|
428
|
1 \input texinfo @c -*-texinfo-*-
|
|
|
2 @setfilename ../info/cl.info
|
|
|
3 @settitle Common Lisp Extensions
|
|
|
4
|
|
|
5 @iftex
|
|
|
6 @finalout
|
|
|
7 @end iftex
|
|
|
8
|
|
|
9 @ifinfo
|
|
|
10 @dircategory XEmacs Editor
|
|
|
11 @direntry
|
|
|
12 * Common Lisp: (cl). GNU Emacs Common Lisp emulation package.
|
|
|
13 @end direntry
|
|
|
14
|
|
|
15 This file documents the GNU Emacs Common Lisp emulation package.
|
|
|
16
|
|
|
17 Copyright (C) 1993 Free Software Foundation, Inc.
|
|
|
18
|
|
|
19 Permission is granted to make and distribute verbatim copies of this
|
|
|
20 manual provided the copyright notice and this permission notice are
|
|
|
21 preserved on all copies.
|
|
|
22
|
|
|
23 @ignore
|
|
|
24 Permission is granted to process this file through TeX and print the
|
|
|
25 results, provided the printed document carries copying permission notice
|
|
|
26 identical to this one except for the removal of this paragraph (this
|
|
|
27 paragraph not being relevant to the printed manual).
|
|
|
28
|
|
|
29 @end ignore
|
|
|
30 Permission is granted to copy and distribute modified versions of this
|
|
|
31 manual under the conditions for verbatim copying, provided also that the
|
|
|
32 section entitled ``GNU General Public License'' is included exactly as
|
|
|
33 in the original, and provided that the entire resulting derived work is
|
|
|
34 distributed under the terms of a permission notice identical to this one.
|
|
|
35
|
|
|
36 Permission is granted to copy and distribute translations of this manual
|
|
|
37 into another language, under the above conditions for modified versions,
|
|
|
38 except that the section entitled ``GNU General Public License'' may be
|
|
|
39 included in a translation approved by the author instead of in the
|
|
|
40 original English.
|
|
|
41 @end ifinfo
|
|
|
42
|
|
|
43 @titlepage
|
|
|
44 @sp 6
|
|
|
45 @center @titlefont{Common Lisp Extensions}
|
|
|
46 @sp 4
|
|
|
47 @center For GNU Emacs Lisp
|
|
|
48 @sp 1
|
|
|
49 @center Version 2.02
|
|
|
50 @sp 5
|
|
|
51 @center Dave Gillespie
|
|
|
52 @center daveg@@synaptics.com
|
|
|
53 @page
|
|
|
54
|
|
|
55 @vskip 0pt plus 1filll
|
|
|
56 Copyright @copyright{} 1993 Free Software Foundation, Inc.
|
|
|
57
|
|
|
58 Permission is granted to make and distribute verbatim copies of
|
|
|
59 this manual provided the copyright notice and this permission notice
|
|
|
60 are preserved on all copies.
|
|
|
61
|
|
|
62 @ignore
|
|
|
63 Permission is granted to process this file through TeX and print the
|
|
|
64 results, provided the printed document carries copying permission notice
|
|
|
65 identical to this one except for the removal of this paragraph (this
|
|
|
66 paragraph not being relevant to the printed manual).
|
|
|
67
|
|
|
68 @end ignore
|
|
|
69 Permission is granted to copy and distribute modified versions of this
|
|
|
70 manual under the conditions for verbatim copying, provided also that the
|
|
|
71 section entitled ``GNU General Public License'' is included exactly as
|
|
|
72 in the original, and provided that the entire resulting derived work is
|
|
|
73 distributed under the terms of a permission notice identical to this one.
|
|
|
74
|
|
|
75 Permission is granted to copy and distribute translations of this manual
|
|
|
76 into another language, under the above conditions for modified versions,
|
|
|
77 except that the section entitled ``GNU General Public License'' may be
|
|
|
78 included in a translation approved by the author instead of in the
|
|
|
79 original English.
|
|
|
80 @end titlepage
|
|
|
81
|
|
|
82 @node Top, Overview,, (dir)
|
|
|
83 @chapter Common Lisp Extensions
|
|
|
84
|
|
|
85 @noindent
|
|
|
86 This document describes a set of Emacs Lisp facilities borrowed from
|
|
|
87 Common Lisp. All the facilities are described here in detail; for
|
|
|
88 more discussion and examples, Guy L. Steele's @cite{Common Lisp, the
|
|
|
89 Language}, second edition, is the definitive book on Common Lisp.
|
|
|
90 @iftex
|
|
|
91 Chapter numbers and most section numbers of this document parallel
|
|
|
92 those of Steele's book.
|
|
|
93 @end iftex
|
|
|
94 While this document does not assume any prior knowledge of Common
|
|
|
95 Lisp, it does assume a basic familiarity with Emacs Lisp.
|
|
|
96
|
|
|
97 @menu
|
|
|
98 * Overview:: Installation, usage, etc.
|
|
|
99 * Program Structure:: Arglists, `eval-when', `defalias'
|
|
|
100 * Predicates:: `typep', `eql', and `equalp'
|
|
|
101 * Control Structure:: `setf', `when', `do', `loop', etc.
|
|
|
102 * Macros:: Destructuring, `define-compiler-macro'
|
|
|
103 * Declarations:: `proclaim', `declare', etc.
|
|
|
104 * Symbols:: Property lists, `gensym'
|
|
|
105 * Numbers:: Predicates, functions, random numbers
|
|
|
106 * Sequences:: Mapping, functions, searching, sorting
|
|
|
107 * Lists:: `cadr', `sublis', `member*', `assoc*', etc.
|
|
|
108 * Hash Tables:: `make-hash-table', `gethash', etc.
|
|
|
109 * Structures:: `defstruct'
|
|
|
110 * Assertions:: `check-type', `assert', `ignore-errors'.
|
|
|
111
|
|
|
112 * Efficiency Concerns:: Hints and techniques
|
|
|
113 * Common Lisp Compatibility:: All known differences with Steele
|
|
|
114 * Old CL Compatibility:: All known differences with old cl.el
|
|
|
115 * Porting Common Lisp:: Hints for porting Common Lisp code
|
|
|
116
|
|
|
117 * Function Index::
|
|
|
118 * Variable Index::
|
|
|
119 @end menu
|
|
|
120
|
|
|
121 @node Overview, Program Structure, Top, Top
|
|
|
122 @ifinfo
|
|
|
123 @chapter Overview
|
|
|
124 @end ifinfo
|
|
|
125 @iftex
|
|
|
126 @section Overview
|
|
|
127 @end iftex
|
|
|
128
|
|
|
129 @noindent
|
|
|
130 Common Lisp is a huge language, and Common Lisp systems tend to be
|
|
|
131 massive and extremely complex. Emacs Lisp, by contrast, is rather
|
|
|
132 minimalist in the choice of Lisp features it offers the programmer.
|
|
|
133 As Emacs Lisp programmers have grown in number, and the applications
|
|
|
134 they write have grown more ambitious, it has become clear that Emacs
|
|
|
135 Lisp could benefit from many of the conveniences of Common Lisp.
|
|
|
136
|
|
|
137 The @dfn{CL} package adds a number of Common Lisp functions and
|
|
|
138 control structures to Emacs Lisp. While not a 100% complete
|
|
|
139 implementation of Common Lisp, @dfn{CL} adds enough functionality
|
|
|
140 to make Emacs Lisp programming significantly more convenient.
|
|
|
141
|
|
|
142 Some Common Lisp features have been omitted from this package
|
|
|
143 for various reasons:
|
|
|
144
|
|
|
145 @itemize @bullet
|
|
|
146 @item
|
|
|
147 Some features are too complex or bulky relative to their benefit
|
|
|
148 to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
|
|
|
149 examples of this group.
|
|
|
150
|
|
|
151 @item
|
|
|
152 Other features cannot be implemented without modification to the
|
|
|
153 Emacs Lisp interpreter itself, such as multiple return values,
|
|
|
154 lexical scoping, case-insensitive symbols, and complex numbers.
|
|
|
155 The @dfn{CL} package generally makes no attempt to emulate these
|
|
|
156 features.
|
|
|
157
|
|
|
158 @item
|
|
|
159 Some features conflict with existing things in Emacs Lisp. For
|
|
|
160 example, Emacs' @code{assoc} function is incompatible with the
|
|
|
161 Common Lisp @code{assoc}. In such cases, this package usually
|
|
|
162 adds the suffix @samp{*} to the function name of the Common
|
|
|
163 Lisp version of the function (e.g., @code{assoc*}).
|
|
|
164 @end itemize
|
|
|
165
|
|
|
166 The package described here was written by Dave Gillespie,
|
|
|
167 @file{daveg@@synaptics.com}. It is a total rewrite of the original
|
|
|
168 1986 @file{cl.el} package by Cesar Quiroz. Most features of
|
|
|
169 the Quiroz package have been retained; any incompatibilities are
|
|
|
170 noted in the descriptions below. Care has been taken in this
|
|
|
171 version to ensure that each function is defined efficiently,
|
|
|
172 concisely, and with minimal impact on the rest of the Emacs
|
|
|
173 environment.
|
|
|
174
|
|
|
175 @menu
|
|
|
176 * Usage:: How to use the CL package
|
|
|
177 * Organization:: The package's five component files
|
|
|
178 * Installation:: Compiling and installing CL
|
|
|
179 * Naming Conventions:: Notes on CL function names
|
|
|
180 @end menu
|
|
|
181
|
|
|
182 @node Usage, Organization, Overview, Overview
|
|
|
183 @section Usage
|
|
|
184
|
|
|
185 @noindent
|
|
|
186 Lisp code that uses features from the @dfn{CL} package should
|
|
|
187 include at the beginning:
|
|
|
188
|
|
|
189 @example
|
|
|
190 (require 'cl)
|
|
|
191 @end example
|
|
|
192
|
|
|
193 @noindent
|
|
|
194 If you want to ensure that the new (Gillespie) version of @dfn{CL}
|
|
|
195 is the one that is present, add an additional @code{(require 'cl-19)}
|
|
|
196 call:
|
|
|
197
|
|
|
198 @example
|
|
|
199 (require 'cl)
|
|
|
200 (require 'cl-19)
|
|
|
201 @end example
|
|
|
202
|
|
|
203 @noindent
|
|
|
204 The second call will fail (with ``@file{cl-19.el} not found'') if
|
|
|
205 the old @file{cl.el} package was in use.
|
|
|
206
|
|
|
207 It is safe to arrange to load @dfn{CL} at all times, e.g.,
|
|
|
208 in your @file{.emacs} file. But it's a good idea, for portability,
|
|
|
209 to @code{(require 'cl)} in your code even if you do this.
