annotate man/cl.texi @ 129:e292c9648bb9 xemacs-20-1p3

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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 This file documents the GNU Emacs Common Lisp emulation package.
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11
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12 Copyright (C) 1993 Free Software Foundation, Inc.
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13
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14 Permission is granted to make and distribute verbatim copies of this
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15 manual provided the copyright notice and this permission notice are
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16 preserved on all copies.
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17
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18 @ignore
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19 Permission is granted to process this file through TeX and print the
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20 results, provided the printed document carries copying permission notice
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21 identical to this one except for the removal of this paragraph (this
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22 paragraph not being relevant to the printed manual).
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23
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24 @end ignore
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25 Permission is granted to copy and distribute modified versions of this
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26 manual under the conditions for verbatim copying, provided also that the
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27 section entitled ``GNU General Public License'' is included exactly as
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28 in the original, and provided that the entire resulting derived work is
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29 distributed under the terms of a permission notice identical to this one.
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30
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31 Permission is granted to copy and distribute translations of this manual
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32 into another language, under the above conditions for modified versions,
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33 except that the section entitled ``GNU General Public License'' may be
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34 included in a translation approved by the author instead of in the
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35 original English.
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36 @end ifinfo
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37
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38 @titlepage
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39 @sp 6
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40 @center @titlefont{Common Lisp Extensions}
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41 @sp 4
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42 @center For GNU Emacs Lisp
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43 @sp 1
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44 @center Version 2.02
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45 @sp 5
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46 @center Dave Gillespie
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47 @center daveg@@synaptics.com
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48 @page
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49
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50 @vskip 0pt plus 1filll
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51 Copyright @copyright{} 1993 Free Software Foundation, Inc.
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52
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53 Permission is granted to make and distribute verbatim copies of
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54 this manual provided the copyright notice and this permission notice
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55 are preserved on all copies.
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56
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57 @ignore
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58 Permission is granted to process this file through TeX and print the
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59 results, provided the printed document carries copying permission notice
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60 identical to this one except for the removal of this paragraph (this
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61 paragraph not being relevant to the printed manual).
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62
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63 @end ignore
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64 Permission is granted to copy and distribute modified versions of this
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65 manual under the conditions for verbatim copying, provided also that the
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66 section entitled ``GNU General Public License'' is included exactly as
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67 in the original, and provided that the entire resulting derived work is
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68 distributed under the terms of a permission notice identical to this one.
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69
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70 Permission is granted to copy and distribute translations of this manual
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71 into another language, under the above conditions for modified versions,
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72 except that the section entitled ``GNU General Public License'' may be
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73 included in a translation approved by the author instead of in the
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74 original English.
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75 @end titlepage
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76
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77 @node Top, Overview,, (dir)
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78 @chapter Common Lisp Extensions
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79
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80 @noindent
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81 This document describes a set of Emacs Lisp facilities borrowed from
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82 Common Lisp. All the facilities are described here in detail; for
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83 more discussion and examples, Guy L. Steele's @cite{Common Lisp, the
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84 Language}, second edition, is the definitive book on Common Lisp.
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85 @iftex
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86 Chapter numbers and most section numbers of this document parallel
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87 those of Steele's book.
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88 @end iftex
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89 While this document does not assume any prior knowledge of Common
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90 Lisp, it does assume a basic familiarity with Emacs Lisp.
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91
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92 @menu
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93 * Overview:: Installation, usage, etc.
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94 * Program Structure:: Arglists, `eval-when', `defalias'
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95 * Predicates:: `typep', `eql', and `equalp'
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96 * Control Structure:: `setf', `when', `do', `loop', etc.
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97 * Macros:: Destructuring, `define-compiler-macro'
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98 * Declarations:: `proclaim', `declare', etc.
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99 * Symbols:: Property lists, `gensym'
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100 * Numbers:: Predicates, functions, random numbers
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101 * Sequences:: Mapping, functions, searching, sorting
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102 * Lists:: `cadr', `sublis', `member*', `assoc*', etc.
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103 * Hash Tables:: `make-hash-table', `gethash', etc.
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104 * Structures:: `defstruct'
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105 * Assertions:: `check-type', `assert', `ignore-errors'.
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106
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107 * Efficiency Concerns:: Hints and techniques
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108 * Common Lisp Compatibility:: All known differences with Steele
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109 * Old CL Compatibility:: All known differences with old cl.el
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110 * Porting Common Lisp:: Hints for porting Common Lisp code
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111
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112 * Function Index::
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113 * Variable Index::
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114 @end menu
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115
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116 @node Overview, Program Structure, Top, Top
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117 @ifinfo
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118 @chapter Overview
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119 @end ifinfo
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120 @iftex
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121 @section Overview
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122 @end iftex
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123
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124 @noindent
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125 Common Lisp is a huge language, and Common Lisp systems tend to be
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126 massive and extremely complex. Emacs Lisp, by contrast, is rather
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127 minimalist in the choice of Lisp features it offers the programmer.
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128 As Emacs Lisp programmers have grown in number, and the applications
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129 they write have grown more ambitious, it has become clear that Emacs
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130 Lisp could benefit from many of the conveniences of Common Lisp.
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131
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132 The @dfn{CL} package adds a number of Common Lisp functions and
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133 control structures to Emacs Lisp. While not a 100% complete
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134 implementation of Common Lisp, @dfn{CL} adds enough functionality
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135 to make Emacs Lisp programming significantly more convenient.
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136
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137 Some Common Lisp features have been omitted from this package
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138 for various reasons:
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139
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140 @itemize @bullet
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141 @item
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142 Some features are too complex or bulky relative to their benefit
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143 to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
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144 examples of this group.
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145
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146 @item
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147 Other features cannot be implemented without modification to the
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148 Emacs Lisp interpreter itself, such as multiple return values,
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149 lexical scoping, case-insensitive symbols, and complex numbers.
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150 The @dfn{CL} package generally makes no attempt to emulate these
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151 features.
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152
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153 @item
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154 Some features conflict with existing things in Emacs Lisp. For
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155 example, Emacs' @code{assoc} function is incompatible with the
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156 Common Lisp @code{assoc}. In such cases, this package usually
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157 adds the suffix @samp{*} to the function name of the Common
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158 Lisp version of the function (e.g., @code{assoc*}).
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159 @end itemize
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160
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161 The package described here was written by Dave Gillespie,
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162 @file{daveg@@synaptics.com}. It is a total rewrite of the original
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163 1986 @file{cl.el} package by Cesar Quiroz. Most features of
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164 the Quiroz package have been retained; any incompatibilities are
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165 noted in the descriptions below. Care has been taken in this
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166 version to ensure that each function is defined efficiently,
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167 concisely, and with minimal impact on the rest of the Emacs
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168 environment.
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169
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170 @menu
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171 * Usage:: How to use the CL package
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172 * Organization:: The package's five component files
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173 * Installation:: Compiling and installing CL
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174 * Naming Conventions:: Notes on CL function names
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175 @end menu
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176
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177 @node Usage, Organization, Overview, Overview
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178 @section Usage
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179
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180 @noindent
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181 Lisp code that uses features from the @dfn{CL} package should
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182 include at the beginning:
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183
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184 @example
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185 (require 'cl)
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186 @end example
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187
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188 @noindent
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189 If you want to ensure that the new (Gillespie) version of @dfn{CL}
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190 is the one that is present, add an additional @code{(require 'cl-19)}
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191 call:
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192
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193 @example
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194 (require 'cl)
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195 (require 'cl-19)
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196 @end example
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197
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198 @noindent
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199 The second call will fail (with ``@file{cl-19.el} not found'') if
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200 the old @file{cl.el} package was in use.
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201
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202 It is safe to arrange to load @dfn{CL} at all times, e.g.,
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203 in your @file{.emacs} file. But it's a good idea, for portability,
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204 to @code{(require 'cl)} in your code even if you do this.
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205
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206 @node Organization, Installation, Usage, Overview
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207 @section Organization
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208
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209 @noindent
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210 The Common Lisp package is organized into four files:
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211
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212 @table @file
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213 @item cl.el
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214 This is the ``main'' file, which contains basic functions
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215 and information about the package. This file is relatively
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216 compact---about 700 lines.
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217
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218 @item cl-extra.el
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219 This file contains the larger, more complex or unusual functions.
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220 It is kept separate so that packages which only want to use Common
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221 Lisp fundamentals like the @code{cadr} function won't need to pay
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222 the overhead of loading the more advanced functions.
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223
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224 @item cl-seq.el
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225 This file contains most of the advanced functions for operating
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226 on sequences or lists, such as @code{delete-if} and @code{assoc*}.
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227
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228 @item cl-macs.el
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229 This file contains the features of the packages which are macros
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230 instead of functions. Macros expand when the caller is compiled,
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231 not when it is run, so the macros generally only need to be
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232 present when the byte-compiler is running (or when the macros are
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233 used in uncompiled code such as a @file{.emacs} file). Most of
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234 the macros of this package are isolated in @file{cl-macs.el} so
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235 that they won't take up memory unless you are compiling.
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236 @end table
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237
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238 The file @file{cl.el} includes all necessary @code{autoload}
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239 commands for the functions and macros in the other three files.
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240 All you have to do is @code{(require 'cl)}, and @file{cl.el}
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241 will take care of pulling in the other files when they are
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242 needed.
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243
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244 There is another file, @file{cl-compat.el}, which defines some
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245 routines from the older @file{cl.el} package that are no longer
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246 present in the new package. This includes internal routines
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247 like @code{setelt} and @code{zip-lists}, deprecated features
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248 like @code{defkeyword}, and an emulation of the old-style
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249 multiple-values feature. @xref{Old CL Compatibility}.
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250
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251 @node Installation, Naming Conventions, Organization, Overview
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252 @section Installation
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253
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254 @noindent
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255 Installation of the @dfn{CL} package is simple: Just put the
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256 byte-compiled files @file{cl.elc}, @file{cl-extra.elc},
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257 @file{cl-seq.elc}, @file{cl-macs.elc}, and @file{cl-compat.elc}
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258 into a directory on your @code{load-path}.
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259
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260 There are no special requirements to compile this package:
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261 The files do not have to be loaded before they are compiled,
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262 nor do they need to be compiled in any particular order.
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263
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264 You may choose to put the files into your main @file{lisp/}
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265 directory, replacing the original @file{cl.el} file there. Or,
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266 you could put them into a directory that comes before @file{lisp/}
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267 on your @code{load-path} so that the old @file{cl.el} is
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268 effectively hidden.
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269
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270 Also, format the @file{cl.texinfo} file and put the resulting
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271 Info files in the @file{info/} directory or another suitable place.
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272
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273 You may instead wish to leave this package's components all in
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274 their own directory, and then add this directory to your
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275 @code{load-path} and (Emacs 19 only) @code{Info-directory-list}.
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276 Add the directory to the front of the list so the old @dfn{CL}
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277 package and its documentation are hidden.
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278
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279 @node Naming Conventions, , Installation, Overview
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280 @section Naming Conventions
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281
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282 @noindent
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283 Except where noted, all functions defined by this package have the
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284 same names and calling conventions as their Common Lisp counterparts.
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285
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286 Following is a complete list of functions whose names were changed
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287 from Common Lisp, usually to avoid conflicts with Emacs. In each
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288 case, a @samp{*} has been appended to the Common Lisp name to obtain
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289 the Emacs name:
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290
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291 @example
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292 defun* defsubst* defmacro* function*
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293 member* assoc* rassoc* get*
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294 remove* delete* mapcar* sort*
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295 floor* ceiling* truncate* round*
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296 mod* rem* random*
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297 @end example
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298
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299 Internal function and variable names in the package are prefixed
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300 by @code{cl-}. Here is a complete list of functions @emph{not}
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301 prefixed by @code{cl-} which were not taken from Common Lisp:
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302
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303 @example
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304 member delete remove remq
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305 rassoc floatp-safe lexical-let lexical-let*
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306 callf callf2 letf letf*
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307 defsubst* defalias add-hook eval-when-compile
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308 @end example
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309
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310 @noindent
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311 (Most of these are Emacs 19 features provided to Emacs 18 users,
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312 or introduced, like @code{remq}, for reasons of symmetry
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313 with similar features.)
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314
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315 The following simple functions and macros are defined in @file{cl.el};
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316 they do not cause other components like @file{cl-extra} to be loaded.
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317
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318 @example
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319 eql floatp-safe abs endp
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320 evenp oddp plusp minusp
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321 last butlast nbutlast caar .. cddddr
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322 list* ldiff rest first .. tenth
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323 member [1] copy-list subst mapcar* [2]
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324 adjoin [3] acons pairlis when
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325 unless pop [4] push [4] pushnew [3,4]
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326 incf [4] decf [4] proclaim declaim
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327 add-hook
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328 @end example
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329
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330 @noindent
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331 [1] This is the Emacs 19-compatible function, not @code{member*}.
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332
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333 @noindent
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334 [2] Only for one sequence argument or two list arguments.
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335
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336 @noindent
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337 [3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
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338 and @code{:key} is not used.
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339
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340 @noindent
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341 [4] Only when @var{place} is a plain variable name.
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342
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343 @iftex
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344 @chapno=4
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345 @end iftex
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346
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347 @node Program Structure, Predicates, Overview, Top
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348 @chapter Program Structure
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349
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350 @noindent
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351 This section describes features of the @dfn{CL} package which have to
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352 do with programs as a whole: advanced argument lists for functions,
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353 and the @code{eval-when} construct.
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354
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355 @menu
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356 * Argument Lists:: `&key', `&aux', `defun*', `defmacro*'.
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357 * Time of Evaluation:: The `eval-when' construct.
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358 * Function Aliases:: The `defalias' function.
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359 @end menu
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360
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361 @iftex
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362 @secno=1
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363 @end iftex
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364
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365 @node Argument Lists, Time of Evaluation, Program Structure, Program Structure
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366 @section Argument Lists
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367
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368 @noindent
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369 Emacs Lisp's notation for argument lists of functions is a subset of
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370 the Common Lisp notation. As well as the familiar @code{&optional}
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371 and @code{&rest} markers, Common Lisp allows you to specify default
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372 values for optional arguments, and it provides the additional markers
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373 @code{&key} and @code{&aux}.
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374
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375 Since argument parsing is built-in to Emacs, there is no way for
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376 this package to implement Common Lisp argument lists seamlessly.
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377 Instead, this package defines alternates for several Lisp forms
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378 which you must use if you need Common Lisp argument lists.
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379
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380 @defspec defun* name arglist body...
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381 This form is identical to the regular @code{defun} form, except
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382 that @var{arglist} is allowed to be a full Common Lisp argument
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383 list. Also, the function body is enclosed in an implicit block
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384 called @var{name}; @pxref{Blocks and Exits}.
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385 @end defspec
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386
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387 @defspec defsubst* name arglist body...
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388 This is just like @code{defun*}, except that the function that
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389 is defined is automatically proclaimed @code{inline}, i.e.,
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390 calls to it may be expanded into in-line code by the byte compiler.
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391 This is analogous to the @code{defsubst} form in Emacs 19;
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392 @code{defsubst*} uses a different method (compiler macros) which
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393 works in all version of Emacs, and also generates somewhat more
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394 efficient inline expansions. In particular, @code{defsubst*}
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395 arranges for the processing of keyword arguments, default values,
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396 etc., to be done at compile-time whenever possible.
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397 @end defspec
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398
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399 @defspec defmacro* name arglist body...
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400 This is identical to the regular @code{defmacro} form,
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401 except that @var{arglist} is allowed to be a full Common Lisp
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402 argument list. The @code{&environment} keyword is supported as
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403 described in Steele. The @code{&whole} keyword is supported only
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404 within destructured lists (see below); top-level @code{&whole}
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405 cannot be implemented with the current Emacs Lisp interpreter.
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406 The macro expander body is enclosed in an implicit block called
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407 @var{name}.
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408 @end defspec
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409
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410 @defspec function* symbol-or-lambda
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411 This is identical to the regular @code{function} form,
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412 except that if the argument is a @code{lambda} form then that
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413 form may use a full Common Lisp argument list.
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414 @end defspec
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415
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416 Also, all forms (such as @code{defsetf} and @code{flet}) defined
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417 in this package that include @var{arglist}s in their syntax allow
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418 full Common Lisp argument lists.
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419
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420 Note that it is @emph{not} necessary to use @code{defun*} in
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421 order to have access to most @dfn{CL} features in your function.
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422 These features are always present; @code{defun*}'s only
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423 difference from @code{defun} is its more flexible argument
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424 lists and its implicit block.
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425
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426 The full form of a Common Lisp argument list is
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427
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428 @example
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429 (@var{var}...
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430 &optional (@var{var} @var{initform} @var{svar})...
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431 &rest @var{var}
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432 &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
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433 &aux (@var{var} @var{initform})...)
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434 @end example
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435
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436 Each of the five argument list sections is optional. The @var{svar},
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437 @var{initform}, and @var{keyword} parts are optional; if they are
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438 omitted, then @samp{(@var{var})} may be written simply @samp{@var{var}}.
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439
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440 The first section consists of zero or more @dfn{required} arguments.
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441 These arguments must always be specified in a call to the function;
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442 there is no difference between Emacs Lisp and Common Lisp as far as
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443 required arguments are concerned.
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444
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445 The second section consists of @dfn{optional} arguments. These
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446 arguments may be specified in the function call; if they are not,
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447 @var{initform} specifies the default value used for the argument.
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448 (No @var{initform} means to use @code{nil} as the default.) The
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449 @var{initform} is evaluated with the bindings for the preceding
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450 arguments already established; @code{(a &optional (b (1+ a)))}
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451 matches one or two arguments, with the second argument defaulting
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452 to one plus the first argument. If the @var{svar} is specified,
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453 it is an auxiliary variable which is bound to @code{t} if the optional
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454 argument was specified, or to @code{nil} if the argument was omitted.
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455 If you don't use an @var{svar}, then there will be no way for your
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456 function to tell whether it was called with no argument, or with
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457 the default value passed explicitly as an argument.
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458
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459 The third section consists of a single @dfn{rest} argument. If
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460 more arguments were passed to the function than are accounted for
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461 by the required and optional arguments, those extra arguments are
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462 collected into a list and bound to the ``rest'' argument variable.
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463 Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp.
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464 Common Lisp accepts @code{&body} as a synonym for @code{&rest} in
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465 macro contexts; this package accepts it all the time.
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466
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467 The fourth section consists of @dfn{keyword} arguments. These
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468 are optional arguments which are specified by name rather than
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469 positionally in the argument list. For example,
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470
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471 @example
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472 (defun* foo (a &optional b &key c d (e 17)))
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473 @end example
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474
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475 @noindent
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476 defines a function which may be called with one, two, or more
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477 arguments. The first two arguments are bound to @code{a} and
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478 @code{b} in the usual way. The remaining arguments must be
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479 pairs of the form @code{:c}, @code{:d}, or @code{:e} followed
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480 by the value to be bound to the corresponding argument variable.
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481 (Symbols whose names begin with a colon are called @dfn{keywords},
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482 and they are self-quoting in the same way as @code{nil} and
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483 @code{t}.)
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484
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485 For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five
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486 arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword
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487 appears more than once in the function call, the first occurrence
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488 takes precedence over the later ones. Note that it is not possible
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489 to specify keyword arguments without specifying the optional
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490 argument @code{b} as well, since @code{(foo 1 :c 2)} would bind
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491 @code{b} to the keyword @code{:c}, then signal an error because
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492 @code{2} is not a valid keyword.
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493
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494 If a @var{keyword} symbol is explicitly specified in the argument
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495 list as shown in the above diagram, then that keyword will be
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496 used instead of just the variable name prefixed with a colon.
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497 You can specify a @var{keyword} symbol which does not begin with
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498 a colon at all, but such symbols will not be self-quoting; you
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499 will have to quote them explicitly with an apostrophe in the
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500 function call.
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501
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502 Ordinarily it is an error to pass an unrecognized keyword to
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503 a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask
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504 Lisp to ignore unrecognized keywords, either by adding the
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505 marker @code{&allow-other-keys} after the keyword section
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506 of the argument list, or by specifying an @code{:allow-other-keys}
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507 argument in the call whose value is non-@code{nil}. If the
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508 function uses both @code{&rest} and @code{&key} at the same time,
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509 the ``rest'' argument is bound to the keyword list as it appears
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510 in the call. For example:
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511
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512 @smallexample
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513 (defun* find-thing (thing &rest rest &key need &allow-other-keys)
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514 (or (apply 'member* thing thing-list :allow-other-keys t rest)
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515 (if need (error "Thing not found"))))
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516 @end smallexample
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517
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518 @noindent
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519 This function takes a @code{:need} keyword argument, but also
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520 accepts other keyword arguments which are passed on to the
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521 @code{member*} function. @code{allow-other-keys} is used to
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522 keep both @code{find-thing} and @code{member*} from complaining
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523 about each others' keywords in the arguments.
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524
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525 In Common Lisp, keywords are recognized by the Lisp parser itself
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526 and treated as special entities. In Emacs, keywords are just
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527 symbols whose names begin with colons, which @code{defun*} has
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528 arranged to set equal to themselves so that they will essentially
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529 be self-quoting.
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530
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531 As a (significant) performance optimization, this package
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532 implements the scan for keyword arguments by calling @code{memq}
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533 to search for keywords in a ``rest'' argument. Technically
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534 speaking, this is incorrect, since @code{memq} looks at the
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535 odd-numbered values as well as the even-numbered keywords.
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536 The net effect is that if you happen to pass a keyword symbol
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537 as the @emph{value} of another keyword argument, where that
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538 keyword symbol happens to equal the name of a valid keyword
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539 argument of the same function, then the keyword parser will
376386a54a3c Import from CVS: tag r19-14
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540 become confused. This minor bug can only affect you if you
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541 use keyword symbols as general-purpose data in your program;
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542 this practice is strongly discouraged in Emacs Lisp.
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543
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544 The fifth section of the argument list consists of @dfn{auxiliary
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545 variables}. These are not really arguments at all, but simply
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546 variables which are bound to @code{nil} or to the specified
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547 @var{initforms} during execution of the function. There is no
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548 difference between the following two functions, except for a
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549 matter of stylistic taste:
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550
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551 @example
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552 (defun* foo (a b &aux (c (+ a b)) d)
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553 @var{body})
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554
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555 (defun* foo (a b)
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556 (let ((c (+ a b)) d)
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557 @var{body}))
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558 @end example
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559
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560 Argument lists support @dfn{destructuring}. In Common Lisp,
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561 destructuring is only allowed with @code{defmacro}; this package
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562 allows it with @code{defun*} and other argument lists as well.
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563 In destructuring, any argument variable (@var{var} in the above
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564 diagram) can be replaced by a list of variables, or more generally,
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565 a recursive argument list. The corresponding argument value must
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566 be a list whose elements match this recursive argument list.
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567 For example:
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568
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569 @example
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570 (defmacro* dolist ((var listform &optional resultform)
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571 &rest body)
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572 ...)
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573 @end example
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574
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575 This says that the first argument of @code{dolist} must be a list
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576 of two or three items; if there are other arguments as well as this
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577 list, they are stored in @code{body}. All features allowed in
376386a54a3c Import from CVS: tag r19-14
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578 regular argument lists are allowed in these recursive argument lists.
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579 In addition, the clause @samp{&whole @var{var}} is allowed at the
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580 front of a recursive argument list. It binds @var{var} to the
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581 whole list being matched; thus @code{(&whole all a b)} matches
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582 a list of two things, with @code{a} bound to the first thing,
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583 @code{b} bound to the second thing, and @code{all} bound to the
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584 list itself. (Common Lisp allows @code{&whole} in top-level
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585 @code{defmacro} argument lists as well, but Emacs Lisp does not
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586 support this usage.)
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587
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588 One last feature of destructuring is that the argument list may be
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589 dotted, so that the argument list @code{(a b . c)} is functionally
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590 equivalent to @code{(a b &rest c)}.
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591
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592 If the optimization quality @code{safety} is set to 0
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593 (@pxref{Declarations}), error checking for wrong number of
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594 arguments and invalid keyword arguments is disabled. By default,
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595 argument lists are rigorously checked.
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596
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597 @node Time of Evaluation, Function Aliases, Argument Lists, Program Structure
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598 @section Time of Evaluation
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599
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600 @noindent
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601 Normally, the byte-compiler does not actually execute the forms in
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602 a file it compiles. For example, if a file contains @code{(setq foo t)},
376386a54a3c Import from CVS: tag r19-14
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603 the act of compiling it will not actually set @code{foo} to @code{t}.
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604 This is true even if the @code{setq} was a top-level form (i.e., not
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605 enclosed in a @code{defun} or other form). Sometimes, though, you
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606 would like to have certain top-level forms evaluated at compile-time.
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607 For example, the compiler effectively evaluates @code{defmacro} forms
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608 at compile-time so that later parts of the file can refer to the
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609 macros that are defined.
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610
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611 @defspec eval-when (situations...) forms...
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612 This form controls when the body @var{forms} are evaluated.
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613 The @var{situations} list may contain any set of the symbols
376386a54a3c Import from CVS: tag r19-14
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614 @code{compile}, @code{load}, and @code{eval} (or their long-winded
376386a54a3c Import from CVS: tag r19-14
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615 ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel},
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616 and @code{:execute}).
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617
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618 The @code{eval-when} form is handled differently depending on
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619 whether or not it is being compiled as a top-level form.
376386a54a3c Import from CVS: tag r19-14
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620 Specifically, it gets special treatment if it is being compiled
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621 by a command such as @code{byte-compile-file} which compiles files
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622 or buffers of code, and it appears either literally at the
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623 top level of the file or inside a top-level @code{progn}.
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624
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625 For compiled top-level @code{eval-when}s, the body @var{forms} are
376386a54a3c Import from CVS: tag r19-14
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626 executed at compile-time if @code{compile} is in the @var{situations}
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627 list, and the @var{forms} are written out to the file (to be executed
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628 at load-time) if @code{load} is in the @var{situations} list.
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629
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630 For non-compiled-top-level forms, only the @code{eval} situation is
376386a54a3c Import from CVS: tag r19-14
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631 relevant. (This includes forms executed by the interpreter, forms
376386a54a3c Import from CVS: tag r19-14
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632 compiled with @code{byte-compile} rather than @code{byte-compile-file},
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633 and non-top-level forms.) The @code{eval-when} acts like a
376386a54a3c Import from CVS: tag r19-14
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634 @code{progn} if @code{eval} is specified, and like @code{nil}
376386a54a3c Import from CVS: tag r19-14
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635 (ignoring the body @var{forms}) if not.
376386a54a3c Import from CVS: tag r19-14
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636
376386a54a3c Import from CVS: tag r19-14
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637 The rules become more subtle when @code{eval-when}s are nested;
376386a54a3c Import from CVS: tag r19-14
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638 consult Steele (second edition) for the gruesome details (and
376386a54a3c Import from CVS: tag r19-14
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639 some gruesome examples).
376386a54a3c Import from CVS: tag r19-14
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640
376386a54a3c Import from CVS: tag r19-14
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641 Some simple examples:
376386a54a3c Import from CVS: tag r19-14
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642
376386a54a3c Import from CVS: tag r19-14
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643 @example
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644 ;; Top-level forms in foo.el:
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645 (eval-when (compile) (setq foo1 'bar))
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646 (eval-when (load) (setq foo2 'bar))
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647 (eval-when (compile load) (setq foo3 'bar))
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648 (eval-when (eval) (setq foo4 'bar))
376386a54a3c Import from CVS: tag r19-14
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649 (eval-when (eval compile) (setq foo5 'bar))
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650 (eval-when (eval load) (setq foo6 'bar))
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651 (eval-when (eval compile load) (setq foo7 'bar))
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652 @end example
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653
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654 When @file{foo.el} is compiled, these variables will be set during
376386a54a3c Import from CVS: tag r19-14
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655 the compilation itself:
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656
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657 @example
376386a54a3c Import from CVS: tag r19-14
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658 foo1 foo3 foo5 foo7 ; `compile'
376386a54a3c Import from CVS: tag r19-14
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659 @end example
376386a54a3c Import from CVS: tag r19-14
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660
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661 When @file{foo.elc} is loaded, these variables will be set:
376386a54a3c Import from CVS: tag r19-14
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662
376386a54a3c Import from CVS: tag r19-14
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663 @example
376386a54a3c Import from CVS: tag r19-14
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664 foo2 foo3 foo6 foo7 ; `load'
376386a54a3c Import from CVS: tag r19-14
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665 @end example
376386a54a3c Import from CVS: tag r19-14
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666
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667 And if @file{foo.el} is loaded uncompiled, these variables will
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668 be set:
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669
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670 @example
376386a54a3c Import from CVS: tag r19-14
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671 foo4 foo5 foo6 foo7 ; `eval'
376386a54a3c Import from CVS: tag r19-14
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672 @end example
376386a54a3c Import from CVS: tag r19-14
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673
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674 If these seven @code{eval-when}s had been, say, inside a @code{defun},
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675 then the first three would have been equivalent to @code{nil} and the
376386a54a3c Import from CVS: tag r19-14
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676 last four would have been equivalent to the corresponding @code{setq}s.
376386a54a3c Import from CVS: tag r19-14
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677
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678 Note that @code{(eval-when (load eval) @dots{})} is equivalent
376386a54a3c Import from CVS: tag r19-14
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679 to @code{(progn @dots{})} in all contexts. The compiler treats
376386a54a3c Import from CVS: tag r19-14
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680 certain top-level forms, like @code{defmacro} (sort-of) and
376386a54a3c Import from CVS: tag r19-14
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681 @code{require}, as if they were wrapped in @code{(eval-when
376386a54a3c Import from CVS: tag r19-14
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682 (compile load eval) @dots{})}.
376386a54a3c Import from CVS: tag r19-14
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683 @end defspec
376386a54a3c Import from CVS: tag r19-14
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684
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685 Emacs 19 includes two special forms related to @code{eval-when}.
