolbar-x.c (x_initialize_frame_toolbars): * toolbar-xlike.c: * toolbar-xlike.c (xlike_draw_blank_toolbar_button): * toolbar-xlike.c (xlike_output_toolbar_button): * toolbar-xlike.c (xlike_get_button_size): * toolbar-xlike.c (XLIKE_OUTPUT_BUTTONS_LOOP): * toolbar-xlike.c (xlike_output_toolbar): * toolbar-xlike.c (xlike_clear_toolbar): * toolbar-xlike.c (xlike_output_frame_toolbars): * toolbar-xlike.c (xlike_clear_frame_toolbars): * toolbar-xlike.c (xlike_redraw_exposed_toolbar): * toolbar-xlike.c (xlike_redraw_exposed_toolbars): * toolbar-xlike.c (xlike_redraw_frame_toolbars): * toolbar-xlike.h: * toolbar-xlike.h (xlike_clear_frame_toolbars): Rename some files to make them consistent with general naming rules: xgccache.c -> gccache-x.c xgccache.h -> gccache-x.h toolbar-common.c -> toolbar-xlike.c toolbar-common.h -> toolbar-xlike.h Fix include-file references. Also change the names of functions in now-named toolbar-xlike.c to be xlike_foo() instead of common_foo(). Add a longish comment in console-xlike-inc.h describing the "xlike" system, how it works and what the various files are used for.
author Ben Wing <ben@xemacs.org>
date Wed, 03 Feb 2010 02:46:50 -0600
parents 755ae5b97edb
children 378a34562cbe
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1 \input texinfo @c -*-texinfo-*-
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2 @setfilename ../info/cl.info
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3 @settitle Common Lisp Extensions
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4
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5 @iftex
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6 @finalout
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7 @end iftex
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8
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9 @ifinfo
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10 @dircategory XEmacs Editor
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11 @direntry
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12 * Common Lisp: (cl). XEmacs Common Lisp emulation package.
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13 @end direntry
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14
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15 This file documents the XEmacs Common Lisp emulation package.
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17 Copyright (C) 1993 Free Software Foundation, Inc.
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18
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19 Permission is granted to make and distribute verbatim copies of this
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20 manual provided the copyright notice and this permission notice are
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21 preserved on all copies.
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22
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23 @ignore
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24 Permission is granted to process this file through TeX and print the
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25 results, provided the printed document carries copying permission notice
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26 identical to this one except for the removal of this paragraph (this
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27 paragraph not being relevant to the printed manual).
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28
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29 @end ignore
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30 Permission is granted to copy and distribute modified versions of this
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31 manual under the conditions for verbatim copying, provided also that the
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32 section entitled ``GNU General Public License'' is included exactly as
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33 in the original, and provided that the entire resulting derived work is
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34 distributed under the terms of a permission notice identical to this one.
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35
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36 Permission is granted to copy and distribute translations of this manual
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37 into another language, under the above conditions for modified versions,
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38 except that the section entitled ``GNU General Public License'' may be
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39 included in a translation approved by the author instead of in the
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40 original English.
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41 @end ifinfo
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42
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43 @titlepage
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44 @sp 6
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45 @center @titlefont{Common Lisp Extensions}
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46 @sp 4
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47 @center For GNU Emacs Lisp
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48 @sp 1
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49 @center Version 2.02
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50 @sp 5
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51 @center Dave Gillespie
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52 @center daveg@@synaptics.com
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53 @page
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54
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55 @vskip 0pt plus 1filll
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56 Copyright @copyright{} 1993 Free Software Foundation, Inc.
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57
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58 Permission is granted to make and distribute verbatim copies of
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59 this manual provided the copyright notice and this permission notice
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60 are preserved on all copies.
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61
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62 @ignore
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63 Permission is granted to process this file through TeX and print the
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64 results, provided the printed document carries copying permission notice
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65 identical to this one except for the removal of this paragraph (this
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66 paragraph not being relevant to the printed manual).
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67
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68 @end ignore
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69 Permission is granted to copy and distribute modified versions of this
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70 manual under the conditions for verbatim copying, provided also that the
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71 section entitled ``GNU General Public License'' is included exactly as
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72 in the original, and provided that the entire resulting derived work is
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73 distributed under the terms of a permission notice identical to this one.
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74
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75 Permission is granted to copy and distribute translations of this manual
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76 into another language, under the above conditions for modified versions,
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77 except that the section entitled ``GNU General Public License'' may be
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78 included in a translation approved by the author instead of in the
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79 original English.
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80 @end titlepage
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81
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82 @node Top, Overview,, (dir)
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83 @chapter Common Lisp Extensions
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84
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85 @noindent
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86 This document describes a set of Emacs Lisp facilities borrowed from
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87 Common Lisp. All the facilities are described here in detail; for
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88 more discussion and examples, Guy L. Steele's @cite{Common Lisp, the
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89 Language}, second edition, is the definitive book on Common Lisp.
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90 @iftex
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91 Chapter numbers and most section numbers of this document parallel
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92 those of Steele's book.
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93 @end iftex
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94 While this document does not assume any prior knowledge of Common
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95 Lisp, it does assume a basic familiarity with Emacs Lisp.
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96
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97 @menu
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98 * Overview:: Installation, usage, etc.
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99 * Program Structure:: Arglists, `eval-when', `defalias'
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100 * Predicates:: `typep', `eql', and `equalp'
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101 * Control Structure:: `setf', `when', `do', `loop', etc.
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102 * Macros:: Destructuring, `define-compiler-macro'
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103 * Declarations:: `proclaim', `declare', etc.
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104 * Symbols:: Property lists, `gensym'
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105 * Numbers:: Predicates, functions, random numbers
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106 * Sequences:: Mapping, functions, searching, sorting
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107 * Lists:: `cadr', `sublis', `member*', `assoc*', etc.
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108 * Hash Tables:: `make-hash-table', `gethash', etc.
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109 * Structures:: `defstruct'
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110 * Assertions:: `check-type', `assert', `ignore-errors'.
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111
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112 * Efficiency Concerns:: Hints and techniques
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113 * Common Lisp Compatibility:: All known differences with Steele
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114 * Old CL Compatibility:: All known differences with old cl.el
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115 * Porting Common Lisp:: Hints for porting Common Lisp code
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116
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117 * Function Index::
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118 * Variable Index::
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119 @end menu
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120
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121 @node Overview, Program Structure, Top, Top
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122 @ifinfo
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123 @chapter Overview
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124 @end ifinfo
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125 @iftex
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126 @section Overview
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127 @end iftex
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128
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129 @noindent
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130 Common Lisp is a huge language, and Common Lisp systems tend to be
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131 massive and extremely complex. Emacs Lisp, by contrast, is rather
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132 minimalist in the choice of Lisp features it offers the programmer.
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133 As Emacs Lisp programmers have grown in number, and the applications
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134 they write have grown more ambitious, it has become clear that Emacs
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135 Lisp could benefit from many of the conveniences of Common Lisp.
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136
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137 The @dfn{CL} package adds a number of Common Lisp functions and
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138 control structures to Emacs Lisp. While not a 100% complete
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139 implementation of Common Lisp, @dfn{CL} adds enough functionality
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140 to make Emacs Lisp programming significantly more convenient.
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141
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142 Some Common Lisp features have been omitted from this package
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143 for various reasons:
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144
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145 @itemize @bullet
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146 @item
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147 Some features are too complex or bulky relative to their benefit
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148 to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
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149 examples of this group.
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150
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151 @item
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152 Other features cannot be implemented without modification to the
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153 Emacs Lisp interpreter itself, such as multiple return values,
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154 lexical scoping, case-insensitive symbols, and complex numbers.
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155 The @dfn{CL} package generally makes no attempt to emulate these
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156 features.
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157
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158 @item
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159 Some features conflict with existing things in Emacs Lisp. For
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160 example, Emacs' @code{assoc} function is incompatible with the
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161 Common Lisp @code{assoc}. In such cases, this package usually
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162 adds the suffix @samp{*} to the function name of the Common
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163 Lisp version of the function (e.g., @code{assoc*}).
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164 @end itemize
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165
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166 The package described here was written by Dave Gillespie,
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167 @file{daveg@@synaptics.com}. It is a total rewrite of the original
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168 1986 @file{cl.el} package by Cesar Quiroz. Most features of
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169 the Quiroz package have been retained; any incompatibilities are
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170 noted in the descriptions below. Care has been taken in this
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171 version to ensure that each function is defined efficiently,
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172 concisely, and with minimal impact on the rest of the Emacs
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173 environment.
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174
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175 @menu
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176 * Usage:: How to use the CL package
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177 * Organization:: The package's five component files
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178 * Installation:: Compiling and installing CL
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179 * Naming Conventions:: Notes on CL function names
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180 @end menu
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181
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182 @node Usage, Organization, Overview, Overview
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183 @section Usage
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184
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185 @noindent
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186 Lisp code that uses features from the @dfn{CL} package should
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187 include at the beginning:
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188
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189 @example
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190 (require 'cl)
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191 @end example
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192
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193 @noindent
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194 If you want to ensure that the new (Gillespie) version of @dfn{CL}
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195 is the one that is present, add an additional @code{(require 'cl-19)}
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196 call:
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197
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198 @example
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199 (require 'cl)
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200 (require 'cl-19)
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201 @end example
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202
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203 @noindent
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204 The second call will fail (with ``@file{cl-19.el} not found'') if
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205 the old @file{cl.el} package was in use.
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206
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207 It is safe to arrange to load @dfn{CL} at all times, e.g.,
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208 in your @file{.emacs} file. But it's a good idea, for portability,
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209 to @code{(require 'cl)} in your code even if you do this.
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210
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211 @node Organization, Installation, Usage, Overview
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212 @section Organization
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213
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214 @noindent
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215 The Common Lisp package is organized into four files:
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216
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217 @table @file
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218 @item cl.el
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219 This is the ``main'' file, which contains basic functions
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220 and information about the package. This file is relatively
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221 compact---about 700 lines.
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222
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223 @item cl-extra.el
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224 This file contains the larger, more complex or unusual functions.
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225 It is kept separate so that packages which only want to use Common
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226 Lisp fundamentals like the @code{cadr} function won't need to pay
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227 the overhead of loading the more advanced functions.
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228
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229 @item cl-seq.el
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230 This file contains most of the advanced functions for operating
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231 on sequences or lists, such as @code{delete-if} and @code{assoc*}.
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232
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233 @item cl-macs.el
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234 This file contains the features of the packages which are macros
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235 instead of functions. Macros expand when the caller is compiled,
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236 not when it is run, so the macros generally only need to be
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237 present when the byte-compiler is running (or when the macros are
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238 used in uncompiled code such as a @file{.emacs} file). Most of
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239 the macros of this package are isolated in @file{cl-macs.el} so
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240 that they won't take up memory unless you are compiling.
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241 @end table
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242
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243 The file @file{cl.el} includes all necessary @code{autoload}
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244 commands for the functions and macros in the other three files.
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245 All you have to do is @code{(require 'cl)}, and @file{cl.el}
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246 will take care of pulling in the other files when they are
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247 needed.
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248
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249 There is another file, @file{cl-compat.el}, which defines some
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250 routines from the older @file{cl.el} package that are no longer
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251 present in the new package. This includes internal routines
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252 like @code{setelt} and @code{zip-lists}, and deprecated features
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253 like @code{defkeyword}. @xref{Old CL Compatibility}.
428
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254
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255 @node Installation, Naming Conventions, Organization, Overview
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256 @section Installation
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257
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258 @noindent
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259 Installation of the @dfn{CL} package is simple: Just put the
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260 byte-compiled files @file{cl.elc}, @file{cl-extra.elc},
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261 @file{cl-seq.elc}, @file{cl-macs.elc}, and @file{cl-compat.elc}
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262 into a directory on your @code{load-path}.
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263
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264 There are no special requirements to compile this package:
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265 The files do not have to be loaded before they are compiled,
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266 nor do they need to be compiled in any particular order.
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267
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268 You may choose to put the files into your main @file{lisp/}
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269 directory, replacing the original @file{cl.el} file there. Or,
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270 you could put them into a directory that comes before @file{lisp/}
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271 on your @code{load-path} so that the old @file{cl.el} is
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272 effectively hidden.
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273
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274 Also, format the @file{cl.texinfo} file and put the resulting
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275 Info files in the @file{info/} directory or another suitable place.
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276
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277 You may instead wish to leave this package's components all in
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278 their own directory, and then add this directory to your
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279 @code{load-path} and (Emacs 19 only) @code{Info-directory-list}.
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280 Add the directory to the front of the list so the old @dfn{CL}
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281 package and its documentation are hidden.
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282
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283 @node Naming Conventions, , Installation, Overview
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284 @section Naming Conventions
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285
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286 @noindent
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287 Except where noted, all functions defined by this package have the
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288 same names and calling conventions as their Common Lisp counterparts.
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289
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290 Following is a complete list of functions whose names were changed
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291 from Common Lisp, usually to avoid conflicts with Emacs. In each
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292 case, a @samp{*} has been appended to the Common Lisp name to obtain
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293 the Emacs name:
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294
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295 @example
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296 defun* defsubst* defmacro* function*
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297 member* assoc* rassoc* remove*
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298 delete* mapcar* sort* floor*
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299 ceiling* truncate* round* mod*
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300 rem* random*
428
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301 @end example
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302
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303 Internal function and variable names in the package are prefixed
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304 by @code{cl-}. Here is a complete list of functions @emph{not}
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305 prefixed by @code{cl-} which were not taken from Common Lisp:
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306
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307 @example
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308 member delete remove remq
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309 rassoc floatp-safe lexical-let lexical-let*
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310 callf callf2 letf letf*
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311 defsubst* defalias add-hook eval-when-compile
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312 @end example
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313
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314 @noindent
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315 (Most of these are Emacs 19 features provided to Emacs 18 users,
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316 or introduced, like @code{remq}, for reasons of symmetry
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317 with similar features.)
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318
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319 The following simple functions and macros are defined in @file{cl.el};
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320 they do not cause other components like @file{cl-extra} to be loaded.
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321
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322 @example
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323 eql floatp-safe abs endp
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324 evenp oddp plusp minusp
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325 last butlast nbutlast caar .. cddddr
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326 list* ldiff rest first .. tenth
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327 member [1] copy-list subst mapcar* [2]
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328 adjoin [3] acons pairlis when
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329 unless pop [4] push [4] pushnew [3,4]
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330 incf [4] decf [4] proclaim declaim
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331 add-hook
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332 @end example
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333
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334 @noindent
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335 [1] This is the Emacs 19-compatible function, not @code{member*}.
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336
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337 @noindent
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338 [2] Only for one sequence argument or two list arguments.
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339
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340 @noindent
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341 [3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
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342 and @code{:key} is not used.
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343
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344 @noindent
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345 [4] Only when @var{place} is a plain variable name.
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346
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347 @iftex
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348 @chapno=4
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349 @end iftex
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350
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351 @node Program Structure, Predicates, Overview, Top
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352 @chapter Program Structure
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353
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354 @noindent
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355 This section describes features of the @dfn{CL} package which have to
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356 do with programs as a whole: advanced argument lists for functions,
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357 and the @code{eval-when} construct.
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358
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359 @menu
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360 * Argument Lists:: `&key', `&aux', `defun*', `defmacro*'.
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361 * Time of Evaluation:: The `eval-when' construct.
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362 * Function Aliases:: The `defalias' function.
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363 @end menu
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364
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365 @iftex
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366 @secno=1
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367 @end iftex
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368
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369 @node Argument Lists, Time of Evaluation, Program Structure, Program Structure
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370 @section Argument Lists
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371
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372 @noindent
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373 Emacs Lisp's notation for argument lists of functions is a subset of
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374 the Common Lisp notation. As well as the familiar @code{&optional}
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375 and @code{&rest} markers, Common Lisp allows you to specify default
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376 values for optional arguments, and it provides the additional markers
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377 @code{&key} and @code{&aux}.
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378
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379 Since argument parsing is built-in to Emacs, there is no way for
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380 this package to implement Common Lisp argument lists seamlessly.
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381 Instead, this package defines alternates for several Lisp forms
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382 which you must use if you need Common Lisp argument lists.
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383
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384 @defspec defun* name arglist body...
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385 This form is identical to the regular @code{defun} form, except
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386 that @var{arglist} is allowed to be a full Common Lisp argument
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387 list. Also, the function body is enclosed in an implicit block
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388 called @var{name}; @pxref{Blocks and Exits}.
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389 @end defspec
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390
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391 @defspec defsubst* name arglist body...
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392 This is just like @code{defun*}, except that the function that
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393 is defined is automatically proclaimed @code{inline}, i.e.,
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394 calls to it may be expanded into in-line code by the byte compiler.
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395 This is analogous to the @code{defsubst} form in Emacs 19;
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396 @code{defsubst*} uses a different method (compiler macros) which
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397 works in all version of Emacs, and also generates somewhat more
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398 efficient inline expansions. In particular, @code{defsubst*}
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399 arranges for the processing of keyword arguments, default values,
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400 etc., to be done at compile-time whenever possible.
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401 @end defspec
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402
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403 @defspec defmacro* name arglist body...
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404 This is identical to the regular @code{defmacro} form,
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405 except that @var{arglist} is allowed to be a full Common Lisp
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406 argument list. The @code{&environment} keyword is supported as
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407 described in Steele. The @code{&whole} keyword is supported only
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408 within destructured lists (see below); top-level @code{&whole}
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409 cannot be implemented with the current Emacs Lisp interpreter.
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410 The macro expander body is enclosed in an implicit block called
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411 @var{name}.
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412 @end defspec
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413
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414 @defspec function* symbol-or-lambda
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415 This is identical to the regular @code{function} form,
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416 except that if the argument is a @code{lambda} form then that
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417 form may use a full Common Lisp argument list.
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418 @end defspec
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419
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420 Also, all forms (such as @code{defsetf} and @code{flet}) defined
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421 in this package that include @var{arglist}s in their syntax allow
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422 full Common Lisp argument lists.
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423
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424 Note that it is @emph{not} necessary to use @code{defun*} in
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425 order to have access to most @dfn{CL} features in your function.
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426 These features are always present; @code{defun*}'s only
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427 difference from @code{defun} is its more flexible argument
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428 lists and its implicit block.
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429
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430 The full form of a Common Lisp argument list is
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431
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432 @example
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433 (@var{var}...
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434 &optional (@var{var} @var{initform} @var{svar})...
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435 &rest @var{var}
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436 &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
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437 &aux (@var{var} @var{initform})...)
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438 @end example
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439
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440 Each of the five argument list sections is optional. The @var{svar},
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441 @var{initform}, and @var{keyword} parts are optional; if they are
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442 omitted, then @samp{(@var{var})} may be written simply @samp{@var{var}}.
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443
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444 The first section consists of zero or more @dfn{required} arguments.
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445 These arguments must always be specified in a call to the function;
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446 there is no difference between Emacs Lisp and Common Lisp as far as
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447 required arguments are concerned.
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448
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449 The second section consists of @dfn{optional} arguments. These
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450 arguments may be specified in the function call; if they are not,
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451 @var{initform} specifies the default value used for the argument.
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452 (No @var{initform} means to use @code{nil} as the default.) The
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453 @var{initform} is evaluated with the bindings for the preceding
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454 arguments already established; @code{(a &optional (b (1+ a)))}
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455 matches one or two arguments, with the second argument defaulting
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456 to one plus the first argument. If the @var{svar} is specified,
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457 it is an auxiliary variable which is bound to @code{t} if the optional
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458 argument was specified, or to @code{nil} if the argument was omitted.
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459 If you don't use an @var{svar}, then there will be no way for your
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460 function to tell whether it was called with no argument, or with
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461 the default value passed explicitly as an argument.
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462
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463 The third section consists of a single @dfn{rest} argument. If
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464 more arguments were passed to the function than are accounted for
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465 by the required and optional arguments, those extra arguments are
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466 collected into a list and bound to the ``rest'' argument variable.
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467 Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp.
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468 Common Lisp accepts @code{&body} as a synonym for @code{&rest} in
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469 macro contexts; this package accepts it all the time.
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470
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471 The fourth section consists of @dfn{keyword} arguments. These
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472 are optional arguments which are specified by name rather than
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473 positionally in the argument list. For example,
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474
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475 @example
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476 (defun* foo (a &optional b &key c d (e 17)))
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477 @end example
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478
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479 @noindent
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480 defines a function which may be called with one, two, or more
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481 arguments. The first two arguments are bound to @code{a} and
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482 @code{b} in the usual way. The remaining arguments must be
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483 pairs of the form @code{:c}, @code{:d}, or @code{:e} followed
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484 by the value to be bound to the corresponding argument variable.
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485 (Symbols whose names begin with a colon are called @dfn{keywords},
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486 and they are self-quoting in the same way as @code{nil} and
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487 @code{t}.)
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488
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489 For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five
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490 arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword
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491 appears more than once in the function call, the first occurrence
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492 takes precedence over the later ones. Note that it is not possible
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493 to specify keyword arguments without specifying the optional
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494 argument @code{b} as well, since @code{(foo 1 :c 2)} would bind
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495 @code{b} to the keyword @code{:c}, then signal an error because
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496 @code{2} is not a valid keyword.
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497
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498 If a @var{keyword} symbol is explicitly specified in the argument
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499 list as shown in the above diagram, then that keyword will be
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500 used instead of just the variable name prefixed with a colon.
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501 You can specify a @var{keyword} symbol which does not begin with
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502 a colon at all, but such symbols will not be self-quoting; you
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503 will have to quote them explicitly with an apostrophe in the
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504 function call.
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505
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506 Ordinarily it is an error to pass an unrecognized keyword to
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507 a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask
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508 Lisp to ignore unrecognized keywords, either by adding the
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509 marker @code{&allow-other-keys} after the keyword section
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510 of the argument list, or by specifying an @code{:allow-other-keys}
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511 argument in the call whose value is non-@code{nil}. If the
3ecd8885ac67 Import from CVS: tag r21-2-22
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512 function uses both @code{&rest} and @code{&key} at the same time,
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513 the ``rest'' argument is bound to the keyword list as it appears
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514 in the call. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
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515
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516 @smallexample
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517 (defun* find-thing (thing &rest rest &key need &allow-other-keys)
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518 (or (apply 'member* thing thing-list :allow-other-keys t rest)
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519 (if need (error "Thing not found"))))
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520 @end smallexample
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521
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522 @noindent
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523 This function takes a @code{:need} keyword argument, but also
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524 accepts other keyword arguments which are passed on to the
3ecd8885ac67 Import from CVS: tag r21-2-22
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525 @code{member*} function. @code{allow-other-keys} is used to
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526 keep both @code{find-thing} and @code{member*} from complaining
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527 about each others' keywords in the arguments.
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528
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529 As a (significant) performance optimization, this package
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530 implements the scan for keyword arguments by calling @code{memq}
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531 to search for keywords in a ``rest'' argument. Technically
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532 speaking, this is incorrect, since @code{memq} looks at the
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533 odd-numbered values as well as the even-numbered keywords.
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534 The net effect is that if you happen to pass a keyword symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
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535 as the @emph{value} of another keyword argument, where that
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536 keyword symbol happens to equal the name of a valid keyword
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537 argument of the same function, then the keyword parser will
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538 become confused. This minor bug can only affect you if you
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539 use keyword symbols as general-purpose data in your program;
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540 this practice is strongly discouraged in Emacs Lisp.
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541
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542 The fifth section of the argument list consists of @dfn{auxiliary
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543 variables}. These are not really arguments at all, but simply
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544 variables which are bound to @code{nil} or to the specified
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545 @var{initforms} during execution of the function. There is no
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546 difference between the following two functions, except for a
3ecd8885ac67 Import from CVS: tag r21-2-22
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547 matter of stylistic taste:
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548
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549 @example
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550 (defun* foo (a b &aux (c (+ a b)) d)
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551 @var{body})
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552
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553 (defun* foo (a b)
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554 (let ((c (+ a b)) d)
3ecd8885ac67 Import from CVS: tag r21-2-22
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555 @var{body}))
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556 @end example
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557
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558 Argument lists support @dfn{destructuring}. In Common Lisp,
3ecd8885ac67 Import from CVS: tag r21-2-22
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559 destructuring is only allowed with @code{defmacro}; this package
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560 allows it with @code{defun*} and other argument lists as well.
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561 In destructuring, any argument variable (@var{var} in the above
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562 diagram) can be replaced by a list of variables, or more generally,
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563 a recursive argument list. The corresponding argument value must
3ecd8885ac67 Import from CVS: tag r21-2-22
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564 be a list whose elements match this recursive argument list.
3ecd8885ac67 Import from CVS: tag r21-2-22
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565 For example:
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566
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567 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
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568 (defmacro* dolist ((var listform &optional resultform)
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569 &rest body)
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570 ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
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571 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
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572
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573 This says that the first argument of @code{dolist} must be a list
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574 of two or three items; if there are other arguments as well as this
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575 list, they are stored in @code{body}. All features allowed in
3ecd8885ac67 Import from CVS: tag r21-2-22
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576 regular argument lists are allowed in these recursive argument lists.
3ecd8885ac67 Import from CVS: tag r21-2-22
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577 In addition, the clause @samp{&whole @var{var}} is allowed at the
3ecd8885ac67 Import from CVS: tag r21-2-22
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578 front of a recursive argument list. It binds @var{var} to the
3ecd8885ac67 Import from CVS: tag r21-2-22
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579 whole list being matched; thus @code{(&whole all a b)} matches
3ecd8885ac67 Import from CVS: tag r21-2-22
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580 a list of two things, with @code{a} bound to the first thing,
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
581 @code{b} bound to the second thing, and @code{all} bound to the
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
582 list itself. (Common Lisp allows @code{&whole} in top-level
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
583 @code{defmacro} argument lists as well, but Emacs Lisp does not
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
584 support this usage.)
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
585
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586 One last feature of destructuring is that the argument list may be
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
587 dotted, so that the argument list @code{(a b . c)} is functionally
3ecd8885ac67 Import from CVS: tag r21-2-22
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588 equivalent to @code{(a b &rest c)}.
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diff changeset
589
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590 If the optimization quality @code{safety} is set to 0
3ecd8885ac67 Import from CVS: tag r21-2-22
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591 (@pxref{Declarations}), error checking for wrong number of
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
592 arguments and invalid keyword arguments is disabled. By default,
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
593 argument lists are rigorously checked.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
594
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diff changeset
595 @node Time of Evaluation, Function Aliases, Argument Lists, Program Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
596 @section Time of Evaluation
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
597
3ecd8885ac67 Import from CVS: tag r21-2-22
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598 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
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599 Normally, the byte-compiler does not actually execute the forms in
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
600 a file it compiles. For example, if a file contains @code{(setq foo t)},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
601 the act of compiling it will not actually set @code{foo} to @code{t}.
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cvs
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diff changeset
602 This is true even if the @code{setq} was a top-level form (i.e., not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
603 enclosed in a @code{defun} or other form). Sometimes, though, you
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604 would like to have certain top-level forms evaluated at compile-time.
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cvs
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diff changeset
605 For example, the compiler effectively evaluates @code{defmacro} forms
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
606 at compile-time so that later parts of the file can refer to the
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
607 macros that are defined.
3ecd8885ac67 Import from CVS: tag r21-2-22
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608
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diff changeset
609 @defspec eval-when (situations...) forms...
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parents:
diff changeset
610 This form controls when the body @var{forms} are evaluated.
3ecd8885ac67 Import from CVS: tag r21-2-22
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611 The @var{situations} list may contain any set of the symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
612 @code{compile}, @code{load}, and @code{eval} (or their long-winded
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
613 ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel},
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
614 and @code{:execute}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
615
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
616 The @code{eval-when} form is handled differently depending on
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
617 whether or not it is being compiled as a top-level form.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
618 Specifically, it gets special treatment if it is being compiled
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
619 by a command such as @code{byte-compile-file} which compiles files
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
620 or buffers of code, and it appears either literally at the
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
621 top level of the file or inside a top-level @code{progn}.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
622
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
623 For compiled top-level @code{eval-when}s, the body @var{forms} are
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
624 executed at compile-time if @code{compile} is in the @var{situations}
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
625 list, and the @var{forms} are written out to the file (to be executed
3ecd8885ac67 Import from CVS: tag r21-2-22
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626 at load-time) if @code{load} is in the @var{situations} list.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
627
3ecd8885ac67 Import from CVS: tag r21-2-22
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628 For non-compiled-top-level forms, only the @code{eval} situation is
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
629 relevant. (This includes forms executed by the interpreter, forms
3ecd8885ac67 Import from CVS: tag r21-2-22
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630 compiled with @code{byte-compile} rather than @code{byte-compile-file},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
631 and non-top-level forms.) The @code{eval-when} acts like a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
632 @code{progn} if @code{eval} is specified, and like @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
633 (ignoring the body @var{forms}) if not.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
634
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
635 The rules become more subtle when @code{eval-when}s are nested;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
636 consult Steele (second edition) for the gruesome details (and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
637 some gruesome examples).