|
|
|
210
|
|
|
211 @node Organization, Installation, Usage, Overview
|
|
|
212 @section Organization
|
|
|
213
|
|
|
214 @noindent
|
|
|
215 The Common Lisp package is organized into four files:
|
|
|
216
|
|
|
217 @table @file
|
|
|
218 @item cl.el
|
|
|
219 This is the ``main'' file, which contains basic functions
|
|
|
220 and information about the package. This file is relatively
|
|
|
221 compact---about 700 lines.
|
|
|
222
|
|
|
223 @item cl-extra.el
|
|
|
224 This file contains the larger, more complex or unusual functions.
|
|
|
225 It is kept separate so that packages which only want to use Common
|
|
|
226 Lisp fundamentals like the @code{cadr} function won't need to pay
|
|
|
227 the overhead of loading the more advanced functions.
|
|
|
228
|
|
|
229 @item cl-seq.el
|
|
|
230 This file contains most of the advanced functions for operating
|
|
|
231 on sequences or lists, such as @code{delete-if} and @code{assoc*}.
|
|
|
232
|
|
|
233 @item cl-macs.el
|
|
|
234 This file contains the features of the packages which are macros
|
|
|
235 instead of functions. Macros expand when the caller is compiled,
|
|
|
236 not when it is run, so the macros generally only need to be
|
|
|
237 present when the byte-compiler is running (or when the macros are
|
|
|
238 used in uncompiled code such as a @file{.emacs} file). Most of
|
|
|
239 the macros of this package are isolated in @file{cl-macs.el} so
|
|
|
240 that they won't take up memory unless you are compiling.
|
|
|
241 @end table
|
|
|
242
|
|
|
243 The file @file{cl.el} includes all necessary @code{autoload}
|
|
|
244 commands for the functions and macros in the other three files.
|
|
|
245 All you have to do is @code{(require 'cl)}, and @file{cl.el}
|
|
|
246 will take care of pulling in the other files when they are
|
|
|
247 needed.
|
|
|
248
|
|
|
249 There is another file, @file{cl-compat.el}, which defines some
|
|
|
250 routines from the older @file{cl.el} package that are no longer
|
|
|
251 present in the new package. This includes internal routines
|
|
|
252 like @code{setelt} and @code{zip-lists}, deprecated features
|
|
|
253 like @code{defkeyword}, and an emulation of the old-style
|
|
|
254 multiple-values feature. @xref{Old CL Compatibility}.
|
|
|
255
|
|
|
256 @node Installation, Naming Conventions, Organization, Overview
|
|
|
257 @section Installation
|
|
|
258
|
|
|
259 @noindent
|
|
|
260 Installation of the @dfn{CL} package is simple: Just put the
|
|
|
261 byte-compiled files @file{cl.elc}, @file{cl-extra.elc},
|
|
|
262 @file{cl-seq.elc}, @file{cl-macs.elc}, and @file{cl-compat.elc}
|
|
|
263 into a directory on your @code{load-path}.
|
|
|
264
|
|
|
265 There are no special requirements to compile this package:
|
|
|
266 The files do not have to be loaded before they are compiled,
|
|
|
267 nor do they need to be compiled in any particular order.
|
|
|
268
|
|
|
269 You may choose to put the files into your main @file{lisp/}
|
|
|
270 directory, replacing the original @file{cl.el} file there. Or,
|
|
|
271 you could put them into a directory that comes before @file{lisp/}
|
|
|
272 on your @code{load-path} so that the old @file{cl.el} is
|
|
|
273 effectively hidden.
|
|
|
274
|
|
|
275 Also, format the @file{cl.texinfo} file and put the resulting
|
|
|
276 Info files in the @file{info/} directory or another suitable place.
|
|
|
277
|
|
|
278 You may instead wish to leave this package's components all in
|
|
|
279 their own directory, and then add this directory to your
|
|
|
280 @code{load-path} and (Emacs 19 only) @code{Info-directory-list}.
|
|
|
281 Add the directory to the front of the list so the old @dfn{CL}
|
|
|
282 package and its documentation are hidden.
|
|
|
283
|
|
|
284 @node Naming Conventions, , Installation, Overview
|
|
|
285 @section Naming Conventions
|
|
|
286
|
|
|
287 @noindent
|
|
|
288 Except where noted, all functions defined by this package have the
|
|
|
289 same names and calling conventions as their Common Lisp counterparts.
|
|
|
290
|
|
|
291 Following is a complete list of functions whose names were changed
|
|
|
292 from Common Lisp, usually to avoid conflicts with Emacs. In each
|
|
|
293 case, a @samp{*} has been appended to the Common Lisp name to obtain
|
|
|
294 the Emacs name:
|
|
|
295
|
|
|
296 @example
|
|
|
297 defun* defsubst* defmacro* function*
|
|
440
|
298 member* assoc* rassoc* remove*
|
|
|
299 delete* mapcar* sort* floor*
|
|
|
300 ceiling* truncate* round* mod*
|
|
|
301 rem* random*
|
|
428
|
302 @end example
|
|
|
303
|
|
|
304 Internal function and variable names in the package are prefixed
|
|
|
305 by @code{cl-}. Here is a complete list of functions @emph{not}
|
|
|
306 prefixed by @code{cl-} which were not taken from Common Lisp:
|
|
|
307
|
|
|
308 @example
|
|
|
309 member delete remove remq
|
|
|
310 rassoc floatp-safe lexical-let lexical-let*
|
|
|
311 callf callf2 letf letf*
|
|
|
312 defsubst* defalias add-hook eval-when-compile
|
|
|
313 @end example
|
|
|
314
|
|
|
315 @noindent
|
|
|
316 (Most of these are Emacs 19 features provided to Emacs 18 users,
|
|
|
317 or introduced, like @code{remq}, for reasons of symmetry
|
|
|
318 with similar features.)
|
|
|
319
|
|
|
320 The following simple functions and macros are defined in @file{cl.el};
|
|
|
321 they do not cause other components like @file{cl-extra} to be loaded.
|
|
|
322
|
|
|
323 @example
|
|
|
324 eql floatp-safe abs endp
|
|
|
325 evenp oddp plusp minusp
|
|
|
326 last butlast nbutlast caar .. cddddr
|
|
|
327 list* ldiff rest first .. tenth
|
|
|
328 member [1] copy-list subst mapcar* [2]
|
|
|
329 adjoin [3] acons pairlis when
|
|
|
330 unless pop [4] push [4] pushnew [3,4]
|
|
|
331 incf [4] decf [4] proclaim declaim
|
|
|
332 add-hook
|
|
|
333 @end example
|
|
|
334
|
|
|
335 @noindent
|
|
|
336 [1] This is the Emacs 19-compatible function, not @code{member*}.
|
|
|
337
|
|
|
338 @noindent
|
|
|
339 [2] Only for one sequence argument or two list arguments.
|
|
|
340
|
|
|
341 @noindent
|
|
|
342 [3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
|
|
|
343 and @code{:key} is not used.
|
|
|
344
|
|
|
345 @noindent
|
|
|
346 [4] Only when @var{place} is a plain variable name.
|
|
|
347
|
|
|
348 @iftex
|
|
|
349 @chapno=4
|
|
|
350 @end iftex
|
|
|
351
|
|
|
352 @node Program Structure, Predicates, Overview, Top
|
|
|
353 @chapter Program Structure
|
|
|
354
|
|
|
355 @noindent
|
|
|
356 This section describes features of the @dfn{CL} package which have to
|
|
|
357 do with programs as a whole: advanced argument lists for functions,
|
|
|
358 and the @code{eval-when} construct.
|
|
|
359
|
|
|
360 @menu
|
|
|
361 * Argument Lists:: `&key', `&aux', `defun*', `defmacro*'.
|
|
|
362 * Time of Evaluation:: The `eval-when' construct.
|
|
|
363 * Function Aliases:: The `defalias' function.
|
|
|
364 @end menu
|
|
|
365
|
|
|
366 @iftex
|
|
|
367 @secno=1
|
|
|
368 @end iftex
|
|
|
369
|
|
|
370 @node Argument Lists, Time of Evaluation, Program Structure, Program Structure
|
|
|
371 @section Argument Lists
|
|
|
372
|
|
|
373 @noindent
|
|
|
374 Emacs Lisp's notation for argument lists of functions is a subset of
|
|
|
375 the Common Lisp notation. As well as the familiar @code{&optional}
|
|
|
376 and @code{&rest} markers, Common Lisp allows you to specify default
|
|
|
377 values for optional arguments, and it provides the additional markers
|
|
|
378 @code{&key} and @code{&aux}.
|
|
|
379
|
|
|
380 Since argument parsing is built-in to Emacs, there is no way for
|
|
|
381 this package to implement Common Lisp argument lists seamlessly.
|
|
|
382 Instead, this package defines alternates for several Lisp forms
|
|
|
383 which you must use if you need Common Lisp argument lists.
|
|
|
384
|
|
|
385 @defspec defun* name arglist body...
|
|
|
386 This form is identical to the regular @code{defun} form, except
|
|
|
387 that @var{arglist} is allowed to be a full Common Lisp argument
|
|
|
388 list. Also, the function body is enclosed in an implicit block
|
|
|
389 called @var{name}; @pxref{Blocks and Exits}.
|
|
|
390 @end defspec
|
|
|
391
|
|
|
392 @defspec defsubst* name arglist body...
|
|
|
393 This is just like @code{defun*}, except that the function that
|
|
|
394 is defined is automatically proclaimed @code{inline}, i.e.,
|
|
|
395 calls to it may be expanded into in-line code by the byte compiler.
|
|
|
396 This is analogous to the @code{defsubst} form in Emacs 19;
|
|
|
397 @code{defsubst*} uses a different method (compiler macros) which
|
|
|
398 works in all version of Emacs, and also generates somewhat more
|
|
|
399 efficient inline expansions. In particular, @code{defsubst*}
|
|
|
400 arranges for the processing of keyword arguments, default values,
|
|
|
401 etc., to be done at compile-time whenever possible.
|
|
|
402 @end defspec
|
|
|
403
|
|
|
404 @defspec defmacro* name arglist body...
|
|
|
405 This is identical to the regular @code{defmacro} form,
|
|
|
406 except that @var{arglist} is allowed to be a full Common Lisp
|
|
|
407 argument list. The @code{&environment} keyword is supported as
|
|
|
408 described in Steele. The @code{&whole} keyword is supported only
|
|
|
409 within destructured lists (see below); top-level @code{&whole}
|
|
|
410 cannot be implemented with the current Emacs Lisp interpreter.
|
|
|
411 The macro expander body is enclosed in an implicit block called
|
|
|
412 @var{name}.
|
|
|
413 @end defspec
|
|
|
414
|
|
|
415 @defspec function* symbol-or-lambda
|
|
|
416 This is identical to the regular @code{function} form,
|
|
|
417 except that if the argument is a @code{lambda} form then that
|
|
|
418 form may use a full Common Lisp argument list.
|
|
|
419 @end defspec
|
|
|
420
|
|
|
421 Also, all forms (such as @code{defsetf} and @code{flet}) defined
|
|
|
422 in this package that include @var{arglist}s in their syntax allow
|
|
|
423 full Common Lisp argument lists.