376386a54a3c Import from CVS: tag r19-14
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686 One of these, @code{eval-when-compile}, is not quite equivalent to
376386a54a3c Import from CVS: tag r19-14
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687 any @code{eval-when} construct and is described below. This package
376386a54a3c Import from CVS: tag r19-14
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688 defines a version of @code{eval-when-compile} for the benefit of
376386a54a3c Import from CVS: tag r19-14
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689 Emacs 18 users.
376386a54a3c Import from CVS: tag r19-14
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690
376386a54a3c Import from CVS: tag r19-14
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691 The other form, @code{(eval-and-compile @dots{})}, is exactly
376386a54a3c Import from CVS: tag r19-14
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692 equivalent to @samp{(eval-when (compile load eval) @dots{})} and
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693 so is not itself defined by this package.
376386a54a3c Import from CVS: tag r19-14
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694
376386a54a3c Import from CVS: tag r19-14
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695 @defspec eval-when-compile forms...
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696 The @var{forms} are evaluated at compile-time; at execution time,
376386a54a3c Import from CVS: tag r19-14
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697 this form acts like a quoted constant of the resulting value. Used
376386a54a3c Import from CVS: tag r19-14
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698 at top-level, @code{eval-when-compile} is just like @samp{eval-when
376386a54a3c Import from CVS: tag r19-14
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699 (compile eval)}. In other contexts, @code{eval-when-compile}
376386a54a3c Import from CVS: tag r19-14
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700 allows code to be evaluated once at compile-time for efficiency
376386a54a3c Import from CVS: tag r19-14
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701 or other reasons.
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702
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703 This form is similar to the @samp{#.} syntax of true Common Lisp.
376386a54a3c Import from CVS: tag r19-14
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704 @end defspec
376386a54a3c Import from CVS: tag r19-14
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705
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706 @defspec load-time-value form
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707 The @var{form} is evaluated at load-time; at execution time,
376386a54a3c Import from CVS: tag r19-14
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708 this form acts like a quoted constant of the resulting value.
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709
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710 Early Common Lisp had a @samp{#,} syntax that was similar to
376386a54a3c Import from CVS: tag r19-14
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711 this, but ANSI Common Lisp replaced it with @code{load-time-value}
376386a54a3c Import from CVS: tag r19-14
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712 and gave it more well-defined semantics.
376386a54a3c Import from CVS: tag r19-14
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713
376386a54a3c Import from CVS: tag r19-14
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714 In a compiled file, @code{load-time-value} arranges for @var{form}
376386a54a3c Import from CVS: tag r19-14
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715 to be evaluated when the @file{.elc} file is loaded and then used
376386a54a3c Import from CVS: tag r19-14
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716 as if it were a quoted constant. In code compiled by
376386a54a3c Import from CVS: tag r19-14
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717 @code{byte-compile} rather than @code{byte-compile-file}, the
376386a54a3c Import from CVS: tag r19-14
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718 effect is identical to @code{eval-when-compile}. In uncompiled
376386a54a3c Import from CVS: tag r19-14
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719 code, both @code{eval-when-compile} and @code{load-time-value}
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720 act exactly like @code{progn}.
376386a54a3c Import from CVS: tag r19-14
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721
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722 @example
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723 (defun report ()
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724 (insert "This function was executed on: "
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725 (current-time-string)
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726 ", compiled on: "
376386a54a3c Import from CVS: tag r19-14
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727 (eval-when-compile (current-time-string))
376386a54a3c Import from CVS: tag r19-14
cvs
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728 ;; or '#.(current-time-string) in real Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
729 ", and loaded on: "
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
730 (load-time-value (current-time-string))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
731 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
732
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
733 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
734 Byte-compiled, the above defun will result in the following code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
735 (or its compiled equivalent, of course) in the @file{.elc} file:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
736
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
737 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
738 (setq --temp-- (current-time-string))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
739 (defun report ()
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
740 (insert "This function was executed on: "
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
741 (current-time-string)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
742 ", compiled on: "
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
743 '"Wed Jun 23 18:33:43 1993"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
744 ", and loaded on: "
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
745 --temp--))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
746 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
747 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
748
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
749 @node Function Aliases, , Time of Evaluation, Program Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
750 @section Function Aliases
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
751
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
752 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
753 This section describes a feature from GNU Emacs 19 which this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
754 package makes available in other versions of Emacs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
755
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
756 @defun defalias symbol function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
757 This function sets @var{symbol}'s function cell to @var{function}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
758 It is equivalent to @code{fset}, except that in GNU Emacs 19 it also
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
759 records the setting in @code{load-history} so that it can be undone
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
760 by a later @code{unload-feature}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
761
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
762 In other versions of Emacs, @code{defalias} is a synonym for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
763 @code{fset}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
764 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
765
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
766 @node Predicates, Control Structure, Program Structure, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
767 @chapter Predicates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
768
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
769 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
770 This section describes functions for testing whether various
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
771 facts are true or false.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
772
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
773 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
774 * Type Predicates:: `typep', `deftype', and `coerce'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
775 * Equality Predicates:: `eql' and `equalp'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
776 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
777
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
778 @node Type Predicates, Equality Predicates, Predicates, Predicates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
779 @section Type Predicates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
780
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
781 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
782 The @dfn{CL} package defines a version of the Common Lisp @code{typep}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
783 predicate.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
784
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
785 @defun typep object type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
786 Check if @var{object} is of type @var{type}, where @var{type} is a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
787 (quoted) type name of the sort used by Common Lisp. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
788 @code{(typep foo 'integer)} is equivalent to @code{(integerp foo)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
789 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
790
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
791 The @var{type} argument to the above function is either a symbol
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
792 or a list beginning with a symbol.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
793
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
794 @itemize @bullet
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
795 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
796 If the type name is a symbol, Emacs appends @samp{-p} to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
797 symbol name to form the name of a predicate function for testing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
798 the type. (Built-in predicates whose names end in @samp{p} rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
799 than @samp{-p} are used when appropriate.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
800
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
801 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
802 The type symbol @code{t} stands for the union of all types.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
803 @code{(typep @var{object} t)} is always true. Likewise, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
804 type symbol @code{nil} stands for nothing at all, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
805 @code{(typep @var{object} nil)} is always false.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
806
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
807 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
808 The type symbol @code{null} represents the symbol @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
809 Thus @code{(typep @var{object} 'null)} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
810 @code{(null @var{object})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
811
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
812 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
813 The type symbol @code{real} is a synonym for @code{number}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
814 @code{fixnum} is a synonym for @code{integer}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
815
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
816 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
817 The type symbols @code{character} and @code{string-char} match
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
818 integers in the range from 0 to 255.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
819
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
820 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
821 The type symbol @code{float} uses the @code{floatp-safe} predicate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
822 defined by this package rather than @code{floatp}, so it will work
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
823 correctly even in Emacs versions without floating-point support.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
824
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
825 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
826 The type list @code{(integer @var{low} @var{high})} represents all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
827 integers between @var{low} and @var{high}, inclusive. Either bound
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
828 may be a list of a single integer to specify an exclusive limit,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
829 or a @code{*} to specify no limit. The type @code{(integer * *)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
830 is thus equivalent to @code{integer}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
831
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
832 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
833 Likewise, lists beginning with @code{float}, @code{real}, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
834 @code{number} represent numbers of that type falling in a particular
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
835 range.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
836
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
837 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
838 Lists beginning with @code{and}, @code{or}, and @code{not} form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
839 combinations of types. For example, @code{(or integer (float 0 *))}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
840 represents all objects that are integers or non-negative floats.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
841
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
842 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
843 Lists beginning with @code{member} or @code{member*} represent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
844 objects @code{eql} to any of the following values. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
845 @code{(member 1 2 3 4)} is equivalent to @code{(integer 1 4)},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
846 and @code{(member nil)} is equivalent to @code{null}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
847
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
848 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
849 Lists of the form @code{(satisfies @var{predicate})} represent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
850 all objects for which @var{predicate} returns true when called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
851 with that object as an argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
852 @end itemize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
853
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
854 The following function and macro (not technically predicates) are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
855 related to @code{typep}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
856
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
857 @defun coerce object type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
858 This function attempts to convert @var{object} to the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
859 @var{type}. If @var{object} is already of that type as determined by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
860 @code{typep}, it is simply returned. Otherwise, certain types of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
861 conversions will be made: If @var{type} is any sequence type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
862 (@code{string}, @code{list}, etc.) then @var{object} will be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
863 converted to that type if possible. If @var{type} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
864 @code{character}, then strings of length one and symbols with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
865 one-character names can be coerced. If @var{type} is @code{float},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
866 then integers can be coerced in versions of Emacs that support
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
867 floats. In all other circumstances, @code{coerce} signals an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
868 error.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
869 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
870
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
871 @defspec deftype name arglist forms...
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
872 This macro defines a new type called @var{name}. It is similar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
873 to @code{defmacro} in many ways; when @var{name} is encountered
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
874 as a type name, the body @var{forms} are evaluated and should
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
875 return a type specifier that is equivalent to the type. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
876 @var{arglist} is a Common Lisp argument list of the sort accepted
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
877 by @code{defmacro*}. The type specifier @samp{(@var{name} @var{args}...)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
878 is expanded by calling the expander with those arguments; the type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
879 symbol @samp{@var{name}} is expanded by calling the expander with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
880 no arguments. The @var{arglist} is processed the same as for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
881 @code{defmacro*} except that optional arguments without explicit
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
882 defaults use @code{*} instead of @code{nil} as the ``default''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
883 default. Some examples:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
884
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
885 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
886 (deftype null () '(satisfies null)) ; predefined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
887 (deftype list () '(or null cons)) ; predefined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
888 (deftype unsigned-byte (&optional bits)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
889 (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits)))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
890 (unsigned-byte 8) @equiv{} (integer 0 255)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
891 (unsigned-byte) @equiv{} (integer 0 *)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
892 unsigned-byte @equiv{} (integer 0 *)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
893 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
894
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
895 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
896 The last example shows how the Common Lisp @code{unsigned-byte}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
897 type specifier could be implemented if desired; this package does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
898 not implement @code{unsigned-byte} by default.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
899 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
900
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
901 The @code{typecase} and @code{check-type} macros also use type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
902 names. @xref{Conditionals}. @xref{Assertions}. The @code{map},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
903 @code{concatenate}, and @code{merge} functions take type-name
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
904 arguments to specify the type of sequence to return. @xref{Sequences}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
905
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
906 @node Equality Predicates, , Type Predicates, Predicates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
907 @section Equality Predicates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
908
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
909 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
910 This package defines two Common Lisp predicates, @code{eql} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
911 @code{equalp}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
912
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
913 @defun eql a b
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
914 This function is almost the same as @code{eq}, except that if @var{a}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
915 and @var{b} are numbers of the same type, it compares them for numeric
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
916 equality (as if by @code{equal} instead of @code{eq}). This makes a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
917 difference only for versions of Emacs that are compiled with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
918 floating-point support, such as Emacs 19. Emacs floats are allocated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
919 objects just like cons cells, which means that @code{(eq 3.0 3.0)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
920 will not necessarily be true---if the two @code{3.0}s were allocated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
921 separately, the pointers will be different even though the numbers are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
922 the same. But @code{(eql 3.0 3.0)} will always be true.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
923
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
924 The types of the arguments must match, so @code{(eql 3 3.0)} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
925 still false.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
926
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
927 Note that Emacs integers are ``direct'' rather than allocated, which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
928 basically means @code{(eq 3 3)} will always be true. Thus @code{eq}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
929 and @code{eql} behave differently only if floating-point numbers are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
930 involved, and are indistinguishable on Emacs versions that don't
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
931 support floats.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
932
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
933 There is a slight inconsistency with Common Lisp in the treatment of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
934 positive and negative zeros. Some machines, notably those with IEEE
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
935 standard arithmetic, represent @code{+0} and @code{-0} as distinct
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
936 values. Normally this doesn't matter because the standard specifies
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
937 that @code{(= 0.0 -0.0)} should always be true, and this is indeed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
938 what Emacs Lisp and Common Lisp do. But the Common Lisp standard
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
939 states that @code{(eql 0.0 -0.0)} and @code{(equal 0.0 -0.0)} should
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
940 be false on IEEE-like machines; Emacs Lisp does not do this, and in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
941 fact the only known way to distinguish between the two zeros in Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
942 Lisp is to @code{format} them and check for a minus sign.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
943 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
944
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
945 @defun equalp a b
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
946 This function is a more flexible version of @code{equal}. In
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
947 particular, it compares strings case-insensitively, and it compares
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
948 numbers without regard to type (so that @code{(equalp 3 3.0)} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
949 true). Vectors and conses are compared recursively. All other
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
950 objects are compared as if by @code{equal}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
951
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
952 This function differs from Common Lisp @code{equalp} in several
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
953 respects. First, Common Lisp's @code{equalp} also compares
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
954 @emph{characters} case-insensitively, which would be impractical
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
955 in this package since Emacs does not distinguish between integers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
956 and characters. In keeping with the idea that strings are less
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
957 vector-like in Emacs Lisp, this package's @code{equalp} also will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
958 not compare strings against vectors of integers. Finally, Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
959 Lisp's @code{equalp} compares hash tables without regard to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
960 ordering, whereas this package simply compares hash tables in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
961 terms of their underlying structure (which means vectors for Lucid
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
962 Emacs 19 hash tables, or lists for other hash tables).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
963 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
964
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
965 Also note that the Common Lisp functions @code{member} and @code{assoc}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
966 use @code{eql} to compare elements, whereas Emacs Lisp follows the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
967 MacLisp tradition and uses @code{equal} for these two functions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
968 In Emacs, use @code{member*} and @code{assoc*} to get functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
969 which use @code{eql} for comparisons.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
970
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
971 @node Control Structure, Macros, Predicates, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
972 @chapter Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
973
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
974 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
975 The features described in the following sections implement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
976 various advanced control structures, including the powerful
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
977 @code{setf} facility and a number of looping and conditional
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
978 constructs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
979
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
980 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
981 * Assignment:: The `psetq' form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
982 * Generalized Variables:: `setf', `incf', `push', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
983 * Variable Bindings:: `progv', `lexical-let', `flet', `macrolet'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
984 * Conditionals:: `when', `unless', `case', `typecase'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
985 * Blocks and Exits:: `block', `return', `return-from'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
986 * Iteration:: `do', `dotimes', `dolist', `do-symbols'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
987 * Loop Facility:: The Common Lisp `loop' macro
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
988 * Multiple Values:: `values', `multiple-value-bind', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
989 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
990
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
991 @node Assignment, Generalized Variables, Control Structure, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
992 @section Assignment
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
993
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
994 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
995 The @code{psetq} form is just like @code{setq}, except that multiple
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
996 assignments are done in parallel rather than sequentially.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
997
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
998 @defspec psetq [symbol form]@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
999 This special form (actually a macro) is used to assign to several
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1000 variables simultaneously. Given only one @var{symbol} and @var{form},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1001 it has the same effect as @code{setq}. Given several @var{symbol}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1002 and @var{form} pairs, it evaluates all the @var{form}s in advance
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1003 and then stores the corresponding variables afterwards.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1004
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1005 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1006 (setq x 2 y 3)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1007 (setq x (+ x y) y (* x y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1008 x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1009 @result{} 5
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1010 y ; @r{@code{y} was computed after @code{x} was set.}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1011 @result{} 15
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1012 (setq x 2 y 3)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1013 (psetq x (+ x y) y (* x y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1014 x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1015 @result{} 5
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1016 y ; @r{@code{y} was computed before @code{x} was set.}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1017 @result{} 6
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1018 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1019
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1020 The simplest use of @code{psetq} is @code{(psetq x y y x)}, which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1021 exchanges the values of two variables. (The @code{rotatef} form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1022 provides an even more convenient way to swap two variables;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1023 @pxref{Modify Macros}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1024
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1025 @code{psetq} always returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1026 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1027
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1028 @node Generalized Variables, Variable Bindings, Assignment, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1029 @section Generalized Variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1030
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1031 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1032 A ``generalized variable'' or ``place form'' is one of the many places
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1033 in Lisp memory where values can be stored. The simplest place form is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1034 a regular Lisp variable. But the cars and cdrs of lists, elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1035 of arrays, properties of symbols, and many other locations are also
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1036 places where Lisp values are stored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1037
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1038 The @code{setf} form is like @code{setq}, except that it accepts
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1039 arbitrary place forms on the left side rather than just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1040 symbols. For example, @code{(setf (car a) b)} sets the car of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1041 @code{a} to @code{b}, doing the same operation as @code{(setcar a b)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1042 but without having to remember two separate functions for setting
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1043 and accessing every type of place.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1044
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1045 Generalized variables are analogous to ``lvalues'' in the C
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1046 language, where @samp{x = a[i]} gets an element from an array
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1047 and @samp{a[i] = x} stores an element using the same notation.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1048 Just as certain forms like @code{a[i]} can be lvalues in C, there
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1049 is a set of forms that can be generalized variables in Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1050
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1051 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1052 * Basic Setf:: `setf' and place forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1053 * Modify Macros:: `incf', `push', `rotatef', `letf', `callf', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1054 * Customizing Setf:: `define-modify-macro', `defsetf', `define-setf-method'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1055 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1056
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1057 @node Basic Setf, Modify Macros, Generalized Variables, Generalized Variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1058 @subsection Basic Setf
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1059
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1060 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1061 The @code{setf} macro is the most basic way to operate on generalized
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1062 variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1063
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1064 @defspec setf [place form]@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1065 This macro evaluates @var{form} and stores it in @var{place}, which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1066 must be a valid generalized variable form. If there are several
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1067 @var{place} and @var{form} pairs, the assignments are done sequentially
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1068 just as with @code{setq}. @code{setf} returns the value of the last
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1069 @var{form}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1070
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1071 The following Lisp forms will work as generalized variables, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1072 so may legally appear in the @var{place} argument of @code{setf}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1073
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1074 @itemize @bullet
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1075 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1076 A symbol naming a variable. In other words, @code{(setf x y)} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1077 exactly equivalent to @code{(setq x y)}, and @code{setq} itself is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1078 strictly speaking redundant now that @code{setf} exists. Many
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1079 programmers continue to prefer @code{setq} for setting simple
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1080 variables, though, purely for stylistic or historical reasons.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1081 The macro @code{(setf x y)} actually expands to @code{(setq x y)},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1082 so there is no performance penalty for using it in compiled code.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1083
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1084 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1085 A call to any of the following Lisp functions:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1086
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1087 @smallexample
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1088 car cdr caar .. cddddr
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1089 nth rest first .. tenth
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1090 aref elt nthcdr
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1091 symbol-function symbol-value symbol-plist
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1092 get get* getf
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1093 gethash subseq
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1094 @end smallexample
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1095
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1096 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1097 Note that for @code{nthcdr} and @code{getf}, the list argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1098 of the function must itself be a valid @var{place} form. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1099 example, @code{(setf (nthcdr 0 foo) 7)} will set @code{foo} itself
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1100 to 7. Note that @code{push} and @code{pop} on an @code{nthcdr}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1101 place can be used to insert or delete at any position in a list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1102 The use of @code{nthcdr} as a @var{place} form is an extension
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1103 to standard Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1104
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1105 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1106 The following Emacs-specific functions are also @code{setf}-able.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1107 (Some of these are defined only in Emacs 19 or only in Lucid Emacs.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1108
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1109 @smallexample
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1110 buffer-file-name marker-position
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1111 buffer-modified-p match-data
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1112 buffer-name mouse-position
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1113 buffer-string overlay-end
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1114 buffer-substring overlay-get
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1115 current-buffer overlay-start
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1116 current-case-table point
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1117 current-column point-marker
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1118 current-global-map point-max
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1119 current-input-mode point-min
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1120 current-local-map process-buffer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1121 current-window-configuration process-filter
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1122 default-file-modes process-sentinel
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1123 default-value read-mouse-position
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1124 documentation-property screen-height
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1125 extent-data screen-menubar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1126 extent-end-position screen-width
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1127 extent-start-position selected-window
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1128 face-background selected-screen
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1129 face-background-pixmap selected-frame
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1130 face-font standard-case-table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1131 face-foreground syntax-table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1132 face-underline-p window-buffer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1133 file-modes window-dedicated-p
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1134 frame-height window-display-table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1135 frame-parameters window-height
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1136 frame-visible-p window-hscroll
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1137 frame-width window-point
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1138 get-register window-start
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1139 getenv window-width
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1140 global-key-binding x-get-cut-buffer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1141 keymap-parent x-get-cutbuffer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1142 local-key-binding x-get-secondary-selection
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1143 mark x-get-selection
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1144 mark-marker
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1145 @end smallexample
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1146
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1147 Most of these have directly corresponding ``set'' functions, like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1148 @code{use-local-map} for @code{current-local-map}, or @code{goto-char}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1149 for @code{point}. A few, like @code{point-min}, expand to longer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1150 sequences of code when they are @code{setf}'d (@code{(narrow-to-region
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1151 x (point-max))} in this case).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1152
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1153 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1154 A call of the form @code{(substring @var{subplace} @var{n} [@var{m}])},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1155 where @var{subplace} is itself a legal generalized variable whose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1156 current value is a string, and where the value stored is also a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1157 string. The new string is spliced into the specified part of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1158 destination string. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1159
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1160 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1161 (setq a (list "hello" "world"))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1162 @result{} ("hello" "world")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1163 (cadr a)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1164 @result{} "world"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1165 (substring (cadr a) 2 4)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1166 @result{} "rl"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1167 (setf (substring (cadr a) 2 4) "o")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1168 @result{} "o"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1169 (cadr a)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1170 @result{} "wood"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1171 a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1172 @result{} ("hello" "wood")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1173 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1174
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1175 The generalized variable @code{buffer-substring}, listed above,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1176 also works in this way by replacing a portion of the current buffer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1177
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1178 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1179 A call of the form @code{(apply '@var{func} @dots{})} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1180 @code{(apply (function @var{func}) @dots{})}, where @var{func}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1181 is a @code{setf}-able function whose store function is ``suitable''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1182 in the sense described in Steele's book; since none of the standard
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1183 Emacs place functions are suitable in this sense, this feature is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1184 only interesting when used with places you define yourself with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1185 @code{define-setf-method} or the long form of @code{defsetf}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1186
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1187 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1188 A macro call, in which case the macro is expanded and @code{setf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1189 is applied to the resulting form.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1190
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1191 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1192 Any form for which a @code{defsetf} or @code{define-setf-method}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1193 has been made.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1194 @end itemize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1195
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1196 Using any forms other than these in the @var{place} argument to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1197 @code{setf} will signal an error.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1198
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1199 The @code{setf} macro takes care to evaluate all subforms in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1200 the proper left-to-right order; for example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1201
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1202 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1203 (setf (aref vec (incf i)) i)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1204 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1205
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1206 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1207 looks like it will evaluate @code{(incf i)} exactly once, before the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1208 following access to @code{i}; the @code{setf} expander will insert
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1209 temporary variables as necessary to ensure that it does in fact work
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1210 this way no matter what setf-method is defined for @code{aref}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1211 (In this case, @code{aset} would be used and no such steps would
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1212 be necessary since @code{aset} takes its arguments in a convenient
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1213 order.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1214
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1215 However, if the @var{place} form is a macro which explicitly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1216 evaluates its arguments in an unusual order, this unusual order
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1217 will be preserved. Adapting an example from Steele, given
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1218
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1219 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1220 (defmacro wrong-order (x y) (list 'aref y x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1221 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1222
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1223 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1224 the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1225 evaluate @var{b} first, then @var{a}, just as in an actual call
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1226 to @code{wrong-order}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1227 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1228
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1229 @node Modify Macros, Customizing Setf, Basic Setf, Generalized Variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1230 @subsection Modify Macros
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1231
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1232 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1233 This package defines a number of other macros besides @code{setf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1234 that operate on generalized variables. Many are interesting and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1235 useful even when the @var{place} is just a variable name.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1236
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1237 @defspec psetf [place form]@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1238 This macro is to @code{setf} what @code{psetq} is to @code{setq}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1239 When several @var{place}s and @var{form}s are involved, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1240 assignments take place in parallel rather than sequentially.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1241 Specifically, all subforms are evaluated from left to right, then
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1242 all the assignments are done (in an undefined order).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1243 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1244
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1245 @defspec incf place &optional x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1246 This macro increments the number stored in @var{place} by one, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1247 by @var{x} if specified. The incremented value is returned. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1248 example, @code{(incf i)} is equivalent to @code{(setq i (1+ i))}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1249 @code{(incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x) 2))}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1250
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1251 Once again, care is taken to preserve the ``apparent'' order of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1252 evaluation. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1253
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1254 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1255 (incf (aref vec (incf i)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1256 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1257
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1258 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1259 appears to increment @code{i} once, then increment the element of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1260 @code{vec} addressed by @code{i}; this is indeed exactly what it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1261 does, which means the above form is @emph{not} equivalent to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1262 ``obvious'' expansion,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1263
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1264 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1265 (setf (aref vec (incf i)) (1+ (aref vec (incf i)))) ; Wrong!