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
638
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
639 Some simple examples:
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
640
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
641 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
642 ;; Top-level forms in foo.el:
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
643 (eval-when (compile) (setq foo1 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
644 (eval-when (load) (setq foo2 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
645 (eval-when (compile load) (setq foo3 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
646 (eval-when (eval) (setq foo4 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
647 (eval-when (eval compile) (setq foo5 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
648 (eval-when (eval load) (setq foo6 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
649 (eval-when (eval compile load) (setq foo7 'bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
650 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
651
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
652 When @file{foo.el} is compiled, these variables will be set during
3ecd8885ac67 Import from CVS: tag r21-2-22
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653 the compilation itself:
3ecd8885ac67 Import from CVS: tag r21-2-22
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654
3ecd8885ac67 Import from CVS: tag r21-2-22
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655 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
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656 foo1 foo3 foo5 foo7 ; `compile'
3ecd8885ac67 Import from CVS: tag r21-2-22
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657 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
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658
3ecd8885ac67 Import from CVS: tag r21-2-22
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659 When @file{foo.elc} is loaded, these variables will be set:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
660
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
661 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
662 foo2 foo3 foo6 foo7 ; `load'
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
663 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
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664
3ecd8885ac67 Import from CVS: tag r21-2-22
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665 And if @file{foo.el} is loaded uncompiled, these variables will
3ecd8885ac67 Import from CVS: tag r21-2-22
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666 be set:
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
667
3ecd8885ac67 Import from CVS: tag r21-2-22
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668 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
669 foo4 foo5 foo6 foo7 ; `eval'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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670 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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671
3ecd8885ac67 Import from CVS: tag r21-2-22
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672 If these seven @code{eval-when}s had been, say, inside a @code{defun},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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673 then the first three would have been equivalent to @code{nil} and the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
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674 last four would have been equivalent to the corresponding @code{setq}s.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
675
3ecd8885ac67 Import from CVS: tag r21-2-22
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676 Note that @code{(eval-when (load eval) @dots{})} is equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
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677 to @code{(progn @dots{})} in all contexts. The compiler treats
3ecd8885ac67 Import from CVS: tag r21-2-22
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678 certain top-level forms, like @code{defmacro} (sort-of) and
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
679 @code{require}, as if they were wrapped in @code{(eval-when
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
680 (compile load eval) @dots{})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
681 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
682
4905
755ae5b97edb Change "special form" to "special operator" in our sources.
Aidan Kehoe <kehoea@parhasard.net>
parents: 4677
diff changeset
683 Emacs 19 includes two special operators related to @code{eval-when}.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
684 One of these, @code{eval-when-compile}, is not quite equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
685 any @code{eval-when} construct and is described below. This package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
686 defines a version of @code{eval-when-compile} for the benefit of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
687 Emacs 18 users.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
688
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
689 The other form, @code{(eval-and-compile @dots{})}, is exactly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
690 equivalent to @samp{(eval-when (compile load eval) @dots{})} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
691 so is not itself defined by this package.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
692
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
693 @defspec eval-when-compile forms...
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
694 The @var{forms} are evaluated at compile-time; at execution time,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
695 this form acts like a quoted constant of the resulting value. Used
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
696 at top-level, @code{eval-when-compile} is just like @samp{eval-when
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
697 (compile eval)}. In other contexts, @code{eval-when-compile}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
698 allows code to be evaluated once at compile-time for efficiency
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
699 or other reasons.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
700
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
701 This form is similar to the @samp{#.} syntax of true Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
702 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
703
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
704 @defspec load-time-value form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
705 The @var{form} is evaluated at load-time; at execution time,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
706 this form acts like a quoted constant of the resulting value.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
707
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
708 Early Common Lisp had a @samp{#,} syntax that was similar to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
709 this, but ANSI Common Lisp replaced it with @code{load-time-value}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
710 and gave it more well-defined semantics.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
711
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
712 In a compiled file, @code{load-time-value} arranges for @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
713 to be evaluated when the @file{.elc} file is loaded and then used
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
714 as if it were a quoted constant. In code compiled by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
715 @code{byte-compile} rather than @code{byte-compile-file}, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
716 effect is identical to @code{eval-when-compile}. In uncompiled
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
717 code, both @code{eval-when-compile} and @code{load-time-value}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
718 act exactly like @code{progn}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
719
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
720 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
721 (defun report ()
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
722 (insert "This function was executed on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
723 (current-time-string)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
724 ", compiled on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
725 (eval-when-compile (current-time-string))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
726 ;; or '#.(current-time-string) in real Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
727 ", and loaded on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
728 (load-time-value (current-time-string))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
729 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
730
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
731 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
732 Byte-compiled, the above defun will result in the following code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
733 (or its compiled equivalent, of course) in the @file{.elc} file:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
734
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
735 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
736 (setq --temp-- (current-time-string))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
737 (defun report ()
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
738 (insert "This function was executed on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
739 (current-time-string)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
740 ", compiled on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
741 '"Wed Jun 23 18:33:43 1993"
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
742 ", and loaded on: "
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
743 --temp--))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
744 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
745 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
746
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
747 @node Function Aliases, , Time of Evaluation, Program Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
748 @section Function Aliases
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
749
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
750 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
751 This section describes a feature from GNU Emacs 19 which this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
752 package makes available in other versions of Emacs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
753
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
754 @defun defalias symbol function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
755 This function sets @var{symbol}'s function cell to @var{function}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
756 It is equivalent to @code{fset}, except that in GNU Emacs 19 it also
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
757 records the setting in @code{load-history} so that it can be undone
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
758 by a later @code{unload-feature}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
759
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
760 In other versions of Emacs, @code{defalias} is a synonym for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
761 @code{fset}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
762 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
763
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
764 @node Predicates, Control Structure, Program Structure, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
765 @chapter Predicates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
766
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
767 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
768 This section describes functions for testing whether various
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
769 facts are true or false.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
770
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
771 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
772 * Type Predicates:: `typep', `deftype', and `coerce'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
773 * Equality Predicates:: `eql' and `equalp'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
774 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
775
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
776 @node Type Predicates, Equality Predicates, Predicates, Predicates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
777 @section Type Predicates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
778
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
779 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
780 The @dfn{CL} package defines a version of the Common Lisp @code{typep}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
781 predicate.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
782
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
783 @defun typep object type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
784 Check if @var{object} is of type @var{type}, where @var{type} is a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
785 (quoted) type name of the sort used by Common Lisp. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
786 @code{(typep foo 'integer)} is equivalent to @code{(integerp foo)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
787 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
788
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
789 The @var{type} argument to the above function is either a symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
790 or a list beginning with a symbol.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
791
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
792 @itemize @bullet
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
793 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
794 If the type name is a symbol, Emacs appends @samp{-p} to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
795 symbol name to form the name of a predicate function for testing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
796 the type. (Built-in predicates whose names end in @samp{p} rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
797 than @samp{-p} are used when appropriate.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
798
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
799 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
800 The type symbol @code{t} stands for the union of all types.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
801 @code{(typep @var{object} t)} is always true. Likewise, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
802 type symbol @code{nil} stands for nothing at all, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
803 @code{(typep @var{object} nil)} is always false.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
804
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
805 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
806 The type symbol @code{null} represents the symbol @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
807 Thus @code{(typep @var{object} 'null)} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
808 @code{(null @var{object})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
809
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
810 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
811 The type symbol @code{real} is a synonym for @code{number}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
812 @code{fixnum} is a synonym for @code{integer}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
813
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
814 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
815 The type symbols @code{character} and @code{string-char} match
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
816 characters. In Emacs-19 and XEmacs-19, characters are the same thing as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
817 integers in the range 0-255. In XEmacs-20, where characters are a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
818 first-class data type, this checks for actual characters, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
819 @code{(typep @var{8bit-integer} 'character)} will return @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
820
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
821 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
822 The type symbol @code{float} uses the @code{floatp-safe} predicate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
823 defined by this package rather than @code{floatp}, so it will work
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
824 correctly even in Emacs versions without floating-point support.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
825
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
826 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
827 The type list @code{(integer @var{low} @var{high})} represents all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
828 integers between @var{low} and @var{high}, inclusive. Either bound
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
829 may be a list of a single integer to specify an exclusive limit,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
830 or a @code{*} to specify no limit. The type @code{(integer * *)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
831 is thus equivalent to @code{integer}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
832
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
833 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
834 Likewise, lists beginning with @code{float}, @code{real}, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
835 @code{number} represent numbers of that type falling in a particular
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
836 range.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
837
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
838 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
839 Lists beginning with @code{and}, @code{or}, and @code{not} form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
840 combinations of types. For example, @code{(or integer (float 0 *))}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
841 represents all objects that are integers or non-negative floats.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
842
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
843 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
844 Lists beginning with @code{member} or @code{member*} represent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
845 objects @code{eql} to any of the following values. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
846 @code{(member 1 2 3 4)} is equivalent to @code{(integer 1 4)},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
847 and @code{(member nil)} is equivalent to @code{null}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
848
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
849 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
850 Lists of the form @code{(satisfies @var{predicate})} represent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
851 all objects for which @var{predicate} returns true when called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
852 with that object as an argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
853 @end itemize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
854
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
855 The following function and macro (not technically predicates) are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
856 related to @code{typep}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
857
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
858 @defun coerce object type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
859 This function attempts to convert @var{object} to the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
860 @var{type}. If @var{object} is already of that type as determined by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
861 @code{typep}, it is simply returned. Otherwise, certain types of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
862 conversions will be made: If @var{type} is any sequence type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
863 (@code{string}, @code{list}, etc.) then @var{object} will be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
864 converted to that type if possible. If @var{type} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
865 @code{character}, then strings of length one and symbols with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
866 one-character names can be coerced. If @var{type} is @code{float},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
867 then integers can be coerced in versions of Emacs that support
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
868 floats. In all other circumstances, @code{coerce} signals an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
869 error.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
870 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
871
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
872 @defspec deftype name arglist forms...
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
873 This macro defines a new type called @var{name}. It is similar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
874 to @code{defmacro} in many ways; when @var{name} is encountered
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
875 as a type name, the body @var{forms} are evaluated and should
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
876 return a type specifier that is equivalent to the type. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
877 @var{arglist} is a Common Lisp argument list of the sort accepted
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
878 by @code{defmacro*}. The type specifier @samp{(@var{name} @var{args}...)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
879 is expanded by calling the expander with those arguments; the type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
880 symbol @samp{@var{name}} is expanded by calling the expander with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
881 no arguments. The @var{arglist} is processed the same as for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
882 @code{defmacro*} except that optional arguments without explicit
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
883 defaults use @code{*} instead of @code{nil} as the ``default''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
884 default. Some examples:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
885
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
886 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
887 (deftype null () '(satisfies null)) ; predefined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
888 (deftype list () '(or null cons)) ; predefined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
889 (deftype unsigned-byte (&optional bits)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
890 (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits)))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
891 (unsigned-byte 8) @equiv{} (integer 0 255)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
892 (unsigned-byte) @equiv{} (integer 0 *)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
893 unsigned-byte @equiv{} (integer 0 *)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
894 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
895
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
896 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
897 The last example shows how the Common Lisp @code{unsigned-byte}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
898 type specifier could be implemented if desired; this package does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
899 not implement @code{unsigned-byte} by default.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
900 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
901
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
902 The @code{typecase} and @code{check-type} macros also use type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
903 names. @xref{Conditionals}. @xref{Assertions}. The @code{map},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
904 @code{concatenate}, and @code{merge} functions take type-name
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
905 arguments to specify the type of sequence to return. @xref{Sequences}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
906
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
907 @node Equality Predicates, , Type Predicates, Predicates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
908 @section Equality Predicates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
909
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
910 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
911 This package defines two Common Lisp predicates, @code{eql} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
912 @code{equalp}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
913
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
914 @defun eql a b
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
915 This function is almost the same as @code{eq}, except that if @var{a}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
916 and @var{b} are numbers of the same type, it compares them for numeric
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
917 equality (as if by @code{equal} instead of @code{eq}). This makes a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
918 difference only for versions of Emacs that are compiled with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
919 floating-point support, such as Emacs 19. Emacs floats are allocated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
920 objects just like cons cells, which means that @code{(eq 3.0 3.0)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
921 will not necessarily be true---if the two @code{3.0}s were allocated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
922 separately, the pointers will be different even though the numbers are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
923 the same. But @code{(eql 3.0 3.0)} will always be true.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
924
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
925 The types of the arguments must match, so @code{(eql 3 3.0)} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
926 still false.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
927
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
928 Note that Emacs integers are ``direct'' rather than allocated, which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
929 basically means @code{(eq 3 3)} will always be true. Thus @code{eq}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
930 and @code{eql} behave differently only if floating-point numbers are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
931 involved, and are indistinguishable on Emacs versions that don't
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
932 support floats.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
933
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
934 There is a slight inconsistency with Common Lisp in the treatment of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
935 positive and negative zeros. Some machines, notably those with IEEE
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
936 standard arithmetic, represent @code{+0} and @code{-0} as distinct
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
937 values. Normally this doesn't matter because the standard specifies
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
938 that @code{(= 0.0 -0.0)} should always be true, and this is indeed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
939 what Emacs Lisp and Common Lisp do. But the Common Lisp standard
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
940 states that @code{(eql 0.0 -0.0)} and @code{(equal 0.0 -0.0)} should
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
941 be false on IEEE-like machines; Emacs Lisp does not do this, and in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
942 fact the only known way to distinguish between the two zeros in Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
943 Lisp is to @code{format} them and check for a minus sign.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
944 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
945
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
946 @defun equalp a b
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
947 This function is a more flexible version of @code{equal}. In
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
948 particular, it compares strings and characters case-insensitively, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
949 it compares numbers without regard to type (so that @code{(equalp 3
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
950 3.0)} is true). Vectors and conses are compared recursively. All other
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
951 objects are compared as if by @code{equal}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
952
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
953 This function differs from Common Lisp @code{equalp} in several
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
954 respects. In keeping with the idea that strings are less
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
955 vector-like in Emacs Lisp, this package's @code{equalp} also will not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
956 compare strings against vectors of integers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
957 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
958
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
959 Also note that the Common Lisp functions @code{member} and @code{assoc}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
960 use @code{eql} to compare elements, whereas Emacs Lisp follows the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
961 MacLisp tradition and uses @code{equal} for these two functions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
962 In Emacs, use @code{member*} and @code{assoc*} to get functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
963 which use @code{eql} for comparisons.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
964
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
965 @node Control Structure, Macros, Predicates, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
966 @chapter Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
967
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
968 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
969 The features described in the following sections implement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
970 various advanced control structures, including the powerful
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
971 @code{setf} facility and a number of looping and conditional
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
972 constructs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
973
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
974 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
975 * Assignment:: The `psetq' form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
976 * Generalized Variables:: `setf', `incf', `push', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
977 * Variable Bindings:: `progv', `lexical-let', `flet', `macrolet'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
978 * Conditionals:: `when', `unless', `case', `typecase'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
979 * Blocks and Exits:: `block', `return', `return-from'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
980 * Iteration:: `do', `dotimes', `dolist', `do-symbols'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
981 * Loop Facility:: The Common Lisp `loop' macro
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
982 * Multiple Values:: `values', `multiple-value-bind', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
983 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
984
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
985 @node Assignment, Generalized Variables, Control Structure, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
986 @section Assignment
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
987
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
988 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
989 The @code{psetq} form is just like @code{setq}, except that multiple
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
990 assignments are done in parallel rather than sequentially.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
991
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
992 @defspec psetq [symbol form]@dots{}
4905
755ae5b97edb Change "special form" to "special operator" in our sources.
Aidan Kehoe <kehoea@parhasard.net>
parents: 4677
diff changeset
993 This macro is used to assign to several
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
994 variables simultaneously. Given only one @var{symbol} and @var{form},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
995 it has the same effect as @code{setq}. Given several @var{symbol}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
996 and @var{form} pairs, it evaluates all the @var{form}s in advance
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
997 and then stores the corresponding variables afterwards.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
998
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
999 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1000 (setq x 2 y 3)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1001 (setq x (+ x y) y (* x y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1002 x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1003 @result{} 5
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1004 y ; @r{@code{y} was computed after @code{x} was set.}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1005 @result{} 15
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1006 (setq x 2 y 3)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1007 (psetq x (+ x y) y (* x y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1008 x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1009 @result{} 5
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1010 y ; @r{@code{y} was computed before @code{x} was set.}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1011 @result{} 6
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1012 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1013
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1014 The simplest use of @code{psetq} is @code{(psetq x y y x)}, which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1015 exchanges the values of two variables. (The @code{rotatef} form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1016 provides an even more convenient way to swap two variables;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1017 @pxref{Modify Macros}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1018
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1019 @code{psetq} always returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1020 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1021
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1022 @node Generalized Variables, Variable Bindings, Assignment, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1023 @section Generalized Variables
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1024
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1025 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1026 A ``generalized variable'' or ``place form'' is one of the many places
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1027 in Lisp memory where values can be stored. The simplest place form is
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1028 a regular Lisp variable. But the cars and cdrs of lists, elements
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1029 of arrays, properties of symbols, and many other locations are also
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1030 places where Lisp values are stored.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1031
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1032 The @code{setf} form is like @code{setq}, except that it accepts
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1033 arbitrary place forms on the left side rather than just
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1034 symbols. For example, @code{(setf (car a) b)} sets the car of
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1035 @code{a} to @code{b}, doing the same operation as @code{(setcar a b)}
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1036 but without having to remember two separate functions for setting
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1037 and accessing every type of place.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1038
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1039 Generalized variables are analogous to ``lvalues'' in the C
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1040 language, where @samp{x = a[i]} gets an element from an array
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1041 and @samp{a[i] = x} stores an element using the same notation.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1042 Just as certain forms like @code{a[i]} can be lvalues in C, there
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1043 is a set of forms that can be generalized variables in Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1044
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1045 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1046 * Basic Setf:: `setf' and place forms
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1047 * Modify Macros:: `incf', `push', `rotatef', `letf', `callf', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1048 * Customizing Setf:: `define-modify-macro', `defsetf', `define-setf-method'
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diff changeset
1049 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1050
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diff changeset
1051 @node Basic Setf, Modify Macros, Generalized Variables, Generalized Variables
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1052 @subsection Basic Setf
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1053
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1054 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1055 The @code{setf} macro is the most basic way to operate on generalized
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1056 variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1057
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diff changeset
1058 @defspec setf [place form]@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1059 This macro evaluates @var{form} and stores it in @var{place}, which
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1060 must be a valid generalized variable form. If there are several
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1061 @var{place} and @var{form} pairs, the assignments are done sequentially
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1062 just as with @code{setq}. @code{setf} returns the value of the last
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1063 @var{form}.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1064
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diff changeset
1065 The following Lisp forms will work as generalized variables, and
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1066 so may legally appear in the @var{place} argument of @code{setf}:
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1067
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diff changeset
1068 @itemize @bullet
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1069 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1070 A symbol naming a variable. In other words, @code{(setf x y)} is
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1071 exactly equivalent to @code{(setq x y)}, and @code{setq} itself is
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1072 strictly speaking redundant now that @code{setf} exists. Many
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1073 programmers continue to prefer @code{setq} for setting simple
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1074 variables, though, purely for stylistic or historical reasons.
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
1075 The form @code{(setf x y)} actually expands to @code{(setq x y)},
428
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1076 so there is no performance penalty for using it in compiled code.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1077
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1078 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1079 A call to any of the following Lisp functions:
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1080
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1081 @smallexample
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1082 car cdr caar .. cddddr
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1083 nth rest first .. tenth
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1084 aref elt nthcdr
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1085 symbol-function symbol-value symbol-plist
440
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
1086 get getf gethash
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
1087 subseq
428
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1088 @end smallexample
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1089
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1090 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1091 Note that for @code{nthcdr} and @code{getf}, the list argument
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1092 of the function must itself be a valid @var{place} form. For
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1093 example, @code{(setf (nthcdr 0 foo) 7)} will set @code{foo} itself
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1094 to 7. Note that @code{push} and @code{pop} on an @code{nthcdr}
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1095 place can be used to insert or delete at any position in a list.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1096 The use of @code{nthcdr} as a @var{place} form is an extension
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1097 to standard Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1098
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1099 @item
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parents:
diff changeset
1100 The following Emacs-specific functions are also @code{setf}-able.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1101 (Some of these are defined only in Emacs 19 or only in XEmacs.)
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1102
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diff changeset
1103 @smallexample
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1104 buffer-file-name marker-position
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1105 buffer-modified-p match-data
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1106 buffer-name mouse-position
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1107 buffer-string overlay-end
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1108 buffer-substring overlay-get
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1109 current-buffer overlay-start
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1110 current-case-table point
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1111 current-column point-marker
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1112 current-global-map point-max
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1113 current-input-mode point-min
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1114 current-local-map process-buffer
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1115 current-window-configuration process-filter
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1116 default-file-modes process-sentinel
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1117 default-value read-mouse-position
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1118 documentation-property screen-height
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1119 extent-data screen-menubar
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1120 extent-end-position screen-width
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1121 extent-start-position selected-window
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1122 face-background selected-screen
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1123 face-background-pixmap selected-frame
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1124 face-font standard-case-table
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1125 face-foreground syntax-table
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1126 face-underline-p window-buffer
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1127 file-modes window-dedicated-p
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1128 frame-height window-display-table
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1129 frame-parameters window-height
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1130 frame-visible-p window-hscroll
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1131 frame-width window-point
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1132 get-register window-start
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1133 getenv window-width
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1134 global-key-binding x-get-cut-buffer
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1135 keymap-parent x-get-cutbuffer
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1136 local-key-binding x-get-secondary-selection
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1137 mark x-get-selection
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1138 mark-marker
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1139 @end smallexample
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1140
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1141 Most of these have directly corresponding ``set'' functions, like
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1142 @code{use-local-map} for @code{current-local-map}, or @code{goto-char}
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1143 for @code{point}. A few, like @code{point-min}, expand to longer
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1144 sequences of code when they are @code{setf}'d (@code{(narrow-to-region
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
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1145 x (point-max))} in this case).
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1146
3ecd8885ac67 Import from CVS: tag r21-2-22
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1147 @item
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diff changeset
1148 A call of the form @code{(substring @var{subplace} @var{n} [@var{m}])},
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1149 where @var{subplace} is itself a legal generalized variable whose
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1150 current value is a string, and where the value stored is also a
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1151 string. The new string is spliced into the specified part of the
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1152 destination string. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1153
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1154 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
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1155 (setq a (list "hello" "world"))
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parents:
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1156 @result{} ("hello" "world")
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1157 (cadr a)
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
1158 @result{} "world"
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1159 (substring (cadr a) 2 4)
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
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1160 @result{} "rl"
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1161 (setf (substring (cadr a) 2 4) "o")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1162 @result{} "o"
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1163 (cadr a)
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1164 @result{} "wood"
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1165 a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1166 @result{} ("hello" "wood")
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1167 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1168
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1169 The generalized variable @code{buffer-substring}, listed above,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1170 also works in this way by replacing a portion of the current buffer.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1171
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1172 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1173 A call of the form @code{(apply '@var{func} @dots{})} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1174 @code{(apply (function @var{func}) @dots{})}, where @var{func}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1175 is a @code{setf}-able function whose store function is ``suitable''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1176 in the sense described in Steele's book; since none of the standard
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1177 Emacs place functions are suitable in this sense, this feature is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1178 only interesting when used with places you define yourself with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1179 @code{define-setf-method} or the long form of @code{defsetf}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1180
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1181 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1182 A macro call, in which case the macro is expanded and @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1183 is applied to the resulting form.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1184
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1185 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1186 Any form for which a @code{defsetf} or @code{define-setf-method}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1187 has been made.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1188 @end itemize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1189
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
1190 Using any forms other than these in the @var{place} argument to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1191 @code{setf} will signal an error.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1192
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
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diff changeset
1193 The @code{setf} macro takes care to evaluate all subforms in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1194 the proper left-to-right order; for example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1195
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1196 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1197 (setf (aref vec (incf i)) i)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1198 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1199
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1200 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1201 looks like it will evaluate @code{(incf i)} exactly once, before the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1202 following access to @code{i}; the @code{setf} expander will insert
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1203 temporary variables as necessary to ensure that it does in fact work
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1204 this way no matter what setf-method is defined for @code{aref}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1205 (In this case, @code{aset} would be used and no such steps would
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1206 be necessary since @code{aset} takes its arguments in a convenient
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1207 order.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1208
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1209 However, if the @var{place} form is a macro which explicitly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1210 evaluates its arguments in an unusual order, this unusual order
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1211 will be preserved. Adapting an example from Steele, given
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1212
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1213 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1214 (defmacro wrong-order (x y) (list 'aref y x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1215 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1216
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1217 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1218 the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1219 evaluate @var{b} first, then @var{a}, just as in an actual call
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1220 to @code{wrong-order}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1221 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1222
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1223 @node Modify Macros, Customizing Setf, Basic Setf, Generalized Variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1224 @subsection Modify Macros
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1225
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1226 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1227 This package defines a number of other macros besides @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1228 that operate on generalized variables. Many are interesting and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1229 useful even when the @var{place} is just a variable name.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1230
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1231 @defspec psetf [place form]@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1232 This macro is to @code{setf} what @code{psetq} is to @code{setq}:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1233 When several @var{place}s and @var{form}s are involved, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1234 assignments take place in parallel rather than sequentially.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1235 Specifically, all subforms are evaluated from left to right, then
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1236 all the assignments are done (in an undefined order).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1237 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1238
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1239 @defspec incf place &optional x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1240 This macro increments the number stored in @var{place} by one, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1241 by @var{x} if specified. The incremented value is returned. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1242 example, @code{(incf i)} is equivalent to @code{(setq i (1+ i))}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1243 @code{(incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x) 2))}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1244
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1245 Once again, care is taken to preserve the ``apparent'' order of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1246 evaluation. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1247
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1248 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1249 (incf (aref vec (incf i)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1250 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1251
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1252 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1253 appears to increment @code{i} once, then increment the element of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1254 @code{vec} addressed by @code{i}; this is indeed exactly what it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1255 does, which means the above form is @emph{not} equivalent to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1256 ``obvious'' expansion,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1257
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1258 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1259 (setf (aref vec (incf i)) (1+ (aref vec (incf i)))) ; Wrong!