|
|
|
424
|
|
|
425 Note that it is @emph{not} necessary to use @code{defun*} in
|
|
|
426 order to have access to most @dfn{CL} features in your function.
|
|
|
427 These features are always present; @code{defun*}'s only
|
|
|
428 difference from @code{defun} is its more flexible argument
|
|
|
429 lists and its implicit block.
|
|
|
430
|
|
|
431 The full form of a Common Lisp argument list is
|
|
|
432
|
|
|
433 @example
|
|
|
434 (@var{var}...
|
|
|
435 &optional (@var{var} @var{initform} @var{svar})...
|
|
|
436 &rest @var{var}
|
|
|
437 &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
|
|
|
438 &aux (@var{var} @var{initform})...)
|
|
|
439 @end example
|
|
|
440
|
|
|
441 Each of the five argument list sections is optional. The @var{svar},
|
|
|
442 @var{initform}, and @var{keyword} parts are optional; if they are
|
|
|
443 omitted, then @samp{(@var{var})} may be written simply @samp{@var{var}}.
|
|
|
444
|
|
|
445 The first section consists of zero or more @dfn{required} arguments.
|
|
|
446 These arguments must always be specified in a call to the function;
|
|
|
447 there is no difference between Emacs Lisp and Common Lisp as far as
|
|
|
448 required arguments are concerned.
|
|
|
449
|
|
|
450 The second section consists of @dfn{optional} arguments. These
|
|
|
451 arguments may be specified in the function call; if they are not,
|
|
|
452 @var{initform} specifies the default value used for the argument.
|
|
|
453 (No @var{initform} means to use @code{nil} as the default.) The
|
|
|
454 @var{initform} is evaluated with the bindings for the preceding
|
|
|
455 arguments already established; @code{(a &optional (b (1+ a)))}
|
|
|
456 matches one or two arguments, with the second argument defaulting
|
|
|
457 to one plus the first argument. If the @var{svar} is specified,
|
|
|
458 it is an auxiliary variable which is bound to @code{t} if the optional
|
|
|
459 argument was specified, or to @code{nil} if the argument was omitted.
|
|
|
460 If you don't use an @var{svar}, then there will be no way for your
|
|
|
461 function to tell whether it was called with no argument, or with
|
|
|
462 the default value passed explicitly as an argument.
|
|
|
463
|
|
|
464 The third section consists of a single @dfn{rest} argument. If
|
|
|
465 more arguments were passed to the function than are accounted for
|
|
|
466 by the required and optional arguments, those extra arguments are
|
|
|
467 collected into a list and bound to the ``rest'' argument variable.
|
|
|
468 Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp.
|
|
|
469 Common Lisp accepts @code{&body} as a synonym for @code{&rest} in
|
|
|
470 macro contexts; this package accepts it all the time.
|
|
|
471
|
|
|
472 The fourth section consists of @dfn{keyword} arguments. These
|
|
|
473 are optional arguments which are specified by name rather than
|
|
|
474 positionally in the argument list. For example,
|
|
|
475
|
|
|
476 @example
|
|
|
477 (defun* foo (a &optional b &key c d (e 17)))
|
|
|
478 @end example
|
|
|
479
|
|
|
480 @noindent
|
|
|
481 defines a function which may be called with one, two, or more
|
|
|
482 arguments. The first two arguments are bound to @code{a} and
|
|
|
483 @code{b} in the usual way. The remaining arguments must be
|
|
|
484 pairs of the form @code{:c}, @code{:d}, or @code{:e} followed
|
|
|
485 by the value to be bound to the corresponding argument variable.
|
|
|
486 (Symbols whose names begin with a colon are called @dfn{keywords},
|
|
|
487 and they are self-quoting in the same way as @code{nil} and
|
|
|
488 @code{t}.)
|
|
|
489
|
|
|
490 For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five
|
|
|
491 arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword
|
|
|
492 appears more than once in the function call, the first occurrence
|
|
|
493 takes precedence over the later ones. Note that it is not possible
|
|
|
494 to specify keyword arguments without specifying the optional
|
|
|
495 argument @code{b} as well, since @code{(foo 1 :c 2)} would bind
|
|
|
496 @code{b} to the keyword @code{:c}, then signal an error because
|
|
|
497 @code{2} is not a valid keyword.
|
|
|
498
|
|
|
499 If a @var{keyword} symbol is explicitly specified in the argument
|
|
|
500 list as shown in the above diagram, then that keyword will be
|
|
|
501 used instead of just the variable name prefixed with a colon.
|
|
|
502 You can specify a @var{keyword} symbol which does not begin with
|
|
|
503 a colon at all, but such symbols will not be self-quoting; you
|
|
|
504 will have to quote them explicitly with an apostrophe in the
|
|
|
505 function call.
|
|
|
506
|
|
|
507 Ordinarily it is an error to pass an unrecognized keyword to
|
|
|
508 a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask
|
|
|
509 Lisp to ignore unrecognized keywords, either by adding the
|
|
|
510 marker @code{&allow-other-keys} after the keyword section
|
|
|
511 of the argument list, or by specifying an @code{:allow-other-keys}
|
|
|
512 argument in the call whose value is non-@code{nil}. If the
|
|
|
513 function uses both @code{&rest} and @code{&key} at the same time,
|
|
|
514 the ``rest'' argument is bound to the keyword list as it appears
|
|
|
515 in the call. For example:
|
|
|
516
|
|
|
517 @smallexample
|
|
|
518 (defun* find-thing (thing &rest rest &key need &allow-other-keys)
|
|
|
519 (or (apply 'member* thing thing-list :allow-other-keys t rest)
|
|
|
520 (if need (error "Thing not found"))))
|
|
|
521 @end smallexample
|
|
|
522
|
|
|
523 @noindent
|
|
|
524 This function takes a @code{:need} keyword argument, but also
|
|
|
525 accepts other keyword arguments which are passed on to the
|
|
|
526 @code{member*} function. @code{allow-other-keys} is used to
|
|
|
527 keep both @code{find-thing} and @code{member*} from complaining
|
|
|
528 about each others' keywords in the arguments.
|
|
|
529
|
|
|
530 As a (significant) performance optimization, this package
|
|
|
531 implements the scan for keyword arguments by calling @code{memq}
|
|
|
532 to search for keywords in a ``rest'' argument. Technically
|
|
|
533 speaking, this is incorrect, since @code{memq} looks at the
|
|
|
534 odd-numbered values as well as the even-numbered keywords.
|
|
|
535 The net effect is that if you happen to pass a keyword symbol
|
|
|
536 as the @emph{value} of another keyword argument, where that
|
|
|
537 keyword symbol happens to equal the name of a valid keyword
|
|
|
538 argument of the same function, then the keyword parser will
|
|
|
539 become confused. This minor bug can only affect you if you
|
|
|
540 use keyword symbols as general-purpose data in your program;
|
|
|
541 this practice is strongly discouraged in Emacs Lisp.
|
|
|
542
|
|
|
543 The fifth section of the argument list consists of @dfn{auxiliary
|
|
|
544 variables}. These are not really arguments at all, but simply
|
|
|
545 variables which are bound to @code{nil} or to the specified
|
|
|
546 @var{initforms} during execution of the function. There is no
|
|
|
547 difference between the following two functions, except for a
|
|
|
548 matter of stylistic taste:
|
|
|
549
|
|
|
550 @example
|
|
|
551 (defun* foo (a b &aux (c (+ a b)) d)
|
|
|
552 @var{body})
|
|
|
553
|
|
|
554 (defun* foo (a b)
|
|
|
555 (let ((c (+ a b)) d)
|
|
|
556 @var{body}))
|
|
|
557 @end example
|
|
|
558
|
|
|
559 Argument lists support @dfn{destructuring}. In Common Lisp,
|
|
|
560 destructuring is only allowed with @code{defmacro}; this package
|
|
|
561 allows it with @code{defun*} and other argument lists as well.
|
|
|
562 In destructuring, any argument variable (@var{var} in the above
|
|
|
563 diagram) can be replaced by a list of variables, or more generally,
|
|
|
564 a recursive argument list. The corresponding argument value must
|
|
|
565 be a list whose elements match this recursive argument list.
|
|
|
566 For example:
|
|
|
567
|
|
|
568 @example
|
|
|
569 (defmacro* dolist ((var listform &optional resultform)
|
|
|
570 &rest body)
|
|
|
571 ...)
|
|
|
572 @end example
|
|
|
573
|
|
|
574 This says that the first argument of @code{dolist} must be a list
|
|
|
575 of two or three items; if there are other arguments as well as this
|
|
|
576 list, they are stored in @code{body}. All features allowed in
|
|
|
577 regular argument lists are allowed in these recursive argument lists.
|
|
|
578 In addition, the clause @samp{&whole @var{var}} is allowed at the
|
|
|
579 front of a recursive argument list. It binds @var{var} to the
|
|
|
580 whole list being matched; thus @code{(&whole all a b)} matches
|
|
|
581 a list of two things, with @code{a} bound to the first thing,
|
|
|
582 @code{b} bound to the second thing, and @code{all} bound to the
|
|
|
583 list itself. (Common Lisp allows @code{&whole} in top-level
|
|
|
584 @code{defmacro} argument lists as well, but Emacs Lisp does not
|
|
|
585 support this usage.)
|
|
|
586
|
|
|
587 One last feature of destructuring is that the argument list may be
|
|
|
588 dotted, so that the argument list @code{(a b . c)} is functionally
|
|
|
589 equivalent to @code{(a b &rest c)}.
|
|
|
590
|
|
|
591 If the optimization quality @code{safety} is set to 0
|
|
|
592 (@pxref{Declarations}), error checking for wrong number of
|
|
|
593 arguments and invalid keyword arguments is disabled. By default,
|
|
|
594 argument lists are rigorously checked.
|
|
|
595
|
|
|
596 @node Time of Evaluation, Function Aliases, Argument Lists, Program Structure
|
|
|
597 @section Time of Evaluation
|
|
|
598
|
|
|
599 @noindent
|
|
|
600 Normally, the byte-compiler does not actually execute the forms in
|
|
|
601 a file it compiles. For example, if a file contains @code{(setq foo t)},
|
|
|
602 the act of compiling it will not actually set @code{foo} to @code{t}.
|
|
|
603 This is true even if the @code{setq} was a top-level form (i.e., not
|
|
|
604 enclosed in a @code{defun} or other form). Sometimes, though, you
|
|
|
605 would like to have certain top-level forms evaluated at compile-time.
|
|
|
606 For example, the compiler effectively evaluates @code{defmacro} forms
|
|
|
607 at compile-time so that later parts of the file can refer to the
|
|
|
608 macros that are defined.
|
|
|
609
|
|
|
610 @defspec eval-when (situations...) forms...