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1266 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1267
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1268 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1269 but rather to something more like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1270
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1271 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1272 (let ((temp (incf i)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1273 (setf (aref vec temp) (1+ (aref vec temp))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1274 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1275
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1276 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1277 Again, all of this is taken care of automatically by @code{incf} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1278 the other generalized-variable macros.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1279
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1280 As a more Emacs-specific example of @code{incf}, the expression
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1281 @code{(incf (point) @var{n})} is essentially equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1282 @code{(forward-char @var{n})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1283 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1284
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1285 @defspec decf place &optional x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1286 This macro decrements the number stored in @var{place} by one, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1287 by @var{x} if specified.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1288 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1289
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1290 @defspec pop place
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1291 This macro removes and returns the first element of the list stored
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1292 in @var{place}. It is analogous to @code{(prog1 (car @var{place})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1293 (setf @var{place} (cdr @var{place})))}, except that it takes care
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1294 to evaluate all subforms only once.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1295 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1296
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1297 @defspec push x place
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1298 This macro inserts @var{x} at the front of the list stored in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1299 @var{place}. It is analogous to @code{(setf @var{place} (cons
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1300 @var{x} @var{place}))}, except for evaluation of the subforms.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1301 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1302
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1303 @defspec pushnew x place @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1304 This macro inserts @var{x} at the front of the list stored in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1305 @var{place}, but only if @var{x} was not @code{eql} to any
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1306 existing element of the list. The optional keyword arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1307 are interpreted in the same way as for @code{adjoin}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1308 @xref{Lists as Sets}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1309 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1310
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1311 @defspec shiftf place@dots{} newvalue
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1312 This macro shifts the @var{place}s left by one, shifting in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1313 value of @var{newvalue} (which may be any Lisp expression, not just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1314 a generalized variable), and returning the value shifted out of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1315 the first @var{place}. Thus, @code{(shiftf @var{a} @var{b} @var{c}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1316 @var{d})} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1317
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1318 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1319 (prog1
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1320 @var{a}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1321 (psetf @var{a} @var{b}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1322 @var{b} @var{c}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1323 @var{c} @var{d}))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1324 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1325
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1326 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1327 except that the subforms of @var{a}, @var{b}, and @var{c} are actually
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1328 evaluated only once each and in the apparent order.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1329 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1330
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1331 @defspec rotatef place@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1332 This macro rotates the @var{place}s left by one in circular fashion.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1333 Thus, @code{(rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1334
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1335 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1336 (psetf @var{a} @var{b}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1337 @var{b} @var{c}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1338 @var{c} @var{d}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1339 @var{d} @var{a})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1340 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1341
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1342 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1343 except for the evaluation of subforms. @code{rotatef} always
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1344 returns @code{nil}. Note that @code{(rotatef @var{a} @var{b})}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1345 conveniently exchanges @var{a} and @var{b}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1346 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1347
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1348 The following macros were invented for this package; they have no
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1349 analogues in Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1350
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1351 @defspec letf (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1352 This macro is analogous to @code{let}, but for generalized variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1353 rather than just symbols. Each @var{binding} should be of the form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1354 @code{(@var{place} @var{value})}; the original contents of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1355 @var{place}s are saved, the @var{value}s are stored in them, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1356 then the body @var{form}s are executed. Afterwards, the @var{places}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1357 are set back to their original saved contents. This cleanup happens
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1358 even if the @var{form}s exit irregularly due to a @code{throw} or an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1359 error.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1360
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1361 For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1362
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1363 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1364 (letf (((point) (point-min))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1365 (a 17))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1366 ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1367 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1368
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1369 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1370 moves ``point'' in the current buffer to the beginning of the buffer,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1371 and also binds @code{a} to 17 (as if by a normal @code{let}, since
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1372 @code{a} is just a regular variable). After the body exits, @code{a}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1373 is set back to its original value and point is moved back to its
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1374 original position.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1375
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1376 Note that @code{letf} on @code{(point)} is not quite like a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1377 @code{save-excursion}, as the latter effectively saves a marker
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1378 which tracks insertions and deletions in the buffer. Actually,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1379 a @code{letf} of @code{(point-marker)} is much closer to this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1380 behavior. (@code{point} and @code{point-marker} are equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1381 as @code{setf} places; each will accept either an integer or a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1382 marker as the stored value.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1383
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1384 Since generalized variables look like lists, @code{let}'s shorthand
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1385 of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1386 be ambiguous in @code{letf} and is not allowed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1387
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1388 However, a @var{binding} specifier may be a one-element list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1389 @samp{(@var{place})}, which is similar to @samp{(@var{place}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1390 @var{place})}. In other words, the @var{place} is not disturbed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1391 on entry to the body, and the only effect of the @code{letf} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1392 to restore the original value of @var{place} afterwards. (The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1393 redundant access-and-store suggested by the @code{(@var{place}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1394 @var{place})} example does not actually occur.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1395
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1396 In most cases, the @var{place} must have a well-defined value on
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1397 entry to the @code{letf} form. The only exceptions are plain
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1398 variables and calls to @code{symbol-value} and @code{symbol-function}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1399 If the symbol is not bound on entry, it is simply made unbound by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1400 @code{makunbound} or @code{fmakunbound} on exit.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1401 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1402
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1403 @defspec letf* (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1404 This macro is to @code{letf} what @code{let*} is to @code{let}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1405 It does the bindings in sequential rather than parallel order.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1406 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1407
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1408 @defspec callf @var{function} @var{place} @var{args}@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1409 This is the ``generic'' modify macro. It calls @var{function},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1410 which should be an unquoted function name, macro name, or lambda.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1411 It passes @var{place} and @var{args} as arguments, and assigns the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1412 result back to @var{place}. For example, @code{(incf @var{place}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1413 @var{n})} is the same as @code{(callf + @var{place} @var{n})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1414 Some more examples:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1415
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1416 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1417 (callf abs my-number)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1418 (callf concat (buffer-name) "<" (int-to-string n) ">")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1419 (callf union happy-people (list joe bob) :test 'same-person)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1420 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1421
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1422 @xref{Customizing Setf}, for @code{define-modify-macro}, a way
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1423 to create even more concise notations for modify macros. Note
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1424 again that @code{callf} is an extension to standard Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1425 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1426
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1427 @defspec callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1428 This macro is like @code{callf}, except that @var{place} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1429 the @emph{second} argument of @var{function} rather than the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1430 first. For example, @code{(push @var{x} @var{place})} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1431 equivalent to @code{(callf2 cons @var{x} @var{place})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1432 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1433
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1434 The @code{callf} and @code{callf2} macros serve as building
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1435 blocks for other macros like @code{incf}, @code{pushnew}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1436 @code{define-modify-macro}. The @code{letf} and @code{letf*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1437 macros are used in the processing of symbol macros;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1438 @pxref{Macro Bindings}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1439
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1440 @node Customizing Setf, , Modify Macros, Generalized Variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1441 @subsection Customizing Setf
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1442
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1443 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1444 Common Lisp defines three macros, @code{define-modify-macro},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1445 @code{defsetf}, and @code{define-setf-method}, that allow the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1446 user to extend generalized variables in various ways.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1447
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1448 @defspec define-modify-macro name arglist function [doc-string]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1449 This macro defines a ``read-modify-write'' macro similar to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1450 @code{incf} and @code{decf}. The macro @var{name} is defined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1451 to take a @var{place} argument followed by additional arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1452 described by @var{arglist}. The call
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1453
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1454 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1455 (@var{name} @var{place} @var{args}...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1456 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1457
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1458 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1459 will be expanded to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1460
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1461 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1462 (callf @var{func} @var{place} @var{args}...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1463 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1464
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1465 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1466 which in turn is roughly equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1467
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1468 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1469 (setf @var{place} (@var{func} @var{place} @var{args}...))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1470 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1471
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1472 For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1473
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1474 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1475 (define-modify-macro incf (&optional (n 1)) +)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1476 (define-modify-macro concatf (&rest args) concat)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1477 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1478
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1479 Note that @code{&key} is not allowed in @var{arglist}, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1480 @code{&rest} is sufficient to pass keywords on to the function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1481
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1482 Most of the modify macros defined by Common Lisp do not exactly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1483 follow the pattern of @code{define-modify-macro}. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1484 @code{push} takes its arguments in the wrong order, and @code{pop}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1485 is completely irregular. You can define these macros ``by hand''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1486 using @code{get-setf-method}, or consult the source file
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1487 @file{cl-macs.el} to see how to use the internal @code{setf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1488 building blocks.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1489 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1490
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1491 @defspec defsetf access-fn update-fn
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1492 This is the simpler of two @code{defsetf} forms. Where
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1493 @var{access-fn} is the name of a function which accesses a place,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1494 this declares @var{update-fn} to be the corresponding store
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1495 function. From now on,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1496
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1497 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1498 (setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1499 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1500
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1501 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1502 will be expanded to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1503
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1504 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1505 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1506 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1507
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1508 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1509 The @var{update-fn} is required to be either a true function, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1510 a macro which evaluates its arguments in a function-like way. Also,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1511 the @var{update-fn} is expected to return @var{value} as its result.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1512 Otherwise, the above expansion would not obey the rules for the way
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1513 @code{setf} is supposed to behave.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1514
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1515 As a special (non-Common-Lisp) extension, a third argument of @code{t}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1516 to @code{defsetf} says that the @code{update-fn}'s return value is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1517 not suitable, so that the above @code{setf} should be expanded to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1518 something more like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1519
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1520 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1521 (let ((temp @var{value}))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1522 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1523 temp)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1524 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1525
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1526 Some examples of the use of @code{defsetf}, drawn from the standard
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1527 suite of setf methods, are:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1528
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1529 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1530 (defsetf car setcar)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1531 (defsetf symbol-value set)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1532 (defsetf buffer-name rename-buffer t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1533 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1534 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1535
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1536 @defspec defsetf access-fn arglist (store-var) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1537 This is the second, more complex, form of @code{defsetf}. It is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1538 rather like @code{defmacro} except for the additional @var{store-var}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1539 argument. The @var{forms} should return a Lisp form which stores
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1540 the value of @var{store-var} into the generalized variable formed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1541 by a call to @var{access-fn} with arguments described by @var{arglist}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1542 The @var{forms} may begin with a string which documents the @code{setf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1543 method (analogous to the doc string that appears at the front of a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1544 function).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1545
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1546 For example, the simple form of @code{defsetf} is shorthand for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1547
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1548 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1549 (defsetf @var{access-fn} (&rest args) (store)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1550 (append '(@var{update-fn}) args (list store)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1551 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1552
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1553 The Lisp form that is returned can access the arguments from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1554 @var{arglist} and @var{store-var} in an unrestricted fashion;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1555 macros like @code{setf} and @code{incf} which invoke this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1556 setf-method will insert temporary variables as needed to make
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1557 sure the apparent order of evaluation is preserved.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1558
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1559 Another example drawn from the standard package:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1560
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1561 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1562 (defsetf nth (n x) (store)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1563 (list 'setcar (list 'nthcdr n x) store))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1564 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1565 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1566
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1567 @defspec define-setf-method access-fn arglist forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1568 This is the most general way to create new place forms. When
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1569 a @code{setf} to @var{access-fn} with arguments described by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1570 @var{arglist} is expanded, the @var{forms} are evaluated and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1571 must return a list of five items:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1572
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1573 @enumerate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1574 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1575 A list of @dfn{temporary variables}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1576
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1577 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1578 A list of @dfn{value forms} corresponding to the temporary variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1579 above. The temporary variables will be bound to these value forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1580 as the first step of any operation on the generalized variable.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1581
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1582 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1583 A list of exactly one @dfn{store variable} (generally obtained
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1584 from a call to @code{gensym}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1585
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1586 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1587 A Lisp form which stores the contents of the store variable into
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1588 the generalized variable, assuming the temporaries have been
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1589 bound as described above.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1590
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1591 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1592 A Lisp form which accesses the contents of the generalized variable,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1593 assuming the temporaries have been bound.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1594 @end enumerate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1595
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1596 This is exactly like the Common Lisp macro of the same name,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1597 except that the method returns a list of five values rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1598 than the five values themselves, since Emacs Lisp does not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1599 support Common Lisp's notion of multiple return values.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1600
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1601 Once again, the @var{forms} may begin with a documentation string.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1602
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1603 A setf-method should be maximally conservative with regard to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1604 temporary variables. In the setf-methods generated by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1605 @code{defsetf}, the second return value is simply the list of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1606 arguments in the place form, and the first return value is a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1607 list of a corresponding number of temporary variables generated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1608 by @code{gensym}. Macros like @code{setf} and @code{incf} which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1609 use this setf-method will optimize away most temporaries that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1610 turn out to be unnecessary, so there is little reason for the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1611 setf-method itself to optimize.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1612 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1613
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1614 @defun get-setf-method place &optional env
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1615 This function returns the setf-method for @var{place}, by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1616 invoking the definition previously recorded by @code{defsetf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1617 or @code{define-setf-method}. The result is a list of five
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1618 values as described above. You can use this function to build
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1619 your own @code{incf}-like modify macros. (Actually, it is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1620 better to use the internal functions @code{cl-setf-do-modify}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1621 and @code{cl-setf-do-store}, which are a bit easier to use and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1622 which also do a number of optimizations; consult the source
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1623 code for the @code{incf} function for a simple example.)
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1624
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1625 The argument @var{env} specifies the ``environment'' to be
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1626 passed on to @code{macroexpand} if @code{get-setf-method} should
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1627 need to expand a macro in @var{place}. It should come from
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1628 an @code{&environment} argument to the macro or setf-method
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1629 that called @code{get-setf-method}.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1630
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parents:
diff changeset
1631 See also the source code for the setf-methods for @code{apply}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1632 and @code{substring}, each of which works by calling
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1633 @code{get-setf-method} on a simpler case, then massaging
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parents:
diff changeset
1634 the result in various ways.
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parents:
diff changeset
1635 @end defun
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parents:
diff changeset
1636
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1637 Modern Common Lisp defines a second, independent way to specify
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1638 the @code{setf} behavior of a function, namely ``@code{setf}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1639 functions'' whose names are lists @code{(setf @var{name})}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1640 rather than symbols. For example, @code{(defun (setf foo) @dots{})}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1641 defines the function that is used when @code{setf} is applied to
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1642 @code{foo}. This package does not currently support @code{setf}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1643 functions. In particular, it is a compile-time error to use
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1644 @code{setf} on a form which has not already been @code{defsetf}'d
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1645 or otherwise declared; in newer Common Lisps, this would not be
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1646 an error since the function @code{(setf @var{func})} might be
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1647 defined later.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1648
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1649 @iftex
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parents:
diff changeset
1650 @secno=4
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1651 @end iftex
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parents:
diff changeset
1652
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parents:
diff changeset
1653 @node Variable Bindings, Conditionals, Generalized Variables, Control Structure
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1654 @section Variable Bindings
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1655
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parents:
diff changeset
1656 @noindent
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parents:
diff changeset
1657 These Lisp forms make bindings to variables and function names,
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1658 analogous to Lisp's built-in @code{let} form.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1659
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1660 @xref{Modify Macros}, for the @code{letf} and @code{letf*} forms which
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1661 are also related to variable bindings.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1662
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1663 @menu
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parents:
diff changeset
1664 * Dynamic Bindings:: The `progv' form
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1665 * Lexical Bindings:: `lexical-let' and lexical closures
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parents:
diff changeset
1666 * Function Bindings:: `flet' and `labels'
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parents:
diff changeset
1667 * Macro Bindings:: `macrolet' and `symbol-macrolet'
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parents:
diff changeset
1668 @end menu
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parents:
diff changeset
1669
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1670 @node Dynamic Bindings, Lexical Bindings, Variable Bindings, Variable Bindings
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1671 @subsection Dynamic Bindings
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1672
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parents:
diff changeset
1673 @noindent
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1674 The standard @code{let} form binds variables whose names are known
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1675 at compile-time. The @code{progv} form provides an easy way to
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1676 bind variables whose names are computed at run-time.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1677
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1678 @defspec progv symbols values forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1679 This form establishes @code{let}-style variable bindings on a
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1680 set of variables computed at run-time. The expressions
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1681 @var{symbols} and @var{values} are evaluated, and must return lists
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1682 of symbols and values, respectively. The symbols are bound to the
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1683 corresponding values for the duration of the body @var{form}s.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1684 If @var{values} is shorter than @var{symbols}, the last few symbols
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1685 are made unbound (as if by @code{makunbound}) inside the body.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1686 If @var{symbols} is shorter than @var{values}, the excess values
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1687 are ignored.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1688 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1689
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1690 @node Lexical Bindings, Function Bindings, Dynamic Bindings, Variable Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1691 @subsection Lexical Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1692
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1693 @noindent
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1694 The @dfn{CL} package defines the following macro which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1695 more closely follows the Common Lisp @code{let} form:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1696
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1697 @defspec lexical-let (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1698 This form is exactly like @code{let} except that the bindings it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1699 establishes are purely lexical. Lexical bindings are similar to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1700 local variables in a language like C: Only the code physically
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1701 within the body of the @code{lexical-let} (after macro expansion)
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1702 may refer to the bound variables.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1703
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1704 @example
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1705 (setq a 5)
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1706 (defun foo (b) (+ a b))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1707 (let ((a 2)) (foo a))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1708 @result{} 4
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1709 (lexical-let ((a 2)) (foo a))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1710 @result{} 7
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1711 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1712
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1713 @noindent
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1714 In this example, a regular @code{let} binding of @code{a} actually
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1715 makes a temporary change to the global variable @code{a}, so @code{foo}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1716 is able to see the binding of @code{a} to 2. But @code{lexical-let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1717 actually creates a distinct local variable @code{a} for use within its
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1718 body, without any effect on the global variable of the same name.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1719
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1720 The most important use of lexical bindings is to create @dfn{closures}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1721 A closure is a function object that refers to an outside lexical
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1722 variable. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1723
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1724 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1725 (defun make-adder (n)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1726 (lexical-let ((n n))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1727 (function (lambda (m) (+ n m)))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1728 (setq add17 (make-adder 17))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1729 (funcall add17 4)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1730 @result{} 21
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1731 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1732
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1733 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1734 The call @code{(make-adder 17)} returns a function object which adds
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1735 17 to its argument. If @code{let} had been used instead of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1736 @code{lexical-let}, the function object would have referred to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1737 global @code{n}, which would have been bound to 17 only during the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1738 call to @code{make-adder} itself.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1739
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1740 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1741 (defun make-counter ()
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1742 (lexical-let ((n 0))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1743 (function* (lambda (&optional (m 1)) (incf n m)))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1744 (setq count-1 (make-counter))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1745 (funcall count-1 3)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1746 @result{} 3
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1747 (funcall count-1 14)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1748 @result{} 17
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1749 (setq count-2 (make-counter))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1750 (funcall count-2 5)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1751 @result{} 5
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1752 (funcall count-1 2)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1753 @result{} 19
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1754 (funcall count-2)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1755 @result{} 6
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1756 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1757
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1758 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1759 Here we see that each call to @code{make-counter} creates a distinct
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1760 local variable @code{n}, which serves as a private counter for the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1761 function object that is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1762
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1763 Closed-over lexical variables persist until the last reference to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1764 them goes away, just like all other Lisp objects. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1765 @code{count-2} refers to a function object which refers to an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1766 instance of the variable @code{n}; this is the only reference
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1767 to that variable, so after @code{(setq count-2 nil)} the garbage
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1768 collector would be able to delete this instance of @code{n}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1769 Of course, if a @code{lexical-let} does not actually create any
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1770 closures, then the lexical variables are free as soon as the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1771 @code{lexical-let} returns.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1772
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1773 Many closures are used only during the extent of the bindings they
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1774 refer to; these are known as ``downward funargs'' in Lisp parlance.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1775 When a closure is used in this way, regular Emacs Lisp dynamic
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1776 bindings suffice and will be more efficient than @code{lexical-let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1777 closures:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1778
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1779 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1780 (defun add-to-list (x list)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1781 (mapcar (function (lambda (y) (+ x y))) list))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1782 (add-to-list 7 '(1 2 5))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1783 @result{} (8 9 12)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1784 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1785
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1786 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1787 Since this lambda is only used while @code{x} is still bound,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1788 it is not necessary to make a true closure out of it.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1789
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1790 You can use @code{defun} or @code{flet} inside a @code{lexical-let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1791 to create a named closure. If several closures are created in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1792 body of a single @code{lexical-let}, they all close over the same
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1793 instance of the lexical variable.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1794
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1795 The @code{lexical-let} form is an extension to Common Lisp. In
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1796 true Common Lisp, all bindings are lexical unless declared otherwise.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1797 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1798
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1799 @defspec lexical-let* (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1800 This form is just like @code{lexical-let}, except that the bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1801 are made sequentially in the manner of @code{let*}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1802 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1803
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1804 @node Function Bindings, Macro Bindings, Lexical Bindings, Variable Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1805 @subsection Function Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1806
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
1807 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1808 These forms make @code{let}-like bindings to functions instead
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1809 of variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1810
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1811 @defspec flet (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1812 This form establishes @code{let}-style bindings on the function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1813 cells of symbols rather than on the value cells. Each @var{binding}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1814 must be a list of the form @samp{(@var{name} @var{arglist}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1815 @var{forms}@dots{})}, which defines a function exactly as if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1816 it were a @code{defun*} form. The function @var{name} is defined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1817 accordingly for the duration of the body of the @code{flet}; then
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1818 the old function definition, or lack thereof, is restored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1819
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1820 While @code{flet} in Common Lisp establishes a lexical binding of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1821 @var{name}, Emacs Lisp @code{flet} makes a dynamic binding. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1822 result is that @code{flet} affects indirect calls to a function as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1823 well as calls directly inside the @code{flet} form itself.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1824
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1825 You can use @code{flet} to disable or modify the behavior of a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1826 function in a temporary fashion. This will even work on Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1827 primitives, although note that some calls to primitive functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1828 internal to Emacs are made without going through the symbol's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1829 function cell, and so will not be affected by @code{flet}. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1830 example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1831
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1832 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1833 (flet ((message (&rest args) (push args saved-msgs)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1834 (do-something))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1835 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1836
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1837 This code attempts to replace the built-in function @code{message}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1838 with a function that simply saves the messages in a list rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1839 than displaying them. The original definition of @code{message}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1840 will be restored after @code{do-something} exits. This code will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1841 work fine on messages generated by other Lisp code, but messages
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1842 generated directly inside Emacs will not be caught since they make
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1843 direct C-language calls to the message routines rather than going
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1844 through the Lisp @code{message} function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1845
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1846 Functions defined by @code{flet} may use the full Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1847 argument notation supported by @code{defun*}; also, the function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1848 body is enclosed in an implicit block as if by @code{defun*}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1849 @xref{Program Structure}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1850 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1851
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1852 @defspec labels (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1853 The @code{labels} form is a synonym for @code{flet}. (In Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1854 Lisp, @code{labels} and @code{flet} differ in ways that depend on
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1855 their lexical scoping; these distinctions vanish in dynamically
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1856 scoped Emacs Lisp.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1857 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1858
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1859 @node Macro Bindings, , Function Bindings, Variable Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1860 @subsection Macro Bindings
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1861
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1862 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1863 These forms create local macros and ``symbol macros.''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1864
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1865 @defspec macrolet (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1866 This form is analogous to @code{flet}, but for macros instead of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1867 functions. Each @var{binding} is a list of the same form as the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1868 arguments to @code{defmacro*} (i.e., a macro name, argument list,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1869 and macro-expander forms). The macro is defined accordingly for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1870 use within the body of the @code{macrolet}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1871
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1872 Because of the nature of macros, @code{macrolet} is lexically
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1873 scoped even in Emacs Lisp: The @code{macrolet} binding will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1874 affect only calls that appear physically within the body
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1875 @var{forms}, possibly after expansion of other macros in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1876 body.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1877 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1878
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1879 @defspec symbol-macrolet (bindings@dots{}) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1880 This form creates @dfn{symbol macros}, which are macros that look
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1881 like variable references rather than function calls. Each
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1882 @var{binding} is a list @samp{(@var{var} @var{expansion})};
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1883 any reference to @var{var} within the body @var{forms} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1884 replaced by @var{expansion}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1885
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1886 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1887 (setq bar '(5 . 9))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1888 (symbol-macrolet ((foo (car bar)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1889 (incf foo))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1890 bar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1891 @result{} (6 . 9)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1892 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1893
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1894 A @code{setq} of a symbol macro is treated the same as a @code{setf}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1895 I.e., @code{(setq foo 4)} in the above would be equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1896 @code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1897
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1898 Likewise, a @code{let} or @code{let*} binding a symbol macro is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1899 treated like a @code{letf} or @code{letf*}. This differs from true
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1900 Common Lisp, where the rules of lexical scoping cause a @code{let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1901 binding to shadow a @code{symbol-macrolet} binding. In this package,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1902 only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1903 macro.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1904
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1905 There is no analogue of @code{defmacro} for symbol macros; all symbol
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1906 macros are local. A typical use of @code{symbol-macrolet} is in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1907 expansion of another macro:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1908
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1909 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1910 (defmacro* my-dolist ((x list) &rest body)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1911 (let ((var (gensym)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1912 (list 'loop 'for var 'on list 'do
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1913 (list* 'symbol-macrolet (list (list x (list 'car var)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1914 body))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1915
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1916 (setq mylist '(1 2 3 4))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1917 (my-dolist (x mylist) (incf x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1918 mylist
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1919 @result{} (2 3 4 5)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1920 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1921
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1922 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1923 In this example, the @code{my-dolist} macro is similar to @code{dolist}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1924 (@pxref{Iteration}) except that the variable @code{x} becomes a true
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1925 reference onto the elements of the list. The @code{my-dolist} call
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1926 shown here expands to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1927
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1928 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1929 (loop for G1234 on mylist do
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1930 (symbol-macrolet ((x (car G1234)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1931 (incf x)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1932 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1933
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1934 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1935 which in turn expands to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1936
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1937 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1938 (loop for G1234 on mylist do (incf (car G1234)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1939 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1940
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1941 @xref{Loop Facility}, for a description of the @code{loop} macro.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1942 This package defines a nonstandard @code{in-ref} loop clause that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1943 works much like @code{my-dolist}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1944 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1945
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1946 @node Conditionals, Blocks and Exits, Variable Bindings, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1947 @section Conditionals
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1948
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1949 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1950 These conditional forms augment Emacs Lisp's simple @code{if},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1951 @code{and}, @code{or}, and @code{cond} forms.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1952
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1953 @defspec when test forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1954 This is a variant of @code{if} where there are no ``else'' forms,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1955 and possibly several ``then'' forms. In particular,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1956
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1957 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1958 (when @var{test} @var{a} @var{b} @var{c})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1959 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1960
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1961 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1962 is entirely equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1963
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1964 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1965 (if @var{test} (progn @var{a} @var{b} @var{c}) nil)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1966 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1967 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1968
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1969 @defspec unless test forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1970 This is a variant of @code{if} where there are no ``then'' forms,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1971 and possibly several ``else'' forms:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1972
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1973 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1974 (unless @var{test} @var{a} @var{b} @var{c})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1975 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1976
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1977 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1978 is entirely equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1979
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1980 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1981 (when (not @var{test}) @var{a} @var{b} @var{c})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1982 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1983 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1984
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1985 @defspec case keyform clause@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1986 This macro evaluates @var{keyform}, then compares it with the key
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1987 values listed in the various @var{clause}s. Whichever clause matches
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1988 the key is executed; comparison is done by @code{eql}. If no clause
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1989 matches, the @code{case} form returns @code{nil}. The clauses are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1990 of the form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1991
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1992 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1993 (@var{keylist} @var{body-forms}@dots{})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1994 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1995
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1996 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1997 where @var{keylist} is a list of key values. If there is exactly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1998 one value, and it is not a cons cell or the symbol @code{nil} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
1999 @code{t}, then it can be used by itself as a @var{keylist} without
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2000 being enclosed in a list. All key values in the @code{case} form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2001 must be distinct. The final clauses may use @code{t} in place of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2002 a @var{keylist} to indicate a default clause that should be taken
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2003 if none of the other clauses match. (The symbol @code{otherwise}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2004 is also recognized in place of @code{t}. To make a clause that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2005 matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2006 enclose the symbol in a list.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2007
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2008 For example, this expression reads a keystroke, then does one of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2009 four things depending on whether it is an @samp{a}, a @samp{b},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2010 a @key{RET} or @key{LFD}, or anything else.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2011
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2012 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2013 (case (read-char)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2014 (?a (do-a-thing))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2015 (?b (do-b-thing))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2016 ((?\r ?\n) (do-ret-thing))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2017 (t (do-other-thing)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2018 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2019 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2020
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2021 @defspec ecase keyform clause@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2022 This macro is just like @code{case}, except that if the key does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2023 not match any of the clauses, an error is signalled rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2024 simply returning @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2025 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2026
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2027 @defspec typecase keyform clause@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2028 This macro is a version of @code{case} that checks for types
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2029 rather than values. Each @var{clause} is of the form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2030 @samp{(@var{type} @var{body}...)}. @xref{Type Predicates},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2031 for a description of type specifiers. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2032
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2033 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2034 (typecase x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2035 (integer (munch-integer x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2036 (float (munch-float x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2037 (string (munch-integer (string-to-int x)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2038 (t (munch-anything x)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2039 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2040
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2041 The type specifier @code{t} matches any type of object; the word
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2042 @code{otherwise} is also allowed. To make one clause match any of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2043 several types, use an @code{(or ...)} type specifier.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2044 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2045
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2046 @defspec etypecase keyform clause@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2047 This macro is just like @code{typecase}, except that if the key does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2048 not match any of the clauses, an error is signalled rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2049 simply returning @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2050 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2051
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2052 @node Blocks and Exits, Iteration, Conditionals, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2053 @section Blocks and Exits
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2054
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2055 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2056 Common Lisp @dfn{blocks} provide a non-local exit mechanism very
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2057 similar to @code{catch} and @code{throw}, but lexically rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2058 dynamically scoped. This package actually implements @code{block}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2059 in terms of @code{catch}; however, the lexical scoping allows the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2060 optimizing byte-compiler to omit the costly @code{catch} step if the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2061 body of the block does not actually @code{return-from} the block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2062
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2063 @defspec block name forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2064 The @var{forms} are evaluated as if by a @code{progn}. However,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2065 if any of the @var{forms} execute @code{(return-from @var{name})},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2066 they will jump out and return directly from the @code{block} form.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2067 The @code{block} returns the result of the last @var{form} unless
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2068 a @code{return-from} occurs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2069
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2070 The @code{block}/@code{return-from} mechanism is quite similar to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2071 the @code{catch}/@code{throw} mechanism. The main differences are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2072 that block @var{name}s are unevaluated symbols, rather than forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2073 (such as quoted symbols) which evaluate to a tag at run-time; and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2074 also that blocks are lexically scoped whereas @code{catch}/@code{throw}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2075 are dynamically scoped. This means that functions called from the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2076 body of a @code{catch} can also @code{throw} to the @code{catch},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2077 but the @code{return-from} referring to a block name must appear
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2078 physically within the @var{forms} that make up the body of the block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2079 They may not appear within other called functions, although they may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2080 appear within macro expansions or @code{lambda}s in the body. Block
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2081 names and @code{catch} names form independent name-spaces.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2082
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2083 In true Common Lisp, @code{defun} and @code{defmacro} surround
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2084 the function or expander bodies with implicit blocks with the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2085 same name as the function or macro. This does not occur in Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2086 Lisp, but this package provides @code{defun*} and @code{defmacro*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2087 forms which do create the implicit block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2088
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2089 The Common Lisp looping constructs defined by this package,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2090 such as @code{loop} and @code{dolist}, also create implicit blocks
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2091 just as in Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2092
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2093 Because they are implemented in terms of Emacs Lisp @code{catch}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2094 and @code{throw}, blocks have the same overhead as actual
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2095 @code{catch} constructs (roughly two function calls). However,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2096 Zawinski and Furuseth's optimizing byte compiler (standard in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2097 Emacs 19) will optimize away the @code{catch} if the block does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2098 not in fact contain any @code{return} or @code{return-from} calls
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2099 that jump to it. This means that @code{do} loops and @code{defun*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2100 functions which don't use @code{return} don't pay the overhead to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2101 support it.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2102 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2103
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2104 @defspec return-from name [result]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2105 This macro returns from the block named @var{name}, which must be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2106 an (unevaluated) symbol. If a @var{result} form is specified, it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2107 is evaluated to produce the result returned from the @code{block}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2108 Otherwise, @code{nil} is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2109 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2110
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2111 @defspec return [result]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2112 This macro is exactly like @code{(return-from nil @var{result})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2113 Common Lisp loops like @code{do} and @code{dolist} implicitly enclose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2114 themselves in @code{nil} blocks.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2115 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2116
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2117 @node Iteration, Loop Facility, Blocks and Exits, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2118 @section Iteration
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2119
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2120 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2121 The macros described here provide more sophisticated, high-level
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2122 looping constructs to complement Emacs Lisp's basic @code{while}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2123 loop.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2124
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2125 @defspec loop forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2126 The @dfn{CL} package supports both the simple, old-style meaning of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2127 @code{loop} and the extremely powerful and flexible feature known as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2128 the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2129 facility is discussed in the following section; @pxref{Loop Facility}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2130 The simple form of @code{loop} is described here.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2131
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2132 If @code{loop} is followed by zero or more Lisp expressions,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2133 then @code{(loop @var{exprs}@dots{})} simply creates an infinite
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2134 loop executing the expressions over and over. The loop is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2135 enclosed in an implicit @code{nil} block. Thus,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2136
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2137 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2138 (loop (foo) (if (no-more) (return 72)) (bar))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2139 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2140
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2141 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2142 is exactly equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2143
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2144 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2145 (block nil (while t (foo) (if (no-more) (return 72)) (bar)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2146 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2147
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2148 If any of the expressions are plain symbols, the loop is instead
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2149 interpreted as a Loop Macro specification as described later.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2150 (This is not a restriction in practice, since a plain symbol
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2151 in the above notation would simply access and throw away the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2152 value of a variable.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2153 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2154
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2155 @defspec do (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2156 This macro creates a general iterative loop. Each @var{spec} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2157 of the form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2158
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2159 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2160 (@var{var} [@var{init} [@var{step}]])
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2161 @end example
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diff changeset
2162
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2163 The loop works as follows: First, each @var{var} is bound to the
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2164 associated @var{init} value as if by a @code{let} form. Then, in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2165 each iteration of the loop, the @var{end-test} is evaluated; if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2166 true, the loop is finished. Otherwise, the body @var{forms} are
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2167 evaluated, then each @var{var} is set to the associated @var{step}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2168 expression (as if by a @code{psetq} form) and the next iteration
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2169 begins. Once the @var{end-test} becomes true, the @var{result}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2170 forms are evaluated (with the @var{var}s still bound to their
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2171 values) to produce the result returned by @code{do}.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2172
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2173 The entire @code{do} loop is enclosed in an implicit @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2174 block, so that you can use @code{(return)} to break out of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2175 loop at any time.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2176
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cvs
parents:
diff changeset
2177 If there are no @var{result} forms, the loop returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2178 If a given @var{var} has no @var{step} form, it is bound to its
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2179 @var{init} value but not otherwise modified during the @code{do}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2180 loop (unless the code explicitly modifies it); this case is just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2181 a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
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parents:
diff changeset
2182 around the loop. If @var{init} is also omitted it defaults to
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2183 @code{nil}, and in this case a plain @samp{@var{var}} can be used
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2184 in place of @samp{(@var{var})}, again following the analogy with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2185 @code{let}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2186
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2187 This example (from Steele) illustrates a loop which applies the
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2188 function @code{f} to successive pairs of values from the lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2189 @code{foo} and @code{bar}; it is equivalent to the call
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2190 @code{(mapcar* 'f foo bar)}. Note that this loop has no body
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2191 @var{forms} at all, performing all its work as side effects of
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parents:
diff changeset
2192 the rest of the loop.