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1260 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1261
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1262 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1263 but rather to something more like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1264
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1265 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1266 (let ((temp (incf i)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1267 (setf (aref vec temp) (1+ (aref vec temp))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1268 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1269
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1270 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1271 Again, all of this is taken care of automatically by @code{incf} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1272 the other generalized-variable macros.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1273
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1274 As a more Emacs-specific example of @code{incf}, the expression
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1275 @code{(incf (point) @var{n})} is essentially equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1276 @code{(forward-char @var{n})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1277 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1278
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1279 @defspec decf place &optional x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1280 This macro decrements the number stored in @var{place} by one, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1281 by @var{x} if specified.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1282 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1283
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1284 @defspec pop place
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1285 This macro removes and returns the first element of the list stored
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1286 in @var{place}. It is analogous to @code{(prog1 (car @var{place})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1287 (setf @var{place} (cdr @var{place})))}, except that it takes care
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1288 to evaluate all subforms only once.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1289 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1290
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1291 @defspec push x place
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1292 This macro inserts @var{x} at the front of the list stored in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1293 @var{place}. It is analogous to @code{(setf @var{place} (cons
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1294 @var{x} @var{place}))}, except for evaluation of the subforms.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1295 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1296
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1297 @defspec pushnew x place @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1298 This macro inserts @var{x} at the front of the list stored in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1299 @var{place}, but only if @var{x} was not @code{eql} to any
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1300 existing element of the list. The optional keyword arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1301 are interpreted in the same way as for @code{adjoin}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1302 @xref{Lists as Sets}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1303 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1304
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1305 @defspec shiftf place@dots{} newvalue
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1306 This macro shifts the @var{place}s left by one, shifting in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1307 value of @var{newvalue} (which may be any Lisp expression, not just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1308 a generalized variable), and returning the value shifted out of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1309 the first @var{place}. Thus, @code{(shiftf @var{a} @var{b} @var{c}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1310 @var{d})} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1311
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1312 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1313 (prog1
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1314 @var{a}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1315 (psetf @var{a} @var{b}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1316 @var{b} @var{c}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1317 @var{c} @var{d}))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1318 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1319
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1320 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1321 except that the subforms of @var{a}, @var{b}, and @var{c} are actually
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1322 evaluated only once each and in the apparent order.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1323 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1324
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1325 @defspec rotatef place@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1326 This macro rotates the @var{place}s left by one in circular fashion.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1327 Thus, @code{(rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1328
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1329 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1330 (psetf @var{a} @var{b}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1331 @var{b} @var{c}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1332 @var{c} @var{d}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1333 @var{d} @var{a})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1334 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1335
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1336 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1337 except for the evaluation of subforms. @code{rotatef} always
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1338 returns @code{nil}. Note that @code{(rotatef @var{a} @var{b})}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1339 conveniently exchanges @var{a} and @var{b}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1340 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1341
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1342 The following macros were invented for this package; they have no
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1343 analogues in Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1344
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1345 @defspec letf (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1346 This macro is analogous to @code{let}, but for generalized variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1347 rather than just symbols. Each @var{binding} should be of the form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1348 @code{(@var{place} @var{value})}; the original contents of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1349 @var{place}s are saved, the @var{value}s are stored in them, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1350 then the body @var{form}s are executed. Afterwards, the @var{places}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1351 are set back to their original saved contents. This cleanup happens
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1352 even if the @var{form}s exit irregularly due to a @code{throw} or an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1353 error.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1354
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1355 For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1356
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1357 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1358 (letf (((point) (point-min))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1359 (a 17))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1360 ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1361 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1362
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1363 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1364 moves ``point'' in the current buffer to the beginning of the buffer,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1365 and also binds @code{a} to 17 (as if by a normal @code{let}, since
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1366 @code{a} is just a regular variable). After the body exits, @code{a}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1367 is set back to its original value and point is moved back to its
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1368 original position.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1369
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1370 Note that @code{letf} on @code{(point)} is not quite like a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1371 @code{save-excursion}, as the latter effectively saves a marker
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1372 which tracks insertions and deletions in the buffer. Actually,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1373 a @code{letf} of @code{(point-marker)} is much closer to this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1374 behavior. (@code{point} and @code{point-marker} are equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1375 as @code{setf} places; each will accept either an integer or a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1376 marker as the stored value.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1377
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1378 Since generalized variables look like lists, @code{let}'s shorthand
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1379 of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1380 be ambiguous in @code{letf} and is not allowed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1381
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1382 However, a @var{binding} specifier may be a one-element list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1383 @samp{(@var{place})}, which is similar to @samp{(@var{place}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1384 @var{place})}. In other words, the @var{place} is not disturbed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1385 on entry to the body, and the only effect of the @code{letf} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1386 to restore the original value of @var{place} afterwards. (The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1387 redundant access-and-store suggested by the @code{(@var{place}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1388 @var{place})} example does not actually occur.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1389
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1390 In most cases, the @var{place} must have a well-defined value on
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1391 entry to the @code{letf} form. The only exceptions are plain
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1392 variables and calls to @code{symbol-value} and @code{symbol-function}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1393 If the symbol is not bound on entry, it is simply made unbound by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1394 @code{makunbound} or @code{fmakunbound} on exit.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1395 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1396
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1397 @defspec letf* (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1398 This macro is to @code{letf} what @code{let*} is to @code{let}:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1399 It does the bindings in sequential rather than parallel order.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
1400 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1401
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1402 @defspec callf @var{function} @var{place} @var{args}@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1403 This is the ``generic'' modify macro. It calls @var{function},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1404 which should be an unquoted function name, macro name, or lambda.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1405 It passes @var{place} and @var{args} as arguments, and assigns the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1406 result back to @var{place}. For example, @code{(incf @var{place}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1407 @var{n})} is the same as @code{(callf + @var{place} @var{n})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1408 Some more examples:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1409
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1410 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1411 (callf abs my-number)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1412 (callf concat (buffer-name) "<" (int-to-string n) ">")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1413 (callf union happy-people (list joe bob) :test 'same-person)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1414 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1415
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1416 @xref{Customizing Setf}, for @code{define-modify-macro}, a way
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1417 to create even more concise notations for modify macros. Note
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1418 again that @code{callf} is an extension to standard Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1419 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1420
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1421 @defspec callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1422 This macro is like @code{callf}, except that @var{place} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1423 the @emph{second} argument of @var{function} rather than the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1424 first. For example, @code{(push @var{x} @var{place})} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1425 equivalent to @code{(callf2 cons @var{x} @var{place})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1426 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1427
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1428 The @code{callf} and @code{callf2} macros serve as building
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1429 blocks for other macros like @code{incf}, @code{pushnew}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1430 @code{define-modify-macro}. The @code{letf} and @code{letf*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1431 macros are used in the processing of symbol macros;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1432 @pxref{Macro Bindings}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1433
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1434 @node Customizing Setf, , Modify Macros, Generalized Variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1435 @subsection Customizing Setf
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1436
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1437 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1438 Common Lisp defines three macros, @code{define-modify-macro},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1439 @code{defsetf}, and @code{define-setf-method}, that allow the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1440 user to extend generalized variables in various ways.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1441
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1442 @defspec define-modify-macro name arglist function [doc-string]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1443 This macro defines a ``read-modify-write'' macro similar to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1444 @code{incf} and @code{decf}. The macro @var{name} is defined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1445 to take a @var{place} argument followed by additional arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1446 described by @var{arglist}. The call
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1447
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1448 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1449 (@var{name} @var{place} @var{args}...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1450 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1451
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1452 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1453 will be expanded to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1454
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1455 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1456 (callf @var{func} @var{place} @var{args}...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1457 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1458
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1459 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1460 which in turn is roughly equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1461
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1462 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1463 (setf @var{place} (@var{func} @var{place} @var{args}...))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1464 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1465
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1466 For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1467
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1468 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1469 (define-modify-macro incf (&optional (n 1)) +)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1470 (define-modify-macro concatf (&rest args) concat)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1471 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1472
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1473 Note that @code{&key} is not allowed in @var{arglist}, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1474 @code{&rest} is sufficient to pass keywords on to the function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1475
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1476 Most of the modify macros defined by Common Lisp do not exactly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1477 follow the pattern of @code{define-modify-macro}. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1478 @code{push} takes its arguments in the wrong order, and @code{pop}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1479 is completely irregular. You can define these macros ``by hand''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1480 using @code{get-setf-method}, or consult the source file
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1481 @file{cl-macs.el} to see how to use the internal @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1482 building blocks.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1483 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1484
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1485 @defspec defsetf access-fn update-fn
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1486 This is the simpler of two @code{defsetf} forms. Where
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1487 @var{access-fn} is the name of a function which accesses a place,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1488 this declares @var{update-fn} to be the corresponding store
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1489 function. From now on,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1490
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1491 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1492 (setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1493 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1494
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1495 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1496 will be expanded to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1497
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1498 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1499 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1500 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1501
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1502 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1503 The @var{update-fn} is required to be either a true function, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1504 a macro which evaluates its arguments in a function-like way. Also,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1505 the @var{update-fn} is expected to return @var{value} as its result.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1506 Otherwise, the above expansion would not obey the rules for the way
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1507 @code{setf} is supposed to behave.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1508
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1509 As a special (non-Common-Lisp) extension, a third argument of @code{t}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1510 to @code{defsetf} says that the @code{update-fn}'s return value is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1511 not suitable, so that the above @code{setf} should be expanded to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1512 something more like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1513
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1514 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1515 (let ((temp @var{value}))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1516 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1517 temp)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1518 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1519
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1520 Some examples of the use of @code{defsetf}, drawn from the standard
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1521 suite of setf methods, are:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1522
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1523 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1524 (defsetf car setcar)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1525 (defsetf symbol-value set)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1526 (defsetf buffer-name rename-buffer t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1527 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1528 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1529
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1530 @defspec defsetf access-fn arglist (store-var) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1531 This is the second, more complex, form of @code{defsetf}. It is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1532 rather like @code{defmacro} except for the additional @var{store-var}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1533 argument. The @var{forms} should return a Lisp form which stores
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1534 the value of @var{store-var} into the generalized variable formed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1535 by a call to @var{access-fn} with arguments described by @var{arglist}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1536 The @var{forms} may begin with a string which documents the @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1537 method (analogous to the doc string that appears at the front of a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1538 function).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1539
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1540 For example, the simple form of @code{defsetf} is shorthand for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1541
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1542 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1543 (defsetf @var{access-fn} (&rest args) (store)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1544 (append '(@var{update-fn}) args (list store)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1545 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1546
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1547 The Lisp form that is returned can access the arguments from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1548 @var{arglist} and @var{store-var} in an unrestricted fashion;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1549 macros like @code{setf} and @code{incf} which invoke this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1550 setf-method will insert temporary variables as needed to make
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1551 sure the apparent order of evaluation is preserved.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1552
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1553 Another example drawn from the standard package:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1554
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1555 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1556 (defsetf nth (n x) (store)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1557 (list 'setcar (list 'nthcdr n x) store))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1558 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1559 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1560
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1561 @defspec define-setf-method access-fn arglist forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1562 This is the most general way to create new place forms. When
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1563 a @code{setf} to @var{access-fn} with arguments described by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1564 @var{arglist} is expanded, the @var{forms} are evaluated and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1565 must return a list of five items:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1566
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1567 @enumerate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1568 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1569 A list of @dfn{temporary variables}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1570
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1571 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1572 A list of @dfn{value forms} corresponding to the temporary variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1573 above. The temporary variables will be bound to these value forms
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1574 as the first step of any operation on the generalized variable.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1575
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1576 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1577 A list of exactly one @dfn{store variable} (generally obtained
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1578 from a call to @code{gensym}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1579
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1580 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1581 A Lisp form which stores the contents of the store variable into
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1582 the generalized variable, assuming the temporaries have been
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1583 bound as described above.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1584
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1585 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1586 A Lisp form which accesses the contents of the generalized variable,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1587 assuming the temporaries have been bound.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1588 @end enumerate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1589
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1590 This is exactly like the Common Lisp macro of the same name,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1591 except that the method returns a list of five values rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1592 than the five values themselves, since Emacs Lisp does not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1593 support Common Lisp's notion of multiple return values.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1594
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1595 Once again, the @var{forms} may begin with a documentation string.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1596
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1597 A setf-method should be maximally conservative with regard to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1598 temporary variables. In the setf-methods generated by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1599 @code{defsetf}, the second return value is simply the list of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1600 arguments in the place form, and the first return value is a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1601 list of a corresponding number of temporary variables generated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1602 by @code{gensym}. Macros like @code{setf} and @code{incf} which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1603 use this setf-method will optimize away most temporaries that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1604 turn out to be unnecessary, so there is little reason for the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1605 setf-method itself to optimize.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1606 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1607
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1608 @defun get-setf-method place &optional env
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1609 This function returns the setf-method for @var{place}, by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1610 invoking the definition previously recorded by @code{defsetf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1611 or @code{define-setf-method}. The result is a list of five
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1612 values as described above. You can use this function to build
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1613 your own @code{incf}-like modify macros. (Actually, it is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1614 better to use the internal functions @code{cl-setf-do-modify}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1615 and @code{cl-setf-do-store}, which are a bit easier to use and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1616 which also do a number of optimizations; consult the source
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1617 code for the @code{incf} function for a simple example.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1618
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1619 The argument @var{env} specifies the ``environment'' to be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1620 passed on to @code{macroexpand} if @code{get-setf-method} should
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1621 need to expand a macro in @var{place}. It should come from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1622 an @code{&environment} argument to the macro or setf-method
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1623 that called @code{get-setf-method}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1624
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1625 See also the source code for the setf-methods for @code{apply}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1626 and @code{substring}, each of which works by calling
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1627 @code{get-setf-method} on a simpler case, then massaging
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1628 the result in various ways.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1629 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1630
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1631 Modern Common Lisp defines a second, independent way to specify
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1632 the @code{setf} behavior of a function, namely ``@code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1633 functions'' whose names are lists @code{(setf @var{name})}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1634 rather than symbols. For example, @code{(defun (setf foo) @dots{})}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1635 defines the function that is used when @code{setf} is applied to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1636 @code{foo}. This package does not currently support @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1637 functions. In particular, it is a compile-time error to use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1638 @code{setf} on a form which has not already been @code{defsetf}'d
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1639 or otherwise declared; in newer Common Lisps, this would not be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1640 an error since the function @code{(setf @var{func})} might be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1641 defined later.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1642
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1643 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1644 @secno=4
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1645 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1646
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1647 @node Variable Bindings, Conditionals, Generalized Variables, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1648 @section Variable Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1649
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1650 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1651 These Lisp forms make bindings to variables and function names,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1652 analogous to Lisp's built-in @code{let} form.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1653
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1654 @xref{Modify Macros}, for the @code{letf} and @code{letf*} forms which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1655 are also related to variable bindings.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1656
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1657 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1658 * Dynamic Bindings:: The `progv' form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1659 * Lexical Bindings:: `lexical-let' and lexical closures
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1660 * Function Bindings:: `flet' and `labels'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1661 * Macro Bindings:: `macrolet' and `symbol-macrolet'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1662 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1663
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1664 @node Dynamic Bindings, Lexical Bindings, Variable Bindings, Variable Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1665 @subsection Dynamic Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1666
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1667 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1668 The standard @code{let} form binds variables whose names are known
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1669 at compile-time. The @code{progv} form provides an easy way to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1670 bind variables whose names are computed at run-time.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1671
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1672 @defspec progv symbols values forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1673 This form establishes @code{let}-style variable bindings on a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1674 set of variables computed at run-time. The expressions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1675 @var{symbols} and @var{values} are evaluated, and must return lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1676 of symbols and values, respectively. The symbols are bound to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1677 corresponding values for the duration of the body @var{form}s.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1678 If @var{values} is shorter than @var{symbols}, the last few symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1679 are made unbound (as if by @code{makunbound}) inside the body.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1680 If @var{symbols} is shorter than @var{values}, the excess values
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1681 are ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1682 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1683
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1684 @node Lexical Bindings, Function Bindings, Dynamic Bindings, Variable Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1685 @subsection Lexical Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1686
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1687 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1688 The @dfn{CL} package defines the following macro which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1689 more closely follows the Common Lisp @code{let} form:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1690
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1691 @defspec lexical-let (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1692 This form is exactly like @code{let} except that the bindings it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1693 establishes are purely lexical. Lexical bindings are similar to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1694 local variables in a language like C: Only the code physically
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1695 within the body of the @code{lexical-let} (after macro expansion)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1696 may refer to the bound variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1697
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1698 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1699 (setq a 5)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1700 (defun foo (b) (+ a b))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1701 (let ((a 2)) (foo a))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1702 @result{} 4
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1703 (lexical-let ((a 2)) (foo a))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1704 @result{} 7
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1705 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1706
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1707 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1708 In this example, a regular @code{let} binding of @code{a} actually
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1709 makes a temporary change to the global variable @code{a}, so @code{foo}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1710 is able to see the binding of @code{a} to 2. But @code{lexical-let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1711 actually creates a distinct local variable @code{a} for use within its
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1712 body, without any effect on the global variable of the same name.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1713
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1714 The most important use of lexical bindings is to create @dfn{closures}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1715 A closure is a function object that refers to an outside lexical
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1716 variable. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1717
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1718 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1719 (defun make-adder (n)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1720 (lexical-let ((n n))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1721 (function (lambda (m) (+ n m)))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1722 (setq add17 (make-adder 17))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1723 (funcall add17 4)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1724 @result{} 21
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1725 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1726
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1727 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1728 The call @code{(make-adder 17)} returns a function object which adds
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1729 17 to its argument. If @code{let} had been used instead of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1730 @code{lexical-let}, the function object would have referred to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1731 global @code{n}, which would have been bound to 17 only during the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1732 call to @code{make-adder} itself.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1733
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1734 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1735 (defun make-counter ()
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1736 (lexical-let ((n 0))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1737 (function* (lambda (&optional (m 1)) (incf n m)))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1738 (setq count-1 (make-counter))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1739 (funcall count-1 3)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1740 @result{} 3
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1741 (funcall count-1 14)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1742 @result{} 17
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1743 (setq count-2 (make-counter))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1744 (funcall count-2 5)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1745 @result{} 5
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1746 (funcall count-1 2)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1747 @result{} 19
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1748 (funcall count-2)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1749 @result{} 6
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1750 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1751
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1752 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1753 Here we see that each call to @code{make-counter} creates a distinct
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1754 local variable @code{n}, which serves as a private counter for the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1755 function object that is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1756
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1757 Closed-over lexical variables persist until the last reference to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1758 them goes away, just like all other Lisp objects. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1759 @code{count-2} refers to a function object which refers to an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1760 instance of the variable @code{n}; this is the only reference
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1761 to that variable, so after @code{(setq count-2 nil)} the garbage
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1762 collector would be able to delete this instance of @code{n}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1763 Of course, if a @code{lexical-let} does not actually create any
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1764 closures, then the lexical variables are free as soon as the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1765 @code{lexical-let} returns.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1766
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1767 Many closures are used only during the extent of the bindings they
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1768 refer to; these are known as ``downward funargs'' in Lisp parlance.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1769 When a closure is used in this way, regular Emacs Lisp dynamic
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1770 bindings suffice and will be more efficient than @code{lexical-let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1771 closures:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1772
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1773 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1774 (defun add-to-list (x list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1775 (mapcar (function (lambda (y) (+ x y))) list))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1776 (add-to-list 7 '(1 2 5))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1777 @result{} (8 9 12)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1778 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1779
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1780 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1781 Since this lambda is only used while @code{x} is still bound,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1782 it is not necessary to make a true closure out of it.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1783
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1784 You can use @code{defun} or @code{flet} inside a @code{lexical-let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1785 to create a named closure. If several closures are created in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1786 body of a single @code{lexical-let}, they all close over the same
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1787 instance of the lexical variable.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1788
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1789 The @code{lexical-let} form is an extension to Common Lisp. In
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1790 true Common Lisp, all bindings are lexical unless declared otherwise.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1791 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1792
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1793 @defspec lexical-let* (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1794 This form is just like @code{lexical-let}, except that the bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1795 are made sequentially in the manner of @code{let*}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1796 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1797
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1798 @node Function Bindings, Macro Bindings, Lexical Bindings, Variable Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1799 @subsection Function Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1800
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1801 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1802 These forms make @code{let}-like bindings to functions instead
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1803 of variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1804
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1805 @defspec flet (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1806 This form establishes @code{let}-style bindings on the function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1807 cells of symbols rather than on the value cells. Each @var{binding}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1808 must be a list of the form @samp{(@var{name} @var{arglist}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1809 @var{forms}@dots{})}, which defines a function exactly as if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1810 it were a @code{defun*} form. The function @var{name} is defined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1811 accordingly for the duration of the body of the @code{flet}; then
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1812 the old function definition, or lack thereof, is restored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1813
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1814 While @code{flet} in Common Lisp establishes a lexical binding of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1815 @var{name}, Emacs Lisp @code{flet} makes a dynamic binding. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1816 result is that @code{flet} affects indirect calls to a function as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1817 well as calls directly inside the @code{flet} form itself.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1818
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1819 You can use @code{flet} to disable or modify the behavior of a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1820 function in a temporary fashion. This will even work on Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1821 primitives, although note that some calls to primitive functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1822 internal to Emacs are made without going through the symbol's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1823 function cell, and so will not be affected by @code{flet}. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1824 example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1825
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1826 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1827 (flet ((message (&rest args) (push args saved-msgs)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1828 (do-something))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1829 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1830
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1831 This code attempts to replace the built-in function @code{message}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1832 with a function that simply saves the messages in a list rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1833 than displaying them. The original definition of @code{message}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1834 will be restored after @code{do-something} exits. This code will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1835 work fine on messages generated by other Lisp code, but messages
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1836 generated directly inside Emacs will not be caught since they make
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1837 direct C-language calls to the message routines rather than going
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1838 through the Lisp @code{message} function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1839
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1840 Functions defined by @code{flet} may use the full Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1841 argument notation supported by @code{defun*}; also, the function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1842 body is enclosed in an implicit block as if by @code{defun*}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1843 @xref{Program Structure}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1844 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1845
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1846 @defspec labels (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1847 The @code{labels} form is a synonym for @code{flet}. (In Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1848 Lisp, @code{labels} and @code{flet} differ in ways that depend on
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1849 their lexical scoping; these distinctions vanish in dynamically
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1850 scoped Emacs Lisp.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1851 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1852
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1853 @node Macro Bindings, , Function Bindings, Variable Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1854 @subsection Macro Bindings
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1855
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1856 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1857 These forms create local macros and ``symbol macros.''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1858
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1859 @defspec macrolet (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1860 This form is analogous to @code{flet}, but for macros instead of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1861 functions. Each @var{binding} is a list of the same form as the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1862 arguments to @code{defmacro*} (i.e., a macro name, argument list,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1863 and macro-expander forms). The macro is defined accordingly for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1864 use within the body of the @code{macrolet}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1865
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1866 Because of the nature of macros, @code{macrolet} is lexically
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1867 scoped even in Emacs Lisp: The @code{macrolet} binding will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1868 affect only calls that appear physically within the body
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1869 @var{forms}, possibly after expansion of other macros in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1870 body.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1871 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1872
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1873 @defspec symbol-macrolet (bindings@dots{}) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1874 This form creates @dfn{symbol macros}, which are macros that look
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1875 like variable references rather than function calls. Each
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1876 @var{binding} is a list @samp{(@var{var} @var{expansion})};
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1877 any reference to @var{var} within the body @var{forms} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1878 replaced by @var{expansion}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1879
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1880 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1881 (setq bar '(5 . 9))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1882 (symbol-macrolet ((foo (car bar)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1883 (incf foo))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1884 bar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1885 @result{} (6 . 9)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1886 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1887
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1888 A @code{setq} of a symbol macro is treated the same as a @code{setf}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1889 I.e., @code{(setq foo 4)} in the above would be equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1890 @code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1891
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1892 Likewise, a @code{let} or @code{let*} binding a symbol macro is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1893 treated like a @code{letf} or @code{letf*}. This differs from true
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1894 Common Lisp, where the rules of lexical scoping cause a @code{let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1895 binding to shadow a @code{symbol-macrolet} binding. In this package,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1896 only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1897 macro.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1898
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1899 There is no analogue of @code{defmacro} for symbol macros; all symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1900 macros are local. A typical use of @code{symbol-macrolet} is in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1901 expansion of another macro:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1902
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1903 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1904 (defmacro* my-dolist ((x list) &rest body)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1905 (let ((var (gensym)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1906 (list 'loop 'for var 'on list 'do
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1907 (list* 'symbol-macrolet (list (list x (list 'car var)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1908 body))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1909
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1910 (setq mylist '(1 2 3 4))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1911 (my-dolist (x mylist) (incf x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1912 mylist
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1913 @result{} (2 3 4 5)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1914 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1915
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1916 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1917 In this example, the @code{my-dolist} macro is similar to @code{dolist}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1918 (@pxref{Iteration}) except that the variable @code{x} becomes a true
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1919 reference onto the elements of the list. The @code{my-dolist} call
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1920 shown here expands to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1921
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1922 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1923 (loop for G1234 on mylist do
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1924 (symbol-macrolet ((x (car G1234)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1925 (incf x)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1926 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1927
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1928 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1929 which in turn expands to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1930
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1931 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1932 (loop for G1234 on mylist do (incf (car G1234)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1933 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1934
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1935 @xref{Loop Facility}, for a description of the @code{loop} macro.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1936 This package defines a nonstandard @code{in-ref} loop clause that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1937 works much like @code{my-dolist}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1938 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1939
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1940 @node Conditionals, Blocks and Exits, Variable Bindings, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1941 @section Conditionals
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1942
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1943 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1944 These conditional forms augment Emacs Lisp's simple @code{if},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1945 @code{and}, @code{or}, and @code{cond} forms.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1946
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1947 @defspec when test forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1948 This is a variant of @code{if} where there are no ``else'' forms,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1949 and possibly several ``then'' forms. In particular,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1950
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1951 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1952 (when @var{test} @var{a} @var{b} @var{c})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1953 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1954
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1955 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1956 is entirely equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1957
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1958 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1959 (if @var{test} (progn @var{a} @var{b} @var{c}) nil)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1960 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1961 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1962
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1963 @defspec unless test forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1964 This is a variant of @code{if} where there are no ``then'' forms,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1965 and possibly several ``else'' forms:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1966
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1967 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1968 (unless @var{test} @var{a} @var{b} @var{c})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1969 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1970
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1971 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1972 is entirely equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1973
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1974 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1975 (when (not @var{test}) @var{a} @var{b} @var{c})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1976 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1977 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1978
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1979 @defspec case keyform clause@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1980 This macro evaluates @var{keyform}, then compares it with the key
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1981 values listed in the various @var{clause}s. Whichever clause matches
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1982 the key is executed; comparison is done by @code{eql}. If no clause
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1983 matches, the @code{case} form returns @code{nil}. The clauses are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1984 of the form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1985
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1986 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1987 (@var{keylist} @var{body-forms}@dots{})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1988 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1989
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1990 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1991 where @var{keylist} is a list of key values. If there is exactly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1992 one value, and it is not a cons cell or the symbol @code{nil} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1993 @code{t}, then it can be used by itself as a @var{keylist} without
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1994 being enclosed in a list. All key values in the @code{case} form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1995 must be distinct. The final clauses may use @code{t} in place of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1996 a @var{keylist} to indicate a default clause that should be taken
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1997 if none of the other clauses match. (The symbol @code{otherwise}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1998 is also recognized in place of @code{t}. To make a clause that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
1999 matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2000 enclose the symbol in a list.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2001
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2002 For example, this expression reads a keystroke, then does one of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2003 four things depending on whether it is an @samp{a}, a @samp{b},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2004 a @key{RET} or @key{LFD}, or anything else.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2005
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2006 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2007 (case (read-char)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2008 (?a (do-a-thing))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2009 (?b (do-b-thing))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2010 ((?\r ?\n) (do-ret-thing))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2011 (t (do-other-thing)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2012 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2013 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2014
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2015 @defspec ecase keyform clause@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2016 This macro is just like @code{case}, except that if the key does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2017 not match any of the clauses, an error is signalled rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2018 simply returning @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2019 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2020
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2021 @defspec typecase keyform clause@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2022 This macro is a version of @code{case} that checks for types
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2023 rather than values. Each @var{clause} is of the form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2024 @samp{(@var{type} @var{body}...)}. @xref{Type Predicates},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2025 for a description of type specifiers. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2026
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2027 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2028 (typecase x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2029 (integer (munch-integer x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2030 (float (munch-float x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2031 (string (munch-integer (string-to-int x)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2032 (t (munch-anything x)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2033 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2034
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2035 The type specifier @code{t} matches any type of object; the word
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2036 @code{otherwise} is also allowed. To make one clause match any of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2037 several types, use an @code{(or ...)} type specifier.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2038 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2039
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2040 @defspec etypecase keyform clause@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2041 This macro is just like @code{typecase}, except that if the key does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2042 not match any of the clauses, an error is signalled rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2043 simply returning @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2044 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2045
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2046 @node Blocks and Exits, Iteration, Conditionals, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2047 @section Blocks and Exits
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2048
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2049 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2050 Common Lisp @dfn{blocks} provide a non-local exit mechanism very
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2051 similar to @code{catch} and @code{throw}, but lexically rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2052 dynamically scoped. This package actually implements @code{block}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2053 in terms of @code{catch}; however, the lexical scoping allows the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2054 optimizing byte-compiler to omit the costly @code{catch} step if the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2055 body of the block does not actually @code{return-from} the block.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2056
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2057 @defspec block name forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2058 The @var{forms} are evaluated as if by a @code{progn}. However,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2059 if any of the @var{forms} execute @code{(return-from @var{name})},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2060 they will jump out and return directly from the @code{block} form.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2061 The @code{block} returns the result of the last @var{form} unless
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2062 a @code{return-from} occurs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2063
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2064 The @code{block}/@code{return-from} mechanism is quite similar to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2065 the @code{catch}/@code{throw} mechanism. The main differences are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2066 that block @var{name}s are unevaluated symbols, rather than forms
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2067 (such as quoted symbols) which evaluate to a tag at run-time; and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2068 also that blocks are lexically scoped whereas @code{catch}/@code{throw}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2069 are dynamically scoped. This means that functions called from the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2070 body of a @code{catch} can also @code{throw} to the @code{catch},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2071 but the @code{return-from} referring to a block name must appear
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2072 physically within the @var{forms} that make up the body of the block.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2073 They may not appear within other called functions, although they may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2074 appear within macro expansions or @code{lambda}s in the body. Block
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2075 names and @code{catch} names form independent name-spaces.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2076
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2077 In true Common Lisp, @code{defun} and @code{defmacro} surround
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2078 the function or expander bodies with implicit blocks with the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2079 same name as the function or macro. This does not occur in Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2080 Lisp, but this package provides @code{defun*} and @code{defmacro*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2081 forms which do create the implicit block.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2082
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2083 The Common Lisp looping constructs defined by this package,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2084 such as @code{loop} and @code{dolist}, also create implicit blocks
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2085 just as in Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2086
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2087 Because they are implemented in terms of Emacs Lisp @code{catch}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2088 and @code{throw}, blocks have the same overhead as actual
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2089 @code{catch} constructs (roughly two function calls). However,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2090 Zawinski and Furuseth's optimizing byte compiler (standard in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2091 Emacs 19) will optimize away the @code{catch} if the block does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2092 not in fact contain any @code{return} or @code{return-from} calls
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2093 that jump to it. This means that @code{do} loops and @code{defun*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2094 functions which don't use @code{return} don't pay the overhead to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2095 support it.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2096 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2097
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2098 @defspec return-from name [result]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2099 This macro returns from the block named @var{name}, which must be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2100 an (unevaluated) symbol. If a @var{result} form is specified, it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2101 is evaluated to produce the result returned from the @code{block}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2102 Otherwise, @code{nil} is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2103 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2104
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2105 @defspec return [result]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2106 This macro is exactly like @code{(return-from nil @var{result})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2107 Common Lisp loops like @code{do} and @code{dolist} implicitly enclose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2108 themselves in @code{nil} blocks.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2109 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2110
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2111 @node Iteration, Loop Facility, Blocks and Exits, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2112 @section Iteration
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2113
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2114 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2115 The macros described here provide more sophisticated, high-level
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2116 looping constructs to complement Emacs Lisp's basic @code{while}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2117 loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2118
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2119 @defspec loop forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2120 The @dfn{CL} package supports both the simple, old-style meaning of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2121 @code{loop} and the extremely powerful and flexible feature known as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2122 the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2123 facility is discussed in the following section; @pxref{Loop Facility}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2124 The simple form of @code{loop} is described here.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2125
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2126 If @code{loop} is followed by zero or more Lisp expressions,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2127 then @code{(loop @var{exprs}@dots{})} simply creates an infinite
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2128 loop executing the expressions over and over. The loop is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2129 enclosed in an implicit @code{nil} block. Thus,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2130
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2131 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2132 (loop (foo) (if (no-more) (return 72)) (bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2133 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2134
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2135 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2136 is exactly equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2137
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2138 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2139 (block nil (while t (foo) (if (no-more) (return 72)) (bar)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2140 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2141
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2142 If any of the expressions are plain symbols, the loop is instead
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2143 interpreted as a Loop Macro specification as described later.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2144 (This is not a restriction in practice, since a plain symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2145 in the above notation would simply access and throw away the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2146 value of a variable.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2147 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2148
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2149 @defspec do (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2150 This macro creates a general iterative loop. Each @var{spec} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2151 of the form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2152
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2153 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2154 (@var{var} [@var{init} [@var{step}]])
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2155 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2156
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2157 The loop works as follows: First, each @var{var} is bound to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2158 associated @var{init} value as if by a @code{let} form. Then, in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2159 each iteration of the loop, the @var{end-test} is evaluated; if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2160 true, the loop is finished. Otherwise, the body @var{forms} are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2161 evaluated, then each @var{var} is set to the associated @var{step}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2162 expression (as if by a @code{psetq} form) and the next iteration
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2163 begins. Once the @var{end-test} becomes true, the @var{result}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2164 forms are evaluated (with the @var{var}s still bound to their
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2165 values) to produce the result returned by @code{do}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2166
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2167 The entire @code{do} loop is enclosed in an implicit @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2168 block, so that you can use @code{(return)} to break out of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2169 loop at any time.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2170
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2171 If there are no @var{result} forms, the loop returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2172 If a given @var{var} has no @var{step} form, it is bound to its
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2173 @var{init} value but not otherwise modified during the @code{do}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2174 loop (unless the code explicitly modifies it); this case is just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2175 a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2176 around the loop. If @var{init} is also omitted it defaults to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2177 @code{nil}, and in this case a plain @samp{@var{var}} can be used
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2178 in place of @samp{(@var{var})}, again following the analogy with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2179 @code{let}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2180
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2181 This example (from Steele) illustrates a loop which applies the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2182 function @code{f} to successive pairs of values from the lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2183 @code{foo} and @code{bar}; it is equivalent to the call
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2184 @code{(mapcar* 'f foo bar)}. Note that this loop has no body
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2185 @var{forms} at all, performing all its work as side effects of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2186 the rest of the loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2187
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2188 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2189 (do ((x foo (cdr x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2190 (y bar (cdr y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2191 (z nil (cons (f (car x) (car y)) z)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2192 ((or (null x) (null y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2193 (nreverse z)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2194 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2195 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2196
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2197 @defspec do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2198 This is to @code{do} what @code{let*} is to @code{let}. In
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2199 particular, the initial values are bound as if by @code{let*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2200 rather than @code{let}, and the steps are assigned as if by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2201 @code{setq} rather than @code{psetq}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2202
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2203 Here is another way to write the above loop:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2204
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2205 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2206 (do* ((xp foo (cdr xp))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2207 (yp bar (cdr yp))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2208 (x (car xp) (car xp))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2209 (y (car yp) (car yp))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2210 z)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2211 ((or (null xp) (null yp))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2212 (nreverse z))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2213 (push (f x y) z))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2214 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2215 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2216
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2217 @defspec dolist (var list [result]) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2218 This is a more specialized loop which iterates across the elements
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2219 of a list. @var{list} should evaluate to a list; the body @var{forms}
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2220 are executed with @var{var} bound to each element of the list in
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2221 turn. Finally, the @var{result} form (or @code{nil}) is evaluated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2222 with @var{var} bound to @code{nil} to produce the result returned by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2223 the loop. The loop is surrounded by an implicit @code{nil} block.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2224 @end defspec
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cvs
parents:
diff changeset
2225
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cvs
parents:
diff changeset
2226 @defspec dotimes (var count [result]) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2227 This is a more specialized loop which iterates a specified number
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2228 of times. The body is executed with @var{var} bound to the integers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2229 from zero (inclusive) to @var{count} (exclusive), in turn. Then
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2230 the @code{result} form is evaluated with @var{var} bound to the total
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2231 number of iterations that were done (i.e., @code{(max 0 @var{count})})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2232 to get the return value for the loop form. The loop is surrounded
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2233 by an implicit @code{nil} block.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2234 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2235
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cvs
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diff changeset
2236 @defspec do-symbols (var [obarray [result]]) forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2237 This loop iterates over all interned symbols. If @var{obarray}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2238 is specified and is not @code{nil}, it loops over all symbols in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2239 that obarray. For each symbol, the body @var{forms} are evaluated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2240 with @var{var} bound to that symbol. The symbols are visited in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2241 an unspecified order. Afterward the @var{result} form, if any,
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2242 is evaluated (with @var{var} bound to @code{nil}) to get the return
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2243 value. The loop is surrounded by an implicit @code{nil} block.