|
|
|
611 This form controls when the body @var{forms} are evaluated.
|
|
|
612 The @var{situations} list may contain any set of the symbols
|
|
|
613 @code{compile}, @code{load}, and @code{eval} (or their long-winded
|
|
|
614 ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel},
|
|
|
615 and @code{:execute}).
|
|
|
616
|
|
|
617 The @code{eval-when} form is handled differently depending on
|
|
|
618 whether or not it is being compiled as a top-level form.
|
|
|
619 Specifically, it gets special treatment if it is being compiled
|
|
|
620 by a command such as @code{byte-compile-file} which compiles files
|
|
|
621 or buffers of code, and it appears either literally at the
|
|
|
622 top level of the file or inside a top-level @code{progn}.
|
|
|
623
|
|
|
624 For compiled top-level @code{eval-when}s, the body @var{forms} are
|
|
|
625 executed at compile-time if @code{compile} is in the @var{situations}
|
|
|
626 list, and the @var{forms} are written out to the file (to be executed
|
|
|
627 at load-time) if @code{load} is in the @var{situations} list.
|
|
|
628
|
|
|
629 For non-compiled-top-level forms, only the @code{eval} situation is
|
|
|
630 relevant. (This includes forms executed by the interpreter, forms
|
|
|
631 compiled with @code{byte-compile} rather than @code{byte-compile-file},
|
|
|
632 and non-top-level forms.) The @code{eval-when} acts like a
|
|
|
633 @code{progn} if @code{eval} is specified, and like @code{nil}
|
|
|
634 (ignoring the body @var{forms}) if not.
|
|
|
635
|
|
|
636 The rules become more subtle when @code{eval-when}s are nested;
|
|
|
637 consult Steele (second edition) for the gruesome details (and
|
|
|
638 some gruesome examples).
|
|
|
639
|
|
|
640 Some simple examples:
|
|
|
641
|
|
|
642 @example
|
|
|
643 ;; Top-level forms in foo.el:
|
|
|
644 (eval-when (compile) (setq foo1 'bar))
|
|
|
645 (eval-when (load) (setq foo2 'bar))
|
|
|
646 (eval-when (compile load) (setq foo3 'bar))
|
|
|
647 (eval-when (eval) (setq foo4 'bar))
|
|
|
648 (eval-when (eval compile) (setq foo5 'bar))
|
|
|
649 (eval-when (eval load) (setq foo6 'bar))
|
|
|
650 (eval-when (eval compile load) (setq foo7 'bar))
|
|
|
651 @end example
|
|
|
652
|
|
|
653 When @file{foo.el} is compiled, these variables will be set during
|
|
|
654 the compilation itself:
|
|
|
655
|
|
|
656 @example
|
|
|
657 foo1 foo3 foo5 foo7 ; `compile'
|
|
|
658 @end example
|
|
|
659
|
|
|
660 When @file{foo.elc} is loaded, these variables will be set:
|
|
|
661
|
|
|
662 @example
|
|
|
663 foo2 foo3 foo6 foo7 ; `load'
|
|
|
664 @end example
|
|
|
665
|
|
|
666 And if @file{foo.el} is loaded uncompiled, these variables will
|
|
|
667 be set:
|
|
|
668
|
|
|
669 @example
|
|
|
670 foo4 foo5 foo6 foo7 ; `eval'
|
|
|
671 @end example
|
|
|
672
|
|
|
673 If these seven @code{eval-when}s had been, say, inside a @code{defun},
|
|
|
674 then the first three would have been equivalent to @code{nil} and the
|
|
|
675 last four would have been equivalent to the corresponding @code{setq}s.
|
|
|
676
|
|
|
677 Note that @code{(eval-when (load eval) @dots{})} is equivalent
|
|
|
678 to @code{(progn @dots{})} in all contexts. The compiler treats
|
|
|
679 certain top-level forms, like @code{defmacro} (sort-of) and
|
|
|
680 @code{require}, as if they were wrapped in @code{(eval-when
|
|
|
681 (compile load eval) @dots{})}.
|
|
|
682 @end defspec
|
|
|
683
|
|
|
684 Emacs 19 includes two special forms related to @code{eval-when}.
|
|
|
685 One of these, @code{eval-when-compile}, is not quite equivalent to
|
|
|
686 any @code{eval-when} construct and is described below. This package
|
|
|
687 defines a version of @code{eval-when-compile} for the benefit of
|
|
|
688 Emacs 18 users.
|
|
|
689
|
|
|
690 The other form, @code{(eval-and-compile @dots{})}, is exactly
|
|
|
691 equivalent to @samp{(eval-when (compile load eval) @dots{})} and
|
|
|
692 so is not itself defined by this package.
|
|
|
693
|
|
|
694 @defspec eval-when-compile forms...
|
|
|
695 The @var{forms} are evaluated at compile-time; at execution time,
|
|
|
696 this form acts like a quoted constant of the resulting value. Used
|
|
|
697 at top-level, @code{eval-when-compile} is just like @samp{eval-when
|
|
|
698 (compile eval)}. In other contexts, @code{eval-when-compile}
|
|
|
699 allows code to be evaluated once at compile-time for efficiency
|
|
|
700 or other reasons.
|
|
|
701
|
|
|
702 This form is similar to the @samp{#.} syntax of true Common Lisp.
|
|
|
703 @end defspec
|
|
|
704
|
|
|
705 @defspec load-time-value form
|
|
|
706 The @var{form} is evaluated at load-time; at execution time,
|
|
|
707 this form acts like a quoted constant of the resulting value.
|
|
|
708
|
|
|
709 Early Common Lisp had a @samp{#,} syntax that was similar to
|
|
|
710 this, but ANSI Common Lisp replaced it with @code{load-time-value}
|
|
|
711 and gave it more well-defined semantics.
|
|
|
712
|
|
|
713 In a compiled file, @code{load-time-value} arranges for @var{form}
|
|
|
714 to be evaluated when the @file{.elc} file is loaded and then used
|
|
|
715 as if it were a quoted constant. In code compiled by
|
|
|
716 @code{byte-compile} rather than @code{byte-compile-file}, the
|
|
|
717 effect is identical to @code{eval-when-compile}. In uncompiled
|
|
|
718 code, both @code{eval-when-compile} and @code{load-time-value}
|
|
|
719 act exactly like @code{progn}.
|
|
|
720
|
|
|
721 @example
|
|
|
722 (defun report ()
|
|
|
723 (insert "This function was executed on: "
|
|
|
724 (current-time-string)
|
|
|
725 ", compiled on: "
|
|
|
726 (eval-when-compile (current-time-string))
|
|
|
727 ;; or '#.(current-time-string) in real Common Lisp
|
|
|
728 ", and loaded on: "
|
|
|
729 (load-time-value (current-time-string))))
|
|
|
730 @end example
|
|
|
731
|
|
|
732 @noindent
|
|
|
733 Byte-compiled, the above defun will result in the following code
|
|
|
734 (or its compiled equivalent, of course) in the @file{.elc} file:
|
|
|
735
|
|
|
736 @example
|
|
|
737 (setq --temp-- (current-time-string))
|
|
|
738 (defun report ()
|
|
|
739 (insert "This function was executed on: "
|
|
|
740 (current-time-string)
|
|
|
741 ", compiled on: "
|
|
|
742 '"Wed Jun 23 18:33:43 1993"
|
|
|
743 ", and loaded on: "
|
|
|
744 --temp--))
|
|
|
745 @end example
|
|
|
746 @end defspec
|
|
|
747
|
|
|
748 @node Function Aliases, , Time of Evaluation, Program Structure
|
|
|
749 @section Function Aliases
|
|
|
750
|
|
|
751 @noindent
|
|
|
752 This section describes a feature from GNU Emacs 19 which this
|
|
|
753 package makes available in other versions of Emacs.
|
|
|
754
|
|
|
755 @defun defalias symbol function
|
|
|
756 This function sets @var{symbol}'s function cell to @var{function}.
|
|
|
757 It is equivalent to @code{fset}, except that in GNU Emacs 19 it also
|
|
|
758 records the setting in @code{load-history} so that it can be undone
|
|
|
759 by a later @code{unload-feature}.
|
|
|
760
|
|
|
761 In other versions of Emacs, @code{defalias} is a synonym for
|
|
|
762 @code{fset}.
|
|
|
763 @end defun
|
|
|
764
|
|
|
765 @node Predicates, Control Structure, Program Structure, Top
|
|
|
766 @chapter Predicates
|
|
|
767
|
|
|
768 @noindent
|
|
|
769 This section describes functions for testing whether various
|
|
|
770 facts are true or false.
|
|
|
771
|
|
|
772 @menu
|
|
|
773 * Type Predicates:: `typep', `deftype', and `coerce'
|
|
|
774 * Equality Predicates:: `eql' and `equalp'
|
|
|
775 @end menu
|
|
|
776
|
|
|
777 @node Type Predicates, Equality Predicates, Predicates, Predicates
|
|
|
778 @section Type Predicates
|
|
|
779
|
|
|
780 @noindent
|
|
|
781 The @dfn{CL} package defines a version of the Common Lisp @code{typep}
|
|
|
782 predicate.
|
|
|
783
|
|
|
784 @defun typep object type
|
|
|
785 Check if @var{object} is of type @var{type}, where @var{type} is a
|
|
|
786 (quoted) type name of the sort used by Common Lisp. For example,
|
|
|
787 @code{(typep foo 'integer)} is equivalent to @code{(integerp foo)}.
|
|
|
788 @end defun
|
|
|
789
|
|
|
790 The @var{type} argument to the above function is either a symbol
|
|
|
791 or a list beginning with a symbol.
|
|
|
792
|
|
|
793 @itemize @bullet
|
|
|
794 @item
|
|
|
795 If the type name is a symbol, Emacs appends @samp{-p} to the
|
|
|
796 symbol name to form the name of a predicate function for testing
|
|
|
797 the type. (Built-in predicates whose names end in @samp{p} rather
|
|
|
798 than @samp{-p} are used when appropriate.)
|
|
|
799
|
|
|
800 @item
|
|
|
801 The type symbol @code{t} stands for the union of all types.
|
|
|
802 @code{(typep @var{object} t)} is always true. Likewise, the
|
|
|
803 type symbol @code{nil} stands for nothing at all, and
|
|
|
804 @code{(typep @var{object} nil)} is always false.
|
|
|
805
|
|
|
806 @item
|
|
|
807 The type symbol @code{null} represents the symbol @code{nil}.
|
|
|
808 Thus @code{(typep @var{object} 'null)} is equivalent to
|
|
|
809 @code{(null @var{object})}.
|
|
|
810
|
|
|
811 @item
|
|
|
812 The type symbol @code{real} is a synonym for @code{number}, and
|
|
|
813 @code{fixnum} is a synonym for @code{integer}.