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2193
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parents:
diff changeset
2194 @example
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parents:
diff changeset
2195 (do ((x foo (cdr x))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2196 (y bar (cdr y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2197 (z nil (cons (f (car x) (car y)) z)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2198 ((or (null x) (null y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2199 (nreverse z)))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2200 @end example
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parents:
diff changeset
2201 @end defspec
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2202
376386a54a3c Import from CVS: tag r19-14
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diff changeset
2203 @defspec do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2204 This is to @code{do} what @code{let*} is to @code{let}. In
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2205 particular, the initial values are bound as if by @code{let*}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2206 rather than @code{let}, and the steps are assigned as if by
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2207 @code{setq} rather than @code{psetq}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2208
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2209 Here is another way to write the above loop:
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2210
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2211 @example
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parents:
diff changeset
2212 (do* ((xp foo (cdr xp))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2213 (yp bar (cdr yp))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2214 (x (car xp) (car xp))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2215 (y (car yp) (car yp))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2216 z)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2217 ((or (null xp) (null yp))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2218 (nreverse z))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2219 (push (f x y) z))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2220 @end example
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2221 @end defspec
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diff changeset
2222
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2223 @defspec dolist (var list [result]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2224 This is a more specialized loop which iterates across the elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2225 of a list. @var{list} should evaluate to a list; the body @var{forms}
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2226 are executed with @var{var} bound to each element of the list in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2227 turn. Finally, the @var{result} form (or @code{nil}) is evaluated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2228 with @var{var} bound to @code{nil} to produce the result returned by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2229 the loop. The loop is surrounded by an implicit @code{nil} block.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2230 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2231
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2232 @defspec dotimes (var count [result]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2233 This is a more specialized loop which iterates a specified number
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2234 of times. The body is executed with @var{var} bound to the integers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2235 from zero (inclusive) to @var{count} (exclusive), in turn. Then
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2236 the @code{result} form is evaluated with @var{var} bound to the total
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2237 number of iterations that were done (i.e., @code{(max 0 @var{count})})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2238 to get the return value for the loop form. The loop is surrounded
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2239 by an implicit @code{nil} block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2240 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2241
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2242 @defspec do-symbols (var [obarray [result]]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2243 This loop iterates over all interned symbols. If @var{obarray}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2244 is specified and is not @code{nil}, it loops over all symbols in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2245 that obarray. For each symbol, the body @var{forms} are evaluated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2246 with @var{var} bound to that symbol. The symbols are visited in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2247 an unspecified order. Afterward the @var{result} form, if any,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2248 is evaluated (with @var{var} bound to @code{nil}) to get the return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2249 value. The loop is surrounded by an implicit @code{nil} block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2250 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2251
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2252 @defspec do-all-symbols (var [result]) forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2253 This is identical to @code{do-symbols} except that the @var{obarray}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2254 argument is omitted; it always iterates over the default obarray.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2255 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2256
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2257 @xref{Mapping over Sequences}, for some more functions for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2258 iterating over vectors or lists.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2259
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2260 @node Loop Facility, Multiple Values, Iteration, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2261 @section Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2262
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2263 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2264 A common complaint with Lisp's traditional looping constructs is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2265 that they are either too simple and limited, such as Common Lisp's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2266 @code{dotimes} or Emacs Lisp's @code{while}, or too unreadable and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2267 obscure, like Common Lisp's @code{do} loop.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2268
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2269 To remedy this, recent versions of Common Lisp have added a new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2270 construct called the ``Loop Facility'' or ``@code{loop} macro,''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2271 with an easy-to-use but very powerful and expressive syntax.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2272
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2273 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2274 * Loop Basics:: `loop' macro, basic clause structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2275 * Loop Examples:: Working examples of `loop' macro
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2276 * For Clauses:: Clauses introduced by `for' or `as'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2277 * Iteration Clauses:: `repeat', `while', `thereis', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2278 * Accumulation Clauses:: `collect', `sum', `maximize', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2279 * Other Clauses:: `with', `if', `initially', `finally'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2280 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2281
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2282 @node Loop Basics, Loop Examples, Loop Facility, Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2283 @subsection Loop Basics
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2284
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2285 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2286 The @code{loop} macro essentially creates a mini-language within
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2287 Lisp that is specially tailored for describing loops. While this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2288 language is a little strange-looking by the standards of regular Lisp,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2289 it turns out to be very easy to learn and well-suited to its purpose.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2290
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2291 Since @code{loop} is a macro, all parsing of the loop language
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2292 takes place at byte-compile time; compiled @code{loop}s are just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2293 as efficient as the equivalent @code{while} loops written longhand.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2294
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2295 @defspec loop clauses@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2296 A loop construct consists of a series of @var{clause}s, each
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2297 introduced by a symbol like @code{for} or @code{do}. Clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2298 are simply strung together in the argument list of @code{loop},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2299 with minimal extra parentheses. The various types of clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2300 specify initializations, such as the binding of temporary
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2301 variables, actions to be taken in the loop, stepping actions,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2302 and final cleanup.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2303
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2304 Common Lisp specifies a certain general order of clauses in a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2305 loop:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2306
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2307 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2308 (loop @var{name-clause}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2309 @var{var-clauses}@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2310 @var{action-clauses}@dots{})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2311 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2312
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2313 The @var{name-clause} optionally gives a name to the implicit
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2314 block that surrounds the loop. By default, the implicit block
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2315 is named @code{nil}. The @var{var-clauses} specify what
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2316 variables should be bound during the loop, and how they should
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2317 be modified or iterated throughout the course of the loop. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2318 @var{action-clauses} are things to be done during the loop, such
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2319 as computing, collecting, and returning values.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2320
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2321 The Emacs version of the @code{loop} macro is less restrictive about
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2322 the order of clauses, but things will behave most predictably if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2323 you put the variable-binding clauses @code{with}, @code{for}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2324 @code{repeat} before the action clauses. As in Common Lisp,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2325 @code{initially} and @code{finally} clauses can go anywhere.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2326
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2327 Loops generally return @code{nil} by default, but you can cause
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2328 them to return a value by using an accumulation clause like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2329 @code{collect}, an end-test clause like @code{always}, or an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2330 explicit @code{return} clause to jump out of the implicit block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2331 (Because the loop body is enclosed in an implicit block, you can
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2332 also use regular Lisp @code{return} or @code{return-from} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2333 break out of the loop.)
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parents:
diff changeset
2334 @end defspec
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cvs
parents:
diff changeset
2335
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2336 The following sections give some examples of the Loop Macro in
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cvs
parents:
diff changeset
2337 action, and describe the particular loop clauses in great detail.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2338 Consult the second edition of Steele's @dfn{Common Lisp, the Language},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2339 for additional discussion and examples of the @code{loop} macro.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2340
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2341 @node Loop Examples, For Clauses, Loop Basics, Loop Facility
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cvs
parents:
diff changeset
2342 @subsection Loop Examples
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2343
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2344 @noindent
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parents:
diff changeset
2345 Before listing the full set of clauses that are allowed, let's
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2346 look at a few example loops just to get a feel for the @code{loop}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2347 language.
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2348
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2349 @example
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parents:
diff changeset
2350 (loop for buf in (buffer-list)
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parents:
diff changeset
2351 collect (buffer-file-name buf))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2352 @end example
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cvs
parents:
diff changeset
2353
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2354 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2355 This loop iterates over all Emacs buffers, using the list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2356 returned by @code{buffer-list}. For each buffer @code{buf},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2357 it calls @code{buffer-file-name} and collects the results into
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cvs
parents:
diff changeset
2358 a list, which is then returned from the @code{loop} construct.
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cvs
parents:
diff changeset
2359 The result is a list of the file names of all the buffers in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2360 Emacs' memory. The words @code{for}, @code{in}, and @code{collect}
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cvs
parents:
diff changeset
2361 are reserved words in the @code{loop} language.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2362
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2363 @example
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cvs
parents:
diff changeset
2364 (loop repeat 20 do (insert "Yowsa\n"))
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cvs
parents:
diff changeset
2365 @end example
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cvs
parents:
diff changeset
2366
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2367 @noindent
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cvs
parents:
diff changeset
2368 This loop inserts the phrase ``Yowsa'' twenty times in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2369 current buffer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2370
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2371 @example
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cvs
parents:
diff changeset
2372 (loop until (eobp) do (munch-line) (forward-line 1))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2373 @end example
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cvs
parents:
diff changeset
2374
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2375 @noindent
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cvs
parents:
diff changeset
2376 This loop calls @code{munch-line} on every line until the end
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2377 of the buffer. If point is already at the end of the buffer,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2378 the loop exits immediately.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2379
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cvs
parents:
diff changeset
2380 @example
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cvs
parents:
diff changeset
2381 (loop do (munch-line) until (eobp) do (forward-line 1))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2382 @end example
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cvs
parents:
diff changeset
2383
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2384 @noindent
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cvs
parents:
diff changeset
2385 This loop is similar to the above one, except that @code{munch-line}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2386 is always called at least once.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2387
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2388 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2389 (loop for x from 1 to 100
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2390 for y = (* x x)
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cvs
parents:
diff changeset
2391 until (>= y 729)
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cvs
parents:
diff changeset
2392 finally return (list x (= y 729)))
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2393 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2394
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2395 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2396 This more complicated loop searches for a number @code{x} whose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2397 square is 729. For safety's sake it only examines @code{x}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2398 values up to 100; dropping the phrase @samp{to 100} would
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2399 cause the loop to count upwards with no limit. The second
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2400 @code{for} clause defines @code{y} to be the square of @code{x}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2401 within the loop; the expression after the @code{=} sign is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2402 reevaluated each time through the loop. The @code{until}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2403 clause gives a condition for terminating the loop, and the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2404 @code{finally} clause says what to do when the loop finishes.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2405 (This particular example was written less concisely than it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2406 could have been, just for the sake of illustration.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2407
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2408 Note that even though this loop contains three clauses (two
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2409 @code{for}s and an @code{until}) that would have been enough to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2410 define loops all by themselves, it still creates a single loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2411 rather than some sort of triple-nested loop. You must explicitly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2412 nest your @code{loop} constructs if you want nested loops.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2413
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2414 @node For Clauses, Iteration Clauses, Loop Examples, Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2415 @subsection For Clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2416
376386a54a3c Import from CVS: tag r19-14
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parents:
diff changeset
2417 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2418 Most loops are governed by one or more @code{for} clauses.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2419 A @code{for} clause simultaneously describes variables to be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2420 bound, how those variables are to be stepped during the loop,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2421 and usually an end condition based on those variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2422
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2423 The word @code{as} is a synonym for the word @code{for}. This
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2424 word is followed by a variable name, then a word like @code{from}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2425 or @code{across} that describes the kind of iteration desired.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2426 In Common Lisp, the phrase @code{being the} sometimes precedes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2427 the type of iteration; in this package both @code{being} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2428 @code{the} are optional. The word @code{each} is a synonym
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2429 for @code{the}, and the word that follows it may be singular
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2430 or plural: @samp{for x being the elements of y} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2431 @samp{for x being each element of y}. Which form you use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2432 is purely a matter of style.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2433
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2434 The variable is bound around the loop as if by @code{let}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2435
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2436 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2437 (setq i 'happy)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2438 (loop for i from 1 to 10 do (do-something-with i))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2439 i
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2440 @result{} happy
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2441 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2442
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2443 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2444 @item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2445 This type of @code{for} clause creates a counting loop. Each of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2446 the three sub-terms is optional, though there must be at least one
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2447 term so that the clause is marked as a counting clause.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2448
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2449 The three expressions are the starting value, the ending value, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2450 the step value, respectively, of the variable. The loop counts
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2451 upwards by default (@var{expr3} must be positive), from @var{expr1}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2452 to @var{expr2} inclusively. If you omit the @code{from} term, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2453 loop counts from zero; if you omit the @code{to} term, the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2454 counts forever without stopping (unless stopped by some other
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2455 loop clause, of course); if you omit the @code{by} term, the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2456 counts in steps of one.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2457
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2458 You can replace the word @code{from} with @code{upfrom} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2459 @code{downfrom} to indicate the direction of the loop. Likewise,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2460 you can replace @code{to} with @code{upto} or @code{downto}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2461 For example, @samp{for x from 5 downto 1} executes five times
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2462 with @code{x} taking on the integers from 5 down to 1 in turn.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2463 Also, you can replace @code{to} with @code{below} or @code{above},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2464 which are like @code{upto} and @code{downto} respectively except
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2465 that they are exclusive rather than inclusive limits:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2466
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2467 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2468 (loop for x to 10 collect x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2469 @result{} (0 1 2 3 4 5 6 7 8 9 10)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2470 (loop for x below 10 collect x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2471 @result{} (0 1 2 3 4 5 6 7 8 9)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2472 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2473
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2474 The @code{by} value is always positive, even for downward-counting
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2475 loops. Some sort of @code{from} value is required for downward
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2476 loops; @samp{for x downto 5} is not a legal loop clause all by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2477 itself.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2478
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2479 @item for @var{var} in @var{list} by @var{function}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2480 This clause iterates @var{var} over all the elements of @var{list},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2481 in turn. If you specify the @code{by} term, then @var{function}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2482 is used to traverse the list instead of @code{cdr}; it must be a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2483 function taking one argument. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2484
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2485 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2486 (loop for x in '(1 2 3 4 5 6) collect (* x x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2487 @result{} (1 4 9 16 25 36)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2488 (loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2489 @result{} (1 9 25)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2490 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2491
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2492 @item for @var{var} on @var{list} by @var{function}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2493 This clause iterates @var{var} over all the cons cells of @var{list}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2494
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2495 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2496 (loop for x on '(1 2 3 4) collect x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2497 @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2498 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2499
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2500 With @code{by}, there is no real reason that the @code{on} expression
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2501 must be a list. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2502
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2503 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2504 (loop for x on first-animal by 'next-animal collect x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2505 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2506
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2507 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2508 where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2509 the next in the (assumed) sequence of animals, or @code{nil} if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2510 @var{x} was the last animal in the sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2511
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2512 @item for @var{var} in-ref @var{list} by @var{function}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2513 This is like a regular @code{in} clause, but @var{var} becomes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2514 a @code{setf}-able ``reference'' onto the elements of the list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2515 rather than just a temporary variable. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2516
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2517 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2518 (loop for x in-ref my-list do (incf x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2519 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2520
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2521 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2522 increments every element of @code{my-list} in place. This clause
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2523 is an extension to standard Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2524
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2525 @item for @var{var} across @var{array}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2526 This clause iterates @var{var} over all the elements of @var{array},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2527 which may be a vector or a string.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2528
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2529 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2530 (loop for x across "aeiou"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2531 do (use-vowel (char-to-string x)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2532 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2533
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2534 @item for @var{var} across-ref @var{array}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2535 This clause iterates over an array, with @var{var} a @code{setf}-able
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2536 reference onto the elements; see @code{in-ref} above.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2537
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2538 @item for @var{var} being the elements of @var{sequence}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2539 This clause iterates over the elements of @var{sequence}, which may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2540 be a list, vector, or string. Since the type must be determined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2541 at run-time, this is somewhat less efficient than @code{in} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2542 @code{across}. The clause may be followed by the additional term
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2543 @samp{using (index @var{var2})} to cause @var{var2} to be bound to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2544 the successive indices (starting at 0) of the elements.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2545
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2546 This clause type is taken from older versions of the @code{loop} macro,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2547 and is not present in modern Common Lisp. The @samp{using (sequence ...)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2548 term of the older macros is not supported.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2549
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2550 @item for @var{var} being the elements of-ref @var{sequence}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2551 This clause iterates over a sequence, with @var{var} a @code{setf}-able
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2552 reference onto the elements; see @code{in-ref} above.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2553
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2554 @item for @var{var} being the symbols [of @var{obarray}]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2555 This clause iterates over symbols, either over all interned symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2556 or over all symbols in @var{obarray}. The loop is executed with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2557 @var{var} bound to each symbol in turn. The symbols are visited in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2558 an unspecified order.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2559
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2560 As an example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2561
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2562 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2563 (loop for sym being the symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2564 when (fboundp sym)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2565 when (string-match "^map" (symbol-name sym))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2566 collect sym)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2567 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2568
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2569 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2570 returns a list of all the functions whose names begin with @samp{map}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2571
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2572 The Common Lisp words @code{external-symbols} and @code{present-symbols}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2573 are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2574
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2575 Due to a minor implementation restriction, it will not work to have
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2576 more than one @code{for} clause iterating over symbols, hash tables,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2577 keymaps, overlays, or intervals in a given @code{loop}. Fortunately,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2578 it would rarely if ever be useful to do so. It @emph{is} legal to mix
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2579 one of these types of clauses with other clauses like @code{for ... to}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2580 or @code{while}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2581
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2582 @item for @var{var} being the hash-keys of @var{hash-table}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2583 This clause iterates over the entries in @var{hash-table}. For each
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2584 hash table entry, @var{var} is bound to the entry's key. If you write
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2585 @samp{the hash-values} instead, @var{var} is bound to the values
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2586 of the entries. The clause may be followed by the additional
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2587 term @samp{using (hash-values @var{var2})} (where @code{hash-values}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2588 is the opposite word of the word following @code{the}) to cause
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2589 @var{var} and @var{var2} to be bound to the two parts of each
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2590 hash table entry.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2591
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2592 @item for @var{var} being the key-codes of @var{keymap}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2593 This clause iterates over the entries in @var{keymap}. In GNU Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2594 18 and 19, keymaps are either alists or vectors, and key-codes are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2595 integers or symbols. In Lucid Emacs 19, keymaps are a special new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2596 data type, and key-codes are symbols or lists of symbols. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2597 iteration does not enter nested keymaps or inherited (parent) keymaps.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2598 You can use @samp{the key-bindings} to access the commands bound to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2599 the keys rather than the key codes, and you can add a @code{using}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2600 clause to access both the codes and the bindings together.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2601
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2602 @item for @var{var} being the key-seqs of @var{keymap}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2603 This clause iterates over all key sequences defined by @var{keymap}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2604 and its nested keymaps, where @var{var} takes on values which are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2605 strings in Emacs 18 or vectors in Emacs 19. The strings or vectors
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2606 are reused for each iteration, so you must copy them if you wish to keep
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2607 them permanently. You can add a @samp{using (key-bindings ...)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2608 clause to get the command bindings as well.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2609
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2610 @item for @var{var} being the overlays [of @var{buffer}] @dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2611 This clause iterates over the Emacs 19 ``overlays'' or Lucid
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2612 Emacs ``extents'' of a buffer (the clause @code{extents} is synonymous
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2613 with @code{overlays}). Under Emacs 18, this clause iterates zero
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2614 times. If the @code{of} term is omitted, the current buffer is used.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2615 This clause also accepts optional @samp{from @var{pos}} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2616 @samp{to @var{pos}} terms, limiting the clause to overlays which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2617 overlap the specified region.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2618
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2619 @item for @var{var} being the intervals [of @var{buffer}] @dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2620 This clause iterates over all intervals of a buffer with constant
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2621 text properties. The variable @var{var} will be bound to conses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2622 of start and end positions, where one start position is always equal
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2623 to the previous end position. The clause allows @code{of},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2624 @code{from}, @code{to}, and @code{property} terms, where the latter
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2625 term restricts the search to just the specified property. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2626 @code{of} term may specify either a buffer or a string. This
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2627 clause is useful only in GNU Emacs 19; in other versions, all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2628 buffers and strings consist of a single interval.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2629
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2630 @item for @var{var} being the frames
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2631 This clause iterates over all frames, i.e., X window system windows
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2632 open on Emacs files. This clause works only under Emacs 19. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2633 clause @code{screens} is a synonym for @code{frames}. The frames
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2634 are visited in @code{next-frame} order starting from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2635 @code{selected-frame}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2636
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2637 @item for @var{var} being the windows [of @var{frame}]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2638 This clause iterates over the windows (in the Emacs sense) of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2639 the current frame, or of the specified @var{frame}. (In Emacs 18
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2640 there is only ever one frame, and the @code{of} term is not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2641 allowed there.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2642
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2643 @item for @var{var} being the buffers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2644 This clause iterates over all buffers in Emacs. It is equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2645 to @samp{for @var{var} in (buffer-list)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2646
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2647 @item for @var{var} = @var{expr1} then @var{expr2}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2648 This clause does a general iteration. The first time through
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2649 the loop, @var{var} will be bound to @var{expr1}. On the second
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2650 and successive iterations it will be set by evaluating @var{expr2}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2651 (which may refer to the old value of @var{var}). For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2652 these two loops are effectively the same:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2653
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2654 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2655 (loop for x on my-list by 'cddr do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2656 (loop for x = my-list then (cddr x) while x do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2657 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2658
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2659 Note that this type of @code{for} clause does not imply any sort
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2660 of terminating condition; the above example combines it with a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2661 @code{while} clause to tell when to end the loop.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2662
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2663 If you omit the @code{then} term, @var{expr1} is used both for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2664 the initial setting and for successive settings:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2665
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2666 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2667 (loop for x = (random) when (> x 0) return x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2668 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2669
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2670 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2671 This loop keeps taking random numbers from the @code{(random)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2672 function until it gets a positive one, which it then returns.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2673 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2674
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2675 If you include several @code{for} clauses in a row, they are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2676 treated sequentially (as if by @code{let*} and @code{setq}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2677 You can instead use the word @code{and} to link the clauses,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2678 in which case they are processed in parallel (as if by @code{let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2679 and @code{psetq}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2680
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2681 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2682 (loop for x below 5 for y = nil then x collect (list x y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2683 @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2684 (loop for x below 5 and y = nil then x collect (list x y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2685 @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2686 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2687
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2688 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2689 In the first loop, @code{y} is set based on the value of @code{x}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2690 that was just set by the previous clause; in the second loop,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2691 @code{x} and @code{y} are set simultaneously so @code{y} is set
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2692 based on the value of @code{x} left over from the previous time
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2693 through the loop.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2694
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2695 Another feature of the @code{loop} macro is @dfn{destructuring},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2696 similar in concept to the destructuring provided by @code{defmacro}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2697 The @var{var} part of any @code{for} clause can be given as a list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2698 of variables instead of a single variable. The values produced
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2699 during loop execution must be lists; the values in the lists are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2700 stored in the corresponding variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2701
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2702 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2703 (loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2704 @result{} (5 9 13)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2705 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2706
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2707 In loop destructuring, if there are more values than variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2708 the trailing values are ignored, and if there are more variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2709 than values the trailing variables get the value @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2710 If @code{nil} is used as a variable name, the corresponding
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2711 values are ignored. Destructuring may be nested, and dotted
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2712 lists of variables like @code{(x . y)} are allowed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2713
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2714 @node Iteration Clauses, Accumulation Clauses, For Clauses, Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2715 @subsection Iteration Clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2716
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2717 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2718 Aside from @code{for} clauses, there are several other loop clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2719 that control the way the loop operates. They might be used by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2720 themselves, or in conjunction with one or more @code{for} clauses.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2721
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2722 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2723 @item repeat @var{integer}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2724 This clause simply counts up to the specified number using an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2725 internal temporary variable. The loops
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2726
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2727 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2728 (loop repeat n do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2729 (loop for temp to n do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2730 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2731
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2732 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2733 are identical except that the second one forces you to choose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2734 a name for a variable you aren't actually going to use.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2735
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2736 @item while @var{condition}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2737 This clause stops the loop when the specified condition (any Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2738 expression) becomes @code{nil}. For example, the following two
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2739 loops are equivalent, except for the implicit @code{nil} block
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2740 that surrounds the second one:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2741
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2742 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2743 (while @var{cond} @var{forms}@dots{})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2744 (loop while @var{cond} do @var{forms}@dots{})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2745 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2746
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2747 @item until @var{condition}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2748 This clause stops the loop when the specified condition is true,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2749 i.e., non-@code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2750
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2751 @item always @var{condition}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2752 This clause stops the loop when the specified condition is @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2753 Unlike @code{while}, it stops the loop using @code{return nil} so that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2754 the @code{finally} clauses are not executed. If all the conditions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2755 were non-@code{nil}, the loop returns @code{t}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2756
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2757 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2758 (if (loop for size in size-list always (> size 10))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2759 (some-big-sizes)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2760 (no-big-sizes))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2761 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2762
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2763 @item never @var{condition}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2764 This clause is like @code{always}, except that the loop returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2765 @code{t} if any conditions were false, or @code{nil} otherwise.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2766
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2767 @item thereis @var{condition}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2768 This clause stops the loop when the specified form is non-@code{nil};
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2769 in this case, it returns that non-@code{nil} value. If all the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2770 values were @code{nil}, the loop returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2771 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2772
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2773 @node Accumulation Clauses, Other Clauses, Iteration Clauses, Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2774 @subsection Accumulation Clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2775
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2776 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2777 These clauses cause the loop to accumulate information about the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2778 specified Lisp @var{form}. The accumulated result is returned
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2779 from the loop unless overridden, say, by a @code{return} clause.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2780
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2781 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2782 @item collect @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2783 This clause collects the values of @var{form} into a list. Several
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2784 examples of @code{collect} appear elsewhere in this manual.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2785
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2786 The word @code{collecting} is a synonym for @code{collect}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2787 likewise for the other accumulation clauses.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2788
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2789 @item append @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2790 This clause collects lists of values into a result list using
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2791 @code{append}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2792
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2793 @item nconc @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2794 This clause collects lists of values into a result list by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2795 destructively modifying the lists rather than copying them.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2796
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2797 @item concat @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2798 This clause concatenates the values of the specified @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2799 into a string. (It and the following clause are extensions to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2800 standard Common Lisp.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2801
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2802 @item vconcat @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2803 This clause concatenates the values of the specified @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2804 into a vector.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2805
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2806 @item count @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2807 This clause counts the number of times the specified @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2808 evaluates to a non-@code{nil} value.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2809
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2810 @item sum @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2811 This clause accumulates the sum of the values of the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2812 @var{form}, which must evaluate to a number.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2813
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2814 @item maximize @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2815 This clause accumulates the maximum value of the specified @var{form},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2816 which must evaluate to a number. The return value is undefined if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2817 @code{maximize} is executed zero times.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2818
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2819 @item minimize @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2820 This clause accumulates the minimum value of the specified @var{form}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2821 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2822
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2823 Accumulation clauses can be followed by @samp{into @var{var}} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2824 cause the data to be collected into variable @var{var} (which is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2825 automatically @code{let}-bound during the loop) rather than an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2826 unnamed temporary variable. Also, @code{into} accumulations do
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2827 not automatically imply a return value. The loop must use some
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2828 explicit mechanism, such as @code{finally return}, to return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2829 the accumulated result.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2830
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2831 It is legal for several accumulation clauses of the same type to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2832 accumulate into the same place. From Steele:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2833
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2834 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2835 (loop for name in '(fred sue alice joe june)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2836 for kids in '((bob ken) () () (kris sunshine) ())
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2837 collect name
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2838 append kids)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2839 @result{} (fred bob ken sue alice joe kris sunshine june)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2840 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2841
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2842 @node Other Clauses, , Accumulation Clauses, Loop Facility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2843 @subsection Other Clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2844
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2845 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2846 This section describes the remaining loop clauses.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2847
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2848 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2849 @item with @var{var} = @var{value}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2850 This clause binds a variable to a value around the loop, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2851 otherwise leaves the variable alone during the loop. The following
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2852 loops are basically equivalent:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2853
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2854 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2855 (loop with x = 17 do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2856 (let ((x 17)) (loop do ...))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2857 (loop for x = 17 then x do ...)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2858 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2859
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2860 Naturally, the variable @var{var} might be used for some purpose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2861 in the rest of the loop. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2862
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2863 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2864 (loop for x in my-list with res = nil do (push x res)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2865 finally return res)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2866 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2867
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2868 This loop inserts the elements of @code{my-list} at the front of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2869 a new list being accumulated in @code{res}, then returns the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2870 list @code{res} at the end of the loop. The effect is similar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2871 to that of a @code{collect} clause, but the list gets reversed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2872 by virtue of the fact that elements are being pushed onto the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2873 front of @code{res} rather than the end.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2874
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2875 If you omit the @code{=} term, the variable is initialized to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2876 @code{nil}. (Thus the @samp{= nil} in the above example is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2877 unnecessary.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2878
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2879 Bindings made by @code{with} are sequential by default, as if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2880 by @code{let*}. Just like @code{for} clauses, @code{with} clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2881 can be linked with @code{and} to cause the bindings to be made by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2882 @code{let} instead.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2883
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2884 @item if @var{condition} @var{clause}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2885 This clause executes the following loop clause only if the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2886 condition is true. The following @var{clause} should be an accumulation,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2887 @code{do}, @code{return}, @code{if}, or @code{unless} clause.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2888 Several clauses may be linked by separating them with @code{and}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2889 These clauses may be followed by @code{else} and a clause or clauses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2890 to execute if the condition was false. The whole construct may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2891 optionally be followed by the word @code{end} (which may be used to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2892 disambiguate an @code{else} or @code{and} in a nested @code{if}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2893
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2894 The actual non-@code{nil} value of the condition form is available
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2895 by the name @code{it} in the ``then'' part. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2896
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2897 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2898 (setq funny-numbers '(6 13 -1))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2899 @result{} (6 13 -1)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2900 (loop for x below 10
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2901 if (oddp x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2902 collect x into odds
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2903 and if (memq x funny-numbers) return (cdr it) end
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2904 else
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2905 collect x into evens
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2906 finally return (vector odds evens))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2907 @result{} [(1 3 5 7 9) (0 2 4 6 8)]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2908 (setq funny-numbers '(6 7 13 -1))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2909 @result{} (6 7 13 -1)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2910 (loop <@r{same thing again}>)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2911 @result{} (13 -1)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2912 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2913
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2914 Note the use of @code{and} to put two clauses into the ``then''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2915 part, one of which is itself an @code{if} clause. Note also that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2916 @code{end}, while normally optional, was necessary here to make
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2917 it clear that the @code{else} refers to the outermost @code{if}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2918 clause. In the first case, the loop returns a vector of lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2919 of the odd and even values of @var{x}. In the second case, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2920 odd number 7 is one of the @code{funny-numbers} so the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2921 returns early; the actual returned value is based on the result
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2922 of the @code{memq} call.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2923
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2924 @item when @var{condition} @var{clause}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2925 This clause is just a synonym for @code{if}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2926
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2927 @item unless @var{condition} @var{clause}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2928 The @code{unless} clause is just like @code{if} except that the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2929 sense of the condition is reversed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2930
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2931 @item named @var{name}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2932 This clause gives a name other than @code{nil} to the implicit
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2933 block surrounding the loop. The @var{name} is the symbol to be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2934 used as the block name.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2935
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2936 @item initially [do] @var{forms}...