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diff changeset
2244 @end defspec
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diff changeset
2245
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diff changeset
2246 @defspec do-all-symbols (var [result]) forms@dots{}
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cvs
parents:
diff changeset
2247 This is identical to @code{do-symbols} except that the @var{obarray}
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2248 argument is omitted; it always iterates over the default obarray.
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diff changeset
2249 @end defspec
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diff changeset
2250
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diff changeset
2251 @xref{Mapping over Sequences}, for some more functions for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2252 iterating over vectors or lists.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
2253
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diff changeset
2254 @node Loop Facility, Multiple Values, Iteration, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2255 @section Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2256
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parents:
diff changeset
2257 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2258 A common complaint with Lisp's traditional looping constructs is
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2259 that they are either too simple and limited, such as Common Lisp's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2260 @code{dotimes} or Emacs Lisp's @code{while}, or too unreadable and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2261 obscure, like Common Lisp's @code{do} loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2262
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2263 To remedy this, recent versions of Common Lisp have added a new
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2264 construct called the ``Loop Facility'' or ``@code{loop} macro,''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2265 with an easy-to-use but very powerful and expressive syntax.
3ecd8885ac67 Import from CVS: tag r21-2-22
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diff changeset
2266
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cvs
parents:
diff changeset
2267 @menu
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parents:
diff changeset
2268 * Loop Basics:: `loop' macro, basic clause structure
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2269 * Loop Examples:: Working examples of `loop' macro
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2270 * For Clauses:: Clauses introduced by `for' or `as'
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2271 * Iteration Clauses:: `repeat', `while', `thereis', etc.
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parents:
diff changeset
2272 * Accumulation Clauses:: `collect', `sum', `maximize', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2273 * Other Clauses:: `with', `if', `initially', `finally'
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parents:
diff changeset
2274 @end menu
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parents:
diff changeset
2275
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2276 @node Loop Basics, Loop Examples, Loop Facility, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2277 @subsection Loop Basics
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2278
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2279 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2280 The @code{loop} macro essentially creates a mini-language within
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2281 Lisp that is specially tailored for describing loops. While this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2282 language is a little strange-looking by the standards of regular Lisp,
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2283 it turns out to be very easy to learn and well-suited to its purpose.
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2284
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2285 Since @code{loop} is a macro, all parsing of the loop language
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2286 takes place at byte-compile time; compiled @code{loop}s are just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2287 as efficient as the equivalent @code{while} loops written longhand.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2288
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2289 @defspec loop clauses@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2290 A loop construct consists of a series of @var{clause}s, each
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2291 introduced by a symbol like @code{for} or @code{do}. Clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2292 are simply strung together in the argument list of @code{loop},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2293 with minimal extra parentheses. The various types of clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2294 specify initializations, such as the binding of temporary
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2295 variables, actions to be taken in the loop, stepping actions,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2296 and final cleanup.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2297
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2298 Common Lisp specifies a certain general order of clauses in a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2299 loop:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2300
3ecd8885ac67 Import from CVS: tag r21-2-22
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parents:
diff changeset
2301 @example
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parents:
diff changeset
2302 (loop @var{name-clause}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2303 @var{var-clauses}@dots{}
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cvs
parents:
diff changeset
2304 @var{action-clauses}@dots{})
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parents:
diff changeset
2305 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2306
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2307 The @var{name-clause} optionally gives a name to the implicit
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2308 block that surrounds the loop. By default, the implicit block
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2309 is named @code{nil}. The @var{var-clauses} specify what
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2310 variables should be bound during the loop, and how they should
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2311 be modified or iterated throughout the course of the loop. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2312 @var{action-clauses} are things to be done during the loop, such
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2313 as computing, collecting, and returning values.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2314
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2315 The Emacs version of the @code{loop} macro is less restrictive about
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2316 the order of clauses, but things will behave most predictably if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2317 you put the variable-binding clauses @code{with}, @code{for}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2318 @code{repeat} before the action clauses. As in Common Lisp,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2319 @code{initially} and @code{finally} clauses can go anywhere.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2320
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2321 Loops generally return @code{nil} by default, but you can cause
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2322 them to return a value by using an accumulation clause like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2323 @code{collect}, an end-test clause like @code{always}, or an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2324 explicit @code{return} clause to jump out of the implicit block.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2325 (Because the loop body is enclosed in an implicit block, you can
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2326 also use regular Lisp @code{return} or @code{return-from} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2327 break out of the loop.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2328 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2329
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2330 The following sections give some examples of the Loop Macro in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2331 action, and describe the particular loop clauses in great detail.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2332 Consult the second edition of Steele's @dfn{Common Lisp, the Language},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2333 for additional discussion and examples of the @code{loop} macro.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2334
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2335 @node Loop Examples, For Clauses, Loop Basics, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2336 @subsection Loop Examples
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2337
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2338 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2339 Before listing the full set of clauses that are allowed, let's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2340 look at a few example loops just to get a feel for the @code{loop}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2341 language.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2342
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2343 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2344 (loop for buf in (buffer-list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2345 collect (buffer-file-name buf))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2346 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2347
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2348 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2349 This loop iterates over all Emacs buffers, using the list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2350 returned by @code{buffer-list}. For each buffer @code{buf},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2351 it calls @code{buffer-file-name} and collects the results into
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2352 a list, which is then returned from the @code{loop} construct.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2353 The result is a list of the file names of all the buffers in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2354 Emacs' memory. The words @code{for}, @code{in}, and @code{collect}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2355 are reserved words in the @code{loop} language.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2356
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2357 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2358 (loop repeat 20 do (insert "Yowsa\n"))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2359 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2360
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2361 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2362 This loop inserts the phrase ``Yowsa'' twenty times in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2363 current buffer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2364
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2365 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2366 (loop until (eobp) do (munch-line) (forward-line 1))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2367 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2368
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2369 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2370 This loop calls @code{munch-line} on every line until the end
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2371 of the buffer. If point is already at the end of the buffer,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2372 the loop exits immediately.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2373
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2374 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2375 (loop do (munch-line) until (eobp) do (forward-line 1))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2376 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2377
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2378 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2379 This loop is similar to the above one, except that @code{munch-line}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2380 is always called at least once.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2381
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2382 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2383 (loop for x from 1 to 100
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2384 for y = (* x x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2385 until (>= y 729)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2386 finally return (list x (= y 729)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2387 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2388
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2389 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2390 This more complicated loop searches for a number @code{x} whose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2391 square is 729. For safety's sake it only examines @code{x}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2392 values up to 100; dropping the phrase @samp{to 100} would
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2393 cause the loop to count upwards with no limit. The second
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2394 @code{for} clause defines @code{y} to be the square of @code{x}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2395 within the loop; the expression after the @code{=} sign is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2396 reevaluated each time through the loop. The @code{until}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2397 clause gives a condition for terminating the loop, and the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2398 @code{finally} clause says what to do when the loop finishes.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2399 (This particular example was written less concisely than it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2400 could have been, just for the sake of illustration.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2401
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2402 Note that even though this loop contains three clauses (two
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2403 @code{for}s and an @code{until}) that would have been enough to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2404 define loops all by themselves, it still creates a single loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2405 rather than some sort of triple-nested loop. You must explicitly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2406 nest your @code{loop} constructs if you want nested loops.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2407
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2408 @node For Clauses, Iteration Clauses, Loop Examples, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2409 @subsection For Clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2410
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2411 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2412 Most loops are governed by one or more @code{for} clauses.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2413 A @code{for} clause simultaneously describes variables to be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2414 bound, how those variables are to be stepped during the loop,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2415 and usually an end condition based on those variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2416
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2417 The word @code{as} is a synonym for the word @code{for}. This
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2418 word is followed by a variable name, then a word like @code{from}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2419 or @code{across} that describes the kind of iteration desired.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2420 In Common Lisp, the phrase @code{being the} sometimes precedes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2421 the type of iteration; in this package both @code{being} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2422 @code{the} are optional. The word @code{each} is a synonym
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2423 for @code{the}, and the word that follows it may be singular
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2424 or plural: @samp{for x being the elements of y} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2425 @samp{for x being each element of y}. Which form you use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2426 is purely a matter of style.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2427
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2428 The variable is bound around the loop as if by @code{let}:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2429
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2430 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2431 (setq i 'happy)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2432 (loop for i from 1 to 10 do (do-something-with i))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2433 i
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2434 @result{} happy
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2435 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2436
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2437 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2438 @item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2439 This type of @code{for} clause creates a counting loop. Each of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2440 the three sub-terms is optional, though there must be at least one
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2441 term so that the clause is marked as a counting clause.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2442
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2443 The three expressions are the starting value, the ending value, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2444 the step value, respectively, of the variable. The loop counts
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2445 upwards by default (@var{expr3} must be positive), from @var{expr1}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2446 to @var{expr2} inclusively. If you omit the @code{from} term, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2447 loop counts from zero; if you omit the @code{to} term, the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2448 counts forever without stopping (unless stopped by some other
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2449 loop clause, of course); if you omit the @code{by} term, the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2450 counts in steps of one.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2451
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2452 You can replace the word @code{from} with @code{upfrom} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2453 @code{downfrom} to indicate the direction of the loop. Likewise,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2454 you can replace @code{to} with @code{upto} or @code{downto}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2455 For example, @samp{for x from 5 downto 1} executes five times
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2456 with @code{x} taking on the integers from 5 down to 1 in turn.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2457 Also, you can replace @code{to} with @code{below} or @code{above},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2458 which are like @code{upto} and @code{downto} respectively except
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2459 that they are exclusive rather than inclusive limits:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2460
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2461 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2462 (loop for x to 10 collect x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2463 @result{} (0 1 2 3 4 5 6 7 8 9 10)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2464 (loop for x below 10 collect x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2465 @result{} (0 1 2 3 4 5 6 7 8 9)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2466 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2467
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2468 The @code{by} value is always positive, even for downward-counting
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2469 loops. Some sort of @code{from} value is required for downward
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2470 loops; @samp{for x downto 5} is not a legal loop clause all by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2471 itself.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2472
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2473 @item for @var{var} in @var{list} by @var{function}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2474 This clause iterates @var{var} over all the elements of @var{list},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2475 in turn. If you specify the @code{by} term, then @var{function}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2476 is used to traverse the list instead of @code{cdr}; it must be a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2477 function taking one argument. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2478
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2479 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2480 (loop for x in '(1 2 3 4 5 6) collect (* x x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2481 @result{} (1 4 9 16 25 36)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2482 (loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2483 @result{} (1 9 25)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2484 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2485
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2486 @item for @var{var} on @var{list} by @var{function}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2487 This clause iterates @var{var} over all the cons cells of @var{list}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2488
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2489 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2490 (loop for x on '(1 2 3 4) collect x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2491 @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2492 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2493
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2494 With @code{by}, there is no real reason that the @code{on} expression
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2495 must be a list. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2496
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2497 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2498 (loop for x on first-animal by 'next-animal collect x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2499 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2500
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2501 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2502 where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2503 the next in the (assumed) sequence of animals, or @code{nil} if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2504 @var{x} was the last animal in the sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2505
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2506 @item for @var{var} in-ref @var{list} by @var{function}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2507 This is like a regular @code{in} clause, but @var{var} becomes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2508 a @code{setf}-able ``reference'' onto the elements of the list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2509 rather than just a temporary variable. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2510
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2511 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2512 (loop for x in-ref my-list do (incf x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2513 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2514
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2515 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2516 increments every element of @code{my-list} in place. This clause
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2517 is an extension to standard Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2518
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2519 @item for @var{var} across @var{array}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2520 This clause iterates @var{var} over all the elements of @var{array},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2521 which may be a vector or a string.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2522
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2523 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2524 (loop for x across "aeiou"
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2525 do (use-vowel (char-to-string x)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2526 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2527
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2528 @item for @var{var} across-ref @var{array}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2529 This clause iterates over an array, with @var{var} a @code{setf}-able
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2530 reference onto the elements; see @code{in-ref} above.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2531
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2532 @item for @var{var} being the elements of @var{sequence}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2533 This clause iterates over the elements of @var{sequence}, which may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2534 be a list, vector, or string. Since the type must be determined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2535 at run-time, this is somewhat less efficient than @code{in} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2536 @code{across}. The clause may be followed by the additional term
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2537 @samp{using (index @var{var2})} to cause @var{var2} to be bound to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2538 the successive indices (starting at 0) of the elements.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2539
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2540 This clause type is taken from older versions of the @code{loop} macro,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2541 and is not present in modern Common Lisp. The @samp{using (sequence ...)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2542 term of the older macros is not supported.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2543
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2544 @item for @var{var} being the elements of-ref @var{sequence}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2545 This clause iterates over a sequence, with @var{var} a @code{setf}-able
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2546 reference onto the elements; see @code{in-ref} above.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2547
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2548 @item for @var{var} being the symbols [of @var{obarray}]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2549 This clause iterates over symbols, either over all interned symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2550 or over all symbols in @var{obarray}. The loop is executed with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2551 @var{var} bound to each symbol in turn. The symbols are visited in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2552 an unspecified order.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2553
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2554 As an example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2555
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2556 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2557 (loop for sym being the symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2558 when (fboundp sym)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2559 when (string-match "^map" (symbol-name sym))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2560 collect sym)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2561 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2562
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2563 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2564 returns a list of all the functions whose names begin with @samp{map}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2565
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2566 The Common Lisp words @code{external-symbols} and @code{present-symbols}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2567 are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2568
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2569 Due to a minor implementation restriction, it will not work to have
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2570 more than one @code{for} clause iterating over symbols, hash tables,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2571 keymaps, overlays, or intervals in a given @code{loop}. Fortunately,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2572 it would rarely if ever be useful to do so. It @emph{is} legal to mix
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2573 one of these types of clauses with other clauses like @code{for ... to}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2574 or @code{while}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2575
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2576 @item for @var{var} being the hash-keys of @var{hash-table}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2577 This clause iterates over the entries in @var{hash-table}. For each
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2578 hash table entry, @var{var} is bound to the entry's key. If you write
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2579 @samp{the hash-values} instead, @var{var} is bound to the values
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2580 of the entries. The clause may be followed by the additional
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2581 term @samp{using (hash-values @var{var2})} (where @code{hash-values}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2582 is the opposite word of the word following @code{the}) to cause
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2583 @var{var} and @var{var2} to be bound to the two parts of each
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2584 hash table entry.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2585
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2586 @item for @var{var} being the key-codes of @var{keymap}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2587 This clause iterates over the entries in @var{keymap}. In GNU Emacs 18
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2588 and 19, keymaps are either alists or vectors, and key-codes are integers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2589 or symbols. In XEmacs, keymaps are a special new data type, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2590 key-codes are symbols or lists of symbols. The iteration does not enter
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2591 nested keymaps or inherited (parent) keymaps. You can use @samp{the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2592 key-bindings} to access the commands bound to the keys rather than the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2593 key codes, and you can add a @code{using} clause to access both the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2594 codes and the bindings together.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2595
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2596 @item for @var{var} being the key-seqs of @var{keymap}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2597 This clause iterates over all key sequences defined by @var{keymap}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2598 and its nested keymaps, where @var{var} takes on values which are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2599 strings in Emacs 18 or vectors in Emacs 19. The strings or vectors
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2600 are reused for each iteration, so you must copy them if you wish to keep
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2601 them permanently. You can add a @samp{using (key-bindings ...)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2602 clause to get the command bindings as well.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2603
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2604 @item for @var{var} being the overlays [of @var{buffer}] @dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2605 This clause iterates over the Emacs 19 ``overlays'' or XEmacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2606 ``extents'' of a buffer (the clause @code{extents} is synonymous with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2607 @code{overlays}). Under Emacs 18, this clause iterates zero times. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2608 the @code{of} term is omitted, the current buffer is used. This clause
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2609 also accepts optional @samp{from @var{pos}} and @samp{to @var{pos}}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2610 terms, limiting the clause to overlays which overlap the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2611 region.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2612
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2613 @item for @var{var} being the intervals [of @var{buffer}] @dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2614 This clause iterates over all intervals of a buffer with constant
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2615 text properties. The variable @var{var} will be bound to conses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2616 of start and end positions, where one start position is always equal
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2617 to the previous end position. The clause allows @code{of},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2618 @code{from}, @code{to}, and @code{property} terms, where the latter
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2619 term restricts the search to just the specified property. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2620 @code{of} term may specify either a buffer or a string. This
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2621 clause is useful only in GNU Emacs 19; in other versions, all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2622 buffers and strings consist of a single interval.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2623
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2624 @item for @var{var} being the frames
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2625 This clause iterates over all frames, i.e., X window system windows
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2626 open on Emacs files. This clause works only under Emacs 19. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2627 clause @code{screens} is a synonym for @code{frames}. The frames
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2628 are visited in @code{next-frame} order starting from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2629 @code{selected-frame}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2630
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2631 @item for @var{var} being the windows [of @var{frame}]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2632 This clause iterates over the windows (in the Emacs sense) of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2633 the current frame, or of the specified @var{frame}. (In Emacs 18
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2634 there is only ever one frame, and the @code{of} term is not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2635 allowed there.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2636
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2637 @item for @var{var} being the buffers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2638 This clause iterates over all buffers in Emacs. It is equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2639 to @samp{for @var{var} in (buffer-list)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2640
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2641 @item for @var{var} = @var{expr1} then @var{expr2}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2642 This clause does a general iteration. The first time through
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2643 the loop, @var{var} will be bound to @var{expr1}. On the second
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2644 and successive iterations it will be set by evaluating @var{expr2}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2645 (which may refer to the old value of @var{var}). For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2646 these two loops are effectively the same:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2647
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2648 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2649 (loop for x on my-list by 'cddr do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2650 (loop for x = my-list then (cddr x) while x do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2651 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2652
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2653 Note that this type of @code{for} clause does not imply any sort
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2654 of terminating condition; the above example combines it with a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2655 @code{while} clause to tell when to end the loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2656
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2657 If you omit the @code{then} term, @var{expr1} is used both for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2658 the initial setting and for successive settings:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2659
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2660 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2661 (loop for x = (random) when (> x 0) return x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2662 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2663
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2664 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2665 This loop keeps taking random numbers from the @code{(random)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2666 function until it gets a positive one, which it then returns.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2667 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2668
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2669 If you include several @code{for} clauses in a row, they are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2670 treated sequentially (as if by @code{let*} and @code{setq}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2671 You can instead use the word @code{and} to link the clauses,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2672 in which case they are processed in parallel (as if by @code{let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2673 and @code{psetq}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2674
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2675 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2676 (loop for x below 5 for y = nil then x collect (list x y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2677 @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2678 (loop for x below 5 and y = nil then x collect (list x y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2679 @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2680 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2681
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2682 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2683 In the first loop, @code{y} is set based on the value of @code{x}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2684 that was just set by the previous clause; in the second loop,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2685 @code{x} and @code{y} are set simultaneously so @code{y} is set
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2686 based on the value of @code{x} left over from the previous time
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2687 through the loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2688
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2689 Another feature of the @code{loop} macro is @dfn{destructuring},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2690 similar in concept to the destructuring provided by @code{defmacro}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2691 The @var{var} part of any @code{for} clause can be given as a list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2692 of variables instead of a single variable. The values produced
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2693 during loop execution must be lists; the values in the lists are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2694 stored in the corresponding variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2695
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2696 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2697 (loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2698 @result{} (5 9 13)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2699 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2700
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2701 In loop destructuring, if there are more values than variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2702 the trailing values are ignored, and if there are more variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2703 than values the trailing variables get the value @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2704 If @code{nil} is used as a variable name, the corresponding
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2705 values are ignored. Destructuring may be nested, and dotted
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2706 lists of variables like @code{(x . y)} are allowed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2707
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2708 @node Iteration Clauses, Accumulation Clauses, For Clauses, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2709 @subsection Iteration Clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2710
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2711 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2712 Aside from @code{for} clauses, there are several other loop clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2713 that control the way the loop operates. They might be used by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2714 themselves, or in conjunction with one or more @code{for} clauses.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2715
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2716 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2717 @item repeat @var{integer}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2718 This clause simply counts up to the specified number using an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2719 internal temporary variable. The loops
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2720
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2721 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2722 (loop repeat n do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2723 (loop for temp to n do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2724 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2725
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2726 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2727 are identical except that the second one forces you to choose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2728 a name for a variable you aren't actually going to use.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2729
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2730 @item while @var{condition}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2731 This clause stops the loop when the specified condition (any Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2732 expression) becomes @code{nil}. For example, the following two
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2733 loops are equivalent, except for the implicit @code{nil} block
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2734 that surrounds the second one:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2735
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2736 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2737 (while @var{cond} @var{forms}@dots{})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2738 (loop while @var{cond} do @var{forms}@dots{})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2739 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2740
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2741 @item until @var{condition}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2742 This clause stops the loop when the specified condition is true,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2743 i.e., non-@code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2744
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2745 @item always @var{condition}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2746 This clause stops the loop when the specified condition is @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2747 Unlike @code{while}, it stops the loop using @code{return nil} so that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2748 the @code{finally} clauses are not executed. If all the conditions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2749 were non-@code{nil}, the loop returns @code{t}:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2750
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2751 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2752 (if (loop for size in size-list always (> size 10))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2753 (some-big-sizes)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2754 (no-big-sizes))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2755 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2756
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2757 @item never @var{condition}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2758 This clause is like @code{always}, except that the loop returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2759 @code{t} if any conditions were false, or @code{nil} otherwise.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2760
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2761 @item thereis @var{condition}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2762 This clause stops the loop when the specified form is non-@code{nil};
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2763 in this case, it returns that non-@code{nil} value. If all the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2764 values were @code{nil}, the loop returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2765 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2766
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2767 @node Accumulation Clauses, Other Clauses, Iteration Clauses, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2768 @subsection Accumulation Clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2769
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2770 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2771 These clauses cause the loop to accumulate information about the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2772 specified Lisp @var{form}. The accumulated result is returned
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2773 from the loop unless overridden, say, by a @code{return} clause.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2774
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2775 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2776 @item collect @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2777 This clause collects the values of @var{form} into a list. Several
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2778 examples of @code{collect} appear elsewhere in this manual.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2779
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2780 The word @code{collecting} is a synonym for @code{collect}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2781 likewise for the other accumulation clauses.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2782
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2783 @item append @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2784 This clause collects lists of values into a result list using
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2785 @code{append}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2786
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2787 @item nconc @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2788 This clause collects lists of values into a result list by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2789 destructively modifying the lists rather than copying them.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2790
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2791 @item concat @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2792 This clause concatenates the values of the specified @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2793 into a string. (It and the following clause are extensions to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2794 standard Common Lisp.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2795
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2796 @item vconcat @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2797 This clause concatenates the values of the specified @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2798 into a vector.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2799
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2800 @item count @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2801 This clause counts the number of times the specified @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2802 evaluates to a non-@code{nil} value.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2803
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2804 @item sum @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2805 This clause accumulates the sum of the values of the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2806 @var{form}, which must evaluate to a number.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2807
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2808 @item maximize @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2809 This clause accumulates the maximum value of the specified @var{form},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2810 which must evaluate to a number. The return value is undefined if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2811 @code{maximize} is executed zero times.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2812
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2813 @item minimize @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2814 This clause accumulates the minimum value of the specified @var{form}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2815 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2816
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2817 Accumulation clauses can be followed by @samp{into @var{var}} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2818 cause the data to be collected into variable @var{var} (which is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2819 automatically @code{let}-bound during the loop) rather than an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2820 unnamed temporary variable. Also, @code{into} accumulations do
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2821 not automatically imply a return value. The loop must use some
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2822 explicit mechanism, such as @code{finally return}, to return
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2823 the accumulated result.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2824
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2825 It is legal for several accumulation clauses of the same type to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2826 accumulate into the same place. From Steele:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2827
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2828 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2829 (loop for name in '(fred sue alice joe june)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2830 for kids in '((bob ken) () () (kris sunshine) ())
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2831 collect name
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2832 append kids)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2833 @result{} (fred bob ken sue alice joe kris sunshine june)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2834 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2835
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2836 @node Other Clauses, , Accumulation Clauses, Loop Facility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2837 @subsection Other Clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2838
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2839 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2840 This section describes the remaining loop clauses.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2841
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2842 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2843 @item with @var{var} = @var{value}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2844 This clause binds a variable to a value around the loop, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2845 otherwise leaves the variable alone during the loop. The following
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2846 loops are basically equivalent:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2847
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2848 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2849 (loop with x = 17 do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2850 (let ((x 17)) (loop do ...))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2851 (loop for x = 17 then x do ...)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2852 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2853
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2854 Naturally, the variable @var{var} might be used for some purpose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2855 in the rest of the loop. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2856
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2857 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2858 (loop for x in my-list with res = nil do (push x res)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2859 finally return res)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2860 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2861
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2862 This loop inserts the elements of @code{my-list} at the front of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2863 a new list being accumulated in @code{res}, then returns the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2864 list @code{res} at the end of the loop. The effect is similar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2865 to that of a @code{collect} clause, but the list gets reversed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2866 by virtue of the fact that elements are being pushed onto the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2867 front of @code{res} rather than the end.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2868
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2869 If you omit the @code{=} term, the variable is initialized to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2870 @code{nil}. (Thus the @samp{= nil} in the above example is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2871 unnecessary.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2872
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2873 Bindings made by @code{with} are sequential by default, as if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2874 by @code{let*}. Just like @code{for} clauses, @code{with} clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2875 can be linked with @code{and} to cause the bindings to be made by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2876 @code{let} instead.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2877
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2878 @item if @var{condition} @var{clause}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2879 This clause executes the following loop clause only if the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2880 condition is true. The following @var{clause} should be an accumulation,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2881 @code{do}, @code{return}, @code{if}, or @code{unless} clause.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2882 Several clauses may be linked by separating them with @code{and}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2883 These clauses may be followed by @code{else} and a clause or clauses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2884 to execute if the condition was false. The whole construct may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2885 optionally be followed by the word @code{end} (which may be used to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2886 disambiguate an @code{else} or @code{and} in a nested @code{if}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2887
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2888 The actual non-@code{nil} value of the condition form is available
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2889 by the name @code{it} in the ``then'' part. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2890
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2891 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2892 (setq funny-numbers '(6 13 -1))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2893 @result{} (6 13 -1)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2894 (loop for x below 10
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2895 if (oddp x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2896 collect x into odds
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2897 and if (memq x funny-numbers) return (cdr it) end
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2898 else
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2899 collect x into evens
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2900 finally return (vector odds evens))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2901 @result{} [(1 3 5 7 9) (0 2 4 6 8)]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2902 (setq funny-numbers '(6 7 13 -1))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2903 @result{} (6 7 13 -1)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2904 (loop <@r{same thing again}>)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2905 @result{} (13 -1)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2906 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2907
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2908 Note the use of @code{and} to put two clauses into the ``then''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2909 part, one of which is itself an @code{if} clause. Note also that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2910 @code{end}, while normally optional, was necessary here to make
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2911 it clear that the @code{else} refers to the outermost @code{if}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2912 clause. In the first case, the loop returns a vector of lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2913 of the odd and even values of @var{x}. In the second case, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2914 odd number 7 is one of the @code{funny-numbers} so the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2915 returns early; the actual returned value is based on the result
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2916 of the @code{memq} call.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2917
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2918 @item when @var{condition} @var{clause}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2919 This clause is just a synonym for @code{if}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2920
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2921 @item unless @var{condition} @var{clause}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2922 The @code{unless} clause is just like @code{if} except that the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2923 sense of the condition is reversed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2924
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2925 @item named @var{name}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2926 This clause gives a name other than @code{nil} to the implicit
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2927 block surrounding the loop. The @var{name} is the symbol to be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2928 used as the block name.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2929
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2930 @item initially [do] @var{forms}...