|
|
|
814
|
|
|
815 @item
|
|
|
816 The type symbols @code{character} and @code{string-char} match
|
|
|
817 characters. In Emacs-19 and XEmacs-19, characters are the same thing as
|
|
|
818 integers in the range 0-255. In XEmacs-20, where characters are a
|
|
|
819 first-class data type, this checks for actual characters, and
|
|
|
820 @code{(typep @var{8bit-integer} 'character)} will return @code{nil}.
|
|
|
821
|
|
|
822 @item
|
|
|
823 The type symbol @code{float} uses the @code{floatp-safe} predicate
|
|
|
824 defined by this package rather than @code{floatp}, so it will work
|
|
|
825 correctly even in Emacs versions without floating-point support.
|
|
|
826
|
|
|
827 @item
|
|
|
828 The type list @code{(integer @var{low} @var{high})} represents all
|
|
|
829 integers between @var{low} and @var{high}, inclusive. Either bound
|
|
|
830 may be a list of a single integer to specify an exclusive limit,
|
|
|
831 or a @code{*} to specify no limit. The type @code{(integer * *)}
|
|
|
832 is thus equivalent to @code{integer}.
|
|
|
833
|
|
|
834 @item
|
|
|
835 Likewise, lists beginning with @code{float}, @code{real}, or
|
|
|
836 @code{number} represent numbers of that type falling in a particular
|
|
|
837 range.
|
|
|
838
|
|
|
839 @item
|
|
|
840 Lists beginning with @code{and}, @code{or}, and @code{not} form
|
|
|
841 combinations of types. For example, @code{(or integer (float 0 *))}
|
|
|
842 represents all objects that are integers or non-negative floats.
|
|
|
843
|
|
|
844 @item
|
|
|
845 Lists beginning with @code{member} or @code{member*} represent
|
|
|
846 objects @code{eql} to any of the following values. For example,
|
|
|
847 @code{(member 1 2 3 4)} is equivalent to @code{(integer 1 4)},
|
|
|
848 and @code{(member nil)} is equivalent to @code{null}.
|
|
|
849
|
|
|
850 @item
|
|
|
851 Lists of the form @code{(satisfies @var{predicate})} represent
|
|
|
852 all objects for which @var{predicate} returns true when called
|
|
|
853 with that object as an argument.
|
|
|
854 @end itemize
|
|
|
855
|
|
|
856 The following function and macro (not technically predicates) are
|
|
|
857 related to @code{typep}.
|
|
|
858
|
|
|
859 @defun coerce object type
|
|
|
860 This function attempts to convert @var{object} to the specified
|
|
|
861 @var{type}. If @var{object} is already of that type as determined by
|
|
|
862 @code{typep}, it is simply returned. Otherwise, certain types of
|
|
|
863 conversions will be made: If @var{type} is any sequence type
|
|
|
864 (@code{string}, @code{list}, etc.) then @var{object} will be
|
|
|
865 converted to that type if possible. If @var{type} is
|
|
|
866 @code{character}, then strings of length one and symbols with
|
|
|
867 one-character names can be coerced. If @var{type} is @code{float},
|
|
|
868 then integers can be coerced in versions of Emacs that support
|
|
|
869 floats. In all other circumstances, @code{coerce} signals an
|
|
|
870 error.
|
|
|
871 @end defun
|
|
|
872
|
|
|
873 @defspec deftype name arglist forms...
|
|
|
874 This macro defines a new type called @var{name}. It is similar
|
|
|
875 to @code{defmacro} in many ways; when @var{name} is encountered
|
|
|
876 as a type name, the body @var{forms} are evaluated and should
|
|
|
877 return a type specifier that is equivalent to the type. The
|
|
|
878 @var{arglist} is a Common Lisp argument list of the sort accepted
|
|
|
879 by @code{defmacro*}. The type specifier @samp{(@var{name} @var{args}...)}
|
|
|
880 is expanded by calling the expander with those arguments; the type
|
|
|
881 symbol @samp{@var{name}} is expanded by calling the expander with
|
|
|
882 no arguments. The @var{arglist} is processed the same as for
|
|
|
883 @code{defmacro*} except that optional arguments without explicit
|
|
|
884 defaults use @code{*} instead of @code{nil} as the ``default''
|
|
|
885 default. Some examples:
|
|
|
886
|
|
|
887 @example
|
|
|
888 (deftype null () '(satisfies null)) ; predefined
|
|
|
889 (deftype list () '(or null cons)) ; predefined
|
|
|
890 (deftype unsigned-byte (&optional bits)
|
|
|
891 (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits)))))
|
|
|
892 (unsigned-byte 8) @equiv{} (integer 0 255)
|
|
|
893 (unsigned-byte) @equiv{} (integer 0 *)
|
|
|
894 unsigned-byte @equiv{} (integer 0 *)
|
|
|
895 @end example
|
|
|
896
|
|
|
897 @noindent
|
|
|
898 The last example shows how the Common Lisp @code{unsigned-byte}
|
|
|
899 type specifier could be implemented if desired; this package does
|
|
|
900 not implement @code{unsigned-byte} by default.
|
|
|
901 @end defspec
|
|
|
902
|
|
|
903 The @code{typecase} and @code{check-type} macros also use type
|
|
|
904 names. @xref{Conditionals}. @xref{Assertions}. The @code{map},
|
|
|
905 @code{concatenate}, and @code{merge} functions take type-name
|
|
|
906 arguments to specify the type of sequence to return. @xref{Sequences}.
|
|
|
907
|
|
|
908 @node Equality Predicates, , Type Predicates, Predicates
|
|
|
909 @section Equality Predicates
|
|
|
910
|
|
|
911 @noindent
|
|
|
912 This package defines two Common Lisp predicates, @code{eql} and
|
|
|
913 @code{equalp}.
|
|
|
914
|
|
|
915 @defun eql a b
|
|
|
916 This function is almost the same as @code{eq}, except that if @var{a}
|
|
|
917 and @var{b} are numbers of the same type, it compares them for numeric
|
|
|
918 equality (as if by @code{equal} instead of @code{eq}). This makes a
|
|
|
919 difference only for versions of Emacs that are compiled with
|
|
|
920 floating-point support, such as Emacs 19. Emacs floats are allocated
|
|
|
921 objects just like cons cells, which means that @code{(eq 3.0 3.0)}
|
|
|
922 will not necessarily be true---if the two @code{3.0}s were allocated
|
|
|
923 separately, the pointers will be different even though the numbers are
|
|
|
924 the same. But @code{(eql 3.0 3.0)} will always be true.
|
|
|
925
|
|
|
926 The types of the arguments must match, so @code{(eql 3 3.0)} is
|
|
|
927 still false.
|
|
|
928
|
|
|
929 Note that Emacs integers are ``direct'' rather than allocated, which
|
|
|
930 basically means @code{(eq 3 3)} will always be true. Thus @code{eq}
|
|
|
931 and @code{eql} behave differently only if floating-point numbers are
|
|
|
932 involved, and are indistinguishable on Emacs versions that don't
|
|
|
933 support floats.
|
|
|
934
|
|
|
935 There is a slight inconsistency with Common Lisp in the treatment of
|
|
|
936 positive and negative zeros. Some machines, notably those with IEEE
|
|
|
937 standard arithmetic, represent @code{+0} and @code{-0} as distinct
|
|
|
938 values. Normally this doesn't matter because the standard specifies
|
|
|
939 that @code{(= 0.0 -0.0)} should always be true, and this is indeed
|
|
|
940 what Emacs Lisp and Common Lisp do. But the Common Lisp standard
|
|
|
941 states that @code{(eql 0.0 -0.0)} and @code{(equal 0.0 -0.0)} should
|
|
|
942 be false on IEEE-like machines; Emacs Lisp does not do this, and in
|
|
|
943 fact the only known way to distinguish between the two zeros in Emacs
|
|
|
944 Lisp is to @code{format} them and check for a minus sign.
|
|
|
945 @end defun
|
|
|
946
|
|
|
947 @defun equalp a b
|
|
|
948 This function is a more flexible version of @code{equal}. In
|
|
|
949 particular, it compares strings and characters case-insensitively, and
|
|
|
950 it compares numbers without regard to type (so that @code{(equalp 3
|
|
|
951 3.0)} is true). Vectors and conses are compared recursively. All other
|
|
|
952 objects are compared as if by @code{equal}.
|
|
|
953
|
|
|
954 This function differs from Common Lisp @code{equalp} in several
|
|
|
955 respects. In keeping with the idea that strings are less
|
|
|
956 vector-like in Emacs Lisp, this package's @code{equalp} also will not
|
|
|
957 compare strings against vectors of integers.
|
|
|
958 @end defun
|
|
|
959
|
|
|
960 Also note that the Common Lisp functions @code{member} and @code{assoc}
|
|
|
961 use @code{eql} to compare elements, whereas Emacs Lisp follows the
|
|
|
962 MacLisp tradition and uses @code{equal} for these two functions.
|
|
|
963 In Emacs, use @code{member*} and @code{assoc*} to get functions
|
|
|
964 which use @code{eql} for comparisons.
|
|
|
965
|
|
|
966 @node Control Structure, Macros, Predicates, Top
|
|
|
967 @chapter Control Structure
|
|
|
968
|
|
|
969 @noindent
|
|
|
970 The features described in the following sections implement
|
|
|
971 various advanced control structures, including the powerful
|
|
|
972 @code{setf} facility and a number of looping and conditional
|
|
|
973 constructs.
|
|
|
974
|
|
|
975 @menu
|
|
|
976 * Assignment:: The `psetq' form
|
|
|
977 * Generalized Variables:: `setf', `incf', `push', etc.
|
|
|
978 * Variable Bindings:: `progv', `lexical-let', `flet', `macrolet'
|
|
|
979 * Conditionals:: `when', `unless', `case', `typecase'
|
|
|
980 * Blocks and Exits:: `block', `return', `return-from'
|
|
|
981 * Iteration:: `do', `dotimes', `dolist', `do-symbols'
|
|
|
982 * Loop Facility:: The Common Lisp `loop' macro
|
|
|
983 * Multiple Values:: `values', `multiple-value-bind', etc.
|
|
|
984 @end menu
|
|
|
985
|
|
|
986 @node Assignment, Generalized Variables, Control Structure, Control Structure
|
|
|
987 @section Assignment
|
|
|
988
|
|
|
989 @noindent
|
|
|
990 The @code{psetq} form is just like @code{setq}, except that multiple
|
|
|
991 assignments are done in parallel rather than sequentially.
|
|
|
992
|
|
|
993 @defspec psetq [symbol form]@dots{}
|
|
|
994 This special form (actually a macro) is used to assign to several
|
|
|
995 variables simultaneously. Given only one @var{symbol} and @var{form},
|
|
|
996 it has the same effect as @code{setq}. Given several @var{symbol}
|
|
|
997 and @var{form} pairs, it evaluates all the @var{form}s in advance
|
|
|
998 and then stores the corresponding variables afterwards.