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2937 This keyword introduces one or more Lisp forms which will be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2938 executed before the loop itself begins (but after any variables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2939 requested by @code{for} or @code{with} have been bound to their
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2940 initial values). @code{initially} clauses can appear anywhere;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2941 if there are several, they are executed in the order they appear
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2942 in the loop. The keyword @code{do} is optional.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2943
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2944 @item finally [do] @var{forms}...
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2945 This introduces Lisp forms which will be executed after the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2946 finishes (say, on request of a @code{for} or @code{while}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2947 @code{initially} and @code{finally} clauses may appear anywhere
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2948 in the loop construct, but they are executed (in the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2949 order) at the beginning or end, respectively, of the loop.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2950
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2951 @item finally return @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2952 This says that @var{form} should be executed after the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2953 is done to obtain a return value. (Without this, or some other
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2954 clause like @code{collect} or @code{return}, the loop will simply
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2955 return @code{nil}.) Variables bound by @code{for}, @code{with},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2956 or @code{into} will still contain their final values when @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2957 is executed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2958
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2959 @item do @var{forms}...
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2960 The word @code{do} may be followed by any number of Lisp expressions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2961 which are executed as an implicit @code{progn} in the body of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2962 loop. Many of the examples in this section illustrate the use of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2963 @code{do}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2964
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2965 @item return @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2966 This clause causes the loop to return immediately. The following
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2967 Lisp form is evaluated to give the return value of the @code{loop}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2968 form. The @code{finally} clauses, if any, are not executed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2969 Of course, @code{return} is generally used inside an @code{if} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2970 @code{unless}, as its use in a top-level loop clause would mean
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2971 the loop would never get to ``loop'' more than once.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2972
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2973 The clause @samp{return @var{form}} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2974 @samp{do (return @var{form})} (or @code{return-from} if the loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2975 was named). The @code{return} clause is implemented a bit more
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2976 efficiently, though.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2977 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2978
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2979 While there is no high-level way to add user extensions to @code{loop}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2980 (comparable to @code{defsetf} for @code{setf}, say), this package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2981 does offer two properties called @code{cl-loop-handler} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2982 @code{cl-loop-for-handler} which are functions to be called when
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2983 a given symbol is encountered as a top-level loop clause or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2984 @code{for} clause, respectively. Consult the source code in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2985 file @file{cl-macs.el} for details.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2986
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2987 This package's @code{loop} macro is compatible with that of Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2988 Lisp, except that a few features are not implemented: @code{loop-finish}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2989 and data-type specifiers. Naturally, the @code{for} clauses which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2990 iterate over keymaps, overlays, intervals, frames, windows, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2991 buffers are Emacs-specific extensions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2992
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2993 @node Multiple Values, , Loop Facility, Control Structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2994 @section Multiple Values
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2995
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2996 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2997 Common Lisp functions can return zero or more results. Emacs Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2998 functions, by contrast, always return exactly one result. This
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
2999 package makes no attempt to emulate Common Lisp multiple return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3000 values; Emacs versions of Common Lisp functions that return more
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3001 than one value either return just the first value (as in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3002 @code{compiler-macroexpand}) or return a list of values (as in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3003 @code{get-setf-method}). This package @emph{does} define placeholders
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3004 for the Common Lisp functions that work with multiple values, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3005 in Emacs Lisp these functions simply operate on lists instead.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3006 The @code{values} form, for example, is a synonym for @code{list}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3007 in Emacs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3008
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3009 @defspec multiple-value-bind (var@dots{}) values-form forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3010 This form evaluates @var{values-form}, which must return a list of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3011 values. It then binds the @var{var}s to these respective values,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3012 as if by @code{let}, and then executes the body @var{forms}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3013 If there are more @var{var}s than values, the extra @var{var}s
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3014 are bound to @code{nil}. If there are fewer @var{var}s than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3015 values, the excess values are ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3016 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3017
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3018 @defspec multiple-value-setq (var@dots{}) form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3019 This form evaluates @var{form}, which must return a list of values.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3020 It then sets the @var{var}s to these respective values, as if by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3021 @code{setq}. Extra @var{var}s or values are treated the same as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3022 in @code{multiple-value-bind}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3023 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3024
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3025 The older Quiroz package attempted a more faithful (but still
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3026 imperfect) emulation of Common Lisp multiple values. The old
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3027 method ``usually'' simulated true multiple values quite well,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3028 but under certain circumstances would leave spurious return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3029 values in memory where a later, unrelated @code{multiple-value-bind}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3030 form would see them.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3031
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3032 Since a perfect emulation is not feasible in Emacs Lisp, this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3033 package opts to keep it as simple and predictable as possible.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3034
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3035 @node Macros, Declarations, Control Structure, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3036 @chapter Macros
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3037
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3038 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3039 This package implements the various Common Lisp features of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3040 @code{defmacro}, such as destructuring, @code{&environment},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3041 and @code{&body}. Top-level @code{&whole} is not implemented
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3042 for @code{defmacro} due to technical difficulties.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3043 @xref{Argument Lists}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3044
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3045 Destructuring is made available to the user by way of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3046 following macro:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3047
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3048 @defspec destructuring-bind arglist expr forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3049 This macro expands to code which executes @var{forms}, with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3050 the variables in @var{arglist} bound to the list of values
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3051 returned by @var{expr}. The @var{arglist} can include all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3052 the features allowed for @code{defmacro} argument lists,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3053 including destructuring. (The @code{&environment} keyword
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3054 is not allowed.) The macro expansion will signal an error
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3055 if @var{expr} returns a list of the wrong number of arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3056 or with incorrect keyword arguments.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3057 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3058
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3059 This package also includes the Common Lisp @code{define-compiler-macro}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3060 facility, which allows you to define compile-time expansions and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3061 optimizations for your functions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3062
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3063 @defspec define-compiler-macro name arglist forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3064 This form is similar to @code{defmacro}, except that it only expands
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3065 calls to @var{name} at compile-time; calls processed by the Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3066 interpreter are not expanded, nor are they expanded by the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3067 @code{macroexpand} function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3068
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3069 The argument list may begin with a @code{&whole} keyword and a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3070 variable. This variable is bound to the macro-call form itself,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3071 i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3072 If the macro expander returns this form unchanged, then the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3073 compiler treats it as a normal function call. This allows
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3074 compiler macros to work as optimizers for special cases of a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3075 function, leaving complicated cases alone.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3076
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3077 For example, here is a simplified version of a definition that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3078 appears as a standard part of this package:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3079
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3080 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3081 (define-compiler-macro member* (&whole form a list &rest keys)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3082 (if (and (null keys)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3083 (eq (car-safe a) 'quote)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3084 (not (floatp-safe (cadr a))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3085 (list 'memq a list)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3086 form))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3087 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3088
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3089 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3090 This definition causes @code{(member* @var{a} @var{list})} to change
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3091 to a call to the faster @code{memq} in the common case where @var{a}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3092 is a non-floating-point constant; if @var{a} is anything else, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3093 if there are any keyword arguments in the call, then the original
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3094 @code{member*} call is left intact. (The actual compiler macro
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3095 for @code{member*} optimizes a number of other cases, including
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3096 common @code{:test} predicates.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3097 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3098
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3099 @defun compiler-macroexpand form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3100 This function is analogous to @code{macroexpand}, except that it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3101 expands compiler macros rather than regular macros. It returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3102 @var{form} unchanged if it is not a call to a function for which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3103 a compiler macro has been defined, or if that compiler macro
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3104 decided to punt by returning its @code{&whole} argument. Like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3105 @code{macroexpand}, it expands repeatedly until it reaches a form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3106 for which no further expansion is possible.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3107 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3108
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3109 @xref{Macro Bindings}, for descriptions of the @code{macrolet}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3110 and @code{symbol-macrolet} forms for making ``local'' macro
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3111 definitions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3112
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3113 @node Declarations, Symbols, Macros, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3114 @chapter Declarations
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3115
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3116 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3117 Common Lisp includes a complex and powerful ``declaration''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3118 mechanism that allows you to give the compiler special hints
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3119 about the types of data that will be stored in particular variables,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3120 and about the ways those variables and functions will be used. This
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3121 package defines versions of all the Common Lisp declaration forms:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3122 @code{declare}, @code{locally}, @code{proclaim}, @code{declaim},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3123 and @code{the}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3124
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3125 Most of the Common Lisp declarations are not currently useful in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3126 Emacs Lisp, as the byte-code system provides little opportunity
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3127 to benefit from type information, and @code{special} declarations
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3128 are redundant in a fully dynamically-scoped Lisp. A few
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3129 declarations are meaningful when the optimizing Emacs 19 byte
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3130 compiler is being used, however. Under the earlier non-optimizing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3131 compiler, these declarations will effectively be ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3132
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3133 @defun proclaim decl-spec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3134 This function records a ``global'' declaration specified by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3135 @var{decl-spec}. Since @code{proclaim} is a function, @var{decl-spec}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3136 is evaluated and thus should normally be quoted.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3137 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3138
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3139 @defspec declaim decl-specs@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3140 This macro is like @code{proclaim}, except that it takes any number
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3141 of @var{decl-spec} arguments, and the arguments are unevaluated and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3142 unquoted. The @code{declaim} macro also puts an @code{(eval-when
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3143 (compile load eval) ...)} around the declarations so that they will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3144 be registered at compile-time as well as at run-time. (This is vital,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3145 since normally the declarations are meant to influence the way the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3146 compiler treats the rest of the file that contains the @code{declaim}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3147 form.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3148 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3149
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3150 @defspec declare decl-specs@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3151 This macro is used to make declarations within functions and other
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3152 code. Common Lisp allows declarations in various locations, generally
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3153 at the beginning of any of the many ``implicit @code{progn}s''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3154 throughout Lisp syntax, such as function bodies, @code{let} bodies,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3155 etc. Currently the only declaration understood by @code{declare}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3156 is @code{special}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3157 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3158
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3159 @defspec locally declarations@dots{} forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3160 In this package, @code{locally} is no different from @code{progn}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3161 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3162
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3163 @defspec the type form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3164 Type information provided by @code{the} is ignored in this package;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3165 in other words, @code{(the @var{type} @var{form})} is equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3166 to @var{form}. Future versions of the optimizing byte-compiler may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3167 make use of this information.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3168
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3169 For example, @code{mapcar} can map over both lists and arrays. It is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3170 hard for the compiler to expand @code{mapcar} into an in-line loop
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3171 unless it knows whether the sequence will be a list or an array ahead
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3172 of time. With @code{(mapcar 'car (the vector foo))}, a future
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3173 compiler would have enough information to expand the loop in-line.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3174 For now, Emacs Lisp will treat the above code as exactly equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3175 to @code{(mapcar 'car foo)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3176 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3177
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3178 Each @var{decl-spec} in a @code{proclaim}, @code{declaim}, or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3179 @code{declare} should be a list beginning with a symbol that says
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3180 what kind of declaration it is. This package currently understands
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3181 @code{special}, @code{inline}, @code{notinline}, @code{optimize},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3182 and @code{warn} declarations. (The @code{warn} declaration is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3183 extension of standard Common Lisp.) Other Common Lisp declarations,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3184 such as @code{type} and @code{ftype}, are silently ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3185
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3186 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3187 @item special
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3188 Since all variables in Emacs Lisp are ``special'' (in the Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3189 Lisp sense), @code{special} declarations are only advisory. They
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3190 simply tell the optimizing byte compiler that the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3191 variables are intentionally being referred to without being
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3192 bound in the body of the function. The compiler normally emits
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3193 warnings for such references, since they could be typographical
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3194 errors for references to local variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3195
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3196 The declaration @code{(declare (special @var{var1} @var{var2}))} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3197 equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3198 optimizing compiler, or to nothing at all in older compilers (which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3199 do not warn for non-local references).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3200
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3201 In top-level contexts, it is generally better to write
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3202 @code{(defvar @var{var})} than @code{(declaim (special @var{var}))},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3203 since @code{defvar} makes your intentions clearer. But the older
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3204 byte compilers can not handle @code{defvar}s appearing inside of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3205 functions, while @code{(declare (special @var{var}))} takes care
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3206 to work correctly with all compilers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3207
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3208 @item inline
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3209 The @code{inline} @var{decl-spec} lists one or more functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3210 whose bodies should be expanded ``in-line'' into calling functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3211 whenever the compiler is able to arrange for it. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3212 the Common Lisp function @code{cadr} is declared @code{inline}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3213 by this package so that the form @code{(cadr @var{x})} will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3214 expand directly into @code{(car (cdr @var{x}))} when it is called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3215 in user functions, for a savings of one (relatively expensive)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3216 function call.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3217
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3218 The following declarations are all equivalent. Note that the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3219 @code{defsubst} form is a convenient way to define a function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3220 and declare it inline all at once, but it is available only in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3221 Emacs 19.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3222
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3223 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3224 (declaim (inline foo bar))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3225 (eval-when (compile load eval) (proclaim '(inline foo bar)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3226 (proclaim-inline foo bar) ; Lucid Emacs only
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3227 (defsubst foo (...) ...) ; instead of defun; Emacs 19 only
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3228 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3229
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3230 @strong{Note:} This declaration remains in effect after the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3231 containing source file is done. It is correct to use it to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3232 request that a function you have defined should be inlined,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3233 but it is impolite to use it to request inlining of an external
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3234 function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3235
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3236 In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3237 before a particular call to a function to cause just that call to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3238 be inlined; the current byte compilers provide no way to implement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3239 this, so @code{(declare (inline @dots{}))} is currently ignored by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3240 this package.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3241
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3242 @item notinline
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3243 The @code{notinline} declaration lists functions which should
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3244 not be inlined after all; it cancels a previous @code{inline}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3245 declaration.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3246
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3247 @item optimize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3248 This declaration controls how much optimization is performed by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3249 the compiler. Naturally, it is ignored by the earlier non-optimizing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3250 compilers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3251
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3252 The word @code{optimize} is followed by any number of lists like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3253 @code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3254 optimization ``qualities''; this package ignores all but @code{speed}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3255 and @code{safety}. The value of a quality should be an integer from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3256 0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important.''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3257 The default level for both qualities is 1.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3258
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3259 In this package, with the Emacs 19 optimizing compiler, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3260 @code{speed} quality is tied to the @code{byte-compile-optimize}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3261 flag, which is set to @code{nil} for @code{(speed 0)} and to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3262 @code{t} for higher settings; and the @code{safety} quality is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3263 tied to the @code{byte-compile-delete-errors} flag, which is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3264 set to @code{t} for @code{(safety 3)} and to @code{nil} for all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3265 lower settings. (The latter flag controls whether the compiler
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3266 is allowed to optimize out code whose only side-effect could
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3267 be to signal an error, e.g., rewriting @code{(progn foo bar)} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3268 @code{bar} when it is not known whether @code{foo} will be bound
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3269 at run-time.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3270
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3271 Note that even compiling with @code{(safety 0)}, the Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3272 byte-code system provides sufficient checking to prevent real
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3273 harm from being done. For example, barring serious bugs in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3274 Emacs itself, Emacs will not crash with a segmentation fault
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3275 just because of an error in a fully-optimized Lisp program.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3276
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3277 The @code{optimize} declaration is normally used in a top-level
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3278 @code{proclaim} or @code{declaim} in a file; Common Lisp allows
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3279 it to be used with @code{declare} to set the level of optimization
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3280 locally for a given form, but this will not work correctly with the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3281 current version of the optimizing compiler. (The @code{declare}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3282 will set the new optimization level, but that level will not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3283 automatically be unset after the enclosing form is done.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3284
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3285 @item warn
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3286 This declaration controls what sorts of warnings are generated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3287 by the byte compiler. Again, only the optimizing compiler
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3288 generates warnings. The word @code{warn} is followed by any
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3289 number of ``warning qualities,'' similar in form to optimization
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3290 qualities. The currently supported warning types are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3291 @code{redefine}, @code{callargs}, @code{unresolved}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3292 @code{free-vars}; in the current system, a value of 0 will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3293 disable these warnings and any higher value will enable them.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3294 See the documentation for the optimizing byte compiler for details.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3295 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3296
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3297 @node Symbols, Numbers, Declarations, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3298 @chapter Symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3299
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3300 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3301 This package defines several symbol-related features that were
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3302 missing from Emacs Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3303
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3304 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3305 * Property Lists:: `get*', `remprop', `getf', `remf'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3306 * Creating Symbols:: `gensym', `gentemp'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3307 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3308
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3309 @node Property Lists, Creating Symbols, Symbols, Symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3310 @section Property Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3311
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3312 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3313 These functions augment the standard Emacs Lisp functions @code{get}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3314 and @code{put} for operating on properties attached to symbols.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3315 There are also functions for working with property lists as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3316 first-class data structures not attached to particular symbols.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3317
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3318 @defun get* symbol property &optional default
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3319 This function is like @code{get}, except that if the property is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3320 not found, the @var{default} argument provides the return value.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3321 (The Emacs Lisp @code{get} function always uses @code{nil} as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3322 the default; this package's @code{get*} is equivalent to Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3323 Lisp's @code{get}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3324
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3325 The @code{get*} function is @code{setf}-able; when used in this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3326 fashion, the @var{default} argument is allowed but ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3327 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3328
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3329 @defun remprop symbol property
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3330 This function removes the entry for @var{property} from the property
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3331 list of @var{symbol}. It returns a true value if the property was
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3332 indeed found and removed, or @code{nil} if there was no such property.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3333 (This function was probably omitted from Emacs originally because,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3334 since @code{get} did not allow a @var{default}, it was very difficult
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3335 to distinguish between a missing property and a property whose value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3336 was @code{nil}; thus, setting a property to @code{nil} was close
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3337 enough to @code{remprop} for most purposes.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3338 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3339
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3340 @defun getf place property &optional default
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3341 This function scans the list @var{place} as if it were a property
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3342 list, i.e., a list of alternating property names and values. If
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3343 an even-numbered element of @var{place} is found which is @code{eq}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3344 to @var{property}, the following odd-numbered element is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3345 Otherwise, @var{default} is returned (or @code{nil} if no default
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3346 is given).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3347
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3348 In particular,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3349
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3350 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3351 (get sym prop) @equiv{} (getf (symbol-plist sym) prop)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3352 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3353
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3354 It is legal to use @code{getf} as a @code{setf} place, in which case
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3355 its @var{place} argument must itself be a legal @code{setf} place.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3356 The @var{default} argument, if any, is ignored in this context.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3357 The effect is to change (via @code{setcar}) the value cell in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3358 list that corresponds to @var{property}, or to cons a new property-value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3359 pair onto the list if the property is not yet present.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3360
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3361 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3362 (put sym prop val) @equiv{} (setf (getf (symbol-plist sym) prop) val)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3363 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3364
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3365 The @code{get} and @code{get*} functions are also @code{setf}-able.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3366 The fact that @code{default} is ignored can sometimes be useful:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3367
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3368 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3369 (incf (get* 'foo 'usage-count 0))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3370 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3371
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3372 Here, symbol @code{foo}'s @code{usage-count} property is incremented
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3373 if it exists, or set to 1 (an incremented 0) otherwise.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3374
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3375 When not used as a @code{setf} form, @code{getf} is just a regular
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3376 function and its @var{place} argument can actually be any Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3377 expression.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3378 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3379
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3380 @defspec remf place property
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3381 This macro removes the property-value pair for @var{property} from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3382 the property list stored at @var{place}, which is any @code{setf}-able
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3383 place expression. It returns true if the property was found. Note
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3384 that if @var{property} happens to be first on the list, this will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3385 effectively do a @code{(setf @var{place} (cddr @var{place}))},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3386 whereas if it occurs later, this simply uses @code{setcdr} to splice
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3387 out the property and value cells.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3388 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3389
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3390 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3391 @secno=2
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3392 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3393
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3394 @node Creating Symbols, , Property Lists, Symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3395 @section Creating Symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3396
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3397 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3398 These functions create unique symbols, typically for use as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3399 temporary variables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3400
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3401 @defun gensym &optional x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3402 This function creates a new, uninterned symbol (using @code{make-symbol})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3403 with a unique name. (The name of an uninterned symbol is relevant
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3404 only if the symbol is printed.) By default, the name is generated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3405 from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3406 @samp{G1002}, etc. If the optional argument @var{x} is a string, that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3407 string is used as a prefix instead of @samp{G}. Uninterned symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3408 are used in macro expansions for temporary variables, to ensure that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3409 their names will not conflict with ``real'' variables in the user's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3410 code.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3411 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3412
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3413 @defvar *gensym-counter*
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3414 This variable holds the counter used to generate @code{gensym} names.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3415 It is incremented after each use by @code{gensym}. In Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3416 this is initialized with 0, but this package initializes it with a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3417 random (time-dependent) value to avoid trouble when two files that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3418 each used @code{gensym} in their compilation are loaded together.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3419 (Uninterned symbols become interned when the compiler writes them
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3420 out to a file and the Emacs loader loads them, so their names have to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3421 be treated a bit more carefully than in Common Lisp where uninterned
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3422 symbols remain uninterned after loading.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3423 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3424
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3425 @defun gentemp &optional x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3426 This function is like @code{gensym}, except that it produces a new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3427 @emph{interned} symbol. If the symbol that is generated already
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3428 exists, the function keeps incrementing the counter and trying
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3429 again until a new symbol is generated.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3430 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3431
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3432 The Quiroz @file{cl.el} package also defined a @code{defkeyword}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3433 form for creating self-quoting keyword symbols. This package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3434 automatically creates all keywords that are called for by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3435 @code{&key} argument specifiers, and discourages the use of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3436 keywords as data unrelated to keyword arguments, so the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3437 @code{defkeyword} form has been discontinued.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3438
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3439 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3440 @chapno=11
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3441 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3442
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3443 @node Numbers, Sequences, Symbols, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3444 @chapter Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3445
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3446 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3447 This section defines a few simple Common Lisp operations on numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3448 which were left out of Emacs Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3449
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3450 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3451 * Predicates on Numbers:: `plusp', `oddp', `floatp-safe', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3452 * Numerical Functions:: `abs', `expt', `floor*', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3453 * Random Numbers:: `random*', `make-random-state'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3454 * Implementation Parameters:: `most-positive-fixnum', `most-positive-float'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3455 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3456
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3457 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3458 @secno=1
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3459 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3460
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3461 @node Predicates on Numbers, Numerical Functions, Numbers, Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3462 @section Predicates on Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3463
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3464 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3465 These functions return @code{t} if the specified condition is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3466 true of the numerical argument, or @code{nil} otherwise.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3467
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3468 @defun plusp number
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3469 This predicate tests whether @var{number} is positive. It is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3470 error if the argument is not a number.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3471 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3472
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3473 @defun minusp number
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3474 This predicate tests whether @var{number} is negative. It is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3475 error if the argument is not a number.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3476 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3477
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3478 @defun oddp integer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3479 This predicate tests whether @var{integer} is odd. It is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3480 error if the argument is not an integer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3481 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3482
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3483 @defun evenp integer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3484 This predicate tests whether @var{integer} is even. It is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3485 error if the argument is not an integer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3486 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3487
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3488 @defun floatp-safe object
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3489 This predicate tests whether @var{object} is a floating-point
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3490 number. On systems that support floating-point, this is equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3491 to @code{floatp}. On other systems, this always returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3492 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3493
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3494 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3495 @secno=3
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3496 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3497
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3498 @node Numerical Functions, Random Numbers, Predicates on Numbers, Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3499 @section Numerical Functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3500
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3501 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3502 These functions perform various arithmetic operations on numbers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3503
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3504 @defun abs number
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3505 This function returns the absolute value of @var{number}. (Newer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3506 versions of Emacs provide this as a built-in function; this package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3507 defines @code{abs} only for Emacs 18 versions which don't provide
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3508 it as a primitive.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3509 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3510
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3511 @defun expt base power
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3512 This function returns @var{base} raised to the power of @var{number}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3513 (Newer versions of Emacs provide this as a built-in function; this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3514 package defines @code{expt} only for Emacs 18 versions which don't
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3515 provide it as a primitive.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3516 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3517
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3518 @defun gcd &rest integers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3519 This function returns the Greatest Common Divisor of the arguments.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3520 For one argument, it returns the absolute value of that argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3521 For zero arguments, it returns zero.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3522 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3523
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3524 @defun lcm &rest integers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3525 This function returns the Least Common Multiple of the arguments.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3526 For one argument, it returns the absolute value of that argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3527 For zero arguments, it returns one.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3528 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3529
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3530 @defun isqrt integer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3531 This function computes the ``integer square root'' of its integer
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3532 argument, i.e., the greatest integer less than or equal to the true
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3533 square root of the argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3534 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3535
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3536 @defun floor* number &optional divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3537 This function implements the Common Lisp @code{floor} function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3538 It is called @code{floor*} to avoid name conflicts with the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3539 simpler @code{floor} function built-in to Emacs 19.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3540
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3541 With one argument, @code{floor*} returns a list of two numbers:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3542 The argument rounded down (toward minus infinity) to an integer,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3543 and the ``remainder'' which would have to be added back to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3544 first return value to yield the argument again. If the argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3545 is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3546 If the argument is an Emacs 19 floating-point number, the first
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3547 result is a Lisp integer and the second is a Lisp float between
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3548 0 (inclusive) and 1 (exclusive).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3549
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3550 With two arguments, @code{floor*} divides @var{number} by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3551 @var{divisor}, and returns the floor of the quotient and the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3552 corresponding remainder as a list of two numbers. If
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3553 @code{(floor* @var{x} @var{y})} returns @code{(@var{q} @var{r})},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3554 then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3555 between 0 (inclusive) and @var{r} (exclusive). Also, note
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3556 that @code{(floor* @var{x})} is exactly equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3557 @code{(floor* @var{x} 1)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3558
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3559 This function is entirely compatible with Common Lisp's @code{floor}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3560 function, except that it returns the two results in a list since
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3561 Emacs Lisp does not support multiple-valued functions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3562 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3563
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3564 @defun ceiling* number &optional divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3565 This function implements the Common Lisp @code{ceiling} function,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3566 which is analogous to @code{floor} except that it rounds the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3567 argument or quotient of the arguments up toward plus infinity.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3568 The remainder will be between 0 and minus @var{r}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3569 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3570
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3571 @defun truncate* number &optional divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3572 This function implements the Common Lisp @code{truncate} function,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3573 which is analogous to @code{floor} except that it rounds the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3574 argument or quotient of the arguments toward zero. Thus it is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3575 equivalent to @code{floor*} if the argument or quotient is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3576 positive, or to @code{ceiling*} otherwise. The remainder has
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3577 the same sign as @var{number}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3578 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3579
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3580 @defun round* number &optional divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3581 This function implements the Common Lisp @code{round} function,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3582 which is analogous to @code{floor} except that it rounds the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3583 argument or quotient of the arguments to the nearest integer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3584 In the case of a tie (the argument or quotient is exactly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3585 halfway between two integers), it rounds to the even integer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3586 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3587
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3588 @defun mod* number divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3589 This function returns the same value as the second return value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3590 of @code{floor}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3591 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3592
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3593 @defun rem* number divisor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3594 This function returns the same value as the second return value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3595 of @code{truncate}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3596 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3597
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3598 These definitions are compatible with those in the Quiroz
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3599 @file{cl.el} package, except that this package appends @samp{*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3600 to certain function names to avoid conflicts with existing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3601 Emacs 19 functions, and that the mechanism for returning
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3602 multiple values is different.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3603
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3604 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3605 @secno=8
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3606 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3607
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3608 @node Random Numbers, Implementation Parameters, Numerical Functions, Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3609 @section Random Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3610
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3611 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3612 This package also provides an implementation of the Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3613 random number generator. It uses its own additive-congruential
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3614 algorithm, which is much more likely to give statistically clean
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3615 random numbers than the simple generators supplied by many
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3616 operating systems.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3617
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3618 @defun random* number &optional state
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3619 This function returns a random nonnegative number less than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3620 @var{number}, and of the same type (either integer or floating-point).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3621 The @var{state} argument should be a @code{random-state} object
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3622 which holds the state of the random number generator. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3623 function modifies this state object as a side effect. If
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3624 @var{state} is omitted, it defaults to the variable
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3625 @code{*random-state*}, which contains a pre-initialized
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3626 @code{random-state} object.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3627 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3628
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3629 @defvar *random-state*
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3630 This variable contains the system ``default'' @code{random-state}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3631 object, used for calls to @code{random*} that do not specify an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3632 alternative state object. Since any number of programs in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3633 Emacs process may be accessing @code{*random-state*} in interleaved
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3634 fashion, the sequence generated from this variable will be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3635 irreproducible for all intents and purposes.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3636 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3637
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3638 @defun make-random-state &optional state
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3639 This function creates or copies a @code{random-state} object.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3640 If @var{state} is omitted or @code{nil}, it returns a new copy of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3641 @code{*random-state*}. This is a copy in the sense that future
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3642 sequences of calls to @code{(random* @var{n})} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3643 @code{(random* @var{n} @var{s})} (where @var{s} is the new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3644 random-state object) will return identical sequences of random
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3645 numbers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3646