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2931 This keyword introduces one or more Lisp forms which will be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2932 executed before the loop itself begins (but after any variables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2933 requested by @code{for} or @code{with} have been bound to their
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2934 initial values). @code{initially} clauses can appear anywhere;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2935 if there are several, they are executed in the order they appear
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2936 in the loop. The keyword @code{do} is optional.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2937
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2938 @item finally [do] @var{forms}...
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2939 This introduces Lisp forms which will be executed after the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2940 finishes (say, on request of a @code{for} or @code{while}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2941 @code{initially} and @code{finally} clauses may appear anywhere
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2942 in the loop construct, but they are executed (in the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2943 order) at the beginning or end, respectively, of the loop.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2944
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2945 @item finally return @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2946 This says that @var{form} should be executed after the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2947 is done to obtain a return value. (Without this, or some other
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2948 clause like @code{collect} or @code{return}, the loop will simply
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2949 return @code{nil}.) Variables bound by @code{for}, @code{with},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2950 or @code{into} will still contain their final values when @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2951 is executed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2952
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2953 @item do @var{forms}...
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2954 The word @code{do} may be followed by any number of Lisp expressions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2955 which are executed as an implicit @code{progn} in the body of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2956 loop. Many of the examples in this section illustrate the use of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2957 @code{do}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2958
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2959 @item return @var{form}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2960 This clause causes the loop to return immediately. The following
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2961 Lisp form is evaluated to give the return value of the @code{loop}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2962 form. The @code{finally} clauses, if any, are not executed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2963 Of course, @code{return} is generally used inside an @code{if} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2964 @code{unless}, as its use in a top-level loop clause would mean
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2965 the loop would never get to ``loop'' more than once.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2966
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2967 The clause @samp{return @var{form}} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2968 @samp{do (return @var{form})} (or @code{return-from} if the loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2969 was named). The @code{return} clause is implemented a bit more
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2970 efficiently, though.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2971 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2972
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2973 While there is no high-level way to add user extensions to @code{loop}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2974 (comparable to @code{defsetf} for @code{setf}, say), this package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2975 does offer two properties called @code{cl-loop-handler} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2976 @code{cl-loop-for-handler} which are functions to be called when
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2977 a given symbol is encountered as a top-level loop clause or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2978 @code{for} clause, respectively. Consult the source code in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2979 file @file{cl-macs.el} for details.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2980
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2981 This package's @code{loop} macro is compatible with that of Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2982 Lisp, except that a few features are not implemented: @code{loop-finish}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2983 and data-type specifiers. Naturally, the @code{for} clauses which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2984 iterate over keymaps, overlays, intervals, frames, windows, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2985 buffers are Emacs-specific extensions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2986
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2987 @node Multiple Values, , Loop Facility, Control Structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2988 @section Multiple Values
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2989
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2990 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2991 Common Lisp functions can return zero or more results. Emacs Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2992 functions, by contrast, always return exactly one result. This
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2993 package makes no attempt to emulate Common Lisp multiple return
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2994 values; Emacs versions of Common Lisp functions that return more
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2995 than one value either return just the first value (as in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2996 @code{compiler-macroexpand}) or return a list of values (as in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2997 @code{get-setf-method}). This package @emph{does} define placeholders
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2998 for the Common Lisp functions that work with multiple values, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
2999 in Emacs Lisp these functions simply operate on lists instead.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3000 The @code{values} form, for example, is a synonym for @code{list}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3001 in Emacs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3002
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3003 @defspec multiple-value-bind (var@dots{}) values-form forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3004 This form evaluates @var{values-form}, which must return a list of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3005 values. It then binds the @var{var}s to these respective values,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3006 as if by @code{let}, and then executes the body @var{forms}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3007 If there are more @var{var}s than values, the extra @var{var}s
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3008 are bound to @code{nil}. If there are fewer @var{var}s than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3009 values, the excess values are ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3010 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3011
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3012 @defspec multiple-value-setq (var@dots{}) form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3013 This form evaluates @var{form}, which must return a list of values.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3014 It then sets the @var{var}s to these respective values, as if by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3015 @code{setq}. Extra @var{var}s or values are treated the same as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3016 in @code{multiple-value-bind}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3017 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3018
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3019 The older Quiroz package attempted a more faithful (but still
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3020 imperfect) emulation of Common Lisp multiple values. The old
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3021 method ``usually'' simulated true multiple values quite well,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3022 but under certain circumstances would leave spurious return
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3023 values in memory where a later, unrelated @code{multiple-value-bind}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3024 form would see them.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3025
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3026 Since a perfect emulation is not feasible in Emacs Lisp, this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3027 package opts to keep it as simple and predictable as possible.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3028
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3029 @node Macros, Declarations, Control Structure, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3030 @chapter Macros
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3031
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3032 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3033 This package implements the various Common Lisp features of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3034 @code{defmacro}, such as destructuring, @code{&environment},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3035 and @code{&body}. Top-level @code{&whole} is not implemented
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3036 for @code{defmacro} due to technical difficulties.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3037 @xref{Argument Lists}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3038
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3039 Destructuring is made available to the user by way of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3040 following macro:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3041
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3042 @defspec destructuring-bind arglist expr forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3043 This macro expands to code which executes @var{forms}, with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3044 the variables in @var{arglist} bound to the list of values
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3045 returned by @var{expr}. The @var{arglist} can include all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3046 the features allowed for @code{defmacro} argument lists,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3047 including destructuring. (The @code{&environment} keyword
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3048 is not allowed.) The macro expansion will signal an error
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3049 if @var{expr} returns a list of the wrong number of arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3050 or with incorrect keyword arguments.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3051 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3052
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3053 This package also includes the Common Lisp @code{define-compiler-macro}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3054 facility, which allows you to define compile-time expansions and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3055 optimizations for your functions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3056
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3057 @defspec define-compiler-macro name arglist forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3058 This form is similar to @code{defmacro}, except that it only expands
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3059 calls to @var{name} at compile-time; calls processed by the Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3060 interpreter are not expanded, nor are they expanded by the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3061 @code{macroexpand} function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3062
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3063 The argument list may begin with a @code{&whole} keyword and a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3064 variable. This variable is bound to the macro-call form itself,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3065 i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3066 If the macro expander returns this form unchanged, then the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3067 compiler treats it as a normal function call. This allows
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3068 compiler macros to work as optimizers for special cases of a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3069 function, leaving complicated cases alone.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3070
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3071 For example, here is a simplified version of a definition that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3072 appears as a standard part of this package:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3073
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3074 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3075 (define-compiler-macro member* (&whole form a list &rest keys)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3076 (if (and (null keys)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3077 (eq (car-safe a) 'quote)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3078 (not (floatp-safe (cadr a))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3079 (list 'memq a list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3080 form))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3081 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3082
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3083 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3084 This definition causes @code{(member* @var{a} @var{list})} to change
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3085 to a call to the faster @code{memq} in the common case where @var{a}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3086 is a non-floating-point constant; if @var{a} is anything else, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3087 if there are any keyword arguments in the call, then the original
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3088 @code{member*} call is left intact. (The actual compiler macro
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3089 for @code{member*} optimizes a number of other cases, including
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3090 common @code{:test} predicates.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3091 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3092
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3093 @defun compiler-macroexpand form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3094 This function is analogous to @code{macroexpand}, except that it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3095 expands compiler macros rather than regular macros. It returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3096 @var{form} unchanged if it is not a call to a function for which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3097 a compiler macro has been defined, or if that compiler macro
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3098 decided to punt by returning its @code{&whole} argument. Like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3099 @code{macroexpand}, it expands repeatedly until it reaches a form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3100 for which no further expansion is possible.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3101 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3102
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3103 @xref{Macro Bindings}, for descriptions of the @code{macrolet}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3104 and @code{symbol-macrolet} forms for making ``local'' macro
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3105 definitions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3106
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3107 @node Declarations, Symbols, Macros, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3108 @chapter Declarations
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3109
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3110 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3111 Common Lisp includes a complex and powerful ``declaration''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3112 mechanism that allows you to give the compiler special hints
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3113 about the types of data that will be stored in particular variables,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3114 and about the ways those variables and functions will be used. This
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3115 package defines versions of all the Common Lisp declaration forms:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3116 @code{declare}, @code{locally}, @code{proclaim}, @code{declaim},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3117 and @code{the}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3118
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3119 Most of the Common Lisp declarations are not currently useful in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3120 Emacs Lisp, as the byte-code system provides little opportunity
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3121 to benefit from type information, and @code{special} declarations
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3122 are redundant in a fully dynamically-scoped Lisp. A few
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3123 declarations are meaningful when the optimizing Emacs 19 byte
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3124 compiler is being used, however. Under the earlier non-optimizing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3125 compiler, these declarations will effectively be ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3126
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3127 @defun proclaim decl-spec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3128 This function records a ``global'' declaration specified by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3129 @var{decl-spec}. Since @code{proclaim} is a function, @var{decl-spec}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3130 is evaluated and thus should normally be quoted.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3131 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3132
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3133 @defspec declaim decl-specs@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3134 This macro is like @code{proclaim}, except that it takes any number
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3135 of @var{decl-spec} arguments, and the arguments are unevaluated and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3136 unquoted. The @code{declaim} macro also puts an @code{(eval-when
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3137 (compile load eval) ...)} around the declarations so that they will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3138 be registered at compile-time as well as at run-time. (This is vital,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3139 since normally the declarations are meant to influence the way the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3140 compiler treats the rest of the file that contains the @code{declaim}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3141 form.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3142 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3143
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3144 @defspec declare decl-specs@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3145 This macro is used to make declarations within functions and other
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3146 code. Common Lisp allows declarations in various locations, generally
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3147 at the beginning of any of the many ``implicit @code{progn}s''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3148 throughout Lisp syntax, such as function bodies, @code{let} bodies,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3149 etc. Currently the only declaration understood by @code{declare}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3150 is @code{special}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3151 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3152
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3153 @defspec locally declarations@dots{} forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3154 In this package, @code{locally} is no different from @code{progn}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3155 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3156
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3157 @defspec the type form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3158 Type information provided by @code{the} is ignored in this package;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3159 in other words, @code{(the @var{type} @var{form})} is equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3160 to @var{form}. Future versions of the optimizing byte-compiler may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3161 make use of this information.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3162
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3163 For example, @code{mapcar} can map over both lists and arrays. It is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3164 hard for the compiler to expand @code{mapcar} into an in-line loop
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3165 unless it knows whether the sequence will be a list or an array ahead
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3166 of time. With @code{(mapcar 'car (the vector foo))}, a future
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3167 compiler would have enough information to expand the loop in-line.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3168 For now, Emacs Lisp will treat the above code as exactly equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3169 to @code{(mapcar 'car foo)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3170 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3171
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3172 Each @var{decl-spec} in a @code{proclaim}, @code{declaim}, or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3173 @code{declare} should be a list beginning with a symbol that says
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3174 what kind of declaration it is. This package currently understands
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3175 @code{special}, @code{inline}, @code{notinline}, @code{optimize},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3176 and @code{warn} declarations. (The @code{warn} declaration is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3177 extension of standard Common Lisp.) Other Common Lisp declarations,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3178 such as @code{type} and @code{ftype}, are silently ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3179
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3180 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3181 @item special
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3182 Since all variables in Emacs Lisp are ``special'' (in the Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3183 Lisp sense), @code{special} declarations are only advisory. They
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3184 simply tell the optimizing byte compiler that the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3185 variables are intentionally being referred to without being
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3186 bound in the body of the function. The compiler normally emits
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3187 warnings for such references, since they could be typographical
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3188 errors for references to local variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3189
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3190 The declaration @code{(declare (special @var{var1} @var{var2}))} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3191 equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3192 optimizing compiler, or to nothing at all in older compilers (which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3193 do not warn for non-local references).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3194
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3195 In top-level contexts, it is generally better to write
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3196 @code{(defvar @var{var})} than @code{(declaim (special @var{var}))},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3197 since @code{defvar} makes your intentions clearer. But the older
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3198 byte compilers can not handle @code{defvar}s appearing inside of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3199 functions, while @code{(declare (special @var{var}))} takes care
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3200 to work correctly with all compilers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3201
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3202 @item inline
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3203 The @code{inline} @var{decl-spec} lists one or more functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3204 whose bodies should be expanded ``in-line'' into calling functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3205 whenever the compiler is able to arrange for it. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3206 the Common Lisp function @code{cadr} is declared @code{inline}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3207 by this package so that the form @code{(cadr @var{x})} will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3208 expand directly into @code{(car (cdr @var{x}))} when it is called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3209 in user functions, for a savings of one (relatively expensive)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3210 function call.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3211
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3212 The following declarations are all equivalent. Note that the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3213 @code{defsubst} form is a convenient way to define a function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3214 and declare it inline all at once, but it is available only in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3215 Emacs 19.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3216
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3217 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3218 (declaim (inline foo bar))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3219 (eval-when (compile load eval) (proclaim '(inline foo bar)))
442
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
3220 (proclaim-inline foo bar) ; XEmacs only
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
3221 (defsubst foo (...) ...) ; instead of defun; Emacs 19 only
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3222 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3223
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3224 @strong{Please note:} This declaration remains in effect after the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3225 containing source file is done. It is correct to use it to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3226 request that a function you have defined should be inlined,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3227 but it is impolite to use it to request inlining of an external
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3228 function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3229
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3230 In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3231 before a particular call to a function to cause just that call to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3232 be inlined; the current byte compilers provide no way to implement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3233 this, so @code{(declare (inline @dots{}))} is currently ignored by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3234 this package.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3235
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3236 @item notinline
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3237 The @code{notinline} declaration lists functions which should
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3238 not be inlined after all; it cancels a previous @code{inline}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3239 declaration.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3240
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3241 @item optimize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3242 This declaration controls how much optimization is performed by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3243 the compiler. Naturally, it is ignored by the earlier non-optimizing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3244 compilers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3245
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3246 The word @code{optimize} is followed by any number of lists like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3247 @code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3248 optimization ``qualities''; this package ignores all but @code{speed}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3249 and @code{safety}. The value of a quality should be an integer from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3250 0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important.''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3251 The default level for both qualities is 1.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3252
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3253 In this package, with the Emacs 19 optimizing compiler, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3254 @code{speed} quality is tied to the @code{byte-compile-optimize}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3255 flag, which is set to @code{nil} for @code{(speed 0)} and to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3256 @code{t} for higher settings; and the @code{safety} quality is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3257 tied to the @code{byte-compile-delete-errors} flag, which is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3258 set to @code{t} for @code{(safety 3)} and to @code{nil} for all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3259 lower settings. (The latter flag controls whether the compiler
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3260 is allowed to optimize out code whose only side-effect could
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3261 be to signal an error, e.g., rewriting @code{(progn foo bar)} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3262 @code{bar} when it is not known whether @code{foo} will be bound
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3263 at run-time.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3264
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3265 Note that even compiling with @code{(safety 0)}, the Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3266 byte-code system provides sufficient checking to prevent real
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3267 harm from being done. For example, barring serious bugs in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3268 Emacs itself, Emacs will not crash with a segmentation fault
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3269 just because of an error in a fully-optimized Lisp program.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3270
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3271 The @code{optimize} declaration is normally used in a top-level
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3272 @code{proclaim} or @code{declaim} in a file; Common Lisp allows
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3273 it to be used with @code{declare} to set the level of optimization
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3274 locally for a given form, but this will not work correctly with the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3275 current version of the optimizing compiler. (The @code{declare}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3276 will set the new optimization level, but that level will not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3277 automatically be unset after the enclosing form is done.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3278
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3279 @item warn
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3280 This declaration controls what sorts of warnings are generated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3281 by the byte compiler. Again, only the optimizing compiler
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3282 generates warnings. The word @code{warn} is followed by any
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3283 number of ``warning qualities,'' similar in form to optimization
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3284 qualities. The currently supported warning types are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3285 @code{redefine}, @code{callargs}, @code{unresolved}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3286 @code{free-vars}; in the current system, a value of 0 will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3287 disable these warnings and any higher value will enable them.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3288 See the documentation for the optimizing byte compiler for details.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3289 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3290
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3291 @node Symbols, Numbers, Declarations, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3292 @chapter Symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3293
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3294 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3295 This package defines several symbol-related features that were
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3296 missing from Emacs Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3297
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3298 @menu
442
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
3299 * Property Lists:: `getf', `remf'
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3300 * Creating Symbols:: `gensym', `gentemp'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3301 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3302
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3303 @node Property Lists, Creating Symbols, Symbols, Symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3304 @section Property Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3305
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3306 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3307 These functions augment the standard Emacs Lisp functions @code{get}
442
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
3308 and @code{put} for operating on properties attached to objects.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3309 There are also functions for working with property lists as
442
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
3310 first-class data structures not attached to particular objects.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3311
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3312 @defun getf place property &optional default
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3313 This function scans the list @var{place} as if it were a property
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3314 list, i.e., a list of alternating property names and values. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3315 an even-numbered element of @var{place} is found which is @code{eq}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3316 to @var{property}, the following odd-numbered element is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3317 Otherwise, @var{default} is returned (or @code{nil} if no default
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3318 is given).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3319
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3320 In particular,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3321
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3322 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3323 (get sym prop) @equiv{} (getf (symbol-plist sym) prop)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3324 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3325
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3326 It is legal to use @code{getf} as a @code{setf} place, in which case
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3327 its @var{place} argument must itself be a legal @code{setf} place.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3328 The @var{default} argument, if any, is ignored in this context.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3329 The effect is to change (via @code{setcar}) the value cell in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3330 list that corresponds to @var{property}, or to cons a new property-value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3331 pair onto the list if the property is not yet present.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3332
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3333 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3334 (put sym prop val) @equiv{} (setf (getf (symbol-plist sym) prop) val)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3335 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3336
440
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
3337 The @code{get} function is also @code{setf}-able. The fact that
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
3338 @code{default} is ignored can sometimes be useful:
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3339
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3340 @example
440
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
3341 (incf (get 'foo 'usage-count 0))
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3342 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3343
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3344 Here, symbol @code{foo}'s @code{usage-count} property is incremented
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3345 if it exists, or set to 1 (an incremented 0) otherwise.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3346
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3347 When not used as a @code{setf} form, @code{getf} is just a regular
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3348 function and its @var{place} argument can actually be any Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3349 expression.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3350 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3351
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3352 @defspec remf place property
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3353 This macro removes the property-value pair for @var{property} from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3354 the property list stored at @var{place}, which is any @code{setf}-able
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3355 place expression. It returns true if the property was found. Note
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3356 that if @var{property} happens to be first on the list, this will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3357 effectively do a @code{(setf @var{place} (cddr @var{place}))},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3358 whereas if it occurs later, this simply uses @code{setcdr} to splice
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3359 out the property and value cells.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3360 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3361
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3362 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3363 @secno=2
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3364 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3365
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3366 @node Creating Symbols, , Property Lists, Symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3367 @section Creating Symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3368
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3369 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3370 These functions create unique symbols, typically for use as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3371 temporary variables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3372
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3373 @defun gensym &optional x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3374 This function creates a new, uninterned symbol (using @code{make-symbol})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3375 with a unique name. (The name of an uninterned symbol is relevant
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3376 only if the symbol is printed.) By default, the name is generated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3377 from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3378 @samp{G1002}, etc. If the optional argument @var{x} is a string, that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3379 string is used as a prefix instead of @samp{G}. Uninterned symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3380 are used in macro expansions for temporary variables, to ensure that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3381 their names will not conflict with ``real'' variables in the user's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3382 code.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3383 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3384
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3385 @defvar *gensym-counter*
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3386 This variable holds the counter used to generate @code{gensym} names.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3387 It is incremented after each use by @code{gensym}. In Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3388 this is initialized with 0, but this package initializes it with a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3389 random (time-dependent) value to avoid trouble when two files that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3390 each used @code{gensym} in their compilation are loaded together.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3391
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3392 @strong{XEmacs note:} As of XEmacs 21.0, an uninterned symbol remains
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3393 uninterned even after being dumped to bytecode. Older versions of Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3394 didn't distinguish the printed representation of interned and uninterned
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3395 symbols, so their names had to be treated more carefully.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3396 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3397
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3398 @defun gentemp &optional x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3399 This function is like @code{gensym}, except that it produces a new
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3400 @emph{interned} symbol. If the symbol that is generated already
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3401 exists, the function keeps incrementing the counter and trying
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3402 again until a new symbol is generated.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3403 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3404
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3405 The Quiroz @file{cl.el} package also defined a @code{defkeyword}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3406 form for creating self-quoting keyword symbols. This package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3407 automatically creates all keywords that are called for by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3408 @code{&key} argument specifiers, and discourages the use of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3409 keywords as data unrelated to keyword arguments, so the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3410 @code{defkeyword} form has been discontinued.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3411
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3412 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3413 @chapno=11
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3414 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3415
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3416 @node Numbers, Sequences, Symbols, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3417 @chapter Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3418
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3419 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3420 This section defines a few simple Common Lisp operations on numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3421 which were left out of Emacs Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3422
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3423 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3424 * Predicates on Numbers:: `plusp', `oddp', `floatp-safe', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3425 * Numerical Functions:: `abs', `expt', `floor*', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3426 * Random Numbers:: `random*', `make-random-state'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3427 * Implementation Parameters:: `most-positive-fixnum', `most-positive-float'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3428 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3429
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3430 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3431 @secno=1
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3432 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3433
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3434 @node Predicates on Numbers, Numerical Functions, Numbers, Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3435 @section Predicates on Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3436
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3437 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3438 These functions return @code{t} if the specified condition is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3439 true of the numerical argument, or @code{nil} otherwise.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3440
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3441 @defun plusp number
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3442 This predicate tests whether @var{number} is positive. It is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3443 error if the argument is not a number.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3444 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3445
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3446 @defun minusp number
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3447 This predicate tests whether @var{number} is negative. It is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3448 error if the argument is not a number.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3449 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3450
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3451 @defun oddp integer
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3452 This predicate tests whether @var{integer} is odd. It is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3453 error if the argument is not an integer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3454 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3455
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3456 @defun evenp integer
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3457 This predicate tests whether @var{integer} is even. It is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3458 error if the argument is not an integer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3459 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3460
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3461 @defun floatp-safe object
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3462 This predicate tests whether @var{object} is a floating-point
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3463 number. On systems that support floating-point, this is equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3464 to @code{floatp}. On other systems, this always returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3465 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3466
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3467 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3468 @secno=3
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3469 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3470
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3471 @node Numerical Functions, Random Numbers, Predicates on Numbers, Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3472 @section Numerical Functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3473
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3474 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3475 These functions perform various arithmetic operations on numbers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3476
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3477 @defun abs number
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3478 This function returns the absolute value of @var{number}. (Newer
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3479 versions of Emacs provide this as a built-in function; this package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3480 defines @code{abs} only for Emacs 18 versions which don't provide
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3481 it as a primitive.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3482 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3483
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3484 @defun expt base power
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3485 This function returns @var{base} raised to the power of @var{number}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3486 (Newer versions of Emacs provide this as a built-in function; this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3487 package defines @code{expt} only for Emacs 18 versions which don't
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3488 provide it as a primitive.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3489 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3490
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3491 @defun gcd &rest integers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3492 This function returns the Greatest Common Divisor of the arguments.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3493 For one argument, it returns the absolute value of that argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3494 For zero arguments, it returns zero.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3495 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3496
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3497 @defun lcm &rest integers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3498 This function returns the Least Common Multiple of the arguments.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3499 For one argument, it returns the absolute value of that argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3500 For zero arguments, it returns one.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3501 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3502
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3503 @defun isqrt integer
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3504 This function computes the ``integer square root'' of its integer
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3505 argument, i.e., the greatest integer less than or equal to the true
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3506 square root of the argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3507 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3508
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3509 @defun floor* number &optional divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3510 This function implements the Common Lisp @code{floor} function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3511 It is called @code{floor*} to avoid name conflicts with the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3512 simpler @code{floor} function built-in to Emacs 19.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3513
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3514 With one argument, @code{floor*} returns a list of two numbers:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3515 The argument rounded down (toward minus infinity) to an integer,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3516 and the ``remainder'' which would have to be added back to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3517 first return value to yield the argument again. If the argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3518 is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3519 If the argument is an Emacs 19 floating-point number, the first
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3520 result is a Lisp integer and the second is a Lisp float between
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3521 0 (inclusive) and 1 (exclusive).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3522
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3523 With two arguments, @code{floor*} divides @var{number} by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3524 @var{divisor}, and returns the floor of the quotient and the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3525 corresponding remainder as a list of two numbers. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3526 @code{(floor* @var{x} @var{y})} returns @code{(@var{q} @var{r})},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3527 then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3528 between 0 (inclusive) and @var{r} (exclusive). Also, note
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3529 that @code{(floor* @var{x})} is exactly equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3530 @code{(floor* @var{x} 1)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3531
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3532 This function is entirely compatible with Common Lisp's @code{floor}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3533 function, except that it returns the two results in a list since
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3534 Emacs Lisp does not support multiple-valued functions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3535 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3536
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3537 @defun ceiling* number &optional divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3538 This function implements the Common Lisp @code{ceiling} function,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3539 which is analogous to @code{floor} except that it rounds the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3540 argument or quotient of the arguments up toward plus infinity.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3541 The remainder will be between 0 and minus @var{r}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3542 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3543
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3544 @defun truncate* number &optional divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3545 This function implements the Common Lisp @code{truncate} function,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3546 which is analogous to @code{floor} except that it rounds the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3547 argument or quotient of the arguments toward zero. Thus it is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3548 equivalent to @code{floor*} if the argument or quotient is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3549 positive, or to @code{ceiling*} otherwise. The remainder has
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3550 the same sign as @var{number}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3551 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3552
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3553 @defun round* number &optional divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3554 This function implements the Common Lisp @code{round} function,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3555 which is analogous to @code{floor} except that it rounds the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3556 argument or quotient of the arguments to the nearest integer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3557 In the case of a tie (the argument or quotient is exactly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3558 halfway between two integers), it rounds to the even integer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3559 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3560
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3561 @defun mod* number divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3562 This function returns the same value as the second return value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3563 of @code{floor}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3564 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3565
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3566 @defun rem* number divisor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3567 This function returns the same value as the second return value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3568 of @code{truncate}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3569 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3570
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3571 These definitions are compatible with those in the Quiroz
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3572 @file{cl.el} package, except that this package appends @samp{*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3573 to certain function names to avoid conflicts with existing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3574 Emacs 19 functions, and that the mechanism for returning
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3575 multiple values is different.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3576
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3577 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3578 @secno=8
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3579 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3580
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3581 @node Random Numbers, Implementation Parameters, Numerical Functions, Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3582 @section Random Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3583
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3584 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3585 This package also provides an implementation of the Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3586 random number generator. It uses its own additive-congruential
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3587 algorithm, which is much more likely to give statistically clean
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3588 random numbers than the simple generators supplied by many
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3589 operating systems.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3590
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3591 @defun random* number &optional state
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3592 This function returns a random nonnegative number less than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3593 @var{number}, and of the same type (either integer or floating-point).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3594 The @var{state} argument should be a @code{random-state} object
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3595 which holds the state of the random number generator. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3596 function modifies this state object as a side effect. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3597 @var{state} is omitted, it defaults to the variable
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3598 @code{*random-state*}, which contains a pre-initialized
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3599 @code{random-state} object.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3600 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3601
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3602 @defvar *random-state*
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3603 This variable contains the system ``default'' @code{random-state}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3604 object, used for calls to @code{random*} that do not specify an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3605 alternative state object. Since any number of programs in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3606 Emacs process may be accessing @code{*random-state*} in interleaved
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3607 fashion, the sequence generated from this variable will be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3608 irreproducible for all intents and purposes.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3609 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3610
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3611 @defun make-random-state &optional state
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3612 This function creates or copies a @code{random-state} object.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3613 If @var{state} is omitted or @code{nil}, it returns a new copy of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3614 @code{*random-state*}. This is a copy in the sense that future
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3615 sequences of calls to @code{(random* @var{n})} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3616 @code{(random* @var{n} @var{s})} (where @var{s} is the new
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3617 random-state object) will return identical sequences of random
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3618 numbers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3619
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3620 If @var{state} is a @code{random-state} object, this function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3621 returns a copy of that object. If @var{state} is @code{t}, this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3622 function returns a new @code{random-state} object seeded from the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3623 date and time. As an extension to Common Lisp, @var{state} may also
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3624 be an integer in which case the new object is seeded from that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3625 integer; each different integer seed will result in a completely
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3626 different sequence of random numbers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3627
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3628 It is legal to print a @code{random-state} object to a buffer or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3629 file and later read it back with @code{read}. If a program wishes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3630 to use a sequence of pseudo-random numbers which can be reproduced
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3631 later for debugging, it can call @code{(make-random-state t)} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3632 get a new sequence, then print this sequence to a file. When the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3633 program is later rerun, it can read the original run's random-state
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3634 from the file.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3635 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3636
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3637 @defun random-state-p object
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3638 This predicate returns @code{t} if @var{object} is a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3639 @code{random-state} object, or @code{nil} otherwise.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3640 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3641
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3642 @node Implementation Parameters, , Random Numbers, Numbers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3643 @section Implementation Parameters
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3644
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3645 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3646 This package defines several useful constants having to with numbers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3647
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3648 @defvar most-positive-fixnum
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3649 This constant equals the largest value a Lisp integer can hold.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3650 It is typically @code{2^23-1} or @code{2^25-1}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3651 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3652
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3653 @defvar most-negative-fixnum
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3654 This constant equals the smallest (most negative) value a Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3655 integer can hold.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3656 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3657
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3658 The following parameters have to do with floating-point numbers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3659 This package determines their values by exercising the computer's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3660 floating-point arithmetic in various ways. Because this operation