|
|
|
999
|
|
|
1000 @example
|
|
|
1001 (setq x 2 y 3)
|
|
|
1002 (setq x (+ x y) y (* x y))
|
|
|
1003 x
|
|
|
1004 @result{} 5
|
|
|
1005 y ; @r{@code{y} was computed after @code{x} was set.}
|
|
|
1006 @result{} 15
|
|
|
1007 (setq x 2 y 3)
|
|
|
1008 (psetq x (+ x y) y (* x y))
|
|
|
1009 x
|
|
|
1010 @result{} 5
|
|
|
1011 y ; @r{@code{y} was computed before @code{x} was set.}
|
|
|
1012 @result{} 6
|
|
|
1013 @end example
|
|
|
1014
|
|
|
1015 The simplest use of @code{psetq} is @code{(psetq x y y x)}, which
|
|
|
1016 exchanges the values of two variables. (The @code{rotatef} form
|
|
|
1017 provides an even more convenient way to swap two variables;
|
|
|
1018 @pxref{Modify Macros}.)
|
|
|
1019
|
|
|
1020 @code{psetq} always returns @code{nil}.
|
|
|
1021 @end defspec
|
|
|
1022
|
|
|
1023 @node Generalized Variables, Variable Bindings, Assignment, Control Structure
|
|
|
1024 @section Generalized Variables
|
|
|
1025
|
|
|
1026 @noindent
|
|
|
1027 A ``generalized variable'' or ``place form'' is one of the many places
|
|
|
1028 in Lisp memory where values can be stored. The simplest place form is
|
|
|
1029 a regular Lisp variable. But the cars and cdrs of lists, elements
|
|
|
1030 of arrays, properties of symbols, and many other locations are also
|
|
|
1031 places where Lisp values are stored.
|
|
|
1032
|
|
|
1033 The @code{setf} form is like @code{setq}, except that it accepts
|
|
|
1034 arbitrary place forms on the left side rather than just
|
|
|
1035 symbols. For example, @code{(setf (car a) b)} sets the car of
|
|
|
1036 @code{a} to @code{b}, doing the same operation as @code{(setcar a b)}
|
|
|
1037 but without having to remember two separate functions for setting
|
|
|
1038 and accessing every type of place.
|
|
|
1039
|
|
|
1040 Generalized variables are analogous to ``lvalues'' in the C
|
|
|
1041 language, where @samp{x = a[i]} gets an element from an array
|
|
|
1042 and @samp{a[i] = x} stores an element using the same notation.
|
|
|
1043 Just as certain forms like @code{a[i]} can be lvalues in C, there
|
|
|
1044 is a set of forms that can be generalized variables in Lisp.
|
|
|
1045
|
|
|
1046 @menu
|
|
|
1047 * Basic Setf:: `setf' and place forms
|
|
|
1048 * Modify Macros:: `incf', `push', `rotatef', `letf', `callf', etc.
|
|
|
1049 * Customizing Setf:: `define-modify-macro', `defsetf', `define-setf-method'
|
|
|
1050 @end menu
|
|
|
1051
|
|
|
1052 @node Basic Setf, Modify Macros, Generalized Variables, Generalized Variables
|
|
|
1053 @subsection Basic Setf
|
|
|
1054
|
|
|
1055 @noindent
|
|
|
1056 The @code{setf} macro is the most basic way to operate on generalized
|
|
|
1057 variables.
|
|
|
1058
|
|
|
1059 @defspec setf [place form]@dots{}
|
|
|
1060 This macro evaluates @var{form} and stores it in @var{place}, which
|
|
|
1061 must be a valid generalized variable form. If there are several
|
|
|
1062 @var{place} and @var{form} pairs, the assignments are done sequentially
|
|
|
1063 just as with @code{setq}. @code{setf} returns the value of the last
|
|
|
1064 @var{form}.
|
|
|
1065
|
|
|
1066 The following Lisp forms will work as generalized variables, and
|
|
|
1067 so may legally appear in the @var{place} argument of @code{setf}:
|
|
|
1068
|
|
|
1069 @itemize @bullet
|
|
|
1070 @item
|
|
|
1071 A symbol naming a variable. In other words, @code{(setf x y)} is
|
|
|
1072 exactly equivalent to @code{(setq x y)}, and @code{setq} itself is
|
|
|
1073 strictly speaking redundant now that @code{setf} exists. Many
|
|
|
1074 programmers continue to prefer @code{setq} for setting simple
|
|
|
1075 variables, though, purely for stylistic or historical reasons.
|
|
446
|
1076 The form @code{(setf x y)} actually expands to @code{(setq x y)},
|
|
428
|
1077 so there is no performance penalty for using it in compiled code.
|
|
|
1078
|
|
|
1079 @item
|
|
|
1080 A call to any of the following Lisp functions:
|
|
|
1081
|
|
|
1082 @smallexample
|
|
|
1083 car cdr caar .. cddddr
|
|
|
1084 nth rest first .. tenth
|
|
|
1085 aref elt nthcdr
|
|
|
1086 symbol-function symbol-value symbol-plist
|
|
440
|
1087 get getf gethash
|
|
|
1088 subseq
|
|
428
|
1089 @end smallexample
|
|
|
1090
|
|
|
1091 @noindent
|
|
|
1092 Note that for @code{nthcdr} and @code{getf}, the list argument
|
|
|
1093 of the function must itself be a valid @var{place} form. For
|
|
|
1094 example, @code{(setf (nthcdr 0 foo) 7)} will set @code{foo} itself
|
|
|
1095 to 7. Note that @code{push} and @code{pop} on an @code{nthcdr}
|
|
|
1096 place can be used to insert or delete at any position in a list.
|
|
|
1097 The use of @code{nthcdr} as a @var{place} form is an extension
|
|
|
1098 to standard Common Lisp.
|
|
|
1099
|
|
|
1100 @item
|
|
|
1101 The following Emacs-specific functions are also @code{setf}-able.
|
|
|
1102 (Some of these are defined only in Emacs 19 or only in XEmacs.)
|
|
|
1103
|
|
|
1104 @smallexample
|
|
|
1105 buffer-file-name marker-position
|
|
|
1106 buffer-modified-p match-data
|
|
|
1107 buffer-name mouse-position
|
|
|
1108 buffer-string overlay-end
|
|
|
1109 buffer-substring overlay-get
|
|
|
1110 current-buffer overlay-start
|
|
|
1111 current-case-table point
|
|
|
1112 current-column point-marker
|
|
|
1113 current-global-map point-max
|
|
|
1114 current-input-mode point-min
|
|
|
1115 current-local-map process-buffer
|
|
|
1116 current-window-configuration process-filter
|
|
|
1117 default-file-modes process-sentinel
|
|
|
1118 default-value read-mouse-position
|
|
|
1119 documentation-property screen-height
|
|
|
1120 extent-data screen-menubar
|
|
|
1121 extent-end-position screen-width
|
|
|
1122 extent-start-position selected-window
|
|
|
1123 face-background selected-screen
|
|
|
1124 face-background-pixmap selected-frame
|
|
|
1125 face-font standard-case-table
|
|
|
1126 face-foreground syntax-table
|
|
|
1127 face-underline-p window-buffer
|
|
|
1128 file-modes window-dedicated-p
|
|
|
1129 frame-height window-display-table
|
|
|
1130 frame-parameters window-height
|
|
|
1131 frame-visible-p window-hscroll
|
|
|
1132 frame-width window-point
|
|
|
1133 get-register window-start
|
|
|
1134 getenv window-width
|
|
|
1135 global-key-binding x-get-cut-buffer
|
|
|
1136 keymap-parent x-get-cutbuffer
|
|
|
1137 local-key-binding x-get-secondary-selection
|
|
|
1138 mark x-get-selection
|
|
|
1139 mark-marker
|
|
|
1140 @end smallexample
|
|
|
1141
|
|
|
1142 Most of these have directly corresponding ``set'' functions, like
|
|
|
1143 @code{use-local-map} for @code{current-local-map}, or @code{goto-char}
|
|
|
1144 for @code{point}. A few, like @code{point-min}, expand to longer
|
|
|
1145 sequences of code when they are @code{setf}'d (@code{(narrow-to-region
|
|
|
1146 x (point-max))} in this case).
|
|
|
1147
|
|
|
1148 @item
|
|
|
1149 A call of the form @code{(substring @var{subplace} @var{n} [@var{m}])},
|
|
|
1150 where @var{subplace} is itself a legal generalized variable whose
|
|
|
1151 current value is a string, and where the value stored is also a
|
|
|
1152 string. The new string is spliced into the specified part of the
|
|
|
1153 destination string. For example:
|
|
|
1154
|
|
|
1155 @example
|
|
|
1156 (setq a (list "hello" "world"))
|
|
|
1157 @result{} ("hello" "world")
|
|
|
1158 (cadr a)
|
|
|
1159 @result{} "world"
|
|
|
1160 (substring (cadr a) 2 4)
|
|
|
1161 @result{} "rl"
|
|
|
1162 (setf (substring (cadr a) 2 4) "o")
|
|
|
1163 @result{} "o"
|
|
|
1164 (cadr a)
|
|
|
1165 @result{} "wood"
|
|
|
1166 a
|
|
|
1167 @result{} ("hello" "wood")
|
|
|
1168 @end example
|
|
|
1169
|
|
|
1170 The generalized variable @code{buffer-substring}, listed above,
|
|
|
1171 also works in this way by replacing a portion of the current buffer.
|
|
|
1172
|
|
|
1173 @item
|
|
|
1174 A call of the form @code{(apply '@var{func} @dots{})} or
|
|
|
1175 @code{(apply (function @var{func}) @dots{})}, where @var{func}
|
|
|
1176 is a @code{setf}-able function whose store function is ``suitable''
|
|
|
1177 in the sense described in Steele's book; since none of the standard
|
|
|
1178 Emacs place functions are suitable in this sense, this feature is
|
|
|
1179 only interesting when used with places you define yourself with
|
|
|
1180 @code{define-setf-method} or the long form of @code{defsetf}.
|
|
|
1181
|
|
|
1182 @item
|
|
|
1183 A macro call, in which case the macro is expanded and @code{setf}
|
|
|
1184 is applied to the resulting form.
|
|
|
1185
|
|
|
1186 @item
|
|
|
1187 Any form for which a @code{defsetf} or @code{define-setf-method}
|
|
|
1188 has been made.
|
|
|
1189 @end itemize
|
|
|
1190
|
|
|
1191 Using any forms other than these in the @var{place} argument to
|
|
|
1192 @code{setf} will signal an error.
|
|
|
1193
|
|
|
1194 The @code{setf} macro takes care to evaluate all subforms in
|
|
|
1195 the proper left-to-right order; for example,
|
|
|
1196
|
|
|
1197 @example
|
|
|
1198 (setf (aref vec (incf i)) i)
|
|
|
1199 @end example
|
|
|
1200
|
|
|
1201 @noindent
|
|
|
1202 looks like it will evaluate @code{(incf i)} exactly once, before the
|
|
|
1203 following access to @code{i}; the @code{setf} expander will insert
|
|
|
1204 temporary variables as necessary to ensure that it does in fact work
|
|
|
1205 this way no matter what setf-method is defined for @code{aref}.