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3647 If @var{state} is a @code{random-state} object, this function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3648 returns a copy of that object. If @var{state} is @code{t}, this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3649 function returns a new @code{random-state} object seeded from the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3650 date and time. As an extension to Common Lisp, @var{state} may also
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3651 be an integer in which case the new object is seeded from that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3652 integer; each different integer seed will result in a completely
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3653 different sequence of random numbers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3654
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3655 It is legal to print a @code{random-state} object to a buffer or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3656 file and later read it back with @code{read}. If a program wishes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3657 to use a sequence of pseudo-random numbers which can be reproduced
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3658 later for debugging, it can call @code{(make-random-state t)} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3659 get a new sequence, then print this sequence to a file. When the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3660 program is later rerun, it can read the original run's random-state
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3661 from the file.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3662 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3663
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3664 @defun random-state-p object
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3665 This predicate returns @code{t} if @var{object} is a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3666 @code{random-state} object, or @code{nil} otherwise.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3667 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3668
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3669 @node Implementation Parameters, , Random Numbers, Numbers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3670 @section Implementation Parameters
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3671
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3672 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3673 This package defines several useful constants having to with numbers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3674
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3675 @defvar most-positive-fixnum
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3676 This constant equals the largest value a Lisp integer can hold.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3677 It is typically @code{2^23-1} or @code{2^25-1}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3678 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3679
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3680 @defvar most-negative-fixnum
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3681 This constant equals the smallest (most negative) value a Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3682 integer can hold.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3683 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3684
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3685 The following parameters have to do with floating-point numbers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3686 This package determines their values by exercising the computer's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3687 floating-point arithmetic in various ways. Because this operation
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3688 might be slow, the code for initializing them is kept in a separate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3689 function that must be called before the parameters can be used.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3690
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3691 @defun cl-float-limits
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3692 This function makes sure that the Common Lisp floating-point
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3693 parameters like @code{most-positive-float} have been initialized.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3694 Until it is called, these parameters will be @code{nil}. If this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3695 version of Emacs does not support floats (e.g., most versions of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3696 Emacs 18), the parameters will remain @code{nil}. If the parameters
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3697 have already been initialized, the function returns immediately.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3698
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3699 The algorithm makes assumptions that will be valid for most modern
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3700 machines, but will fail if the machine's arithmetic is extremely
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3701 unusual, e.g., decimal.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3702 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3703
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3704 Since true Common Lisp supports up to four different floating-point
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3705 precisions, it has families of constants like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3706 @code{most-positive-single-float}, @code{most-positive-double-float},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3707 @code{most-positive-long-float}, and so on. Emacs has only one
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3708 floating-point precision, so this package omits the precision word
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3709 from the constants' names.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3710
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3711 @defvar most-positive-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3712 This constant equals the largest value a Lisp float can hold.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3713 For those systems whose arithmetic supports infinities, this is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3714 the largest @emph{finite} value. For IEEE machines, the value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3715 is approximately @code{1.79e+308}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3716 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3717
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3718 @defvar most-negative-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3719 This constant equals the most-negative value a Lisp float can hold.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3720 (It is assumed to be equal to @code{(- most-positive-float)}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3721 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3722
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3723 @defvar least-positive-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3724 This constant equals the smallest Lisp float value greater than zero.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3725 For IEEE machines, it is about @code{4.94e-324} if denormals are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3726 supported or @code{2.22e-308} if not.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3727 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3728
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3729 @defvar least-positive-normalized-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3730 This constant equals the smallest @emph{normalized} Lisp float greater
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3731 than zero, i.e., the smallest value for which IEEE denormalization
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3732 will not result in a loss of precision. For IEEE machines, this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3733 value is about @code{2.22e-308}. For machines that do not support
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3734 the concept of denormalization and gradual underflow, this constant
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3735 will always equal @code{least-positive-float}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3736 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3737
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3738 @defvar least-negative-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3739 This constant is the negative counterpart of @code{least-positive-float}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3740 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3741
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3742 @defvar least-negative-normalized-float
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3743 This constant is the negative counterpart of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3744 @code{least-positive-normalized-float}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3745 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3746
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3747 @defvar float-epsilon
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3748 This constant is the smallest positive Lisp float that can be added
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3749 to 1.0 to produce a distinct value. Adding a smaller number to 1.0
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3750 will yield 1.0 again due to roundoff. For IEEE machines, epsilon
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3751 is about @code{2.22e-16}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3752 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3753
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3754 @defvar float-negative-epsilon
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3755 This is the smallest positive value that can be subtracted from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3756 1.0 to produce a distinct value. For IEEE machines, it is about
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3757 @code{1.11e-16}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3758 @end defvar
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3759
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3760 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3761 @chapno=13
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3762 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3763
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3764 @node Sequences, Lists, Numbers, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3765 @chapter Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3766
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3767 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3768 Common Lisp defines a number of functions that operate on
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3769 @dfn{sequences}, which are either lists, strings, or vectors.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3770 Emacs Lisp includes a few of these, notably @code{elt} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3771 @code{length}; this package defines most of the rest.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3772
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3773 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3774 * Sequence Basics:: Arguments shared by all sequence functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3775 * Mapping over Sequences:: `mapcar*', `mapcan', `map', `every', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3776 * Sequence Functions:: `subseq', `remove*', `substitute', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3777 * Searching Sequences:: `find', `position', `count', `search', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3778 * Sorting Sequences:: `sort*', `stable-sort', `merge'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3779 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3780
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3781 @node Sequence Basics, Mapping over Sequences, Sequences, Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3782 @section Sequence Basics
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3783
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3784 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3785 Many of the sequence functions take keyword arguments; @pxref{Argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3786 Lists}. All keyword arguments are optional and, if specified,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3787 may appear in any order.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3788
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3789 The @code{:key} argument should be passed either @code{nil}, or a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3790 function of one argument. This key function is used as a filter
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3791 through which the elements of the sequence are seen; for example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3792 @code{(find x y :key 'car)} is similar to @code{(assoc* x y)}:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3793 It searches for an element of the list whose @code{car} equals
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3794 @code{x}, rather than for an element which equals @code{x} itself.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3795 If @code{:key} is omitted or @code{nil}, the filter is effectively
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3796 the identity function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3797
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3798 The @code{:test} and @code{:test-not} arguments should be either
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3799 @code{nil}, or functions of two arguments. The test function is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3800 used to compare two sequence elements, or to compare a search value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3801 with sequence elements. (The two values are passed to the test
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3802 function in the same order as the original sequence function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3803 arguments from which they are derived, or, if they both come from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3804 the same sequence, in the same order as they appear in that sequence.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3805 The @code{:test} argument specifies a function which must return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3806 true (non-@code{nil}) to indicate a match; instead, you may use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3807 @code{:test-not} to give a function which returns @emph{false} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3808 indicate a match. The default test function is @code{:test 'eql}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3809
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3810 Many functions which take @var{item} and @code{:test} or @code{:test-not}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3811 arguments also come in @code{-if} and @code{-if-not} varieties,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3812 where a @var{predicate} function is passed instead of @var{item},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3813 and sequence elements match if the predicate returns true on them
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3814 (or false in the case of @code{-if-not}). For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3815
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3816 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3817 (remove* 0 seq :test '=) @equiv{} (remove-if 'zerop seq)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3818 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3819
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3820 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3821 to remove all zeros from sequence @code{seq}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3822
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3823 Some operations can work on a subsequence of the argument sequence;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3824 these function take @code{:start} and @code{:end} arguments which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3825 default to zero and the length of the sequence, respectively.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3826 Only elements between @var{start} (inclusive) and @var{end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3827 (exclusive) are affected by the operation. The @var{end} argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3828 may be passed @code{nil} to signify the length of the sequence;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3829 otherwise, both @var{start} and @var{end} must be integers, with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3830 @code{0 <= @var{start} <= @var{end} <= (length @var{seq})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3831 If the function takes two sequence arguments, the limits are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3832 defined by keywords @code{:start1} and @code{:end1} for the first,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3833 and @code{:start2} and @code{:end2} for the second.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3834
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3835 A few functions accept a @code{:from-end} argument, which, if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3836 non-@code{nil}, causes the operation to go from right-to-left
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3837 through the sequence instead of left-to-right, and a @code{:count}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3838 argument, which specifies an integer maximum number of elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3839 to be removed or otherwise processed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3840
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3841 The sequence functions make no guarantees about the order in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3842 which the @code{:test}, @code{:test-not}, and @code{:key} functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3843 are called on various elements. Therefore, it is a bad idea to depend
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3844 on side effects of these functions. For example, @code{:from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3845 may cause the sequence to be scanned actually in reverse, or it may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3846 be scanned forwards but computing a result ``as if'' it were scanned
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3847 backwards. (Some functions, like @code{mapcar*} and @code{every},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3848 @emph{do} specify exactly the order in which the function is called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3849 so side effects are perfectly acceptable in those cases.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3850
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3851 Strings in GNU Emacs 19 may contain ``text properties'' as well
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3852 as character data. Except as noted, it is undefined whether or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3853 not text properties are preserved by sequence functions. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3854 example, @code{(remove* ?A @var{str})} may or may not preserve
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3855 the properties of the characters copied from @var{str} into the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3856 result.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3857
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3858 @node Mapping over Sequences, Sequence Functions, Sequence Basics, Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3859 @section Mapping over Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3860
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3861 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3862 These functions ``map'' the function you specify over the elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3863 of lists or arrays. They are all variations on the theme of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3864 built-in function @code{mapcar}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3865
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3866 @defun mapcar* function seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3867 This function calls @var{function} on successive parallel sets of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3868 elements from its argument sequences. Given a single @var{seq}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3869 argument it is equivalent to @code{mapcar}; given @var{n} sequences,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3870 it calls the function with the first elements of each of the sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3871 as the @var{n} arguments to yield the first element of the result
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3872 list, then with the second elements, and so on. The mapping stops as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3873 soon as the shortest sequence runs out. The argument sequences may
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3874 be any mixture of lists, strings, and vectors; the return sequence
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3875 is always a list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3876
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3877 Common Lisp's @code{mapcar} accepts multiple arguments but works
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3878 only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3879 argument. This package's @code{mapcar*} works as a compatible
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3880 superset of both.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3881 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3882
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3883 @defun map result-type function seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3884 This function maps @var{function} over the argument sequences,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3885 just like @code{mapcar*}, but it returns a sequence of type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3886 @var{result-type} rather than a list. @var{result-type} must
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3887 be one of the following symbols: @code{vector}, @code{string},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3888 @code{list} (in which case the effect is the same as for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3889 @code{mapcar*}), or @code{nil} (in which case the results are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3890 thrown away and @code{map} returns @code{nil}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3891 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3892
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3893 @defun maplist function list &rest more-lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3894 This function calls @var{function} on each of its argument lists,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3895 then on the @code{cdr}s of those lists, and so on, until the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3896 shortest list runs out. The results are returned in the form
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3897 of a list. Thus, @code{maplist} is like @code{mapcar*} except
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3898 that it passes in the list pointers themselves rather than the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3899 @code{car}s of the advancing pointers.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3900 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3901
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3902 @defun mapc function seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3903 This function is like @code{mapcar*}, except that the values
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3904 returned by @var{function} are ignored and thrown away rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3905 than being collected into a list. The return value of @code{mapc}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3906 is @var{seq}, the first sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3907 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3908
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3909 @defun mapl function list &rest more-lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3910 This function is like @code{maplist}, except that it throws away
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3911 the values returned by @var{function}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3912 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3913
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3914 @defun mapcan function seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3915 This function is like @code{mapcar*}, except that it concatenates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3916 the return values (which must be lists) using @code{nconc},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3917 rather than simply collecting them into a list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3918 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3919
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3920 @defun mapcon function list &rest more-lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3921 This function is like @code{maplist}, except that it concatenates
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3922 the return values using @code{nconc}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3923 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3924
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3925 @defun some predicate seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3926 This function calls @var{predicate} on each element of @var{seq}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3927 in turn; if @var{predicate} returns a non-@code{nil} value,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3928 @code{some} returns that value, otherwise it returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3929 Given several sequence arguments, it steps through the sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3930 in parallel until the shortest one runs out, just as in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3931 @code{mapcar*}. You can rely on the left-to-right order in which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3932 the elements are visited, and on the fact that mapping stops
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3933 immediately as soon as @var{predicate} returns non-@code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3934 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3935
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3936 @defun every predicate seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3937 This function calls @var{predicate} on each element of the sequence(s)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3938 in turn; it returns @code{nil} as soon as @var{predicate} returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3939 @code{nil} for any element, or @code{t} if the predicate was true
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3940 for all elements.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3941 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3942
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3943 @defun notany predicate seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3944 This function calls @var{predicate} on each element of the sequence(s)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3945 in turn; it returns @code{nil} as soon as @var{predicate} returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3946 a non-@code{nil} value for any element, or @code{t} if the predicate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3947 was @code{nil} for all elements.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3948 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3949
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3950 @defun notevery predicate seq &rest more-seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3951 This function calls @var{predicate} on each element of the sequence(s)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3952 in turn; it returns a non-@code{nil} value as soon as @var{predicate}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3953 returns @code{nil} for any element, or @code{t} if the predicate was
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3954 true for all elements.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3955 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3956
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3957 @defun reduce function seq @t{&key :from-end :start :end :initial-value :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3958 This function combines the elements of @var{seq} using an associative
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3959 binary operation. Suppose @var{function} is @code{*} and @var{seq} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3960 the list @code{(2 3 4 5)}. The first two elements of the list are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3961 combined with @code{(* 2 3) = 6}; this is combined with the next
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3962 element, @code{(* 6 4) = 24}, and that is combined with the final
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3963 element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3964 to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3965 an explicit call to @code{reduce}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3966
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3967 If @code{:from-end} is true, the reduction is right-associative instead
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3968 of left-associative:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3969
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3970 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3971 (reduce '- '(1 2 3 4))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3972 @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3973 (reduce '- '(1 2 3 4) :from-end t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3974 @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3975 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3976
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3977 If @code{:key} is specified, it is a function of one argument which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3978 is called on each of the sequence elements in turn.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3979
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3980 If @code{:initial-value} is specified, it is effectively added to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3981 front (or rear in the case of @code{:from-end}) of the sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3982 The @code{:key} function is @emph{not} applied to the initial value.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3983
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3984 If the sequence, including the initial value, has exactly one element
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3985 then that element is returned without ever calling @var{function}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3986 If the sequence is empty (and there is no initial value), then
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3987 @var{function} is called with no arguments to obtain the return value.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3988 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3989
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3990 All of these mapping operations can be expressed conveniently in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3991 terms of the @code{loop} macro. In compiled code, @code{loop} will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3992 be faster since it generates the loop as in-line code with no
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3993 function calls.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3994
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3995 @node Sequence Functions, Searching Sequences, Mapping over Sequences, Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3996 @section Sequence Functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3997
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3998 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
3999 This section describes a number of Common Lisp functions for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4000 operating on sequences.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4001
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4002 @defun subseq sequence start &optional end
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4003 This function returns a given subsequence of the argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4004 @var{sequence}, which may be a list, string, or vector.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4005 The indices @var{start} and @var{end} must be in range, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4006 @var{start} must be no greater than @var{end}. If @var{end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4007 is omitted, it defaults to the length of the sequence. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4008 return value is always a copy; it does not share structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4009 with @var{sequence}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4010
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4011 As an extension to Common Lisp, @var{start} and/or @var{end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4012 may be negative, in which case they represent a distance back
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4013 from the end of the sequence. This is for compatibility with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4014 Emacs' @code{substring} function. Note that @code{subseq} is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4015 the @emph{only} sequence function that allows negative
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4016 @var{start} and @var{end}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4017
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4018 You can use @code{setf} on a @code{subseq} form to replace a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4019 specified range of elements with elements from another sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4020 The replacement is done as if by @code{replace}, described below.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4021 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4022
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4023 @defun concatenate result-type &rest seqs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4024 This function concatenates the argument sequences together to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4025 form a result sequence of type @var{result-type}, one of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4026 symbols @code{vector}, @code{string}, or @code{list}. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4027 arguments are always copied, even in cases such as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4028 @code{(concatenate 'list '(1 2 3))} where the result is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4029 identical to an argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4030 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4031
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4032 @defun fill seq item @t{&key :start :end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4033 This function fills the elements of the sequence (or the specified
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4034 part of the sequence) with the value @var{item}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4035 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4036
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4037 @defun replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4038 This function copies part of @var{seq2} into part of @var{seq1}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4039 The sequence @var{seq1} is not stretched or resized; the amount
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4040 of data copied is simply the shorter of the source and destination
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4041 (sub)sequences. The function returns @var{seq1}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4042
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4043 If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4044 will work correctly even if the regions indicated by the start
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4045 and end arguments overlap. However, if @var{seq1} and @var{seq2}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4046 are lists which share storage but are not @code{eq}, and the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4047 start and end arguments specify overlapping regions, the effect
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4048 is undefined.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4049 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4050
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4051 @defun remove* item seq @t{&key :test :test-not :key :count :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4052 This returns a copy of @var{seq} with all elements matching
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4053 @var{item} removed. The result may share storage with or be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4054 @code{eq} to @var{seq} in some circumstances, but the original
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4055 @var{seq} will not be modified. The @code{:test}, @code{:test-not},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4056 and @code{:key} arguments define the matching test that is used;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4057 by default, elements @code{eql} to @var{item} are removed. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4058 @code{:count} argument specifies the maximum number of matching
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4059 elements that can be removed (only the leftmost @var{count} matches
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4060 are removed). The @code{:start} and @code{:end} arguments specify
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4061 a region in @var{seq} in which elements will be removed; elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4062 outside that region are not matched or removed. The @code{:from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4063 argument, if true, says that elements should be deleted from the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4064 end of the sequence rather than the beginning (this matters only
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4065 if @var{count} was also specified).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4066 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4067
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4068 @defun delete* item seq @t{&key :test :test-not :key :count :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4069 This deletes all elements of @var{seq} which match @var{item}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4070 It is a destructive operation. Since Emacs Lisp does not support
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4071 stretchable strings or vectors, this is the same as @code{remove*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4072 for those sequence types. On lists, @code{remove*} will copy the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4073 list if necessary to preserve the original list, whereas
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4074 @code{delete*} will splice out parts of the argument list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4075 Compare @code{append} and @code{nconc}, which are analogous
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4076 non-destructive and destructive list operations in Emacs Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4077 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4078
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4079 @findex remove-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4080 @findex remove-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4081 @findex delete-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4082 @findex delete-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4083 The predicate-oriented functions @code{remove-if}, @code{remove-if-not},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4084 @code{delete-if}, and @code{delete-if-not} are defined similarly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4085
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4086 @defun delete item list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4087 This MacLisp-compatible function deletes from @var{list} all elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4088 which are @code{equal} to @var{item}. The @code{delete} function is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4089 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4090 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4091
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4092 @defun remove item list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4093 This function removes from @var{list} all elements which are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4094 @code{equal} to @var{item}. This package defines it for symmetry
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4095 with @code{delete}, even though @code{remove} is not built-in to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4096 Emacs 19.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4097 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4098
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4099 @defun remq item list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4100 This function removes from @var{list} all elements which are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4101 @code{eq} to @var{item}. This package defines it for symmetry
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4102 with @code{delq}, even though @code{remq} is not built-in to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4103 Emacs 19.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4104 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4105
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4106 @defun remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4107 This function returns a copy of @var{seq} with duplicate elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4108 removed. Specifically, if two elements from the sequence match
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4109 according to the @code{:test}, @code{:test-not}, and @code{:key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4110 arguments, only the rightmost one is retained. If @code{:from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4111 is true, the leftmost one is retained instead. If @code{:start} or
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4112 @code{:end} is specified, only elements within that subsequence are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4113 examined or removed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4114 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4115
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4116 @defun delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4117 This function deletes duplicate elements from @var{seq}. It is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4118 a destructive version of @code{remove-duplicates}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4119 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4120
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4121 @defun substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4122 This function returns a copy of @var{seq}, with all elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4123 matching @var{old} replaced with @var{new}. The @code{:count},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4124 @code{:start}, @code{:end}, and @code{:from-end} arguments may be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4125 used to limit the number of substitutions made.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4126 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4127
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4128 @defun nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4129 This is a destructive version of @code{substitute}; it performs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4130 the substitution using @code{setcar} or @code{aset} rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4131 by returning a changed copy of the sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4132 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4133
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4134 @findex substitute-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4135 @findex substitute-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4136 @findex nsubstitute-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4137 @findex nsubstitute-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4138 The @code{substitute-if}, @code{substitute-if-not}, @code{nsubstitute-if},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4139 and @code{nsubstitute-if-not} functions are defined similarly. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4140 these, a @var{predicate} is given in place of the @var{old} argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4141
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4142 @node Searching Sequences, Sorting Sequences, Sequence Functions, Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4143 @section Searching Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4144
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4145 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4146 These functions search for elements or subsequences in a sequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4147 (See also @code{member*} and @code{assoc*}; @pxref{Lists}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4148
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4149 @defun find item seq @t{&key :test :test-not :key :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4150 This function searches @var{seq} for an element matching @var{item}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4151 If it finds a match, it returns the matching element. Otherwise,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4152 it returns @code{nil}. It returns the leftmost match, unless
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4153 @code{:from-end} is true, in which case it returns the rightmost
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4154 match. The @code{:start} and @code{:end} arguments may be used to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4155 limit the range of elements that are searched.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4156 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4157
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4158 @defun position item seq @t{&key :test :test-not :key :start :end :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4159 This function is like @code{find}, except that it returns the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4160 integer position in the sequence of the matching item rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4161 the item itself. The position is relative to the start of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4162 sequence as a whole, even if @code{:start} is non-zero. The function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4163 returns @code{nil} if no matching element was found.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4164 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4165
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4166 @defun count item seq @t{&key :test :test-not :key :start :end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4167 This function returns the number of elements of @var{seq} which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4168 match @var{item}. The result is always a nonnegative integer.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4169 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4170
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4171 @findex find-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4172 @findex find-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4173 @findex position-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4174 @findex position-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4175 @findex count-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4176 @findex count-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4177 The @code{find-if}, @code{find-if-not}, @code{position-if},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4178 @code{position-if-not}, @code{count-if}, and @code{count-if-not}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4179 functions are defined similarly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4180
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4181 @defun mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4182 This function compares the specified parts of @var{seq1} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4183 @var{seq2}. If they are the same length and the corresponding
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4184 elements match (according to @code{:test}, @code{:test-not},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4185 and @code{:key}), the function returns @code{nil}. If there is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4186 a mismatch, the function returns the index (relative to @var{seq1})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4187 of the first mismatching element. This will be the leftmost pair of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4188 elements which do not match, or the position at which the shorter of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4189 the two otherwise-matching sequences runs out.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4190
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4191 If @code{:from-end} is true, then the elements are compared from right
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4192 to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4193 If the sequences differ, then one plus the index of the rightmost
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4194 difference (relative to @var{seq1}) is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4195
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4196 An interesting example is @code{(mismatch str1 str2 :key 'upcase)},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4197 which compares two strings case-insensitively.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4198 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4199
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4200 @defun search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4201 This function searches @var{seq2} for a subsequence that matches
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4202 @var{seq1} (or part of it specified by @code{:start1} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4203 @code{:end1}.) Only matches which fall entirely within the region
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4204 defined by @code{:start2} and @code{:end2} will be considered.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4205 The return value is the index of the leftmost element of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4206 leftmost match, relative to the start of @var{seq2}, or @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4207 if no matches were found. If @code{:from-end} is true, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4208 function finds the @emph{rightmost} matching subsequence.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4209 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4210
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4211 @node Sorting Sequences, , Searching Sequences, Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4212 @section Sorting Sequences
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4213
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4214 @defun sort* seq predicate @t{&key :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4215 This function sorts @var{seq} into increasing order as determined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4216 by using @var{predicate} to compare pairs of elements. @var{predicate}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4217 should return true (non-@code{nil}) if and only if its first argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4218 is less than (not equal to) its second argument. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4219 @code{<} and @code{string-lessp} are suitable predicate functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4220 for sorting numbers and strings, respectively; @code{>} would sort
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4221 numbers into decreasing rather than increasing order.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4222
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4223 This function differs from Emacs' built-in @code{sort} in that it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4224 can operate on any type of sequence, not just lists. Also, it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4225 accepts a @code{:key} argument which is used to preprocess data
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4226 fed to the @var{predicate} function. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4227
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4228 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4229 (setq data (sort data 'string-lessp :key 'downcase))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4230 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4231
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4232 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4233 sorts @var{data}, a sequence of strings, into increasing alphabetical
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4234 order without regard to case. A @code{:key} function of @code{car}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4235 would be useful for sorting association lists.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4236
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4237 The @code{sort*} function is destructive; it sorts lists by actually
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4238 rearranging the @code{cdr} pointers in suitable fashion.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4239 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4240
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4241 @defun stable-sort seq predicate @t{&key :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4242 This function sorts @var{seq} @dfn{stably}, meaning two elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4243 which are equal in terms of @var{predicate} are guaranteed not to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4244 be rearranged out of their original order by the sort.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4245
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4246 In practice, @code{sort*} and @code{stable-sort} are equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4247 in Emacs Lisp because the underlying @code{sort} function is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4248 stable by default. However, this package reserves the right to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4249 use non-stable methods for @code{sort*} in the future.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4250 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4251
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4252 @defun merge type seq1 seq2 predicate @t{&key :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4253 This function merges two sequences @var{seq1} and @var{seq2} by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4254 interleaving their elements. The result sequence, of type @var{type}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4255 (in the sense of @code{concatenate}), has length equal to the sum
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4256 of the lengths of the two input sequences. The sequences may be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4257 modified destructively. Order of elements within @var{seq1} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4258 @var{seq2} is preserved in the interleaving; elements of the two
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4259 sequences are compared by @var{predicate} (in the sense of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4260 @code{sort}) and the lesser element goes first in the result.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4261 When elements are equal, those from @var{seq1} precede those from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4262 @var{seq2} in the result. Thus, if @var{seq1} and @var{seq2} are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4263 both sorted according to @var{predicate}, then the result will be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4264 a merged sequence which is (stably) sorted according to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4265 @var{predicate}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4266 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4267
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4268 @node Lists, Hash Tables, Sequences, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4269 @chapter Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4270
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4271 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4272 The functions described here operate on lists.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4273
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4274 @menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4275 * List Functions:: `caddr', `first', `last', `list*', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4276 * Substitution of Expressions:: `subst', `sublis', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4277 * Lists as Sets:: `member*', `adjoin', `union', etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4278 * Association Lists:: `assoc*', `rassoc*', `acons', `pairlis'
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4279 @end menu
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4280
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4281 @node List Functions, Substitution of Expressions, Lists, Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4282 @section List Functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4283
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4284 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4285 This section describes a number of simple operations on lists,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4286 i.e., chains of cons cells.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4287
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4288 @defun caddr x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4289 This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4290 Likewise, this package defines all 28 @code{c@var{xxx}r} functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4291 where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4292 All of these functions are @code{setf}-able, and calls to them
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4293 are expanded inline by the byte-compiler for maximum efficiency.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4294 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4295
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4296 @defun first x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4297 This function is a synonym for @code{(car @var{x})}. Likewise,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4298 the functions @code{second}, @code{third}, @dots{}, through
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4299 @code{tenth} return the given element of the list @var{x}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4300 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4301
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4302 @defun rest x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4303 This function is a synonym for @code{(cdr @var{x})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4304 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4305
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4306 @defun endp x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4307 Common Lisp defines this function to act like @code{null}, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4308 signalling an error if @code{x} is neither a @code{nil} nor a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4309 cons cell. This package simply defines @code{endp} as a synonym
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4310 for @code{null}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4311 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4312
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4313 @defun list-length x
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4314 This function returns the length of list @var{x}, exactly like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4315 @code{(length @var{x})}, except that if @var{x} is a circular
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4316 list (where the cdr-chain forms a loop rather than terminating
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4317 with @code{nil}), this function returns @code{nil}. (The regular
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4318 @code{length} function would get stuck if given a circular list.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4319 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4320
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4321 @defun last x &optional n
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4322 This function returns the last cons, or the @var{n}th-to-last cons,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4323 of the list @var{x}. If @var{n} is omitted it defaults to 1.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4324 The ``last cons'' means the first cons cell of the list whose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4325 @code{cdr} is not another cons cell. (For normal lists, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4326 @code{cdr} of the last cons will be @code{nil}.) This function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4327 returns @code{nil} if @var{x} is @code{nil} or shorter than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4328 @var{n}. Note that the last @emph{element} of the list is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4329 @code{(car (last @var{x}))}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4330 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4331
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4332 @defun butlast x &optional n
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4333 This function returns the list @var{x} with the last element,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4334 or the last @var{n} elements, removed. If @var{n} is greater
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4335 than zero it makes a copy of the list so as not to damage the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4336 original list. In general, @code{(append (butlast @var{x} @var{n})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4337 (last @var{x} @var{n}))} will return a list equal to @var{x}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4338 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4339
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4340 @defun nbutlast x &optional n
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4341 This is a version of @code{butlast} that works by destructively
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4342 modifying the @code{cdr} of the appropriate element, rather than
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4343 making a copy of the list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4344 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4345
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4346 @defun list* arg &rest others
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4347 This function constructs a list of its arguments. The final
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4348 argument becomes the @code{cdr} of the last cell constructed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4349 Thus, @code{(list* @var{a} @var{b} @var{c})} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4350 @code{(cons @var{a} (cons @var{b} @var{c}))}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4351 @code{(list* @var{a} @var{b} nil)} is equivalent to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4352 @code{(list @var{a} @var{b})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4353