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3661 might be slow, the code for initializing them is kept in a separate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3662 function that must be called before the parameters can be used.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3663
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3664 @defun cl-float-limits
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3665 This function makes sure that the Common Lisp floating-point
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3666 parameters like @code{most-positive-float} have been initialized.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3667 Until it is called, these parameters will be @code{nil}. If this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3668 version of Emacs does not support floats (e.g., most versions of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3669 Emacs 18), the parameters will remain @code{nil}. If the parameters
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3670 have already been initialized, the function returns immediately.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3671
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3672 The algorithm makes assumptions that will be valid for most modern
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3673 machines, but will fail if the machine's arithmetic is extremely
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3674 unusual, e.g., decimal.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3675 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3676
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3677 Since true Common Lisp supports up to four different floating-point
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3678 precisions, it has families of constants like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3679 @code{most-positive-single-float}, @code{most-positive-double-float},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3680 @code{most-positive-long-float}, and so on. Emacs has only one
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3681 floating-point precision, so this package omits the precision word
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3682 from the constants' names.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3683
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3684 @defvar most-positive-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3685 This constant equals the largest value a Lisp float can hold.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3686 For those systems whose arithmetic supports infinities, this is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3687 the largest @emph{finite} value. For IEEE machines, the value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3688 is approximately @code{1.79e+308}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3689 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3690
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3691 @defvar most-negative-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3692 This constant equals the most-negative value a Lisp float can hold.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3693 (It is assumed to be equal to @code{(- most-positive-float)}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3694 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3695
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3696 @defvar least-positive-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3697 This constant equals the smallest Lisp float value greater than zero.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3698 For IEEE machines, it is about @code{4.94e-324} if denormals are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3699 supported or @code{2.22e-308} if not.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3700 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3701
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3702 @defvar least-positive-normalized-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3703 This constant equals the smallest @emph{normalized} Lisp float greater
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3704 than zero, i.e., the smallest value for which IEEE denormalization
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3705 will not result in a loss of precision. For IEEE machines, this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3706 value is about @code{2.22e-308}. For machines that do not support
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3707 the concept of denormalization and gradual underflow, this constant
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3708 will always equal @code{least-positive-float}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3709 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3710
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3711 @defvar least-negative-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3712 This constant is the negative counterpart of @code{least-positive-float}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3713 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3714
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3715 @defvar least-negative-normalized-float
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3716 This constant is the negative counterpart of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3717 @code{least-positive-normalized-float}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3718 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3719
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3720 @defvar float-epsilon
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3721 This constant is the smallest positive Lisp float that can be added
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3722 to 1.0 to produce a distinct value. Adding a smaller number to 1.0
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3723 will yield 1.0 again due to roundoff. For IEEE machines, epsilon
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3724 is about @code{2.22e-16}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3725 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3726
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3727 @defvar float-negative-epsilon
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3728 This is the smallest positive value that can be subtracted from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3729 1.0 to produce a distinct value. For IEEE machines, it is about
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3730 @code{1.11e-16}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3731 @end defvar
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3732
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3733 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3734 @chapno=13
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3735 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3736
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3737 @node Sequences, Lists, Numbers, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3738 @chapter Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3739
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3740 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3741 Common Lisp defines a number of functions that operate on
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3742 @dfn{sequences}, which are either lists, strings, or vectors.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3743 Emacs Lisp includes a few of these, notably @code{elt} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3744 @code{length}; this package defines most of the rest.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3745
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3746 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3747 * Sequence Basics:: Arguments shared by all sequence functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3748 * Mapping over Sequences:: `mapcar*', `mapcan', `map', `every', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3749 * Sequence Functions:: `subseq', `remove*', `substitute', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3750 * Searching Sequences:: `find', `position', `count', `search', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3751 * Sorting Sequences:: `sort*', `stable-sort', `merge'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3752 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3753
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3754 @node Sequence Basics, Mapping over Sequences, Sequences, Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3755 @section Sequence Basics
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3756
778
2923009caf47 [xemacs-hg @ 2002-03-16 10:38:59 by ben]
ben
parents: 446
diff changeset
3757 @noindent Many of the sequence functions take keyword arguments;
2923009caf47 [xemacs-hg @ 2002-03-16 10:38:59 by ben]
ben
parents: 446
diff changeset
3758 @pxref{Argument Lists}. All keyword arguments are optional and, if
2923009caf47 [xemacs-hg @ 2002-03-16 10:38:59 by ben]
ben
parents: 446
diff changeset
3759 specified, may appear in any order.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3760
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3761 The @code{:key} argument should be passed either @code{nil}, or a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3762 function of one argument. This key function is used as a filter
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3763 through which the elements of the sequence are seen; for example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3764 @code{(find x y :key 'car)} is similar to @code{(assoc* x y)}:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3765 It searches for an element of the list whose @code{car} equals
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3766 @code{x}, rather than for an element which equals @code{x} itself.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3767 If @code{:key} is omitted or @code{nil}, the filter is effectively
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3768 the identity function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3769
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3770 The @code{:test} and @code{:test-not} arguments should be either
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3771 @code{nil}, or functions of two arguments. The test function is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3772 used to compare two sequence elements, or to compare a search value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3773 with sequence elements. (The two values are passed to the test
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3774 function in the same order as the original sequence function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3775 arguments from which they are derived, or, if they both come from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3776 the same sequence, in the same order as they appear in that sequence.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3777 The @code{:test} argument specifies a function which must return
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3778 true (non-@code{nil}) to indicate a match; instead, you may use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3779 @code{:test-not} to give a function which returns @emph{false} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3780 indicate a match. The default test function is @code{:test 'eql}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3781
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3782 Many functions which take @var{item} and @code{:test} or @code{:test-not}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3783 arguments also come in @code{-if} and @code{-if-not} varieties,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3784 where a @var{predicate} function is passed instead of @var{item},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3785 and sequence elements match if the predicate returns true on them
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3786 (or false in the case of @code{-if-not}). For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3787
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3788 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3789 (remove* 0 seq :test '=) @equiv{} (remove-if 'zerop seq)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3790 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3791
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3792 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3793 to remove all zeros from sequence @code{seq}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3794
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3795 Some operations can work on a subsequence of the argument sequence;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3796 these function take @code{:start} and @code{:end} arguments which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3797 default to zero and the length of the sequence, respectively.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3798 Only elements between @var{start} (inclusive) and @var{end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3799 (exclusive) are affected by the operation. The @var{end} argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3800 may be passed @code{nil} to signify the length of the sequence;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3801 otherwise, both @var{start} and @var{end} must be integers, with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3802 @code{0 <= @var{start} <= @var{end} <= (length @var{seq})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3803 If the function takes two sequence arguments, the limits are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3804 defined by keywords @code{:start1} and @code{:end1} for the first,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3805 and @code{:start2} and @code{:end2} for the second.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3806
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3807 A few functions accept a @code{:from-end} argument, which, if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3808 non-@code{nil}, causes the operation to go from right-to-left
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3809 through the sequence instead of left-to-right, and a @code{:count}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3810 argument, which specifies an integer maximum number of elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3811 to be removed or otherwise processed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3812
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3813 The sequence functions make no guarantees about the order in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3814 which the @code{:test}, @code{:test-not}, and @code{:key} functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3815 are called on various elements. Therefore, it is a bad idea to depend
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3816 on side effects of these functions. For example, @code{:from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3817 may cause the sequence to be scanned actually in reverse, or it may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3818 be scanned forwards but computing a result ``as if'' it were scanned
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3819 backwards. (Some functions, like @code{mapcar*} and @code{every},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3820 @emph{do} specify exactly the order in which the function is called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3821 so side effects are perfectly acceptable in those cases.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3822
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3823 Strings in GNU Emacs 19 may contain ``text properties'' as well
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3824 as character data. Except as noted, it is undefined whether or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3825 not text properties are preserved by sequence functions. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3826 example, @code{(remove* ?A @var{str})} may or may not preserve
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3827 the properties of the characters copied from @var{str} into the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3828 result.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3829
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3830 @node Mapping over Sequences, Sequence Functions, Sequence Basics, Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3831 @section Mapping over Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3832
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3833 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3834 These functions ``map'' the function you specify over the elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3835 of lists or arrays. They are all variations on the theme of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3836 built-in function @code{mapcar}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3837
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3838 @defun mapcar* function seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3839 This function calls @var{function} on successive parallel sets of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3840 elements from its argument sequences. Given a single @var{seq}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3841 argument it is equivalent to @code{mapcar}; given @var{n} sequences,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3842 it calls the function with the first elements of each of the sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3843 as the @var{n} arguments to yield the first element of the result
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3844 list, then with the second elements, and so on. The mapping stops as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3845 soon as the shortest sequence runs out. The argument sequences may
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3846 be any mixture of lists, strings, and vectors; the return sequence
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3847 is always a list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3848
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3849 Common Lisp's @code{mapcar} accepts multiple arguments but works
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3850 only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3851 argument. This package's @code{mapcar*} works as a compatible
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3852 superset of both.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3853 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3854
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3855 @defun map result-type function seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3856 This function maps @var{function} over the argument sequences,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3857 just like @code{mapcar*}, but it returns a sequence of type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3858 @var{result-type} rather than a list. @var{result-type} must
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3859 be one of the following symbols: @code{vector}, @code{string},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3860 @code{list} (in which case the effect is the same as for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3861 @code{mapcar*}), or @code{nil} (in which case the results are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3862 thrown away and @code{map} returns @code{nil}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3863 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3864
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3865 @defun maplist function list &rest more-lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3866 This function calls @var{function} on each of its argument lists,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3867 then on the @code{cdr}s of those lists, and so on, until the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3868 shortest list runs out. The results are returned in the form
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3869 of a list. Thus, @code{maplist} is like @code{mapcar*} except
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3870 that it passes in the list pointers themselves rather than the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3871 @code{car}s of the advancing pointers.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3872 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3873
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3874 @defun mapc function seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3875 This function is like @code{mapcar*}, except that the values
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3876 returned by @var{function} are ignored and thrown away rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3877 than being collected into a list. The return value of @code{mapc}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3878 is @var{seq}, the first sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3879 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3880
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3881 @defun mapl function list &rest more-lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3882 This function is like @code{maplist}, except that it throws away
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3883 the values returned by @var{function}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3884 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3885
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3886 @defun mapcan function seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3887 This function is like @code{mapcar*}, except that it concatenates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3888 the return values (which must be lists) using @code{nconc},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3889 rather than simply collecting them into a list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3890 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3891
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3892 @defun mapcon function list &rest more-lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3893 This function is like @code{maplist}, except that it concatenates
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3894 the return values using @code{nconc}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3895 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3896
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3897 @defun some predicate seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3898 This function calls @var{predicate} on each element of @var{seq}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3899 in turn; if @var{predicate} returns a non-@code{nil} value,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3900 @code{some} returns that value, otherwise it returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3901 Given several sequence arguments, it steps through the sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3902 in parallel until the shortest one runs out, just as in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3903 @code{mapcar*}. You can rely on the left-to-right order in which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3904 the elements are visited, and on the fact that mapping stops
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3905 immediately as soon as @var{predicate} returns non-@code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3906 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3907
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3908 @defun every predicate seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3909 This function calls @var{predicate} on each element of the sequence(s)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3910 in turn; it returns @code{nil} as soon as @var{predicate} returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3911 @code{nil} for any element, or @code{t} if the predicate was true
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3912 for all elements.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3913 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3914
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3915 @defun notany predicate seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3916 This function calls @var{predicate} on each element of the sequence(s)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3917 in turn; it returns @code{nil} as soon as @var{predicate} returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3918 a non-@code{nil} value for any element, or @code{t} if the predicate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3919 was @code{nil} for all elements.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3920 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3921
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3922 @defun notevery predicate seq &rest more-seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3923 This function calls @var{predicate} on each element of the sequence(s)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3924 in turn; it returns a non-@code{nil} value as soon as @var{predicate}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3925 returns @code{nil} for any element, or @code{t} if the predicate was
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3926 true for all elements.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3927 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3928
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3929 @defun reduce function seq @t{&key :from-end :start :end :initial-value :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3930 This function combines the elements of @var{seq} using an associative
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3931 binary operation. Suppose @var{function} is @code{*} and @var{seq} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3932 the list @code{(2 3 4 5)}. The first two elements of the list are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3933 combined with @code{(* 2 3) = 6}; this is combined with the next
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3934 element, @code{(* 6 4) = 24}, and that is combined with the final
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3935 element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3936 to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3937 an explicit call to @code{reduce}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3938
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3939 If @code{:from-end} is true, the reduction is right-associative instead
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3940 of left-associative:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3941
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3942 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3943 (reduce '- '(1 2 3 4))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3944 @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3945 (reduce '- '(1 2 3 4) :from-end t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3946 @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3947 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3948
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3949 If @code{:key} is specified, it is a function of one argument which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3950 is called on each of the sequence elements in turn.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3951
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3952 If @code{:initial-value} is specified, it is effectively added to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3953 front (or rear in the case of @code{:from-end}) of the sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3954 The @code{:key} function is @emph{not} applied to the initial value.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3955
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3956 If the sequence, including the initial value, has exactly one element
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3957 then that element is returned without ever calling @var{function}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3958 If the sequence is empty (and there is no initial value), then
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3959 @var{function} is called with no arguments to obtain the return value.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3960 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3961
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3962 All of these mapping operations can be expressed conveniently in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3963 terms of the @code{loop} macro. In compiled code, @code{loop} will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3964 be faster since it generates the loop as in-line code with no
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3965 function calls.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3966
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3967 @node Sequence Functions, Searching Sequences, Mapping over Sequences, Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3968 @section Sequence Functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3969
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3970 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3971 This section describes a number of Common Lisp functions for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3972 operating on sequences.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3973
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3974 @defun subseq sequence start &optional end
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3975 This function returns a given subsequence of the argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3976 @var{sequence}, which may be a list, string, or vector.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3977 The indices @var{start} and @var{end} must be in range, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3978 @var{start} must be no greater than @var{end}. If @var{end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3979 is omitted, it defaults to the length of the sequence. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3980 return value is always a copy; it does not share structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3981 with @var{sequence}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3982
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3983 As an extension to Common Lisp, @var{start} and/or @var{end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3984 may be negative, in which case they represent a distance back
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3985 from the end of the sequence. This is for compatibility with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3986 Emacs' @code{substring} function. Note that @code{subseq} is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3987 the @emph{only} sequence function that allows negative
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3988 @var{start} and @var{end}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3989
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3990 You can use @code{setf} on a @code{subseq} form to replace a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3991 specified range of elements with elements from another sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3992 The replacement is done as if by @code{replace}, described below.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3993 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3994
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3995 @defun concatenate result-type &rest seqs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3996 This function concatenates the argument sequences together to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3997 form a result sequence of type @var{result-type}, one of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3998 symbols @code{vector}, @code{string}, or @code{list}. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
3999 arguments are always copied, even in cases such as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4000 @code{(concatenate 'list '(1 2 3))} where the result is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4001 identical to an argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4002 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4003
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4004 @defun fill seq item @t{&key :start :end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4005 This function fills the elements of the sequence (or the specified
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4006 part of the sequence) with the value @var{item}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4007 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4008
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4009 @defun replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4010 This function copies part of @var{seq2} into part of @var{seq1}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4011 The sequence @var{seq1} is not stretched or resized; the amount
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4012 of data copied is simply the shorter of the source and destination
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4013 (sub)sequences. The function returns @var{seq1}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4014
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4015 If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4016 will work correctly even if the regions indicated by the start
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4017 and end arguments overlap. However, if @var{seq1} and @var{seq2}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4018 are lists which share storage but are not @code{eq}, and the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4019 start and end arguments specify overlapping regions, the effect
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4020 is undefined.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4021 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4022
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4023 @defun remove* item seq @t{&key :test :test-not :key :count :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4024 This returns a copy of @var{seq} with all elements matching
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4025 @var{item} removed. The result may share storage with or be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4026 @code{eq} to @var{seq} in some circumstances, but the original
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4027 @var{seq} will not be modified. The @code{:test}, @code{:test-not},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4028 and @code{:key} arguments define the matching test that is used;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4029 by default, elements @code{eql} to @var{item} are removed. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4030 @code{:count} argument specifies the maximum number of matching
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4031 elements that can be removed (only the leftmost @var{count} matches
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4032 are removed). The @code{:start} and @code{:end} arguments specify
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4033 a region in @var{seq} in which elements will be removed; elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4034 outside that region are not matched or removed. The @code{:from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4035 argument, if true, says that elements should be deleted from the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4036 end of the sequence rather than the beginning (this matters only
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4037 if @var{count} was also specified).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4038 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4039
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4040 @defun delete* item seq @t{&key :test :test-not :key :count :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4041 This deletes all elements of @var{seq} which match @var{item}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4042 It is a destructive operation. Since Emacs Lisp does not support
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4043 stretchable strings or vectors, this is the same as @code{remove*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4044 for those sequence types. On lists, @code{remove*} will copy the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4045 list if necessary to preserve the original list, whereas
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4046 @code{delete*} will splice out parts of the argument list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4047 Compare @code{append} and @code{nconc}, which are analogous
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4048 non-destructive and destructive list operations in Emacs Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4049 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4050
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4051 @findex remove-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4052 @findex remove-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4053 @findex delete-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4054 @findex delete-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4055 The predicate-oriented functions @code{remove-if}, @code{remove-if-not},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4056 @code{delete-if}, and @code{delete-if-not} are defined similarly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4057
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4058 @defun delete item list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4059 This MacLisp-compatible function deletes from @var{list} all elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4060 which are @code{equal} to @var{item}. The @code{delete} function is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4061 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4062 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4063
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4064 @defun remove item list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4065 This function removes from @var{list} all elements which are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4066 @code{equal} to @var{item}. This package defines it for symmetry
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4067 with @code{delete}, even though @code{remove} is not built-in to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4068 Emacs 19.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4069 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4070
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4071 @defun remq item list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4072 This function removes from @var{list} all elements which are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4073 @code{eq} to @var{item}. This package defines it for symmetry
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4074 with @code{delq}, even though @code{remq} is not built-in to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4075 Emacs 19.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4076 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4077
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4078 @defun remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4079 This function returns a copy of @var{seq} with duplicate elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4080 removed. Specifically, if two elements from the sequence match
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4081 according to the @code{:test}, @code{:test-not}, and @code{:key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4082 arguments, only the rightmost one is retained. If @code{:from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4083 is true, the leftmost one is retained instead. If @code{:start} or
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4084 @code{:end} is specified, only elements within that subsequence are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4085 examined or removed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4086 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4087
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4088 @defun delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4089 This function deletes duplicate elements from @var{seq}. It is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4090 a destructive version of @code{remove-duplicates}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4091 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4092
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4093 @defun substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4094 This function returns a copy of @var{seq}, with all elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4095 matching @var{old} replaced with @var{new}. The @code{:count},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4096 @code{:start}, @code{:end}, and @code{:from-end} arguments may be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4097 used to limit the number of substitutions made.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4098 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4099
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4100 @defun nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4101 This is a destructive version of @code{substitute}; it performs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4102 the substitution using @code{setcar} or @code{aset} rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4103 by returning a changed copy of the sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4104 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4105
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4106 @findex substitute-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4107 @findex substitute-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4108 @findex nsubstitute-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4109 @findex nsubstitute-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4110 The @code{substitute-if}, @code{substitute-if-not}, @code{nsubstitute-if},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4111 and @code{nsubstitute-if-not} functions are defined similarly. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4112 these, a @var{predicate} is given in place of the @var{old} argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4113
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4114 @node Searching Sequences, Sorting Sequences, Sequence Functions, Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4115 @section Searching Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4116
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4117 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4118 These functions search for elements or subsequences in a sequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4119 (See also @code{member*} and @code{assoc*}; @pxref{Lists}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4120
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4121 @defun find item seq @t{&key :test :test-not :key :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4122 This function searches @var{seq} for an element matching @var{item}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4123 If it finds a match, it returns the matching element. Otherwise,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4124 it returns @code{nil}. It returns the leftmost match, unless
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4125 @code{:from-end} is true, in which case it returns the rightmost
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4126 match. The @code{:start} and @code{:end} arguments may be used to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4127 limit the range of elements that are searched.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4128 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4129
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4130 @defun position item seq @t{&key :test :test-not :key :start :end :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4131 This function is like @code{find}, except that it returns the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4132 integer position in the sequence of the matching item rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4133 the item itself. The position is relative to the start of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4134 sequence as a whole, even if @code{:start} is non-zero. The function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4135 returns @code{nil} if no matching element was found.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4136 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4137
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4138 @defun count item seq @t{&key :test :test-not :key :start :end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4139 This function returns the number of elements of @var{seq} which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4140 match @var{item}. The result is always a nonnegative integer.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4141 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4142
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4143 @findex find-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4144 @findex find-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4145 @findex position-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4146 @findex position-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4147 @findex count-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4148 @findex count-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4149 The @code{find-if}, @code{find-if-not}, @code{position-if},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4150 @code{position-if-not}, @code{count-if}, and @code{count-if-not}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4151 functions are defined similarly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4152
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4153 @defun mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4154 This function compares the specified parts of @var{seq1} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4155 @var{seq2}. If they are the same length and the corresponding
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4156 elements match (according to @code{:test}, @code{:test-not},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4157 and @code{:key}), the function returns @code{nil}. If there is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4158 a mismatch, the function returns the index (relative to @var{seq1})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4159 of the first mismatching element. This will be the leftmost pair of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4160 elements which do not match, or the position at which the shorter of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4161 the two otherwise-matching sequences runs out.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4162
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4163 If @code{:from-end} is true, then the elements are compared from right
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4164 to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4165 If the sequences differ, then one plus the index of the rightmost
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4166 difference (relative to @var{seq1}) is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4167
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4168 An interesting example is @code{(mismatch str1 str2 :key 'upcase)},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4169 which compares two strings case-insensitively.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4170 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4171
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4172 @defun search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4173 This function searches @var{seq2} for a subsequence that matches
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4174 @var{seq1} (or part of it specified by @code{:start1} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4175 @code{:end1}.) Only matches which fall entirely within the region
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4176 defined by @code{:start2} and @code{:end2} will be considered.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4177 The return value is the index of the leftmost element of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4178 leftmost match, relative to the start of @var{seq2}, or @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4179 if no matches were found. If @code{:from-end} is true, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4180 function finds the @emph{rightmost} matching subsequence.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4181 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4182
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4183 @node Sorting Sequences, , Searching Sequences, Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4184 @section Sorting Sequences
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4185
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4186 @defun sort* seq predicate @t{&key :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4187 This function sorts @var{seq} into increasing order as determined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4188 by using @var{predicate} to compare pairs of elements. @var{predicate}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4189 should return true (non-@code{nil}) if and only if its first argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4190 is less than (not equal to) its second argument. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4191 @code{<} and @code{string-lessp} are suitable predicate functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4192 for sorting numbers and strings, respectively; @code{>} would sort
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4193 numbers into decreasing rather than increasing order.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4194
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4195 This function differs from Emacs' built-in @code{sort} in that it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4196 can operate on any type of sequence, not just lists. Also, it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4197 accepts a @code{:key} argument which is used to preprocess data
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4198 fed to the @var{predicate} function. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4199
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4200 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4201 (setq data (sort data 'string-lessp :key 'downcase))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4202 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4203
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4204 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4205 sorts @var{data}, a sequence of strings, into increasing alphabetical
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4206 order without regard to case. A @code{:key} function of @code{car}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4207 would be useful for sorting association lists.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4208
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4209 The @code{sort*} function is destructive; it sorts lists by actually
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4210 rearranging the @code{cdr} pointers in suitable fashion.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4211 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4212
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4213 @defun stable-sort seq predicate @t{&key :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4214 This function sorts @var{seq} @dfn{stably}, meaning two elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4215 which are equal in terms of @var{predicate} are guaranteed not to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4216 be rearranged out of their original order by the sort.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4217
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4218 In practice, @code{sort*} and @code{stable-sort} are equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4219 in Emacs Lisp because the underlying @code{sort} function is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4220 stable by default. However, this package reserves the right to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4221 use non-stable methods for @code{sort*} in the future.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4222 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4223
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4224 @defun merge type seq1 seq2 predicate @t{&key :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4225 This function merges two sequences @var{seq1} and @var{seq2} by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4226 interleaving their elements. The result sequence, of type @var{type}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4227 (in the sense of @code{concatenate}), has length equal to the sum
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4228 of the lengths of the two input sequences. The sequences may be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4229 modified destructively. Order of elements within @var{seq1} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4230 @var{seq2} is preserved in the interleaving; elements of the two
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4231 sequences are compared by @var{predicate} (in the sense of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4232 @code{sort}) and the lesser element goes first in the result.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4233 When elements are equal, those from @var{seq1} precede those from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4234 @var{seq2} in the result. Thus, if @var{seq1} and @var{seq2} are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4235 both sorted according to @var{predicate}, then the result will be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4236 a merged sequence which is (stably) sorted according to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4237 @var{predicate}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4238 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4239
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4240 @node Lists, Hash Tables, Sequences, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4241 @chapter Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4242
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4243 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4244 The functions described here operate on lists.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4245
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4246 @menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4247 * List Functions:: `caddr', `first', `last', `list*', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4248 * Substitution of Expressions:: `subst', `sublis', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4249 * Lists as Sets:: `member*', `adjoin', `union', etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4250 * Association Lists:: `assoc*', `rassoc*', `acons', `pairlis'
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4251 @end menu
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4252
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4253 @node List Functions, Substitution of Expressions, Lists, Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4254 @section List Functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4255
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4256 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4257 This section describes a number of simple operations on lists,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4258 i.e., chains of cons cells.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4259
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4260 @defun caddr x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4261 This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4262 Likewise, this package defines all 28 @code{c@var{xxx}r} functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4263 where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4264 All of these functions are @code{setf}-able, and calls to them
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4265 are expanded inline by the byte-compiler for maximum efficiency.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4266 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4267
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4268 @defun first x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4269 This function is a synonym for @code{(car @var{x})}. Likewise,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4270 the functions @code{second}, @code{third}, @dots{}, through
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4271 @code{tenth} return the given element of the list @var{x}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4272 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4273
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4274 @defun rest x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4275 This function is a synonym for @code{(cdr @var{x})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4276 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4277
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4278 @defun endp x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4279 Common Lisp defines this function to act like @code{null}, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4280 signalling an error if @code{x} is neither a @code{nil} nor a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4281 cons cell. This package simply defines @code{endp} as a synonym
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4282 for @code{null}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4283 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4284
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4285 @defun list-length x
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4286 This function returns the length of list @var{x}, exactly like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4287 @code{(length @var{x})}, except that if @var{x} is a circular
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4288 list (where the cdr-chain forms a loop rather than terminating
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4289 with @code{nil}), this function returns @code{nil}. (The regular
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4290 @code{length} function would get stuck if given a circular list.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4291 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4292
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4293 @defun last x &optional n
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4294 This function returns the last cons, or the @var{n}th-to-last cons,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4295 of the list @var{x}. If @var{n} is omitted it defaults to 1.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4296 The ``last cons'' means the first cons cell of the list whose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4297 @code{cdr} is not another cons cell. (For normal lists, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4298 @code{cdr} of the last cons will be @code{nil}.) This function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4299 returns @code{nil} if @var{x} is @code{nil} or shorter than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4300 @var{n}. Note that the last @emph{element} of the list is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4301 @code{(car (last @var{x}))}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4302 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4303
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4304 @defun butlast x &optional n
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4305 This function returns the list @var{x} with the last element,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4306 or the last @var{n} elements, removed. If @var{n} is greater
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4307 than zero it makes a copy of the list so as not to damage the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4308 original list. In general, @code{(append (butlast @var{x} @var{n})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4309 (last @var{x} @var{n}))} will return a list equal to @var{x}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4310 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4311
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4312 @defun nbutlast x &optional n
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4313 This is a version of @code{butlast} that works by destructively
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4314 modifying the @code{cdr} of the appropriate element, rather than
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4315 making a copy of the list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4316 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4317
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4318 @defun list* arg &rest others
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4319 This function constructs a list of its arguments. The final
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4320 argument becomes the @code{cdr} of the last cell constructed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4321 Thus, @code{(list* @var{a} @var{b} @var{c})} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4322 @code{(cons @var{a} (cons @var{b} @var{c}))}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4323 @code{(list* @var{a} @var{b} nil)} is equivalent to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4324 @code{(list @var{a} @var{b})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4325
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4326 (Note that this function really is called @code{list*} in Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4327 Lisp; it is not a name invented for this package like @code{member*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4328 or @code{defun*}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4329 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4330
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4331 @defun ldiff list sublist
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4332 If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4333 one of the cons cells of @var{list}, then this function returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4334 a copy of the part of @var{list} up to but not including
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4335 @var{sublist}. For example, @code{(ldiff x (cddr x))} returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4336 the first two elements of the list @code{x}. The result is a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4337 copy; the original @var{list} is not modified. If @var{sublist}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4338 is not a sublist of @var{list}, a copy of the entire @var{list}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4339 is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4340 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4341
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4342 @defun copy-list list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4343 This function returns a copy of the list @var{list}. It copies
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4344 dotted lists like @code{(1 2 . 3)} correctly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4345 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4346
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4347 @defun copy-tree x &optional vecp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4348 This function returns a copy of the tree of cons cells @var{x}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4349 Unlike @code{copy-sequence} (and its alias @code{copy-list}),
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4350 which copies only along the @code{cdr} direction, this function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4351 copies (recursively) along both the @code{car} and the @code{cdr}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4352 directions. If @var{x} is not a cons cell, the function simply
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4353 returns @var{x} unchanged. If the optional @var{vecp} argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4354 is true, this function copies vectors (recursively) as well as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4355 cons cells.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4356 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4357
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4358 @defun tree-equal x y @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4359 This function compares two trees of cons cells. If @var{x} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4360 @var{y} are both cons cells, their @code{car}s and @code{cdr}s are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4361 compared recursively. If neither @var{x} nor @var{y} is a cons
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4362 cell, they are compared by @code{eql}, or according to the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4363 specified test. The @code{:key} function, if specified, is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4364 applied to the elements of both trees. @xref{Sequences}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4365 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4366
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4367 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4368 @secno=3
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4369 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4370
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4371 @node Substitution of Expressions, Lists as Sets, List Functions, Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4372 @section Substitution of Expressions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4373
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4374 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4375 These functions substitute elements throughout a tree of cons
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4376 cells. (@xref{Sequence Functions}, for the @code{substitute}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4377 function, which works on just the top-level elements of a list.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4378
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4379 @defun subst new old tree @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4380 This function substitutes occurrences of @var{old} with @var{new}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4381 in @var{tree}, a tree of cons cells. It returns a substituted
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4382 tree, which will be a copy except that it may share storage with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4383 the argument @var{tree} in parts where no substitutions occurred.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4384 The original @var{tree} is not modified. This function recurses
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4385 on, and compares against @var{old}, both @code{car}s and @code{cdr}s
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4386 of the component cons cells. If @var{old} is itself a cons cell,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4387 then matching cells in the tree are substituted as usual without