|
|
|
1206 (In this case, @code{aset} would be used and no such steps would
|
|
|
1207 be necessary since @code{aset} takes its arguments in a convenient
|
|
|
1208 order.)
|
|
|
1209
|
|
|
1210 However, if the @var{place} form is a macro which explicitly
|
|
|
1211 evaluates its arguments in an unusual order, this unusual order
|
|
|
1212 will be preserved. Adapting an example from Steele, given
|
|
|
1213
|
|
|
1214 @example
|
|
|
1215 (defmacro wrong-order (x y) (list 'aref y x))
|
|
|
1216 @end example
|
|
|
1217
|
|
|
1218 @noindent
|
|
|
1219 the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will
|
|
|
1220 evaluate @var{b} first, then @var{a}, just as in an actual call
|
|
|
1221 to @code{wrong-order}.
|
|
|
1222 @end defspec
|
|
|
1223
|
|
|
1224 @node Modify Macros, Customizing Setf, Basic Setf, Generalized Variables
|
|
|
1225 @subsection Modify Macros
|
|
|
1226
|
|
|
1227 @noindent
|
|
|
1228 This package defines a number of other macros besides @code{setf}
|
|
|
1229 that operate on generalized variables. Many are interesting and
|
|
|
1230 useful even when the @var{place} is just a variable name.
|
|
|
1231
|
|
|
1232 @defspec psetf [place form]@dots{}
|
|
|
1233 This macro is to @code{setf} what @code{psetq} is to @code{setq}:
|
|
|
1234 When several @var{place}s and @var{form}s are involved, the
|
|
|
1235 assignments take place in parallel rather than sequentially.
|
|
|
1236 Specifically, all subforms are evaluated from left to right, then
|
|
|
1237 all the assignments are done (in an undefined order).
|
|
|
1238 @end defspec
|
|
|
1239
|
|
|
1240 @defspec incf place &optional x
|
|
|
1241 This macro increments the number stored in @var{place} by one, or
|
|
|
1242 by @var{x} if specified. The incremented value is returned. For
|
|
|
1243 example, @code{(incf i)} is equivalent to @code{(setq i (1+ i))}, and
|
|
|
1244 @code{(incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x) 2))}.
|
|
|
1245
|
|
|
1246 Once again, care is taken to preserve the ``apparent'' order of
|
|
|
1247 evaluation. For example,
|
|
|
1248
|
|
|
1249 @example
|
|
|
1250 (incf (aref vec (incf i)))
|
|
|
1251 @end example
|
|
|
1252
|
|
|
1253 @noindent
|
|
|
1254 appears to increment @code{i} once, then increment the element of
|
|
|
1255 @code{vec} addressed by @code{i}; this is indeed exactly what it
|
|
|
1256 does, which means the above form is @emph{not} equivalent to the
|
|
|
1257 ``obvious'' expansion,
|
|
|
1258
|
|
|
1259 @example
|
|
|
1260 (setf (aref vec (incf i)) (1+ (aref vec (incf i)))) ; Wrong!
|
|
|
1261 @end example
|
|
|
1262
|
|
|
1263 @noindent
|
|
|
1264 but rather to something more like
|
|
|
1265
|
|
|
1266 @example
|
|
|
1267 (let ((temp (incf i)))
|
|
|
1268 (setf (aref vec temp) (1+ (aref vec temp))))
|
|
|
1269 @end example
|
|
|
1270
|
|
|
1271 @noindent
|
|
|
1272 Again, all of this is taken care of automatically by @code{incf} and
|
|
|
1273 the other generalized-variable macros.
|
|
|
1274
|
|
|
1275 As a more Emacs-specific example of @code{incf}, the expression
|
|
|
1276 @code{(incf (point) @var{n})} is essentially equivalent to
|
|
|
1277 @code{(forward-char @var{n})}.
|
|
|
1278 @end defspec
|
|
|
1279
|
|
|
1280 @defspec decf place &optional x
|
|
|
1281 This macro decrements the number stored in @var{place} by one, or
|
|
|
1282 by @var{x} if specified.
|
|
|
1283 @end defspec
|
|
|
1284
|
|
|
1285 @defspec pop place
|
|
|
1286 This macro removes and returns the first element of the list stored
|
|
|
1287 in @var{place}. It is analogous to @code{(prog1 (car @var{place})
|
|
|
1288 (setf @var{place} (cdr @var{place})))}, except that it takes care
|
|
|
1289 to evaluate all subforms only once.
|
|
|
1290 @end defspec
|
|
|
1291
|
|
|
1292 @defspec push x place
|
|
|
1293 This macro inserts @var{x} at the front of the list stored in
|
|
|
1294 @var{place}. It is analogous to @code{(setf @var{place} (cons
|
|
|
1295 @var{x} @var{place}))}, except for evaluation of the subforms.
|
|
|
1296 @end defspec
|
|
|
1297
|
|
|
1298 @defspec pushnew x place @t{&key :test :test-not :key}
|
|
|
1299 This macro inserts @var{x} at the front of the list stored in
|
|
|
1300 @var{place}, but only if @var{x} was not @code{eql} to any
|
|
|
1301 existing element of the list. The optional keyword arguments
|
|
|
1302 are interpreted in the same way as for @code{adjoin}.
|
|
|
1303 @xref{Lists as Sets}.
|
|
|
1304 @end defspec
|
|
|
1305
|
|
|
1306 @defspec shiftf place@dots{} newvalue
|
|
|
1307 This macro shifts the @var{place}s left by one, shifting in the
|
|
|
1308 value of @var{newvalue} (which may be any Lisp expression, not just
|
|
|
1309 a generalized variable), and returning the value shifted out of
|
|
|
1310 the first @var{place}. Thus, @code{(shiftf @var{a} @var{b} @var{c}
|
|
|
1311 @var{d})} is equivalent to
|
|
|
1312
|
|
|
1313 @example
|
|
|
1314 (prog1
|
|
|
1315 @var{a}
|
|
|
1316 (psetf @var{a} @var{b}
|
|
|
1317 @var{b} @var{c}
|
|
|
1318 @var{c} @var{d}))
|
|
|
1319 @end example
|
|
|
1320
|
|
|
1321 @noindent
|
|
|
1322 except that the subforms of @var{a}, @var{b}, and @var{c} are actually
|
|
|
1323 evaluated only once each and in the apparent order.
|
|
|
1324 @end defspec
|
|
|
1325
|
|
|
1326 @defspec rotatef place@dots{}
|
|
|
1327 This macro rotates the @var{place}s left by one in circular fashion.
|
|
|
1328 Thus, @code{(rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
|
|
|
1329
|
|
|
1330 @example
|
|
|
1331 (psetf @var{a} @var{b}
|
|
|
1332 @var{b} @var{c}
|
|
|
1333 @var{c} @var{d}
|
|
|
1334 @var{d} @var{a})
|
|
|
1335 @end example
|
|
|
1336
|
|
|
1337 @noindent
|
|
|
1338 except for the evaluation of subforms. @code{rotatef} always
|
|
|
1339 returns @code{nil}. Note that @code{(rotatef @var{a} @var{b})}
|
|
|
1340 conveniently exchanges @var{a} and @var{b}.
|
|
|
1341 @end defspec
|
|
|
1342
|
|
|
1343 The following macros were invented for this package; they have no
|
|
|
1344 analogues in Common Lisp.
|
|
|
1345
|
|
|
1346 @defspec letf (bindings@dots{}) forms@dots{}
|
|
|
1347 This macro is analogous to @code{let}, but for generalized variables
|
|
|
1348 rather than just symbols. Each @var{binding} should be of the form
|
|
|
1349 @code{(@var{place} @var{value})}; the original contents of the
|
|
|
1350 @var{place}s are saved, the @var{value}s are stored in them, and
|
|
|
1351 then the body @var{form}s are executed. Afterwards, the @var{places}
|
|
|
1352 are set back to their original saved contents. This cleanup happens
|
|
|
1353 even if the @var{form}s exit irregularly due to a @code{throw} or an
|
|
|
1354 error.
|
|
|
1355
|
|
|
1356 For example,
|
|
|
1357
|
|
|
1358 @example
|
|
|
1359 (letf (((point) (point-min))
|
|
|
1360 (a 17))
|
|
|
1361 ...)
|
|
|
1362 @end example
|
|
|
1363
|
|
|
1364 @noindent
|
|
|
1365 moves ``point'' in the current buffer to the beginning of the buffer,
|
|
|
1366 and also binds @code{a} to 17 (as if by a normal @code{let}, since
|
|
|
1367 @code{a} is just a regular variable). After the body exits, @code{a}
|
|
|
1368 is set back to its original value and point is moved back to its
|
|
|
1369 original position.
|
|
|
1370
|
|
|
1371 Note that @code{letf} on @code{(point)} is not quite like a
|
|
|
1372 @code{save-excursion}, as the latter effectively saves a marker
|
|
|
1373 which tracks insertions and deletions in the buffer. Actually,
|
|
|
1374 a @code{letf} of @code{(point-marker)} is much closer to this
|
|
|
1375 behavior. (@code{point} and @code{point-marker} are equivalent
|
|
|
1376 as @code{setf} places; each will accept either an integer or a
|
|
|
1377 marker as the stored value.)
|
|
|
1378
|
|
|
1379 Since generalized variables look like lists, @code{let}'s shorthand
|
|
|
1380 of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
|
|
|
1381 be ambiguous in @code{letf} and is not allowed.
|
|
|
1382
|
|
|
1383 However, a @var{binding} specifier may be a one-element list
|
|
|
1384 @samp{(@var{place})}, which is similar to @samp{(@var{place}
|
|
|
1385 @var{place})}. In other words, the @var{place} is not disturbed
|
|
|
1386 on entry to the body, and the only effect of the @code{letf} is
|
|
|
1387 to restore the original value of @var{place} afterwards. (The
|
|
|
1388 redundant access-and-store suggested by the @code{(@var{place}
|
|
|
1389 @var{place})} example does not actually occur.)
|
|
|
1390
|
|
|
1391 In most cases, the @var{place} must have a well-defined value on
|
|
|
1392 entry to the @code{letf} form. The only exceptions are plain
|
|
|
1393 variables and calls to @code{symbol-value} and @code{symbol-function}.
|
|
|
1394 If the symbol is not bound on entry, it is simply made unbound by
|
|
|
1395 @code{makunbound} or @code{fmakunbound} on exit.
|
|
|
1396 @end defspec
|
|
|
1397
|
|
|
1398 @defspec letf* (bindings@dots{}) forms@dots{}
|
|
|
1399 This macro is to @code{letf} what @code{let*} is to @code{let}:
|
|
|
1400 It does the bindings in sequential rather than parallel order.
|
|
|
1401 @end defspec
|
|
|
1402
|
|
|
1403 @defspec callf @var{function} @var{place} @var{args}@dots{}
|
|
|
1404 This is the ``generic'' modify macro. It calls @var{function},
|
|
|
1405 which should be an unquoted function name, macro name, or lambda.