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4354 (Note that this function really is called @code{list*} in Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4355 Lisp; it is not a name invented for this package like @code{member*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4356 or @code{defun*}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4357 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4358
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4359 @defun ldiff list sublist
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4360 If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4361 one of the cons cells of @var{list}, then this function returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4362 a copy of the part of @var{list} up to but not including
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4363 @var{sublist}. For example, @code{(ldiff x (cddr x))} returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4364 the first two elements of the list @code{x}. The result is a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4365 copy; the original @var{list} is not modified. If @var{sublist}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4366 is not a sublist of @var{list}, a copy of the entire @var{list}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4367 is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4368 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4369
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4370 @defun copy-list list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4371 This function returns a copy of the list @var{list}. It copies
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4372 dotted lists like @code{(1 2 . 3)} correctly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4373 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4374
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4375 @defun copy-tree x &optional vecp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4376 This function returns a copy of the tree of cons cells @var{x}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4377 Unlike @code{copy-sequence} (and its alias @code{copy-list}),
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4378 which copies only along the @code{cdr} direction, this function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4379 copies (recursively) along both the @code{car} and the @code{cdr}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4380 directions. If @var{x} is not a cons cell, the function simply
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4381 returns @var{x} unchanged. If the optional @var{vecp} argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4382 is true, this function copies vectors (recursively) as well as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4383 cons cells.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4384 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4385
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4386 @defun tree-equal x y @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4387 This function compares two trees of cons cells. If @var{x} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4388 @var{y} are both cons cells, their @code{car}s and @code{cdr}s are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4389 compared recursively. If neither @var{x} nor @var{y} is a cons
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4390 cell, they are compared by @code{eql}, or according to the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4391 specified test. The @code{:key} function, if specified, is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4392 applied to the elements of both trees. @xref{Sequences}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4393 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4394
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4395 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4396 @secno=3
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4397 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4398
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4399 @node Substitution of Expressions, Lists as Sets, List Functions, Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4400 @section Substitution of Expressions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4401
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4402 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4403 These functions substitute elements throughout a tree of cons
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4404 cells. (@xref{Sequence Functions}, for the @code{substitute}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4405 function, which works on just the top-level elements of a list.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4406
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4407 @defun subst new old tree @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4408 This function substitutes occurrences of @var{old} with @var{new}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4409 in @var{tree}, a tree of cons cells. It returns a substituted
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4410 tree, which will be a copy except that it may share storage with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4411 the argument @var{tree} in parts where no substitutions occurred.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4412 The original @var{tree} is not modified. This function recurses
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4413 on, and compares against @var{old}, both @code{car}s and @code{cdr}s
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4414 of the component cons cells. If @var{old} is itself a cons cell,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4415 then matching cells in the tree are substituted as usual without
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4416 recursively substituting in that cell. Comparisons with @var{old}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4417 are done according to the specified test (@code{eql} by default).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4418 The @code{:key} function is applied to the elements of the tree
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4419 but not to @var{old}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4420 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4421
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4422 @defun nsubst new old tree @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4423 This function is like @code{subst}, except that it works by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4424 destructive modification (by @code{setcar} or @code{setcdr})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4425 rather than copying.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4426 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4427
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4428 @findex subst-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4429 @findex subst-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4430 @findex nsubst-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4431 @findex nsubst-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4432 The @code{subst-if}, @code{subst-if-not}, @code{nsubst-if}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4433 @code{nsubst-if-not} functions are defined similarly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4434
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4435 @defun sublis alist tree @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4436 This function is like @code{subst}, except that it takes an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4437 association list @var{alist} of @var{old}-@var{new} pairs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4438 Each element of the tree (after applying the @code{:key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4439 function, if any), is compared with the @code{car}s of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4440 @var{alist}; if it matches, it is replaced by the corresponding
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4441 @code{cdr}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4442 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4443
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4444 @defun nsublis alist tree @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4445 This is a destructive version of @code{sublis}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4446 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4447
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4448 @node Lists as Sets, Association Lists, Substitution of Expressions, Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4449 @section Lists as Sets
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4450
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4451 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4452 These functions perform operations on lists which represent sets
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4453 of elements.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4454
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4455 @defun member item list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4456 This MacLisp-compatible function searches @var{list} for an element
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4457 which is @code{equal} to @var{item}. The @code{member} function is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4458 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4459 See the following function for a Common-Lisp compatible version.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4460 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4461
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4462 @defun member* item list @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4463 This function searches @var{list} for an element matching @var{item}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4464 If a match is found, it returns the cons cell whose @code{car} was
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4465 the matching element. Otherwise, it returns @code{nil}. Elements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4466 are compared by @code{eql} by default; you can use the @code{:test},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4467 @code{:test-not}, and @code{:key} arguments to modify this behavior.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4468 @xref{Sequences}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4469
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4470 Note that this function's name is suffixed by @samp{*} to avoid
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4471 the incompatible @code{member} function defined in Emacs 19.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4472 (That function uses @code{equal} for comparisons; it is equivalent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4473 to @code{(member* @var{item} @var{list} :test 'equal)}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4474 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4475
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4476 @findex member-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4477 @findex member-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4478 The @code{member-if} and @code{member-if-not} functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4479 analogously search for elements which satisfy a given predicate.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4480
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4481 @defun tailp sublist list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4482 This function returns @code{t} if @var{sublist} is a sublist of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4483 @var{list}, i.e., if @var{sublist} is @code{eql} to @var{list} or to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4484 any of its @code{cdr}s.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4485 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4486
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4487 @defun adjoin item list @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4488 This function conses @var{item} onto the front of @var{list},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4489 like @code{(cons @var{item} @var{list})}, but only if @var{item}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4490 is not already present on the list (as determined by @code{member*}).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4491 If a @code{:key} argument is specified, it is applied to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4492 @var{item} as well as to the elements of @var{list} during
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4493 the search, on the reasoning that @var{item} is ``about'' to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4494 become part of the list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4495 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4496
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4497 @defun union list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4498 This function combines two lists which represent sets of items,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4499 returning a list that represents the union of those two sets.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4500 The result list will contain all items which appear in @var{list1}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4501 or @var{list2}, and no others. If an item appears in both
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4502 @var{list1} and @var{list2} it will be copied only once. If
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4503 an item is duplicated in @var{list1} or @var{list2}, it is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4504 undefined whether or not that duplication will survive in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4505 result list. The order of elements in the result list is also
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4506 undefined.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4507 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4508
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4509 @defun nunion list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4510 This is a destructive version of @code{union}; rather than copying,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4511 it tries to reuse the storage of the argument lists if possible.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4512 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4513
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4514 @defun intersection list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4515 This function computes the intersection of the sets represented
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4516 by @var{list1} and @var{list2}. It returns the list of items
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4517 which appear in both @var{list1} and @var{list2}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4518 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4519
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4520 @defun nintersection list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4521 This is a destructive version of @code{intersection}. It
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4522 tries to reuse storage of @var{list1} rather than copying.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4523 It does @emph{not} reuse the storage of @var{list2}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4524 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4525
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4526 @defun set-difference list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4527 This function computes the ``set difference'' of @var{list1}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4528 and @var{list2}, i.e., the set of elements that appear in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4529 @var{list1} but @emph{not} in @var{list2}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4530 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4531
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4532 @defun nset-difference list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4533 This is a destructive @code{set-difference}, which will try
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4534 to reuse @var{list1} if possible.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4535 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4536
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4537 @defun set-exclusive-or list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4538 This function computes the ``set exclusive or'' of @var{list1}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4539 and @var{list2}, i.e., the set of elements that appear in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4540 exactly one of @var{list1} and @var{list2}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4541 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4542
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4543 @defun nset-exclusive-or list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4544 This is a destructive @code{set-exclusive-or}, which will try
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4545 to reuse @var{list1} and @var{list2} if possible.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4546 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4547
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4548 @defun subsetp list1 list2 @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4549 This function checks whether @var{list1} represents a subset
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4550 of @var{list2}, i.e., whether every element of @var{list1}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4551 also appears in @var{list2}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4552 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4553
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4554 @node Association Lists, , Lists as Sets, Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4555 @section Association Lists
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4556
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4557 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4558 An @dfn{association list} is a list representing a mapping from
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4559 one set of values to another; any list whose elements are cons
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4560 cells is an association list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4561
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4562 @defun assoc* item a-list @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4563 This function searches the association list @var{a-list} for an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4564 element whose @code{car} matches (in the sense of @code{:test},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4565 @code{:test-not}, and @code{:key}, or by comparison with @code{eql})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4566 a given @var{item}. It returns the matching element, if any,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4567 otherwise @code{nil}. It ignores elements of @var{a-list} which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4568 are not cons cells. (This corresponds to the behavior of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4569 @code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4570 @code{assoc} ignores @code{nil}s but considers any other non-cons
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4571 elements of @var{a-list} to be an error.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4572 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4573
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4574 @defun rassoc* item a-list @t{&key :test :test-not :key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4575 This function searches for an element whose @code{cdr} matches
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4576 @var{item}. If @var{a-list} represents a mapping, this applies
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4577 the inverse of the mapping to @var{item}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4578 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4579
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4580 @defun rassoc item a-list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4581 This function searches like @code{rassoc*} with a @code{:test}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4582 argument of @code{equal}. It is analogous to Emacs Lisp's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4583 standard @code{assoc} function, which derives from the MacLisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4584 rather than the Common Lisp tradition.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4585 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4586
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4587 @findex assoc-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4588 @findex assoc-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4589 @findex rassoc-if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4590 @findex rassoc-if-not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4591 The @code{assoc-if}, @code{assoc-if-not}, @code{rassoc-if},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4592 and @code{rassoc-if-not} functions are defined similarly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4593
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4594 Two simple functions for constructing association lists are:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4595
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4596 @defun acons key value alist
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4597 This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4598 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4599
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4600 @defun pairlis keys values &optional alist
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4601 This is equivalent to @code{(nconc (mapcar* 'cons @var{keys} @var{values})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4602 @var{alist})}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4603 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4604
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4605 @node Hash Tables, Structures, Lists, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4606 @chapter Hash Tables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4607
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4608 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4609 A @dfn{hash table} is a data structure that maps ``keys'' onto
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4610 ``values.'' Keys and values can be arbitrary Lisp data objects.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4611 Hash tables have the property that the time to search for a given
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4612 key is roughly constant; simpler data structures like association
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4613 lists take time proportional to the number of entries in the list.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4614
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4615 @defun make-hash-table @t{&key :test :size}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4616 This function creates and returns a hash-table object whose
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4617 function for comparing elements is @code{:test} (@code{eql}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4618 by default), and which is allocated to fit about @code{:size}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4619 elements. The @code{:size} argument is purely advisory; the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4620 table will stretch automatically if you store more elements in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4621 it. If @code{:size} is omitted, a reasonable default is used.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4622
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4623 Common Lisp allows only @code{eq}, @code{eql}, @code{equal},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4624 and @code{equalp} as legal values for the @code{:test} argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4625 In this package, any reasonable predicate function will work,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4626 though if you use something else you should check the details of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4627 the hashing function described below to make sure it is suitable
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4628 for your predicate.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4629
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4630 Some versions of Emacs (like Lucid Emacs 19) include a built-in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4631 hash table type; in these versions, @code{make-hash-table} with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4632 a test of @code{eq} will use these built-in hash tables. In all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4633 other cases, it will return a hash-table object which takes the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4634 form of a list with an identifying ``tag'' symbol at the front.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4635 All of the hash table functions in this package can operate on
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4636 both types of hash table; normally you will never know which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4637 type is being used.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4638
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4639 This function accepts the additional Common Lisp keywords
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4640 @code{:rehash-size} and @code{:rehash-threshold}, but it ignores
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4641 their values.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4642 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4643
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4644 @defun gethash key table &optional default
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4645 This function looks up @var{key} in @var{table}. If @var{key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4646 exists in the table, in the sense that it matches any of the existing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4647 keys according to the table's test function, then the associated value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4648 is returned. Otherwise, @var{default} (or @code{nil}) is returned.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4649
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4650 To store new data in the hash table, use @code{setf} on a call to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4651 @code{gethash}. If @var{key} already exists in the table, the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4652 corresponding value is changed to the stored value. If @var{key}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4653 does not already exist, a new entry is added to the table and the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4654 table is reallocated to a larger size if necessary. The @var{default}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4655 argument is allowed but ignored in this case. The situation is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4656 exactly analogous to that of @code{get*}; @pxref{Property Lists}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4657 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4658
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4659 @defun remhash key table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4660 This function removes the entry for @var{key} from @var{table}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4661 If an entry was removed, it returns @code{t}. If @var{key} does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4662 not appear in the table, it does nothing and returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4663 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4664
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4665 @defun clrhash table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4666 This function removes all the entries from @var{table}, leaving
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4667 an empty hash table.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4668 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4669
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4670 @defun maphash function table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4671 This function calls @var{function} for each entry in @var{table}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4672 It passes two arguments to @var{function}, the key and the value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4673 of the given entry. The return value of @var{function} is ignored;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4674 @var{maphash} itself returns @code{nil}. @xref{Loop Facility}, for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4675 an alternate way of iterating over hash tables.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4676 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4677
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4678 @defun hash-table-count table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4679 This function returns the number of entries in @var{table}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4680 @strong{Warning:} The current implementation of Lucid Emacs 19
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4681 hash-tables does not decrement the stored @code{count} when
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4682 @code{remhash} removes an entry. Therefore, the return value of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4683 this function is not dependable if you have used @code{remhash}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4684 on the table and the table's test is @code{eq}. A slower, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4685 reliable, way to count the entries is @code{(loop for x being the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4686 hash-keys of @var{table} count t)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4687 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4688
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4689 @defun hash-table-p object
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4690 This function returns @code{t} if @var{object} is a hash table,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4691 @code{nil} otherwise. It recognizes both types of hash tables
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4692 (both Lucid Emacs built-in tables and tables implemented with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4693 special lists.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4694 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4695
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4696 Sometimes when dealing with hash tables it is useful to know the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4697 exact ``hash function'' that is used. This package implements
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4698 hash tables using Emacs Lisp ``obarrays,'' which are the same
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4699 data structure that Emacs Lisp uses to keep track of symbols.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4700 Each hash table includes an embedded obarray. Key values given
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4701 to @code{gethash} are converted by various means into strings,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4702 which are then looked up in the obarray using @code{intern} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4703 @code{intern-soft}. The symbol, or ``bucket,'' corresponding to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4704 a given key string includes as its @code{symbol-value} an association
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4705 list of all key-value pairs which hash to that string. Depending
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4706 on the test function, it is possible for many entries to hash to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4707 the same bucket. For example, if the test is @code{eql}, then the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4708 symbol @code{foo} and two separately built strings @code{"foo"} will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4709 create three entries in the same bucket. Search time is linear
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4710 within buckets, so hash tables will be most effective if you arrange
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4711 not to store too many things that hash the same.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4712
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4713 The following algorithm is used to convert Lisp objects to hash
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4714 strings:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4715
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4716 @itemize @bullet
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4717 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4718 Strings are used directly as hash strings. (However, if the test
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4719 function is @code{equalp}, strings are @code{downcase}d first.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4720
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4721 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4722 Symbols are hashed according to their @code{symbol-name}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4723
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4724 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4725 Integers are hashed into one of 16 buckets depending on their value
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4726 modulo 16. Floating-point numbers are truncated to integers and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4727 hashed modulo 16.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4728
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4729 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4730 Cons cells are hashed according to their @code{car}s; nonempty vectors
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4731 are hashed according to their first element.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4732
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4733 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4734 All other types of objects hash into a single bucket named @code{"*"}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4735 @end itemize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4736
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4737 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4738 Thus, for example, searching among many buffer objects in a hash table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4739 will devolve to a (still fairly fast) linear-time search through a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4740 single bucket, whereas searching for different symbols will be very
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4741 fast since each symbol will, in general, hash into its own bucket.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4742
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4743 The size of the obarray in a hash table is automatically adjusted
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4744 as the number of elements increases.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4745
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4746 As a special case, @code{make-hash-table} with a @code{:size} argument
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4747 of 0 or 1 will create a hash-table object that uses a single association
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4748 list rather than an obarray of many lists. For very small tables this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4749 structure will be more efficient since lookup does not require
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4750 converting the key to a string or looking it up in an obarray.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4751 However, such tables are guaranteed to take time proportional to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4752 their size to do a search.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4753
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4754 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4755 @chapno=18
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4756 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4757
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4758 @node Structures, Assertions, Hash Tables, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4759 @chapter Structures
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4760
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4761 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4762 The Common Lisp @dfn{structure} mechanism provides a general way
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4763 to define data types similar to C's @code{struct} types. A
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4764 structure is a Lisp object containing some number of @dfn{slots},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4765 each of which can hold any Lisp data object. Functions are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4766 provided for accessing and setting the slots, creating or copying
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4767 structure objects, and recognizing objects of a particular structure
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4768 type.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4769
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4770 In true Common Lisp, each structure type is a new type distinct
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4771 from all existing Lisp types. Since the underlying Emacs Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4772 system provides no way to create new distinct types, this package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4773 implements structures as vectors (or lists upon request) with a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4774 special ``tag'' symbol to identify them.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4775
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4776 @defspec defstruct name slots@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4777 The @code{defstruct} form defines a new structure type called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4778 @var{name}, with the specified @var{slots}. (The @var{slots}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4779 may begin with a string which documents the structure type.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4780 In the simplest case, @var{name} and each of the @var{slots}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4781 are symbols. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4782
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4783 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4784 (defstruct person name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4785 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4786
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4787 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4788 defines a struct type called @code{person} which contains three
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4789 slots. Given a @code{person} object @var{p}, you can access those
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4790 slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4791 and @code{(person-sex @var{p})}. You can also change these slots by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4792 using @code{setf} on any of these place forms:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4793
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4794 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4795 (incf (person-age birthday-boy))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4796 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4797
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4798 You can create a new @code{person} by calling @code{make-person},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4799 which takes keyword arguments @code{:name}, @code{:age}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4800 @code{:sex} to specify the initial values of these slots in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4801 new object. (Omitting any of these arguments leaves the corresponding
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4802 slot ``undefined,'' according to the Common Lisp standard; in Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4803 Lisp, such uninitialized slots are filled with @code{nil}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4804
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4805 Given a @code{person}, @code{(copy-person @var{p})} makes a new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4806 object of the same type whose slots are @code{eq} to those of @var{p}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4807
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4808 Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4809 true if @var{x} looks like a @code{person}, false otherwise. (Again,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4810 in Common Lisp this predicate would be exact; in Emacs Lisp the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4811 best it can do is verify that @var{x} is a vector of the correct
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4812 length which starts with the correct tag symbol.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4813
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4814 Accessors like @code{person-name} normally check their arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4815 (effectively using @code{person-p}) and signal an error if the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4816 argument is the wrong type. This check is affected by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4817 @code{(optimize (safety @dots{}))} declarations. Safety level 1,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4818 the default, uses a somewhat optimized check that will detect all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4819 incorrect arguments, but may use an uninformative error message
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4820 (e.g., ``expected a vector'' instead of ``expected a @code{person}'').
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4821 Safety level 0 omits all checks except as provided by the underlying
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4822 @code{aref} call; safety levels 2 and 3 do rigorous checking that will
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4823 always print a descriptive error message for incorrect inputs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4824 @xref{Declarations}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4825
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4826 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4827 (setq dave (make-person :name "Dave" :sex 'male))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4828 @result{} [cl-struct-person "Dave" nil male]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4829 (setq other (copy-person dave))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4830 @result{} [cl-struct-person "Dave" nil male]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4831 (eq dave other)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4832 @result{} nil
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4833 (eq (person-name dave) (person-name other))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4834 @result{} t
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4835 (person-p dave)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4836 @result{} t
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4837 (person-p [1 2 3 4])
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4838 @result{} nil
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4839 (person-p "Bogus")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4840 @result{} nil
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4841 (person-p '[cl-struct-person counterfeit person object])
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4842 @result{} t
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4843 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4844
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4845 In general, @var{name} is either a name symbol or a list of a name
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4846 symbol followed by any number of @dfn{struct options}; each @var{slot}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4847 is either a slot symbol or a list of the form @samp{(@var{slot-name}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4848 @var{default-value} @var{slot-options}@dots{})}. The @var{default-value}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4849 is a Lisp form which is evaluated any time an instance of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4850 structure type is created without specifying that slot's value.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4851
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4852 Common Lisp defines several slot options, but the only one
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4853 implemented in this package is @code{:read-only}. A non-@code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4854 value for this option means the slot should not be @code{setf}-able;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4855 the slot's value is determined when the object is created and does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4856 not change afterward.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4857
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4858 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4859 (defstruct person
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4860 (name nil :read-only t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4861 age
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4862 (sex 'unknown))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4863 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4864
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4865 Any slot options other than @code{:read-only} are ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4866
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4867 For obscure historical reasons, structure options take a different
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4868 form than slot options. A structure option is either a keyword
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4869 symbol, or a list beginning with a keyword symbol possibly followed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4870 by arguments. (By contrast, slot options are key-value pairs not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4871 enclosed in lists.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4872
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4873 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4874 (defstruct (person (:constructor create-person)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4875 (:type list)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4876 :named)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4877 name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4878 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4879
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4880 The following structure options are recognized.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4881
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4882 @table @code
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4883 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4884 @itemmax=0 in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4885 @advance@leftskip-.5@tableindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4886 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4887 @item :conc-name
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4888 The argument is a symbol whose print name is used as the prefix for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4889 the names of slot accessor functions. The default is the name of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4890 the struct type followed by a hyphen. The option @code{(:conc-name p-)}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4891 would change this prefix to @code{p-}. Specifying @code{nil} as an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4892 argument means no prefix, so that the slot names themselves are used
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4893 to name the accessor functions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4894
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4895 @item :constructor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4896 In the simple case, this option takes one argument which is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4897 alternate name to use for the constructor function. The default
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4898 is @code{make-@var{name}}, e.g., @code{make-person}. The above
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4899 example changes this to @code{create-person}. Specifying @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4900 as an argument means that no standard constructor should be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4901 generated at all.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4902
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4903 In the full form of this option, the constructor name is followed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4904 by an arbitrary argument list. @xref{Program Structure}, for a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4905 description of the format of Common Lisp argument lists. All
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4906 options, such as @code{&rest} and @code{&key}, are supported.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4907 The argument names should match the slot names; each slot is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4908 initialized from the corresponding argument. Slots whose names
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4909 do not appear in the argument list are initialized based on the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4910 @var{default-value} in their slot descriptor. Also, @code{&optional}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4911 and @code{&key} arguments which don't specify defaults take their
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4912 defaults from the slot descriptor. It is legal to include arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4913 which don't correspond to slot names; these are useful if they are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4914 referred to in the defaults for optional, keyword, or @code{&aux}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4915 arguments which @emph{do} correspond to slots.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4916
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4917 You can specify any number of full-format @code{:constructor}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4918 options on a structure. The default constructor is still generated
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4919 as well unless you disable it with a simple-format @code{:constructor}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4920 option.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4921
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4922 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4923 (defstruct
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4924 (person
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4925 (:constructor nil) ; no default constructor
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4926 (:constructor new-person (name sex &optional (age 0)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4927 (:constructor new-hound (&key (name "Rover")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4928 (dog-years 0)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4929 &aux (age (* 7 dog-years))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4930 (sex 'canine))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4931 name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4932 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4933
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4934 The first constructor here takes its arguments positionally rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4935 than by keyword. (In official Common Lisp terminology, constructors
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4936 that work By Order of Arguments instead of by keyword are called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4937 ``BOA constructors.'' No, I'm not making this up.) For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4938 @code{(new-person "Jane" 'female)} generates a person whose slots
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4939 are @code{"Jane"}, 0, and @code{female}, respectively.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4940
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4941 The second constructor takes two keyword arguments, @code{:name},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4942 which initializes the @code{name} slot and defaults to @code{"Rover"},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4943 and @code{:dog-years}, which does not itself correspond to a slot
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4944 but which is used to initialize the @code{age} slot. The @code{sex}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4945 slot is forced to the symbol @code{canine} with no syntax for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4946 overriding it.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4947
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4948 @item :copier
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4949 The argument is an alternate name for the copier function for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4950 this type. The default is @code{copy-@var{name}}. @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4951 means not to generate a copier function. (In this implementation,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4952 all copier functions are simply synonyms for @code{copy-sequence}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4953
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4954 @item :predicate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4955 The argument is an alternate name for the predicate which recognizes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4956 objects of this type. The default is @code{@var{name}-p}. @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4957 means not to generate a predicate function. (If the @code{:type}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4958 option is used without the @code{:named} option, no predicate is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4959 ever generated.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4960
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4961 In true Common Lisp, @code{typep} is always able to recognize a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4962 structure object even if @code{:predicate} was used. In this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4963 package, @code{typep} simply looks for a function called
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4964 @code{@var{typename}-p}, so it will work for structure types
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4965 only if they used the default predicate name.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4966
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4967 @item :include
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4968 This option implements a very limited form of C++-style inheritance.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4969 The argument is the name of another structure type previously
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4970 created with @code{defstruct}. The effect is to cause the new
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4971 structure type to inherit all of the included structure's slots
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4972 (plus, of course, any new slots described by this struct's slot
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4973 descriptors). The new structure is considered a ``specialization''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4974 of the included one. In fact, the predicate and slot accessors
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4975 for the included type will also accept objects of the new type.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4976
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4977 If there are extra arguments to the @code{:include} option after
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4978 the included-structure name, these options are treated as replacement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4979 slot descriptors for slots in the included structure, possibly with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4980 modified default values. Borrowing an example from Steele:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4981
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4982 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4983 (defstruct person name (age 0) sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4984 @result{} person
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4985 (defstruct (astronaut (:include person (age 45)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4986 helmet-size
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4987 (favorite-beverage 'tang))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4988 @result{} astronaut
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4989
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4990 (setq joe (make-person :name "Joe"))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4991 @result{} [cl-struct-person "Joe" 0 nil]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4992 (setq buzz (make-astronaut :name "Buzz"))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4993 @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4994
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4995 (list (person-p joe) (person-p buzz))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4996 @result{} (t t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4997 (list (astronaut-p joe) (astronaut-p buzz))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4998 @result{} (nil t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
4999
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5000 (person-name buzz)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5001 @result{} "Buzz"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5002 (astronaut-name joe)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5003 @result{} error: "astronaut-name accessing a non-astronaut"
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5004 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5005
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5006 Thus, if @code{astronaut} is a specialization of @code{person},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5007 then every @code{astronaut} is also a @code{person} (but not the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5008 other way around). Every @code{astronaut} includes all the slots
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5009 of a @code{person}, plus extra slots that are specific to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5010 astronauts. Operations that work on people (like @code{person-name})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5011 work on astronauts just like other people.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5012
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5013 @item :print-function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5014 In full Common Lisp, this option allows you to specify a function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5015 which is called to print an instance of the structure type. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5016 Emacs Lisp system offers no hooks into the Lisp printer which would
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5017 allow for such a feature, so this package simply ignores
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5018 @code{:print-function}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5019
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5020 @item :type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5021 The argument should be one of the symbols @code{vector} or @code{list}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5022 This tells which underlying Lisp data type should be used to implement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5023 the new structure type. Vectors are used by default, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5024 @code{(:type list)} will cause structure objects to be stored as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5025 lists instead.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5026
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5027 The vector representation for structure objects has the advantage
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5028 that all structure slots can be accessed quickly, although creating
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5029 vectors is a bit slower in Emacs Lisp. Lists are easier to create,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5030 but take a relatively long time accessing the later slots.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5031
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5032 @item :named
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5033 This option, which takes no arguments, causes a characteristic ``tag''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5034 symbol to be stored at the front of the structure object. Using
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5035 @code{:type} without also using @code{:named} will result in a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5036 structure type stored as plain vectors or lists with no identifying
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5037 features.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5038
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5039 The default, if you don't specify @code{:type} explicitly, is to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5040 use named vectors. Therefore, @code{:named} is only useful in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5041 conjunction with @code{:type}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5042
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5043 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5044 (defstruct (person1) name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5045 (defstruct (person2 (:type list) :named) name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5046 (defstruct (person3 (:type list)) name age sex)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5047
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5048 (setq p1 (make-person1))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5049 @result{} [cl-struct-person1 nil nil nil]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5050 (setq p2 (make-person2))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5051 @result{} (person2 nil nil nil)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5052 (setq p3 (make-person3))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5053 @result{} (nil nil nil)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5054
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5055 (person1-p p1)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5056 @result{} t
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5057 (person2-p p2)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5058 @result{} t
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5059 (person3-p p3)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5060 @result{} error: function person3-p undefined
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5061 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5062
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5063 Since unnamed structures don't have tags, @code{defstruct} is not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5064 able to make a useful predicate for recognizing them. Also,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5065 accessors like @code{person3-name} will be generated but they
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5066 will not be able to do any type checking. The @code{person3-name}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5067 function, for example, will simply be a synonym for @code{car} in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5068 this case. By contrast, @code{person2-name} is able to verify
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5069 that its argument is indeed a @code{person2} object before
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5070 proceeding.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5071
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5072 @item :initial-offset