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4388 recursively substituting in that cell. Comparisons with @var{old}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4389 are done according to the specified test (@code{eql} by default).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4390 The @code{:key} function is applied to the elements of the tree
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4391 but not to @var{old}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4392 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4393
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4394 @defun nsubst new old tree @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4395 This function is like @code{subst}, except that it works by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4396 destructive modification (by @code{setcar} or @code{setcdr})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4397 rather than copying.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4398 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4399
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4400 @findex subst-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4401 @findex subst-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4402 @findex nsubst-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4403 @findex nsubst-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4404 The @code{subst-if}, @code{subst-if-not}, @code{nsubst-if}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4405 @code{nsubst-if-not} functions are defined similarly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4406
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4407 @defun sublis alist tree @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4408 This function is like @code{subst}, except that it takes an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4409 association list @var{alist} of @var{old}-@var{new} pairs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4410 Each element of the tree (after applying the @code{:key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4411 function, if any), is compared with the @code{car}s of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4412 @var{alist}; if it matches, it is replaced by the corresponding
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4413 @code{cdr}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4414 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4415
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4416 @defun nsublis alist tree @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4417 This is a destructive version of @code{sublis}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4418 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4419
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4420 @node Lists as Sets, Association Lists, Substitution of Expressions, Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4421 @section Lists as Sets
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4422
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4423 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4424 These functions perform operations on lists which represent sets
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4425 of elements.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4426
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4427 @defun member item list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4428 This MacLisp-compatible function searches @var{list} for an element
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4429 which is @code{equal} to @var{item}. The @code{member} function is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4430 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4431 See the following function for a Common-Lisp compatible version.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4432 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4433
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4434 @defun member* item list @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4435 This function searches @var{list} for an element matching @var{item}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4436 If a match is found, it returns the cons cell whose @code{car} was
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4437 the matching element. Otherwise, it returns @code{nil}. Elements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4438 are compared by @code{eql} by default; you can use the @code{:test},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4439 @code{:test-not}, and @code{:key} arguments to modify this behavior.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4440 @xref{Sequences}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4441
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4442 Note that this function's name is suffixed by @samp{*} to avoid
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4443 the incompatible @code{member} function defined in Emacs 19.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4444 (That function uses @code{equal} for comparisons; it is equivalent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4445 to @code{(member* @var{item} @var{list} :test 'equal)}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4446 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4447
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4448 @findex member-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4449 @findex member-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4450 The @code{member-if} and @code{member-if-not} functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4451 analogously search for elements which satisfy a given predicate.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4452
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4453 @defun tailp sublist list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4454 This function returns @code{t} if @var{sublist} is a sublist of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4455 @var{list}, i.e., if @var{sublist} is @code{eql} to @var{list} or to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4456 any of its @code{cdr}s.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4457 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4458
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4459 @defun adjoin item list @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4460 This function conses @var{item} onto the front of @var{list},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4461 like @code{(cons @var{item} @var{list})}, but only if @var{item}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4462 is not already present on the list (as determined by @code{member*}).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4463 If a @code{:key} argument is specified, it is applied to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4464 @var{item} as well as to the elements of @var{list} during
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4465 the search, on the reasoning that @var{item} is ``about'' to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4466 become part of the list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4467 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4468
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4469 @defun union list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4470 This function combines two lists which represent sets of items,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4471 returning a list that represents the union of those two sets.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4472 The result list will contain all items which appear in @var{list1}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4473 or @var{list2}, and no others. If an item appears in both
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4474 @var{list1} and @var{list2} it will be copied only once. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4475 an item is duplicated in @var{list1} or @var{list2}, it is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4476 undefined whether or not that duplication will survive in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4477 result list. The order of elements in the result list is also
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4478 undefined.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4479 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4480
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4481 @defun nunion list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4482 This is a destructive version of @code{union}; rather than copying,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4483 it tries to reuse the storage of the argument lists if possible.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4484 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4485
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4486 @defun intersection list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4487 This function computes the intersection of the sets represented
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4488 by @var{list1} and @var{list2}. It returns the list of items
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4489 which appear in both @var{list1} and @var{list2}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4490 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4491
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4492 @defun nintersection list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4493 This is a destructive version of @code{intersection}. It
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4494 tries to reuse storage of @var{list1} rather than copying.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4495 It does @emph{not} reuse the storage of @var{list2}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4496 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4497
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4498 @defun set-difference list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4499 This function computes the ``set difference'' of @var{list1}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4500 and @var{list2}, i.e., the set of elements that appear in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4501 @var{list1} but @emph{not} in @var{list2}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4502 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4503
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4504 @defun nset-difference list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4505 This is a destructive @code{set-difference}, which will try
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4506 to reuse @var{list1} if possible.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4507 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4508
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4509 @defun set-exclusive-or list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4510 This function computes the ``set exclusive or'' of @var{list1}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4511 and @var{list2}, i.e., the set of elements that appear in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4512 exactly one of @var{list1} and @var{list2}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4513 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4514
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4515 @defun nset-exclusive-or list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4516 This is a destructive @code{set-exclusive-or}, which will try
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4517 to reuse @var{list1} and @var{list2} if possible.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4518 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4519
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4520 @defun subsetp list1 list2 @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4521 This function checks whether @var{list1} represents a subset
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4522 of @var{list2}, i.e., whether every element of @var{list1}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4523 also appears in @var{list2}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4524 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4525
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4526 @node Association Lists, , Lists as Sets, Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4527 @section Association Lists
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4528
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4529 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4530 An @dfn{association list} is a list representing a mapping from
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4531 one set of values to another; any list whose elements are cons
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4532 cells is an association list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4533
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4534 @defun assoc* item a-list @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4535 This function searches the association list @var{a-list} for an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4536 element whose @code{car} matches (in the sense of @code{:test},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4537 @code{:test-not}, and @code{:key}, or by comparison with @code{eql})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4538 a given @var{item}. It returns the matching element, if any,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4539 otherwise @code{nil}. It ignores elements of @var{a-list} which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4540 are not cons cells. (This corresponds to the behavior of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4541 @code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4542 @code{assoc} ignores @code{nil}s but considers any other non-cons
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4543 elements of @var{a-list} to be an error.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4544 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4545
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4546 @defun rassoc* item a-list @t{&key :test :test-not :key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4547 This function searches for an element whose @code{cdr} matches
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4548 @var{item}. If @var{a-list} represents a mapping, this applies
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4549 the inverse of the mapping to @var{item}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4550 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4551
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4552 @defun rassoc item a-list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4553 This function searches like @code{rassoc*} with a @code{:test}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4554 argument of @code{equal}. It is analogous to Emacs Lisp's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4555 standard @code{assoc} function, which derives from the MacLisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4556 rather than the Common Lisp tradition.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4557 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4558
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4559 @findex assoc-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4560 @findex assoc-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4561 @findex rassoc-if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4562 @findex rassoc-if-not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4563 The @code{assoc-if}, @code{assoc-if-not}, @code{rassoc-if},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4564 and @code{rassoc-if-not} functions are defined similarly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4565
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4566 Two simple functions for constructing association lists are:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4567
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4568 @defun acons key value alist
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4569 This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4570 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4571
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4572 @defun pairlis keys values &optional alist
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4573 This is equivalent to @code{(nconc (mapcar* 'cons @var{keys} @var{values})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4574 @var{alist})}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4575 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4576
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4577 @node Hash Tables, Structures, Lists, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4578 @chapter Hash Tables
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4579
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4580 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4581 Hash tables are now implemented directly in the C code and documented in
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
4582 @ref{Hash Tables,,, lispref, XEmacs Lisp Reference Manual}.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4583
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4584 @ignore
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4585 A @dfn{hash table} is a data structure that maps ``keys'' onto
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4586 ``values.'' Keys and values can be arbitrary Lisp data objects.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4587 Hash tables have the property that the time to search for a given
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4588 key is roughly constant; simpler data structures like association
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4589 lists take time proportional to the number of entries in the list.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4590
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4591 @defun make-hash-table @t{&key :test :size}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4592 This function creates and returns a hash-table object whose
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4593 function for comparing elements is @code{:test} (@code{eql}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4594 by default), and which is allocated to fit about @code{:size}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4595 elements. The @code{:size} argument is purely advisory; the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4596 table will stretch automatically if you store more elements in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4597 it. If @code{:size} is omitted, a reasonable default is used.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4598
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4599 Common Lisp allows only @code{eq}, @code{eql}, @code{equal},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4600 and @code{equalp} as legal values for the @code{:test} argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4601 In this package, any reasonable predicate function will work,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4602 though if you use something else you should check the details of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4603 the hashing function described below to make sure it is suitable
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4604 for your predicate.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4605
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4606 Some versions of Emacs (like XEmacs) include a built-in hash
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4607 table type; in these versions, @code{make-hash-table} with a test of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4608 @code{eq}, @code{eql}, or @code{equal} will use these built-in hash
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4609 tables. In all other cases, it will return a hash-table object which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4610 takes the form of a list with an identifying ``tag'' symbol at the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4611 front. All of the hash table functions in this package can operate on
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4612 both types of hash table; normally you will never know which type is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4613 being used.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4614
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4615 This function accepts the additional Common Lisp keywords
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4616 @code{:rehash-size} and @code{:rehash-threshold}, but it ignores
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4617 their values.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4618 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4619
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4620 @defun gethash key table &optional default
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4621 This function looks up @var{key} in @var{table}. If @var{key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4622 exists in the table, in the sense that it matches any of the existing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4623 keys according to the table's test function, then the associated value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4624 is returned. Otherwise, @var{default} (or @code{nil}) is returned.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4625
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4626 To store new data in the hash table, use @code{setf} on a call to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4627 @code{gethash}. If @var{key} already exists in the table, the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4628 corresponding value is changed to the stored value. If @var{key}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4629 does not already exist, a new entry is added to the table and the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4630 table is reallocated to a larger size if necessary. The @var{default}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4631 argument is allowed but ignored in this case. The situation is
440
8de8e3f6228a Import from CVS: tag r21-2-28
cvs
parents: 428
diff changeset
4632 exactly analogous to that of @code{get}; @pxref{Property Lists}.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4633 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4634
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4635 @defun remhash key table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4636 This function removes the entry for @var{key} from @var{table}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4637 If an entry was removed, it returns @code{t}. If @var{key} does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4638 not appear in the table, it does nothing and returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4639 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4640
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4641 @defun clrhash table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4642 This function removes all the entries from @var{table}, leaving
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4643 an empty hash table.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4644 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4645
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4646 @defun maphash function table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4647 This function calls @var{function} for each entry in @var{table}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4648 It passes two arguments to @var{function}, the key and the value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4649 of the given entry. The return value of @var{function} is ignored;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4650 @var{maphash} itself returns @code{nil}. @xref{Loop Facility}, for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4651 an alternate way of iterating over hash tables.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4652 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4653
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4654 @defun hash-table-count table This function returns the number of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4655 entries in @var{table}. @strong{Warning:} The current implementation of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4656 XEmacs hash-tables does not decrement the stored @code{count}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4657 when @code{remhash} removes an entry. Therefore, the return value of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4658 this function is not dependable if you have used @code{remhash} on the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4659 table and the table's test is @code{eq}, @code{eql}, or @code{equal}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4660 A slower, but reliable, way to count the entries is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4661 @code{(loop for x being the hash-keys of @var{table} count t)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4662 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4663
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4664 @defun hash-table-p object This function returns @code{t} if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4665 @var{object} is a hash table, @code{nil} otherwise. It recognizes both
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4666 types of hash tables (both XEmacs built-in tables and tables implemented
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4667 with special lists.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4668 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4669
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4670 Sometimes when dealing with hash tables it is useful to know the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4671 exact ``hash function'' that is used. This package implements
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4672 hash tables using Emacs Lisp ``obarrays,'' which are the same
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4673 data structure that Emacs Lisp uses to keep track of symbols.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4674 Each hash table includes an embedded obarray. Key values given
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4675 to @code{gethash} are converted by various means into strings,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4676 which are then looked up in the obarray using @code{intern} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4677 @code{intern-soft}. The symbol, or ``bucket,'' corresponding to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4678 a given key string includes as its @code{symbol-value} an association
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4679 list of all key-value pairs which hash to that string. Depending
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4680 on the test function, it is possible for many entries to hash to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4681 the same bucket. For example, if the test is @code{eql}, then the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4682 symbol @code{foo} and two separately built strings @code{"foo"} will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4683 create three entries in the same bucket. Search time is linear
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4684 within buckets, so hash tables will be most effective if you arrange
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4685 not to store too many things that hash the same.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4686
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4687 The following algorithm is used to convert Lisp objects to hash
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4688 strings:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4689
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4690 @itemize @bullet
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4691 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4692 Strings are used directly as hash strings. (However, if the test
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4693 function is @code{equalp}, strings are @code{downcase}d first.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4694
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4695 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4696 Symbols are hashed according to their @code{symbol-name}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4697
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4698 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4699 Integers are hashed into one of 16 buckets depending on their value
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4700 modulo 16. Floating-point numbers are truncated to integers and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4701 hashed modulo 16.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4702
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4703 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4704 Cons cells are hashed according to their @code{car}s; nonempty vectors
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4705 are hashed according to their first element.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4706
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4707 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4708 All other types of objects hash into a single bucket named @code{"*"}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4709 @end itemize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4710
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4711 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4712 Thus, for example, searching among many buffer objects in a hash table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4713 will devolve to a (still fairly fast) linear-time search through a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4714 single bucket, whereas searching for different symbols will be very
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4715 fast since each symbol will, in general, hash into its own bucket.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4716
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4717 The size of the obarray in a hash table is automatically adjusted
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4718 as the number of elements increases.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4719
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4720 As a special case, @code{make-hash-table} with a @code{:size} argument
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4721 of 0 or 1 will create a hash-table object that uses a single association
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4722 list rather than an obarray of many lists. For very small tables this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4723 structure will be more efficient since lookup does not require
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4724 converting the key to a string or looking it up in an obarray.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4725 However, such tables are guaranteed to take time proportional to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4726 their size to do a search.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4727 @end ignore
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4728
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4729 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4730 @chapno=18
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4731 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4732
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4733 @node Structures, Assertions, Hash Tables, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4734 @chapter Structures
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4735
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4736 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4737 The Common Lisp @dfn{structure} mechanism provides a general way
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4738 to define data types similar to C's @code{struct} types. A
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4739 structure is a Lisp object containing some number of @dfn{slots},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4740 each of which can hold any Lisp data object. Functions are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4741 provided for accessing and setting the slots, creating or copying
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4742 structure objects, and recognizing objects of a particular structure
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4743 type.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4744
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4745 In true Common Lisp, each structure type is a new type distinct
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4746 from all existing Lisp types. Since the underlying Emacs Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4747 system provides no way to create new distinct types, this package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4748 implements structures as vectors (or lists upon request) with a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4749 special ``tag'' symbol to identify them.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4750
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4751 @defspec defstruct name slots@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4752 The @code{defstruct} form defines a new structure type called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4753 @var{name}, with the specified @var{slots}. (The @var{slots}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4754 may begin with a string which documents the structure type.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4755 In the simplest case, @var{name} and each of the @var{slots}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4756 are symbols. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4757
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4758 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4759 (defstruct person name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4760 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4761
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4762 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4763 defines a struct type called @code{person} which contains three
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4764 slots. Given a @code{person} object @var{p}, you can access those
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4765 slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4766 and @code{(person-sex @var{p})}. You can also change these slots by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4767 using @code{setf} on any of these place forms:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4768
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4769 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4770 (incf (person-age birthday-boy))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4771 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4772
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4773 You can create a new @code{person} by calling @code{make-person},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4774 which takes keyword arguments @code{:name}, @code{:age}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4775 @code{:sex} to specify the initial values of these slots in the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4776 new object. (Omitting any of these arguments leaves the corresponding
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4777 slot ``undefined,'' according to the Common Lisp standard; in Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4778 Lisp, such uninitialized slots are filled with @code{nil}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4779
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4780 Given a @code{person}, @code{(copy-person @var{p})} makes a new
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4781 object of the same type whose slots are @code{eq} to those of @var{p}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4782
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4783 Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4784 true if @var{x} looks like a @code{person}, false otherwise. (Again,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4785 in Common Lisp this predicate would be exact; in Emacs Lisp the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4786 best it can do is verify that @var{x} is a vector of the correct
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4787 length which starts with the correct tag symbol.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4788
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4789 Accessors like @code{person-name} normally check their arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4790 (effectively using @code{person-p}) and signal an error if the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4791 argument is the wrong type. This check is affected by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4792 @code{(optimize (safety @dots{}))} declarations. Safety level 1,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4793 the default, uses a somewhat optimized check that will detect all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4794 incorrect arguments, but may use an uninformative error message
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4795 (e.g., ``expected a vector'' instead of ``expected a @code{person}'').
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4796 Safety level 0 omits all checks except as provided by the underlying
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4797 @code{aref} call; safety levels 2 and 3 do rigorous checking that will
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4798 always print a descriptive error message for incorrect inputs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4799 @xref{Declarations}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4800
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4801 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4802 (setq dave (make-person :name "Dave" :sex 'male))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4803 @result{} [cl-struct-person "Dave" nil male]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4804 (setq other (copy-person dave))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4805 @result{} [cl-struct-person "Dave" nil male]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4806 (eq dave other)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4807 @result{} nil
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4808 (eq (person-name dave) (person-name other))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4809 @result{} t
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4810 (person-p dave)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4811 @result{} t
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4812 (person-p [1 2 3 4])
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4813 @result{} nil
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4814 (person-p "Bogus")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4815 @result{} nil
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4816 (person-p '[cl-struct-person counterfeit person object])
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4817 @result{} t
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4818 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4819
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4820 In general, @var{name} is either a name symbol or a list of a name
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4821 symbol followed by any number of @dfn{struct options}; each @var{slot}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4822 is either a slot symbol or a list of the form @samp{(@var{slot-name}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4823 @var{default-value} @var{slot-options}@dots{})}. The @var{default-value}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4824 is a Lisp form which is evaluated any time an instance of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4825 structure type is created without specifying that slot's value.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4826
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4827 Common Lisp defines several slot options, but the only one
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4828 implemented in this package is @code{:read-only}. A non-@code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4829 value for this option means the slot should not be @code{setf}-able;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4830 the slot's value is determined when the object is created and does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4831 not change afterward.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4832
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4833 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4834 (defstruct person
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4835 (name nil :read-only t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4836 age
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4837 (sex 'unknown))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4838 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4839
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4840 Any slot options other than @code{:read-only} are ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4841
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4842 For obscure historical reasons, structure options take a different
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4843 form than slot options. A structure option is either a keyword
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4844 symbol, or a list beginning with a keyword symbol possibly followed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4845 by arguments. (By contrast, slot options are key-value pairs not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4846 enclosed in lists.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4847
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4848 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4849 (defstruct (person (:constructor create-person)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4850 (:type list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4851 :named)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4852 name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4853 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4854
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4855 The following structure options are recognized.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4856
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4857 @table @code
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4858 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4859 @itemmax=0 in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4860 @advance@leftskip-.5@tableindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4861 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4862 @item :conc-name
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4863 The argument is a symbol whose print name is used as the prefix for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4864 the names of slot accessor functions. The default is the name of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4865 the struct type followed by a hyphen. The option @code{(:conc-name p-)}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4866 would change this prefix to @code{p-}. Specifying @code{nil} as an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4867 argument means no prefix, so that the slot names themselves are used
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4868 to name the accessor functions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4869
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4870 @item :constructor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4871 In the simple case, this option takes one argument which is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4872 alternate name to use for the constructor function. The default
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4873 is @code{make-@var{name}}, e.g., @code{make-person}. The above
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4874 example changes this to @code{create-person}. Specifying @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4875 as an argument means that no standard constructor should be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4876 generated at all.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4877
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4878 In the full form of this option, the constructor name is followed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4879 by an arbitrary argument list. @xref{Program Structure}, for a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4880 description of the format of Common Lisp argument lists. All
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4881 options, such as @code{&rest} and @code{&key}, are supported.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4882 The argument names should match the slot names; each slot is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4883 initialized from the corresponding argument. Slots whose names
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4884 do not appear in the argument list are initialized based on the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4885 @var{default-value} in their slot descriptor. Also, @code{&optional}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4886 and @code{&key} arguments which don't specify defaults take their
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4887 defaults from the slot descriptor. It is legal to include arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4888 which don't correspond to slot names; these are useful if they are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4889 referred to in the defaults for optional, keyword, or @code{&aux}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4890 arguments which @emph{do} correspond to slots.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4891
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4892 You can specify any number of full-format @code{:constructor}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4893 options on a structure. The default constructor is still generated
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4894 as well unless you disable it with a simple-format @code{:constructor}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4895 option.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4896
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4897 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4898 (defstruct
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4899 (person
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4900 (:constructor nil) ; no default constructor
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4901 (:constructor new-person (name sex &optional (age 0)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4902 (:constructor new-hound (&key (name "Rover")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4903 (dog-years 0)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4904 &aux (age (* 7 dog-years))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4905 (sex 'canine))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4906 name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4907 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4908
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4909 The first constructor here takes its arguments positionally rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4910 than by keyword. (In official Common Lisp terminology, constructors
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4911 that work By Order of Arguments instead of by keyword are called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4912 ``BOA constructors.'' No, I'm not making this up.) For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4913 @code{(new-person "Jane" 'female)} generates a person whose slots
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4914 are @code{"Jane"}, 0, and @code{female}, respectively.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4915
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4916 The second constructor takes two keyword arguments, @code{:name},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4917 which initializes the @code{name} slot and defaults to @code{"Rover"},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4918 and @code{:dog-years}, which does not itself correspond to a slot
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4919 but which is used to initialize the @code{age} slot. The @code{sex}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4920 slot is forced to the symbol @code{canine} with no syntax for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4921 overriding it.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4922
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4923 @item :copier
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4924 The argument is an alternate name for the copier function for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4925 this type. The default is @code{copy-@var{name}}. @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4926 means not to generate a copier function. (In this implementation,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4927 all copier functions are simply synonyms for @code{copy-sequence}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4928
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4929 @item :predicate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4930 The argument is an alternate name for the predicate which recognizes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4931 objects of this type. The default is @code{@var{name}-p}. @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4932 means not to generate a predicate function. (If the @code{:type}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4933 option is used without the @code{:named} option, no predicate is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4934 ever generated.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4935
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4936 In true Common Lisp, @code{typep} is always able to recognize a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4937 structure object even if @code{:predicate} was used. In this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4938 package, @code{typep} simply looks for a function called
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4939 @code{@var{typename}-p}, so it will work for structure types
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4940 only if they used the default predicate name.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4941
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4942 @item :include
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4943 This option implements a very limited form of C++-style inheritance.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4944 The argument is the name of another structure type previously
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4945 created with @code{defstruct}. The effect is to cause the new
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4946 structure type to inherit all of the included structure's slots
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4947 (plus, of course, any new slots described by this struct's slot
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4948 descriptors). The new structure is considered a ``specialization''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4949 of the included one. In fact, the predicate and slot accessors
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4950 for the included type will also accept objects of the new type.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4951
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4952 If there are extra arguments to the @code{:include} option after
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4953 the included-structure name, these options are treated as replacement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4954 slot descriptors for slots in the included structure, possibly with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4955 modified default values. Borrowing an example from Steele:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4956
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4957 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4958 (defstruct person name (age 0) sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4959 @result{} person
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4960 (defstruct (astronaut (:include person (age 45)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4961 helmet-size
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4962 (favorite-beverage 'tang))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4963 @result{} astronaut
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4964
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4965 (setq joe (make-person :name "Joe"))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4966 @result{} [cl-struct-person "Joe" 0 nil]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4967 (setq buzz (make-astronaut :name "Buzz"))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4968 @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4969
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4970 (list (person-p joe) (person-p buzz))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4971 @result{} (t t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4972 (list (astronaut-p joe) (astronaut-p buzz))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4973 @result{} (nil t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4974
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4975 (person-name buzz)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4976 @result{} "Buzz"
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4977 (astronaut-name joe)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4978 @result{} error: "astronaut-name accessing a non-astronaut"
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4979 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4980
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4981 Thus, if @code{astronaut} is a specialization of @code{person},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4982 then every @code{astronaut} is also a @code{person} (but not the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4983 other way around). Every @code{astronaut} includes all the slots
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4984 of a @code{person}, plus extra slots that are specific to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4985 astronauts. Operations that work on people (like @code{person-name})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4986 work on astronauts just like other people.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4987
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4988 @item :print-function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4989 In full Common Lisp, this option allows you to specify a function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4990 which is called to print an instance of the structure type. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4991 Emacs Lisp system offers no hooks into the Lisp printer which would
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4992 allow for such a feature, so this package simply ignores
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4993 @code{:print-function}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4994
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4995 @item :type
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4996 The argument should be one of the symbols @code{vector} or @code{list}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4997 This tells which underlying Lisp data type should be used to implement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4998 the new structure type. Vectors are used by default, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
4999 @code{(:type list)} will cause structure objects to be stored as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5000 lists instead.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5001
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5002 The vector representation for structure objects has the advantage
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5003 that all structure slots can be accessed quickly, although creating
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5004 vectors is a bit slower in Emacs Lisp. Lists are easier to create,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5005 but take a relatively long time accessing the later slots.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5006
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5007 @item :named
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5008 This option, which takes no arguments, causes a characteristic ``tag''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5009 symbol to be stored at the front of the structure object. Using
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5010 @code{:type} without also using @code{:named} will result in a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5011 structure type stored as plain vectors or lists with no identifying
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5012 features.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5013
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5014 The default, if you don't specify @code{:type} explicitly, is to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5015 use named vectors. Therefore, @code{:named} is only useful in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5016 conjunction with @code{:type}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5017
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5018 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5019 (defstruct (person1) name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5020 (defstruct (person2 (:type list) :named) name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5021 (defstruct (person3 (:type list)) name age sex)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5022
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5023 (setq p1 (make-person1))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5024 @result{} [cl-struct-person1 nil nil nil]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5025 (setq p2 (make-person2))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5026 @result{} (person2 nil nil nil)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5027 (setq p3 (make-person3))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5028 @result{} (nil nil nil)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5029
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5030 (person1-p p1)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5031 @result{} t
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5032 (person2-p p2)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5033 @result{} t
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5034 (person3-p p3)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5035 @result{} error: function person3-p undefined
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5036 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5037
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5038 Since unnamed structures don't have tags, @code{defstruct} is not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5039 able to make a useful predicate for recognizing them. Also,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5040 accessors like @code{person3-name} will be generated but they
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5041 will not be able to do any type checking. The @code{person3-name}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5042 function, for example, will simply be a synonym for @code{car} in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5043 this case. By contrast, @code{person2-name} is able to verify
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5044 that its argument is indeed a @code{person2} object before
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5045 proceeding.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5046
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5047 @item :initial-offset
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5048 The argument must be a nonnegative integer. It specifies a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5049 number of slots to be left ``empty'' at the front of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5050 structure. If the structure is named, the tag appears at the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5051 specified position in the list or vector; otherwise, the first
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5052 slot appears at that position. Earlier positions are filled
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5053 with @code{nil} by the constructors and ignored otherwise. If
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5054 the type @code{:include}s another type, then @code{:initial-offset}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5055 specifies a number of slots to be skipped between the last slot
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5056 of the included type and the first new slot.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5057 @end table
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5058 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5059
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5060 Except as noted, the @code{defstruct} facility of this package is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5061 entirely compatible with that of Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5062
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5063 @iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5064 @chapno=23
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5065 @end iftex
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5066
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5067 @node Assertions, Efficiency Concerns, Structures, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5068 @chapter Assertions and Errors
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5069
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5070 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5071 This section describes two macros that test @dfn{assertions}, i.e.,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5072 conditions which must be true if the program is operating correctly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5073 Assertions never add to the behavior of a Lisp program; they simply
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5074 make ``sanity checks'' to make sure everything is as it should be.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5075
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5076 If the optimization property @code{speed} has been set to 3, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5077 @code{safety} is less than 3, then the byte-compiler will optimize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5078 away the following assertions. Because assertions might be optimized
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5079 away, it is a bad idea for them to include side-effects.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5080
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5081 @defspec assert test-form [show-args string args@dots{}]
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5082 This form verifies that @var{test-form} is true (i.e., evaluates to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5083 a non-@code{nil} value). If so, it returns @code{nil}. If the test
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5084 is not satisfied, @code{assert} signals an error.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5085
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5086 A default error message will be supplied which includes @var{test-form}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5087 You can specify a different error message by including a @var{string}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5088 argument plus optional extra arguments. Those arguments are simply
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5089 passed to @code{error} to signal the error.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5090
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5091 If the optional second argument @var{show-args} is @code{t} instead
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5092 of @code{nil}, then the error message (with or without @var{string})
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5093 will also include all non-constant arguments of the top-level
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5094 @var{form}. For example:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5095
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5096 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5097 (assert (> x 10) t "x is too small: %d")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5098 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5099
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5100 This usage of @var{show-args} is a change to Common Lisp. In
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5101 true Common Lisp, the second argument gives a list of @var{places}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5102 which can be @code{setf}'d by the user before continuing from the
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5103 error.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5104 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5105
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5106 @defspec check-type place type &optional string
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5107 This form verifies that @var{place} evaluates to a value of type
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5108 @var{type}. If so, it returns @code{nil}. If not, @code{check-type}
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5109 signals a continuable @code{wrong-type-argument} error. The default
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5110 error message lists the erroneous value along with @var{type} and
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5111 @var{place} themselves. If @var{string} is specified, it is included in
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5112 the error message in place of @var{type}. For example:
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5113
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5114 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5115 (check-type x (integer 1 *) "a positive integer")
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5116 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5117
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5118 @xref{Type Predicates}, for a description of the type specifiers
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5119 that may be used for @var{type}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5120
446
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5121 Note that as in Common Lisp, the first argument to @code{check-type}
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5122 should be a @var{place} suitable for use by @code{setf}, because
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5123 @code{check-type} signals a continuable error that allows the user to
1ccc32a20af4 Import from CVS: tag r21-2-38
cvs
parents: 442
diff changeset
5124 modify @var{place}, most simply by returning a value from the debugger.
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5125 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5126
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5127 The following error-related macro is also defined:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5128
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5129 @defspec ignore-errors forms@dots{}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5130 This executes @var{forms} exactly like a @code{progn}, except that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5131 errors are ignored during the @var{forms}. More precisely, if
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5132 an error is signalled then @code{ignore-errors} immediately
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5133 aborts execution of the @var{forms} and returns @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5134 If the @var{forms} complete successfully, @code{ignore-errors}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5135 returns the result of the last @var{form}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5136 @end defspec
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5137
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5138 @node Efficiency Concerns, Common Lisp Compatibility, Assertions, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5139 @appendix Efficiency Concerns
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5140
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5141 @appendixsec Macros
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5142
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5143 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5144 Many of the advanced features of this package, such as @code{defun*},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5145 @code{loop}, and @code{setf}, are implemented as Lisp macros. In
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5146 byte-compiled code, these complex notations will be expanded into
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5147 equivalent Lisp code which is simple and efficient. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5148 the forms
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5149
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5150 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5151 (incf i n)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5152 (push x (car p))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5153 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5154
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5155 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5156 are expanded at compile-time to the Lisp forms
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5157
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5158 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5159 (setq i (+ i n))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5160 (setcar p (cons x (car p)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5161 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5162
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5163 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5164 which are the most efficient ways of doing these respective operations
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5165 in Lisp. Thus, there is no performance penalty for using the more
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5166 readable @code{incf} and @code{push} forms in your compiled code.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5167
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5168 @emph{Interpreted} code, on the other hand, must expand these macros
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5169 every time they are executed. For this reason it is strongly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5170 recommended that code making heavy use of macros be compiled.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5171 (The features labelled ``Special Form'' instead of ``Function'' in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5172 this manual are macros.) A loop using @code{incf} a hundred times
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5173 will execute considerably faster if compiled, and will also
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5174 garbage-collect less because the macro expansion will not have
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5175 to be generated, used, and thrown away a hundred times.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5176
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5177 You can find out how a macro expands by using the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5178 @code{cl-prettyexpand} function.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5179
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5180 @defun cl-prettyexpand form &optional full
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5181 This function takes a single Lisp form as an argument and inserts
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5182 a nicely formatted copy of it in the current buffer (which must be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5183 in Lisp mode so that indentation works properly). It also expands
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5184 all Lisp macros which appear in the form. The easiest way to use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5185 this function is to go to the @code{*scratch*} buffer and type, say,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5186
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5187 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5188 (cl-prettyexpand '(loop for x below 10 collect x))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5189 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5190
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5191 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5192 and type @kbd{C-x C-e} immediately after the closing parenthesis;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5193 the expansion
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5194
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5195 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5196 (block nil
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5197 (let* ((x 0)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5198 (G1004 nil))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5199 (while (< x 10)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5200 (setq G1004 (cons x G1004))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5201 (setq x (+ x 1)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5202 (nreverse G1004)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5203 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5204
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5205 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5206 will be inserted into the buffer. (The @code{block} macro is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5207 expanded differently in the interpreter and compiler, so
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5208 @code{cl-prettyexpand} just leaves it alone. The temporary
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5209 variable @code{G1004} was created by @code{gensym}.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5210
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5211 If the optional argument @var{full} is true, then @emph{all}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5212 macros are expanded, including @code{block}, @code{eval-when},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5213 and compiler macros. Expansion is done as if @var{form} were
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5214 a top-level form in a file being compiled. For example,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5215
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5216 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5217 (cl-prettyexpand '(pushnew 'x list))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5218 @print{} (setq list (adjoin 'x list))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5219 (cl-prettyexpand '(pushnew 'x list) t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5220 @print{} (setq list (if (memq 'x list) list (cons 'x list)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5221 (cl-prettyexpand '(caddr (member* 'a list)) t)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5222 @print{} (car (cdr (cdr (memq 'a list))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5223 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5224
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5225 Note that @code{adjoin}, @code{caddr}, and @code{member*} all
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5226 have built-in compiler macros to optimize them in common cases.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5227 @end defun
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5228
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5229 @ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5230 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5231
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5232 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5233 @end ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5234 @appendixsec Error Checking
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5235
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5236 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5237 Common Lisp compliance has in general not been sacrificed for the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5238 sake of efficiency. A few exceptions have been made for cases
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5239 where substantial gains were possible at the expense of marginal
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5240 incompatibility. One example is the use of @code{memq} (which is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5241 treated very efficiently by the byte-compiler) to scan for keyword
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5242 arguments; this can become confused in rare cases when keyword
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5243 symbols are used as both keywords and data values at once. This
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5244 is extremely unlikely to occur in practical code, and the use of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5245 @code{memq} allows functions with keyword arguments to be nearly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5246 as fast as functions that use @code{&optional} arguments.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5247
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5248 The Common Lisp standard (as embodied in Steele's book) uses the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5249 phrase ``it is an error if'' to indicate a situation which is not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5250 supposed to arise in complying programs; implementations are strongly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5251 encouraged but not required to signal an error in these situations.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5252 This package sometimes omits such error checking in the interest of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5253 compactness and efficiency. For example, @code{do} variable
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5254 specifiers are supposed to be lists of one, two, or three forms;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5255 extra forms are ignored by this package rather than signalling a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5256 syntax error. The @code{endp} function is simply a synonym for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5257 @code{null} in this package. Functions taking keyword arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5258 will accept an odd number of arguments, treating the trailing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5259 keyword as if it were followed by the value @code{nil}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5260
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5261 Argument lists (as processed by @code{defun*} and friends)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5262 @emph{are} checked rigorously except for the minor point just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5263 mentioned; in particular, keyword arguments are checked for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5264 validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5265 are fully implemented. Keyword validity checking is slightly
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5266 time consuming (though not too bad in byte-compiled code);
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5267 you can use @code{&allow-other-keys} to omit this check. Functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5268 defined in this package such as @code{find} and @code{member*}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5269 do check their keyword arguments for validity.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5270
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5271 @ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5272 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5273
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5274 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5275 @end ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5276 @appendixsec Optimizing Compiler
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5277
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5278 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5279 The byte-compiler that comes with Emacs 18 normally fails to expand
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5280 macros that appear in top-level positions in the file (i.e., outside
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5281 of @code{defun}s or other enclosing forms). This would have
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5282 disastrous consequences to programs that used such top-level macros
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5283 as @code{defun*}, @code{eval-when}, and @code{defstruct}. To
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5284 work around this problem, the @dfn{CL} package patches the Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5285 18 compiler to expand top-level macros. This patch will apply to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5286 your own macros, too, if they are used in a top-level context.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5287 The patch will not harm versions of the Emacs 18 compiler which
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5288 have already had a similar patch applied, nor will it affect the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5289 optimizing Emacs 19 byte-compiler written by Jamie Zawinski and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5290 Hallvard Furuseth. The patch is applied to the byte compiler's
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5291 code in Emacs' memory, @emph{not} to the @file{bytecomp.elc} file
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5292 stored on disk.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5293
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5294 The Emacs 19 compiler (for Emacs 18) is available from various
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5295 Emacs Lisp archive sites such as @code{archive.cis.ohio-state.edu}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5296 Its use is highly recommended; many of the Common Lisp macros emit
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5297 code which can be improved by optimization. In particular,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5298 @code{block}s (whether explicit or implicit in constructs like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5299 @code{defun*} and @code{loop}) carry a fair run-time penalty; the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5300 optimizing compiler removes @code{block}s which are not actually
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5301 referenced by @code{return} or @code{return-from} inside the block.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5302
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5303 @node Common Lisp Compatibility, Old CL Compatibility, Efficiency Concerns, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5304 @appendix Common Lisp Compatibility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5305
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5306 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5307 Following is a list of all known incompatibilities between this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5308 package and Common Lisp as documented in Steele (2nd edition).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5309
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5310 Certain function names, such as @code{member}, @code{assoc}, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5311 @code{floor}, were already taken by (incompatible) Emacs Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5312 functions; this package appends @samp{*} to the names of its
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5313 Common Lisp versions of these functions.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5314
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5315 The word @code{defun*} is required instead of @code{defun} in order
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5316 to use extended Common Lisp argument lists in a function. Likewise,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5317 @code{defmacro*} and @code{function*} are versions of those forms
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5318 which understand full-featured argument lists. The @code{&whole}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5319 keyword does not work in @code{defmacro} argument lists (except
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5320 inside recursive argument lists).
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5321
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5322 In order to allow an efficient implementation, keyword arguments use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5323 a slightly cheesy parser which may be confused if a keyword symbol
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5324 is passed as the @emph{value} of another keyword argument.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5325 (Specifically, @code{(memq :@var{keyword} @var{rest-of-arguments})}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5326 is used to scan for @code{:@var{keyword}} among the supplied
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5327 keyword arguments.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5328
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5329 The @code{eql} and @code{equal} predicates do not distinguish
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5330 between IEEE floating-point plus and minus zero. The @code{equalp}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5331 predicate has several differences with Common Lisp; @pxref{Predicates}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5332
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5333 The @code{setf} mechanism is entirely compatible, except that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5334 setf-methods return a list of five values rather than five
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5335 values directly. Also, the new ``@code{setf} function'' concept
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5336 (typified by @code{(defun (setf foo) @dots{})}) is not implemented.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5337
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5338 The @code{do-all-symbols} form is the same as @code{do-symbols}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5339 with no @var{obarray} argument. In Common Lisp, this form would
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5340 iterate over all symbols in all packages. Since Emacs obarrays
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5341 are not a first-class package mechanism, there is no way for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5342 @code{do-all-symbols} to locate any but the default obarray.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5343
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5344 The @code{loop} macro is complete except that @code{loop-finish}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5345 and type specifiers are unimplemented.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5346
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5347 Many Common Lisp declarations are ignored, and others match
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5348 the Common Lisp standard in concept but not in detail. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5349 example, local @code{special} declarations, which are purely
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5350 advisory in Emacs Lisp, do not rigorously obey the scoping rules
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5351 set down in Steele's book.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5352
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5353 The variable @code{*gensym-counter*} starts out with a pseudo-random
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5354 value rather than with zero. This is to cope with the fact that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5355 generated symbols become interned when they are written to and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5356 loaded back from a file.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5357
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5358 The @code{defstruct} facility is compatible, except that structures
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5359 are of type @code{:type vector :named} by default rather than some
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5360 special, distinct type. Also, the @code{:type} slot option is ignored.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5361
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5362 The second argument of @code{check-type} is treated differently.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5363
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5364 @node Old CL Compatibility, Porting Common Lisp, Common Lisp Compatibility, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5365 @appendix Old CL Compatibility
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5366
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5367 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5368 Following is a list of all known incompatibilities between this package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5369 and the older Quiroz @file{cl.el} package.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5370
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5371 The @code{defkeyword} form and @code{keywordp} function are not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5372 implemented in this package.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5373
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5374 The @code{member}, @code{floor}, @code{ceiling}, @code{truncate},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5375 @code{round}, @code{mod}, and @code{rem} functions are suffixed
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5376 by @samp{*} in this package to avoid collision with existing
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5377 functions in Emacs 18 or Emacs 19. The older package simply
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5378 redefined these functions, overwriting the built-in meanings and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5379 causing serious portability problems with Emacs 19. (Some more
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5380 recent versions of the Quiroz package changed the names to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5381 @code{cl-member}, etc.; this package defines the latter names as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5382 aliases for @code{member*}, etc.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5383
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5384 Certain functions in the old package which were buggy or inconsistent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5385 with the Common Lisp standard are incompatible with the conforming
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5386 versions in this package. For example, @code{eql} and @code{member}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5387 were synonyms for @code{eq} and @code{memq} in that package, @code{setf}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5388 failed to preserve correct order of evaluation of its arguments, etc.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5389
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5390 Finally, unlike the older package, this package is careful to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5391 prefix all of its internal names with @code{cl-}. Except for a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5392 few functions which are explicitly defined as additional features
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5393 (such as @code{floatp-safe} and @code{letf}), this package does not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5394 export any non-@samp{cl-} symbols which are not also part of Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5395 Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5396
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5397 @ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5398 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5399
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5400 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5401 @end ifinfo
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5402 @appendixsec The @code{cl-compat} package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5403
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5404 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5405 The @dfn{CL} package includes emulations of some features of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5406 old @file{cl.el}, in the form of a compatibility package
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5407 @code{cl-compat}. To use it, put @code{(require 'cl-compat)} in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5408 your program.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5409
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5410 The old package defined a number of internal routines without
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5411 @code{cl-} prefixes or other annotations. Call to these routines
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5412 may have crept into existing Lisp code. @code{cl-compat}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5413 provides emulations of the following internal routines:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5414 @code{pair-with-newsyms}, @code{zip-lists}, @code{unzip-lists},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5415 @code{reassemble-arglists}, @code{duplicate-symbols-p},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5416 @code{safe-idiv}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5417
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5418 Some @code{setf} forms translated into calls to internal
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5419 functions that user code might call directly. The functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5420 @code{setnth}, @code{setnthcdr}, and @code{setelt} fall in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5421 this category; they are defined by @code{cl-compat}, but the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5422 best fix is to change to use @code{setf} properly.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5423
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5424 The @code{cl-compat} file defines the keyword functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5425 @code{keywordp}, @code{keyword-of}, and @code{defkeyword},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5426 which are not defined by the new @dfn{CL} package because the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5427 use of keywords as data is discouraged.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5429 The @code{build-klist} mechanism for parsing keyword arguments
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5430 is emulated by @code{cl-compat}; the @code{with-keyword-args}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5431 macro is not, however, and in any case it's best to change to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5432 use the more natural keyword argument processing offered by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5433 @code{defun*}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5434
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5435 The functions @code{cl-floor}, @code{cl-ceiling}, @code{cl-truncate},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5436 and @code{cl-round} are defined by @code{cl-compat} to use the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5437 old-style multiple-value mechanism, just as they did in the old
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5438 package. The newer @code{floor*} and friends return their two
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5439 results in a list rather than as multiple values. Note that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5440 older versions of the old package used the unadorned names
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5441 @code{floor}, @code{ceiling}, etc.; @code{cl-compat} cannot use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5442 these names because they conflict with Emacs 19 built-ins.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5443
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5444 @node Porting Common Lisp, Function Index, Old CL Compatibility, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5445 @appendix Porting Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5446
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5447 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5448 This package is meant to be used as an extension to Emacs Lisp,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5449 not as an Emacs implementation of true Common Lisp. Some of the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5450 remaining differences between Emacs Lisp and Common Lisp make it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5451 difficult to port large Common Lisp applications to Emacs. For
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5452 one, some of the features in this package are not fully compliant
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5453 with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5454 are also quite a few features that this package does not provide
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5455 at all. Here are some major omissions that you will want watch out
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5456 for when bringing Common Lisp code into Emacs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5457
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5458 @itemize @bullet
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5459 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5460 Case-insensitivity. Symbols in Common Lisp are case-insensitive
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5461 by default. Some programs refer to a function or variable as
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5462 @code{foo} in one place and @code{Foo} or @code{FOO} in another.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5463 Emacs Lisp will treat these as three distinct symbols.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5464
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5465 Some Common Lisp code is written in all upper-case. While Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5466 is happy to let the program's own functions and variables use
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5467 this convention, calls to Lisp builtins like @code{if} and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5468 @code{defun} will have to be changed to lower-case.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5469
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5470 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5471 Lexical scoping. In Common Lisp, function arguments and @code{let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5472 bindings apply only to references physically within their bodies
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5473 (or within macro expansions in their bodies). Emacs Lisp, by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5474 contrast, uses @dfn{dynamic scoping} wherein a binding to a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5475 variable is visible even inside functions called from the body.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5476
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5477 Variables in Common Lisp can be made dynamically scoped by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5478 declaring them @code{special} or using @code{defvar}. In Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5479 Lisp it is as if all variables were declared @code{special}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5480
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5481 Often you can use code that was written for lexical scoping
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5482 even in a dynamically scoped Lisp, but not always. Here is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5483 an example of a Common Lisp code fragment that would fail in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5484 Emacs Lisp:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5485
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5486 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5487 (defun map-odd-elements (func list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5488 (loop for x in list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5489 for flag = t then (not flag)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5490 collect (if flag x (funcall func x))))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5491
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5492 (defun add-odd-elements (list x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5493 (map-odd-elements (function (lambda (a) (+ a x))) list))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5494 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5495
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5496 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5497 In Common Lisp, the two functions' usages of @code{x} are completely
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5498 independent. In Emacs Lisp, the binding to @code{x} made by
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5499 @code{add-odd-elements} will have been hidden by the binding
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5500 in @code{map-odd-elements} by the time the @code{(+ a x)} function
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5501 is called.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5502
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5503 (This package avoids such problems in its own mapping functions
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5504 by using names like @code{cl-x} instead of @code{x} internally;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5505 as long as you don't use the @code{cl-} prefix for your own
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5506 variables no collision can occur.)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5507
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5508 @xref{Lexical Bindings}, for a description of the @code{lexical-let}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5509 form which establishes a Common Lisp-style lexical binding, and some
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5510 examples of how it differs from Emacs' regular @code{let}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5511
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5512 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5513 Common Lisp allows the shorthand @code{#'x} to stand for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5514 @code{(function x)}, just as @code{'x} stands for @code{(quote x)}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5515 In Common Lisp, one traditionally uses @code{#'} notation when
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5516 referring to the name of a function. In Emacs Lisp, it works
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5517 just as well to use a regular quote:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5518
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5519 @example
442
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
5520 (loop for x in y by #'cddr collect (mapcar #'plusp x)) ; Common Lisp
abe6d1db359e Import from CVS: tag r21-2-36
cvs
parents: 440
diff changeset
5521 (loop for x in y by 'cddr collect (mapcar 'plusp x)) ; Emacs Lisp
428
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5522 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5523
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5524 When @code{#'} introduces a @code{lambda} form, it is best to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5525 write out @code{(function ...)} longhand in Emacs Lisp. You can
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5526 use a regular quote, but then the byte-compiler won't know that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5527 the @code{lambda} expression is code that can be compiled.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5528
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5529 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5530 (mapcar #'(lambda (x) (* x 2)) list) ; Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5531 (mapcar (function (lambda (x) (* x 2))) list) ; Emacs Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5532 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5533
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5534 XEmacs supports @code{#'} notation starting with version 19.8.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5535
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5536 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5537 Reader macros. Common Lisp includes a second type of macro that
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5538 works at the level of individual characters. For example, Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5539 Lisp implements the quote notation by a reader macro called @code{'},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5540 whereas Emacs Lisp's parser just treats quote as a special case.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5541 Some Lisp packages use reader macros to create special syntaxes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5542 for themselves, which the Emacs parser is incapable of reading.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5543
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5544 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5545 Other syntactic features. Common Lisp provides a number of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5546 notations beginning with @code{#} that the Emacs Lisp parser
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5547 won't understand. For example, @samp{#| ... |#} is an
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5548 alternate comment notation, and @samp{#+lucid (foo)} tells
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5549 the parser to ignore the @code{(foo)} except in Lucid Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5550 Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5551
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5552 The number prefixes `#b', `#o', and `#x', however, are supported
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5553 by the Emacs Lisp parser to represent numbers in binary, octal,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5554 and hexadecimal notation (or radix), just like in Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5555
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5556 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5557 Packages. In Common Lisp, symbols are divided into @dfn{packages}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5558 Symbols that are Lisp built-ins are typically stored in one package;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5559 symbols that are vendor extensions are put in another, and each
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5560 application program would have a package for its own symbols.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5561 Certain symbols are ``exported'' by a package and others are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5562 internal; certain packages ``use'' or import the exported symbols
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5563 of other packages. To access symbols that would not normally be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5564 visible due to this importing and exporting, Common Lisp provides
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5565 a syntax like @code{package:symbol} or @code{package::symbol}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5566
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5567 Emacs Lisp has a single namespace for all interned symbols, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5568 then uses a naming convention of putting a prefix like @code{cl-}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5569 in front of the name. Some Emacs packages adopt the Common Lisp-like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5570 convention of using @code{cl:} or @code{cl::} as the prefix.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5571 However, the Emacs parser does not understand colons and just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5572 treats them as part of the symbol name. Thus, while @code{mapcar}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5573 and @code{lisp:mapcar} may refer to the same symbol in Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5574 Lisp, they are totally distinct in Emacs Lisp. Common Lisp
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5575 programs which refer to a symbol by the full name sometimes
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5576 and the short name other times will not port cleanly to Emacs.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5577
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5578 Emacs Lisp does have a concept of ``obarrays,'' which are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5579 package-like collections of symbols, but this feature is not
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5580 strong enough to be used as a true package mechanism.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5581
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5582 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5583 Keywords. The notation @code{:test-not} in Common Lisp really
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5584 is a shorthand for @code{keyword:test-not}; keywords are just
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5585 symbols in a built-in @code{keyword} package with the special
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5586 property that all its symbols are automatically self-evaluating.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5587 Common Lisp programs often use keywords liberally to avoid
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5588 having to use quotes.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5589
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5590 In Emacs Lisp a keyword is just a symbol whose name begins with
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5591 a colon; since the Emacs parser does not treat them specially,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5592 they have to be explicitly made self-evaluating by a statement
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5593 like @code{(setq :test-not ':test-not)}. This package arranges
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5594 to execute such a statement whenever @code{defun*} or some
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5595 other form sees a keyword being used as an argument. Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5596 Lisp code that assumes that a symbol @code{:mumble} will be
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5597 self-evaluating even though it was never introduced by a
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5598 @code{defun*} will have to be fixed.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5599
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5600 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5601 The @code{format} function is quite different between Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5602 Lisp and Emacs Lisp. It takes an additional ``destination''
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5603 argument before the format string. A destination of @code{nil}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5604 means to format to a string as in Emacs Lisp; a destination
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5605 of @code{t} means to write to the terminal (similar to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5606 @code{message} in Emacs). Also, format control strings are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5607 utterly different; @code{~} is used instead of @code{%} to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5608 introduce format codes, and the set of available codes is
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5609 much richer. There are no notations like @code{\n} for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5610 string literals; instead, @code{format} is used with the
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5611 ``newline'' format code, @code{~%}. More advanced formatting
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5612 codes provide such features as paragraph filling, case
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5613 conversion, and even loops and conditionals.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5614
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5615 While it would have been possible to implement most of Common
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5616 Lisp @code{format} in this package (under the name @code{format*},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5617 of course), it was not deemed worthwhile. It would have required
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5618 a huge amount of code to implement even a decent subset of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5619 @code{format*}, yet the functionality it would provide over
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5620 Emacs Lisp's @code{format} would rarely be useful.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5621
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5622 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5623 Vector constants use square brackets in Emacs Lisp, but
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5624 @code{#(a b c)} notation in Common Lisp. To further complicate
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5625 matters, Emacs 19 introduces its own @code{#(} notation for
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5626 something entirely different---strings with properties.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5627
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5628 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5629 Characters are distinct from integers in Common Lisp. The
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5630 notation for character constants is also different: @code{#\A}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5631 instead of @code{?A}. Also, @code{string=} and @code{string-equal}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5632 are synonyms in Emacs Lisp whereas the latter is case-insensitive
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5633 in Common Lisp.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5634
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5635 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5636 Data types. Some Common Lisp data types do not exist in Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5637 Lisp. Rational numbers and complex numbers are not present,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5638 nor are large integers (all integers are ``fixnums''). All
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5639 arrays are one-dimensional. There are no readtables or pathnames;
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5640 streams are a set of existing data types rather than a new data
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5641 type of their own. Hash tables, random-states, structures, and
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5642 packages (obarrays) are built from Lisp vectors or lists rather
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5643 than being distinct types.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5644
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5645 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5646 The Common Lisp Object System (CLOS) is not implemented,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5647 nor is the Common Lisp Condition System.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5648
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5649 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5650 Common Lisp features that are completely redundant with Emacs
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5651 Lisp features of a different name generally have not been
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5652 implemented. For example, Common Lisp writes @code{defconstant}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5653 where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5654 takes its arguments in different ways in the two Lisps but does
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5655 exactly the same thing, so this package has not bothered to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5656 implement a Common Lisp-style @code{make-list}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5657
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5658 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5659 A few more notable Common Lisp features not included in this
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5660 package: @code{compiler-let}, @code{tagbody}, @code{prog},
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5661 @code{ldb/dpb}, @code{parse-integer}, @code{cerror}.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5662
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5663 @item
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5664 Recursion. While recursion works in Emacs Lisp just like it
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5665 does in Common Lisp, various details of the Emacs Lisp system
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5666 and compiler make recursion much less efficient than it is in
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5667 most Lisps. Some schools of thought prefer to use recursion
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5668 in Lisp over other techniques; they would sum a list of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5669 numbers using something like
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5670
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5671 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5672 (defun sum-list (list)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5673 (if list
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5674 (+ (car list) (sum-list (cdr list)))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5675 0))
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5676 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5677
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5678 @noindent
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5679 where a more iteratively-minded programmer might write one of
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5680 these forms:
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5681
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5682 @example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5683 (let ((total 0)) (dolist (x my-list) (incf total x)) total)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5684 (loop for x in my-list sum x)
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5685 @end example
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5686
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5687 While this would be mainly a stylistic choice in most Common Lisps,
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5688 in Emacs Lisp you should be aware that the iterative forms are
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5689 much faster than recursion. Also, Lisp programmers will want to
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5690 note that the current Emacs Lisp compiler does not optimize tail
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5691 recursion.
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5692 @end itemize
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5693
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5694 @node Function Index, Variable Index, Porting Common Lisp, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5695 @unnumbered Function Index
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5696
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5697 @printindex fn
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5698
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5699 @node Variable Index, , Function Index, Top
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5700 @unnumbered Variable Index
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5701
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5702 @printindex vr
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5703
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5704 @contents
3ecd8885ac67 Import from CVS: tag r21-2-22
cvs
parents:
diff changeset
5705 @bye