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5073 The argument must be a nonnegative integer. It specifies a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5074 number of slots to be left ``empty'' at the front of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5075 structure. If the structure is named, the tag appears at the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5076 specified position in the list or vector; otherwise, the first
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5077 slot appears at that position. Earlier positions are filled
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5078 with @code{nil} by the constructors and ignored otherwise. If
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5079 the type @code{:include}s another type, then @code{:initial-offset}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5080 specifies a number of slots to be skipped between the last slot
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5081 of the included type and the first new slot.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5082 @end table
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5083 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5084
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5085 Except as noted, the @code{defstruct} facility of this package is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5086 entirely compatible with that of Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5087
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5088 @iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5089 @chapno=23
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5090 @end iftex
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5091
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5092 @node Assertions, Efficiency Concerns, Structures, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5093 @chapter Assertions and Errors
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5094
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5095 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5096 This section describes two macros that test @dfn{assertions}, i.e.,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5097 conditions which must be true if the program is operating correctly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5098 Assertions never add to the behavior of a Lisp program; they simply
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5099 make ``sanity checks'' to make sure everything is as it should be.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5100
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5101 If the optimization property @code{speed} has been set to 3, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5102 @code{safety} is less than 3, then the byte-compiler will optimize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5103 away the following assertions. Because assertions might be optimized
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5104 away, it is a bad idea for them to include side-effects.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5105
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5106 @defspec assert test-form [show-args string args@dots{}]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5107 This form verifies that @var{test-form} is true (i.e., evaluates to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5108 a non-@code{nil} value). If so, it returns @code{nil}. If the test
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5109 is not satisfied, @code{assert} signals an error.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5110
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5111 A default error message will be supplied which includes @var{test-form}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5112 You can specify a different error message by including a @var{string}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5113 argument plus optional extra arguments. Those arguments are simply
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5114 passed to @code{error} to signal the error.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5115
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5116 If the optional second argument @var{show-args} is @code{t} instead
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5117 of @code{nil}, then the error message (with or without @var{string})
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5118 will also include all non-constant arguments of the top-level
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5119 @var{form}. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5120
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5121 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5122 (assert (> x 10) t "x is too small: %d")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5123 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5124
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5125 This usage of @var{show-args} is an extension to Common Lisp. In
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5126 true Common Lisp, the second argument gives a list of @var{places}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5127 which can be @code{setf}'d by the user before continuing from the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5128 error. Since Emacs Lisp does not support continuable errors, it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5129 makes no sense to specify @var{places}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5130 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5131
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5132 @defspec check-type form type [string]
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5133 This form verifies that @var{form} evaluates to a value of type
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5134 @var{type}. If so, it returns @code{nil}. If not, @code{check-type}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5135 signals a @code{wrong-type-argument} error. The default error message
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5136 lists the erroneous value along with @var{type} and @var{form}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5137 themselves. If @var{string} is specified, it is included in the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5138 error message in place of @var{type}. For example:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5139
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5140 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5141 (check-type x (integer 1 *) "a positive integer")
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5142 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5143
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5144 @xref{Type Predicates}, for a description of the type specifiers
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5145 that may be used for @var{type}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5146
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5147 Note that in Common Lisp, the first argument to @code{check-type}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5148 must be a @var{place} suitable for use by @code{setf}, because
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5149 @code{check-type} signals a continuable error that allows the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5150 user to modify @var{place}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5151 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5152
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5153 The following error-related macro is also defined:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5154
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5155 @defspec ignore-errors forms@dots{}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5156 This executes @var{forms} exactly like a @code{progn}, except that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5157 errors are ignored during the @var{forms}. More precisely, if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5158 an error is signalled then @code{ignore-errors} immediately
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5159 aborts execution of the @var{forms} and returns @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5160 If the @var{forms} complete successfully, @code{ignore-errors}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5161 returns the result of the last @var{form}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5162 @end defspec
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5163
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5164 @node Efficiency Concerns, Common Lisp Compatibility, Assertions, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5165 @appendix Efficiency Concerns
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5166
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5167 @appendixsec Macros
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5168
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5169 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5170 Many of the advanced features of this package, such as @code{defun*},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5171 @code{loop}, and @code{setf}, are implemented as Lisp macros. In
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5172 byte-compiled code, these complex notations will be expanded into
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5173 equivalent Lisp code which is simple and efficient. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5174 the forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5175
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5176 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5177 (incf i n)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5178 (push x (car p))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5179 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5180
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5181 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5182 are expanded at compile-time to the Lisp forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5183
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5184 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5185 (setq i (+ i n))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5186 (setcar p (cons x (car p)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5187 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5188
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5189 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5190 which are the most efficient ways of doing these respective operations
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5191 in Lisp. Thus, there is no performance penalty for using the more
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5192 readable @code{incf} and @code{push} forms in your compiled code.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5193
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5194 @emph{Interpreted} code, on the other hand, must expand these macros
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5195 every time they are executed. For this reason it is strongly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5196 recommended that code making heavy use of macros be compiled.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5197 (The features labelled ``Special Form'' instead of ``Function'' in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5198 this manual are macros.) A loop using @code{incf} a hundred times
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5199 will execute considerably faster if compiled, and will also
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5200 garbage-collect less because the macro expansion will not have
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5201 to be generated, used, and thrown away a hundred times.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5202
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5203 You can find out how a macro expands by using the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5204 @code{cl-prettyexpand} function.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5205
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5206 @defun cl-prettyexpand form &optional full
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5207 This function takes a single Lisp form as an argument and inserts
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5208 a nicely formatted copy of it in the current buffer (which must be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5209 in Lisp mode so that indentation works properly). It also expands
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5210 all Lisp macros which appear in the form. The easiest way to use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5211 this function is to go to the @code{*scratch*} buffer and type, say,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5212
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5213 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5214 (cl-prettyexpand '(loop for x below 10 collect x))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5215 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5216
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5217 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5218 and type @kbd{C-x C-e} immediately after the closing parenthesis;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5219 the expansion
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5220
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5221 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5222 (block nil
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5223 (let* ((x 0)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5224 (G1004 nil))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5225 (while (< x 10)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5226 (setq G1004 (cons x G1004))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5227 (setq x (+ x 1)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5228 (nreverse G1004)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5229 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5230
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5231 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5232 will be inserted into the buffer. (The @code{block} macro is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5233 expanded differently in the interpreter and compiler, so
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5234 @code{cl-prettyexpand} just leaves it alone. The temporary
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5235 variable @code{G1004} was created by @code{gensym}.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5236
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5237 If the optional argument @var{full} is true, then @emph{all}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5238 macros are expanded, including @code{block}, @code{eval-when},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5239 and compiler macros. Expansion is done as if @var{form} were
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5240 a top-level form in a file being compiled. For example,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5241
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5242 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5243 (cl-prettyexpand '(pushnew 'x list))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5244 @print{} (setq list (adjoin 'x list))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5245 (cl-prettyexpand '(pushnew 'x list) t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5246 @print{} (setq list (if (memq 'x list) list (cons 'x list)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5247 (cl-prettyexpand '(caddr (member* 'a list)) t)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5248 @print{} (car (cdr (cdr (memq 'a list))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5249 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5250
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5251 Note that @code{adjoin}, @code{caddr}, and @code{member*} all
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5252 have built-in compiler macros to optimize them in common cases.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5253 @end defun
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5254
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5255 @ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5256 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5257
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5258 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5259 @end ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5260 @appendixsec Error Checking
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5261
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5262 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5263 Common Lisp compliance has in general not been sacrificed for the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5264 sake of efficiency. A few exceptions have been made for cases
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5265 where substantial gains were possible at the expense of marginal
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5266 incompatibility. One example is the use of @code{memq} (which is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5267 treated very efficiently by the byte-compiler) to scan for keyword
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5268 arguments; this can become confused in rare cases when keyword
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5269 symbols are used as both keywords and data values at once. This
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5270 is extremely unlikely to occur in practical code, and the use of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5271 @code{memq} allows functions with keyword arguments to be nearly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5272 as fast as functions that use @code{&optional} arguments.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5273
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5274 The Common Lisp standard (as embodied in Steele's book) uses the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5275 phrase ``it is an error if'' to indicate a situation which is not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5276 supposed to arise in complying programs; implementations are strongly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5277 encouraged but not required to signal an error in these situations.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5278 This package sometimes omits such error checking in the interest of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5279 compactness and efficiency. For example, @code{do} variable
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5280 specifiers are supposed to be lists of one, two, or three forms;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5281 extra forms are ignored by this package rather than signalling a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5282 syntax error. The @code{endp} function is simply a synonym for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5283 @code{null} in this package. Functions taking keyword arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5284 will accept an odd number of arguments, treating the trailing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5285 keyword as if it were followed by the value @code{nil}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5286
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5287 Argument lists (as processed by @code{defun*} and friends)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5288 @emph{are} checked rigorously except for the minor point just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5289 mentioned; in particular, keyword arguments are checked for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5290 validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5291 are fully implemented. Keyword validity checking is slightly
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5292 time consuming (though not too bad in byte-compiled code);
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5293 you can use @code{&allow-other-keys} to omit this check. Functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5294 defined in this package such as @code{find} and @code{member*}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5295 do check their keyword arguments for validity.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5296
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5297 @ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5298 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5299
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5300 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5301 @end ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5302 @appendixsec Optimizing Compiler
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5303
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5304 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5305 The byte-compiler that comes with Emacs 18 normally fails to expand
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5306 macros that appear in top-level positions in the file (i.e., outside
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5307 of @code{defun}s or other enclosing forms). This would have
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5308 disastrous consequences to programs that used such top-level macros
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5309 as @code{defun*}, @code{eval-when}, and @code{defstruct}. To
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5310 work around this problem, the @dfn{CL} package patches the Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5311 18 compiler to expand top-level macros. This patch will apply to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5312 your own macros, too, if they are used in a top-level context.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5313 The patch will not harm versions of the Emacs 18 compiler which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5314 have already had a similar patch applied, nor will it affect the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5315 optimizing Emacs 19 byte-compiler written by Jamie Zawinski and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5316 Hallvard Furuseth. The patch is applied to the byte compiler's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5317 code in Emacs' memory, @emph{not} to the @file{bytecomp.elc} file
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5318 stored on disk.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5319
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5320 The Emacs 19 compiler (for Emacs 18) is available from various
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5321 Emacs Lisp archive sites such as @code{archive.cis.ohio-state.edu}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5322 Its use is highly recommended; many of the Common Lisp macros emit
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5323 code which can be improved by optimization. In particular,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5324 @code{block}s (whether explicit or implicit in constructs like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5325 @code{defun*} and @code{loop}) carry a fair run-time penalty; the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5326 optimizing compiler removes @code{block}s which are not actually
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5327 referenced by @code{return} or @code{return-from} inside the block.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5328
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5329 @node Common Lisp Compatibility, Old CL Compatibility, Efficiency Concerns, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5330 @appendix Common Lisp Compatibility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5331
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5332 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5333 Following is a list of all known incompatibilities between this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5334 package and Common Lisp as documented in Steele (2nd edition).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5335
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5336 Certain function names, such as @code{member}, @code{assoc}, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5337 @code{floor}, were already taken by (incompatible) Emacs Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5338 functions; this package appends @samp{*} to the names of its
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5339 Common Lisp versions of these functions.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5340
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5341 The word @code{defun*} is required instead of @code{defun} in order
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5342 to use extended Common Lisp argument lists in a function. Likewise,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5343 @code{defmacro*} and @code{function*} are versions of those forms
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5344 which understand full-featured argument lists. The @code{&whole}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5345 keyword does not work in @code{defmacro} argument lists (except
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5346 inside recursive argument lists).
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5347
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5348 In order to allow an efficient implementation, keyword arguments use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5349 a slightly cheesy parser which may be confused if a keyword symbol
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5350 is passed as the @emph{value} of another keyword argument.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5351 (Specifically, @code{(memq :@var{keyword} @var{rest-of-arguments})}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5352 is used to scan for @code{:@var{keyword}} among the supplied
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5353 keyword arguments.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5354
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5355 The @code{eql} and @code{equal} predicates do not distinguish
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5356 between IEEE floating-point plus and minus zero. The @code{equalp}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5357 predicate has several differences with Common Lisp; @pxref{Predicates}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5358
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5359 The @code{setf} mechanism is entirely compatible, except that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5360 setf-methods return a list of five values rather than five
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5361 values directly. Also, the new ``@code{setf} function'' concept
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5362 (typified by @code{(defun (setf foo) @dots{})}) is not implemented.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5363
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5364 The @code{do-all-symbols} form is the same as @code{do-symbols}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5365 with no @var{obarray} argument. In Common Lisp, this form would
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5366 iterate over all symbols in all packages. Since Emacs obarrays
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5367 are not a first-class package mechanism, there is no way for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5368 @code{do-all-symbols} to locate any but the default obarray.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5369
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5370 The @code{loop} macro is complete except that @code{loop-finish}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5371 and type specifiers are unimplemented.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5372
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5373 The multiple-value return facility treats lists as multiple
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5374 values, since Emacs Lisp cannot support multiple return values
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5375 directly. The macros will be compatible with Common Lisp if
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5376 @code{values} or @code{values-list} is always used to return to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5377 a @code{multiple-value-bind} or other multiple-value receiver;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5378 if @code{values} is used without @code{multiple-value-@dots{}}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5379 or vice-versa the effect will be different from Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5380
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5381 Many Common Lisp declarations are ignored, and others match
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5382 the Common Lisp standard in concept but not in detail. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5383 example, local @code{special} declarations, which are purely
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5384 advisory in Emacs Lisp, do not rigorously obey the scoping rules
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5385 set down in Steele's book.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5386
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5387 The variable @code{*gensym-counter*} starts out with a pseudo-random
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5388 value rather than with zero. This is to cope with the fact that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5389 generated symbols become interned when they are written to and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5390 loaded back from a file.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5391
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5392 The @code{defstruct} facility is compatible, except that structures
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5393 are of type @code{:type vector :named} by default rather than some
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5394 special, distinct type. Also, the @code{:type} slot option is ignored.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5395
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5396 The second argument of @code{check-type} is treated differently.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5397
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5398 @node Old CL Compatibility, Porting Common Lisp, Common Lisp Compatibility, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5399 @appendix Old CL Compatibility
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5400
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5401 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5402 Following is a list of all known incompatibilities between this package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5403 and the older Quiroz @file{cl.el} package.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5404
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5405 This package's emulation of multiple return values in functions is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5406 incompatible with that of the older package. That package attempted
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5407 to come as close as possible to true Common Lisp multiple return
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5408 values; unfortunately, it could not be 100% reliable and so was prone
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5409 to occasional surprises if used freely. This package uses a simpler
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5410 method, namely replacing multiple values with lists of values, which
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5411 is more predictable though more noticeably different from Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5412
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5413 The @code{defkeyword} form and @code{keywordp} function are not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5414 implemented in this package.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5415
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5416 The @code{member}, @code{floor}, @code{ceiling}, @code{truncate},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5417 @code{round}, @code{mod}, and @code{rem} functions are suffixed
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5418 by @samp{*} in this package to avoid collision with existing
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5419 functions in Emacs 18 or Emacs 19. The older package simply
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5420 redefined these functions, overwriting the built-in meanings and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5421 causing serious portability problems with Emacs 19. (Some more
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5422 recent versions of the Quiroz package changed the names to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5423 @code{cl-member}, etc.; this package defines the latter names as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5424 aliases for @code{member*}, etc.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5425
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5426 Certain functions in the old package which were buggy or inconsistent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5427 with the Common Lisp standard are incompatible with the conforming
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5428 versions in this package. For example, @code{eql} and @code{member}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5429 were synonyms for @code{eq} and @code{memq} in that package, @code{setf}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5430 failed to preserve correct order of evaluation of its arguments, etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5431
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5432 Finally, unlike the older package, this package is careful to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5433 prefix all of its internal names with @code{cl-}. Except for a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5434 few functions which are explicitly defined as additional features
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5435 (such as @code{floatp-safe} and @code{letf}), this package does not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5436 export any non-@samp{cl-} symbols which are not also part of Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5437 Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5438
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5439 @ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5440 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5441
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5442 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5443 @end ifinfo
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5444 @appendixsec The @code{cl-compat} package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5445
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5446 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5447 The @dfn{CL} package includes emulations of some features of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5448 old @file{cl.el}, in the form of a compatibility package
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5449 @code{cl-compat}. To use it, put @code{(require 'cl-compat)} in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5450 your program.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5451
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5452 The old package defined a number of internal routines without
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5453 @code{cl-} prefixes or other annotations. Call to these routines
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5454 may have crept into existing Lisp code. @code{cl-compat}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5455 provides emulations of the following internal routines:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5456 @code{pair-with-newsyms}, @code{zip-lists}, @code{unzip-lists},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5457 @code{reassemble-arglists}, @code{duplicate-symbols-p},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5458 @code{safe-idiv}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5459
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5460 Some @code{setf} forms translated into calls to internal
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5461 functions that user code might call directly. The functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5462 @code{setnth}, @code{setnthcdr}, and @code{setelt} fall in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5463 this category; they are defined by @code{cl-compat}, but the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5464 best fix is to change to use @code{setf} properly.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5465
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5466 The @code{cl-compat} file defines the keyword functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5467 @code{keywordp}, @code{keyword-of}, and @code{defkeyword},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5468 which are not defined by the new @dfn{CL} package because the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5469 use of keywords as data is discouraged.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5470
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5471 The @code{build-klist} mechanism for parsing keyword arguments
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5472 is emulated by @code{cl-compat}; the @code{with-keyword-args}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5473 macro is not, however, and in any case it's best to change to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5474 use the more natural keyword argument processing offered by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5475 @code{defun*}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5476
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5477 Multiple return values are treated differently by the two
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5478 Common Lisp packages. The old package's method was more
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5479 compatible with true Common Lisp, though it used heuristics
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5480 that caused it to report spurious multiple return values in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5481 certain cases. The @code{cl-compat} package defines a set
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5482 of multiple-value macros that are compatible with the old
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5483 CL package; again, they are heuristic in nature, but they
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5484 are guaranteed to work in any case where the old package's
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5485 macros worked. To avoid name collision with the ``official''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5486 multiple-value facilities, the ones in @code{cl-compat} have
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5487 capitalized names: @code{Values}, @code{Values-list},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5488 @code{Multiple-value-bind}, etc.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5489
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5490 The functions @code{cl-floor}, @code{cl-ceiling}, @code{cl-truncate},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5491 and @code{cl-round} are defined by @code{cl-compat} to use the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5492 old-style multiple-value mechanism, just as they did in the old
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5493 package. The newer @code{floor*} and friends return their two
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5494 results in a list rather than as multiple values. Note that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5495 older versions of the old package used the unadorned names
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5496 @code{floor}, @code{ceiling}, etc.; @code{cl-compat} cannot use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5497 these names because they conflict with Emacs 19 built-ins.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5498
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5499 @node Porting Common Lisp, Function Index, Old CL Compatibility, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5500 @appendix Porting Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5501
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5502 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5503 This package is meant to be used as an extension to Emacs Lisp,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5504 not as an Emacs implementation of true Common Lisp. Some of the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5505 remaining differences between Emacs Lisp and Common Lisp make it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5506 difficult to port large Common Lisp applications to Emacs. For
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5507 one, some of the features in this package are not fully compliant
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5508 with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5509 are also quite a few features that this package does not provide
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5510 at all. Here are some major omissions that you will want watch out
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5511 for when bringing Common Lisp code into Emacs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5512
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5513 @itemize @bullet
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5514 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5515 Case-insensitivity. Symbols in Common Lisp are case-insensitive
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5516 by default. Some programs refer to a function or variable as
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5517 @code{foo} in one place and @code{Foo} or @code{FOO} in another.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5518 Emacs Lisp will treat these as three distinct symbols.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5519
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5520 Some Common Lisp code is written in all upper-case. While Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5521 is happy to let the program's own functions and variables use
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5522 this convention, calls to Lisp builtins like @code{if} and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5523 @code{defun} will have to be changed to lower-case.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5524
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5525 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5526 Lexical scoping. In Common Lisp, function arguments and @code{let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5527 bindings apply only to references physically within their bodies
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5528 (or within macro expansions in their bodies). Emacs Lisp, by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5529 contrast, uses @dfn{dynamic scoping} wherein a binding to a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5530 variable is visible even inside functions called from the body.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5531
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5532 Variables in Common Lisp can be made dynamically scoped by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5533 declaring them @code{special} or using @code{defvar}. In Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5534 Lisp it is as if all variables were declared @code{special}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5535
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5536 Often you can use code that was written for lexical scoping
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5537 even in a dynamically scoped Lisp, but not always. Here is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5538 an example of a Common Lisp code fragment that would fail in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5539 Emacs Lisp:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5540
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5541 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5542 (defun map-odd-elements (func list)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5543 (loop for x in list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5544 for flag = t then (not flag)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5545 collect (if flag x (funcall func x))))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5546
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5547 (defun add-odd-elements (list x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5548 (map-odd-elements (function (lambda (a) (+ a x))) list))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5549 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5550
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5551 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5552 In Common Lisp, the two functions' usages of @code{x} are completely
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5553 independent. In Emacs Lisp, the binding to @code{x} made by
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5554 @code{add-odd-elements} will have been hidden by the binding
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5555 in @code{map-odd-elements} by the time the @code{(+ a x)} function
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5556 is called.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5557
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5558 (This package avoids such problems in its own mapping functions
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5559 by using names like @code{cl-x} instead of @code{x} internally;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5560 as long as you don't use the @code{cl-} prefix for your own
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5561 variables no collision can occur.)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5562
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5563 @xref{Lexical Bindings}, for a description of the @code{lexical-let}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5564 form which establishes a Common Lisp-style lexical binding, and some
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5565 examples of how it differs from Emacs' regular @code{let}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5566
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5567 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5568 Common Lisp allows the shorthand @code{#'x} to stand for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5569 @code{(function x)}, just as @code{'x} stands for @code{(quote x)}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5570 In Common Lisp, one traditionally uses @code{#'} notation when
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5571 referring to the name of a function. In Emacs Lisp, it works
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5572 just as well to use a regular quote:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5573
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5574 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5575 (loop for x in y by #'cddr collect (mapcar #'plusp x)) ; Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5576 (loop for x in y by 'cddr collect (mapcar 'plusp x)) ; Emacs Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5577 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5578
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5579 When @code{#'} introduces a @code{lambda} form, it is best to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5580 write out @code{(function ...)} longhand in Emacs Lisp. You can
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5581 use a regular quote, but then the byte-compiler won't know that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5582 the @code{lambda} expression is code that can be compiled.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5583
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5584 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5585 (mapcar #'(lambda (x) (* x 2)) list) ; Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5586 (mapcar (function (lambda (x) (* x 2))) list) ; Emacs Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5587 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5588
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5589 Lucid Emacs supports @code{#'} notation starting with version 19.8.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5590
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5591 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5592 The ``backquote'' feature uses a different syntax in Emacs Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5593
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5594 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5595 (defmacro foo (v &rest body) `(let ((,v 0)) @@,body)) ; Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5596 (defmacro foo (v &rest body) (` (let (((, v) 0)) (@@, body))) ; Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5597 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5598
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5599 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5600 Reader macros. Common Lisp includes a second type of macro that
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5601 works at the level of individual characters. For example, Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5602 Lisp implements the quote notation by a reader macro called @code{'},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5603 whereas Emacs Lisp's parser just treats quote as a special case.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5604 Some Lisp packages use reader macros to create special syntaxes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5605 for themselves, which the Emacs parser is incapable of reading.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5606
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5607 The lack of reader macros, incidentally, is the reason behind
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5608 Emacs Lisp's unusual backquote syntax. Since backquotes are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5609 implemented as a Lisp package and not built-in to the Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5610 parser, they are forced to use a regular macro named @code{`}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5611 which is used with the standard function/macro call notation.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5612
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5613 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5614 Other syntactic features. Common Lisp provides a number of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5615 notations beginning with @code{#} that the Emacs Lisp parser
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5616 won't understand. For example, @samp{#| ... |#} is an
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5617 alternate comment notation, and @samp{#+lucid (foo)} tells
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5618 the parser to ignore the @code{(foo)} except in Lucid Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5619 Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5620
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5621 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5622 Packages. In Common Lisp, symbols are divided into @dfn{packages}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5623 Symbols that are Lisp built-ins are typically stored in one package;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5624 symbols that are vendor extensions are put in another, and each
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5625 application program would have a package for its own symbols.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5626 Certain symbols are ``exported'' by a package and others are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5627 internal; certain packages ``use'' or import the exported symbols
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5628 of other packages. To access symbols that would not normally be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5629 visible due to this importing and exporting, Common Lisp provides
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5630 a syntax like @code{package:symbol} or @code{package::symbol}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5631
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5632 Emacs Lisp has a single namespace for all interned symbols, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5633 then uses a naming convention of putting a prefix like @code{cl-}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5634 in front of the name. Some Emacs packages adopt the Common Lisp-like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5635 convention of using @code{cl:} or @code{cl::} as the prefix.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5636 However, the Emacs parser does not understand colons and just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5637 treats them as part of the symbol name. Thus, while @code{mapcar}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5638 and @code{lisp:mapcar} may refer to the same symbol in Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5639 Lisp, they are totally distinct in Emacs Lisp. Common Lisp
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5640 programs which refer to a symbol by the full name sometimes
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5641 and the short name other times will not port cleanly to Emacs.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5642
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5643 Emacs Lisp does have a concept of ``obarrays,'' which are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5644 package-like collections of symbols, but this feature is not
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5645 strong enough to be used as a true package mechanism.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5646
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5647 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5648 Keywords. The notation @code{:test-not} in Common Lisp really
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5649 is a shorthand for @code{keyword:test-not}; keywords are just
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5650 symbols in a built-in @code{keyword} package with the special
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5651 property that all its symbols are automatically self-evaluating.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5652 Common Lisp programs often use keywords liberally to avoid
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5653 having to use quotes.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5654
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5655 In Emacs Lisp a keyword is just a symbol whose name begins with
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5656 a colon; since the Emacs parser does not treat them specially,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5657 they have to be explicitly made self-evaluating by a statement
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5658 like @code{(setq :test-not ':test-not)}. This package arranges
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5659 to execute such a statement whenever @code{defun*} or some
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5660 other form sees a keyword being used as an argument. Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5661 Lisp code that assumes that a symbol @code{:mumble} will be
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5662 self-evaluating even though it was never introduced by a
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5663 @code{defun*} will have to be fixed.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5664
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5665 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5666 The @code{format} function is quite different between Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5667 Lisp and Emacs Lisp. It takes an additional ``destination''
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5668 argument before the format string. A destination of @code{nil}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5669 means to format to a string as in Emacs Lisp; a destination
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5670 of @code{t} means to write to the terminal (similar to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5671 @code{message} in Emacs). Also, format control strings are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5672 utterly different; @code{~} is used instead of @code{%} to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5673 introduce format codes, and the set of available codes is
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5674 much richer. There are no notations like @code{\n} for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5675 string literals; instead, @code{format} is used with the
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5676 ``newline'' format code, @code{~%}. More advanced formatting
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5677 codes provide such features as paragraph filling, case
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5678 conversion, and even loops and conditionals.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5679
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5680 While it would have been possible to implement most of Common
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5681 Lisp @code{format} in this package (under the name @code{format*},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5682 of course), it was not deemed worthwhile. It would have required
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5683 a huge amount of code to implement even a decent subset of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5684 @code{format*}, yet the functionality it would provide over
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5685 Emacs Lisp's @code{format} would rarely be useful.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5686
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5687 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5688 Vector constants use square brackets in Emacs Lisp, but
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5689 @code{#(a b c)} notation in Common Lisp. To further complicate
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5690 matters, Emacs 19 introduces its own @code{#(} notation for
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5691 something entirely different---strings with properties.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5692
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5693 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5694 Characters are distinct from integers in Common Lisp. The
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5695 notation for character constants is also different: @code{#\A}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5696 instead of @code{?A}. Also, @code{string=} and @code{string-equal}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5697 are synonyms in Emacs Lisp whereas the latter is case-insensitive
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5698 in Common Lisp.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5699
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5700 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5701 Data types. Some Common Lisp data types do not exist in Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5702 Lisp. Rational numbers and complex numbers are not present,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5703 nor are large integers (all integers are ``fixnums''). All
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5704 arrays are one-dimensional. There are no readtables or pathnames;
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5705 streams are a set of existing data types rather than a new data
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5706 type of their own. Hash tables, random-states, structures, and
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5707 packages (obarrays) are built from Lisp vectors or lists rather
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5708 than being distinct types.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5709
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5710 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5711 The Common Lisp Object System (CLOS) is not implemented,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5712 nor is the Common Lisp Condition System.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5713
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5714 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5715 Common Lisp features that are completely redundant with Emacs
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5716 Lisp features of a different name generally have not been
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5717 implemented. For example, Common Lisp writes @code{defconstant}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5718 where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5719 takes its arguments in different ways in the two Lisps but does
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5720 exactly the same thing, so this package has not bothered to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5721 implement a Common Lisp-style @code{make-list}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5722
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5723 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5724 A few more notable Common Lisp features not included in this
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5725 package: @code{compiler-let}, @code{tagbody}, @code{prog},
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5726 @code{ldb/dpb}, @code{parse-integer}, @code{cerror}.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5727
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5728 @item
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5729 Recursion. While recursion works in Emacs Lisp just like it
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5730 does in Common Lisp, various details of the Emacs Lisp system
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5731 and compiler make recursion much less efficient than it is in
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5732 most Lisps. Some schools of thought prefer to use recursion
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5733 in Lisp over other techniques; they would sum a list of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5734 numbers using something like
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5735
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5736 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5737 (defun sum-list (list)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5738 (if list
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5739 (+ (car list) (sum-list (cdr list)))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5740 0))
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5741 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5742
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5743 @noindent
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5744 where a more iteratively-minded programmer might write one of
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5745 these forms:
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5746
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5747 @example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5748 (let ((total 0)) (dolist (x my-list) (incf total x)) total)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5749 (loop for x in my-list sum x)
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5750 @end example
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5751
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5752 While this would be mainly a stylistic choice in most Common Lisps,
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5753 in Emacs Lisp you should be aware that the iterative forms are
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5754 much faster than recursion. Also, Lisp programmers will want to
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5755 note that the current Emacs Lisp compiler does not optimize tail
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5756 recursion.
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5757 @end itemize
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5758
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5759 @node Function Index, Variable Index, Porting Common Lisp, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5760 @unnumbered Function Index
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5761
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5762 @printindex fn
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5763
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5764 @node Variable Index, , Function Index, Top
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5765 @unnumbered Variable Index
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5766
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5767 @printindex vr
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5768
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5769 @contents
376386a54a3c Import from CVS: tag r19-14
cvs
parents:
diff changeset
5770 @bye