|
|
|
1406 It passes @var{place} and @var{args} as arguments, and assigns the
|
|
|
1407 result back to @var{place}. For example, @code{(incf @var{place}
|
|
|
1408 @var{n})} is the same as @code{(callf + @var{place} @var{n})}.
|
|
|
1409 Some more examples:
|
|
|
1410
|
|
|
1411 @example
|
|
|
1412 (callf abs my-number)
|
|
|
1413 (callf concat (buffer-name) "<" (int-to-string n) ">")
|
|
|
1414 (callf union happy-people (list joe bob) :test 'same-person)
|
|
|
1415 @end example
|
|
|
1416
|
|
|
1417 @xref{Customizing Setf}, for @code{define-modify-macro}, a way
|
|
|
1418 to create even more concise notations for modify macros. Note
|
|
|
1419 again that @code{callf} is an extension to standard Common Lisp.
|
|
|
1420 @end defspec
|
|
|
1421
|
|
|
1422 @defspec callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{}
|
|
|
1423 This macro is like @code{callf}, except that @var{place} is
|
|
|
1424 the @emph{second} argument of @var{function} rather than the
|
|
|
1425 first. For example, @code{(push @var{x} @var{place})} is
|
|
|
1426 equivalent to @code{(callf2 cons @var{x} @var{place})}.
|
|
|
1427 @end defspec
|
|
|
1428
|
|
|
1429 The @code{callf} and @code{callf2} macros serve as building
|
|
|
1430 blocks for other macros like @code{incf}, @code{pushnew}, and
|
|
|
1431 @code{define-modify-macro}. The @code{letf} and @code{letf*}
|
|
|
1432 macros are used in the processing of symbol macros;
|
|
|
1433 @pxref{Macro Bindings}.
|
|
|
1434
|
|
|
1435 @node Customizing Setf, , Modify Macros, Generalized Variables
|
|
|
1436 @subsection Customizing Setf
|
|
|
1437
|
|
|
1438 @noindent
|
|
|
1439 Common Lisp defines three macros, @code{define-modify-macro},
|
|
|
1440 @code{defsetf}, and @code{define-setf-method}, that allow the
|
|
|
1441 user to extend generalized variables in various ways.
|
|
|
1442
|
|
|
1443 @defspec define-modify-macro name arglist function [doc-string]
|
|
|
1444 This macro defines a ``read-modify-write'' macro similar to
|
|
|
1445 @code{incf} and @code{decf}. The macro @var{name} is defined
|
|
|
1446 to take a @var{place} argument followed by additional arguments
|
|
|
1447 described by @var{arglist}. The call
|
|
|
1448
|
|
|
1449 @example
|
|
|
1450 (@var{name} @var{place} @var{args}...)
|
|
|
1451 @end example
|
|
|
1452
|
|
|
1453 @noindent
|
|
|
1454 will be expanded to
|
|
|
1455
|
|
|
1456 @example
|
|
|
1457 (callf @var{func} @var{place} @var{args}...)
|
|
|
1458 @end example
|
|
|
1459
|
|
|
1460 @noindent
|
|
|
1461 which in turn is roughly equivalent to
|
|
|
1462
|
|
|
1463 @example
|
|
|
1464 (setf @var{place} (@var{func} @var{place} @var{args}...))
|
|
|
1465 @end example
|
|
|
1466
|
|
|
1467 For example:
|
|
|
1468
|
|
|
1469 @example
|
|
|
1470 (define-modify-macro incf (&optional (n 1)) +)
|
|
|
1471 (define-modify-macro concatf (&rest args) concat)
|
|
|
1472 @end example
|
|
|
1473
|
|
|
1474 Note that @code{&key} is not allowed in @var{arglist}, but
|
|
|
1475 @code{&rest} is sufficient to pass keywords on to the function.
|
|
|
1476
|
|
|
1477 Most of the modify macros defined by Common Lisp do not exactly
|
|
|
1478 follow the pattern of @code{define-modify-macro}. For example,
|
|
|
1479 @code{push} takes its arguments in the wrong order, and @code{pop}
|
|
|
1480 is completely irregular. You can define these macros ``by hand''
|
|
|
1481 using @code{get-setf-method}, or consult the source file
|
|
|
1482 @file{cl-macs.el} to see how to use the internal @code{setf}
|
|
|
1483 building blocks.
|
|
|
1484 @end defspec
|
|
|
1485
|
|
|
1486 @defspec defsetf access-fn update-fn
|
|
|
1487 This is the simpler of two @code{defsetf} forms. Where
|
|
|
1488 @var{access-fn} is the name of a function which accesses a place,
|
|
|
1489 this declares @var{update-fn} to be the corresponding store
|
|
|
1490 function. From now on,
|
|
|
1491
|
|
|
1492 @example
|
|
|
1493 (setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
|
|
|
1494 @end example
|
|
|
1495
|
|
|
1496 @noindent
|
|
|
1497 will be expanded to
|
|
|
1498
|
|
|
1499 @example
|
|
|
1500 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
|
|
|
1501 @end example
|
|
|
1502
|
|
|
1503 @noindent
|
|
|
1504 The @var{update-fn} is required to be either a true function, or
|
|
|
1505 a macro which evaluates its arguments in a function-like way. Also,
|
|
|
1506 the @var{update-fn} is expected to return @var{value} as its result.
|
|
|
1507 Otherwise, the above expansion would not obey the rules for the way
|
|
|
1508 @code{setf} is supposed to behave.
|
|
|
1509
|
|
|
1510 As a special (non-Common-Lisp) extension, a third argument of @code{t}
|
|
|
1511 to @code{defsetf} says that the @code{update-fn}'s return value is
|
|
|
1512 not suitable, so that the above @code{setf} should be expanded to
|
|
|
1513 something more like
|
|
|
1514
|
|
|
1515 @example
|
|
|
1516 (let ((temp @var{value}))
|
|
|
1517 (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
|
|
|
1518 temp)
|
|
|
1519 @end example
|
|
|
1520
|
|
|
1521 Some examples of the use of @code{defsetf}, drawn from the standard
|
|
|
1522 suite of setf methods, are:
|
|
|
1523
|
|
|
1524 @example
|
|
|
1525 (defsetf car setcar)
|
|
|
1526 (defsetf symbol-value set)
|
|
|
1527 (defsetf buffer-name rename-buffer t)
|
|
|
1528 @end example
|
|
|
1529 @end defspec
|
|
|
1530
|
|
|
1531 @defspec defsetf access-fn arglist (store-var) forms@dots{}
|
|
|
1532 This is the second, more complex, form of @code{defsetf}. It is
|
|
|
1533 rather like @code{defmacro} except for the additional @var{store-var}
|
|
|
1534 argument. The @var{forms} should return a Lisp form which stores
|
|
|
1535 the value of @var{store-var} into the generalized variable formed
|
|
|
1536 by a call to @var{access-fn} with arguments described by @var{arglist}.
|
|
|
1537 The @var{forms} may begin with a string which documents the @code{setf}
|
|
|
1538 method (analogous to the doc string that appears at the front of a
|
|
|
1539 function).
|
|
|
1540
|
|
|
1541 For example, the simple form of @code{defsetf} is shorthand for
|
|
|
1542
|
|
|
1543 @example
|
|
|
1544 (defsetf @var{access-fn} (&rest args) (store)
|
|
|
1545 (append '(@var{update-fn}) args (list store)))
|
|
|
1546 @end example
|
|
|
1547
|
|
|
1548 The Lisp form that is returned can access the arguments from
|
|
|
1549 @var{arglist} and @var{store-var} in an unrestricted fashion;
|
|
|
1550 macros like @code{setf} and @code{incf} which invoke this
|
|
|
1551 setf-method will insert temporary variables as needed to make
|
|
|
1552 sure the apparent order of evaluation is preserved.
|
|
|
1553
|
|
|
1554 Another example drawn from the standard package:
|
|
|
1555
|
|
|
1556 @example
|
|
|
1557 (defsetf nth (n x) (store)
|
|
|
1558 (list 'setcar (list 'nthcdr n x) store))
|
|
|
1559 @end example
|
|
|
1560 @end defspec
|
|
|
1561
|
|
|
1562 @defspec define-setf-method access-fn arglist forms@dots{}
|
|
|
1563 This is the most general way to create new place forms. When
|
|
|
1564 a @code{setf} to @var{access-fn} with arguments described by
|
|
|
1565 @var{arglist} is expanded, the @var{forms} are evaluated and
|
|
|
1566 must return a list of five items:
|
|
|
1567
|
|
|
1568 @enumerate
|
|
|
1569 @item
|
|
|
1570 A list of @dfn{temporary variables}.
|
|
|
1571
|
|
|
1572 @item
|
|
|
1573 A list of @dfn{value forms} corresponding to the temporary variables
|
|
|
1574 above. The temporary variables will be bound to these value forms
|
|
|
1575 as the first step of any operation on the generalized variable.
|
|
|
1576
|
|
|
1577 @item
|
|
|
1578 A list of exactly one @dfn{store variable} (generally obtained
|
|
|
1579 from a call to @code{gensym}).
|
|
|
1580
|
|
|
1581 @item
|
|
|
1582 A Lisp form which stores the contents of the store variable into
|
|
|
1583 the generalized variable, assuming the temporaries have been
|
|
|
1584 bound as described above.
|
|
|
1585
|
|
|
1586 @item
|
|
|
1587 A Lisp form which accesses the contents of the generalized variable,
|
|
|
1588 assuming the temporaries have been bound.
|
|
|
1589 @end enumerate
|
|
|
1590
|
|
|
1591 This is exactly like the Common Lisp macro of the same name,
|
|
|
1592 except that the method returns a list of five values rather
|
|
|
1593 than the five values themselves, since Emacs Lisp does not
|
|
|
1594 support Common Lisp's notion of multiple return values.
|
|
|
1595
|
|
|
1596 Once again, the @var{forms} may begin with a documentation string.
|
|
|
1597
|
|
|
1598 A setf-method should be maximally conservative with regard to
|
|
|
1599 temporary variables. In the setf-methods generated by
|
|
|
1600 @code{defsetf}, the second return value is simply the list of
|
|
|
1601 arguments in the place form, and the first return value is a
|
|
|
1602 list of a corresponding number of temporary variables generated
|
|
|
1603 by @code{gensym}. Macros like @code{setf} and @code{incf} which
|
|
|
1604 use this setf-method will optimize away most temporaries that
|
|
|
1605 turn out to be unnecessary, so there is little reason for the
|
|
|
1606 setf-method itself to optimize.
|
|
|
1607 @end defspec
|
|
|
1608
|
|
|
1609 @defun get-setf-method place &optional env
|
|
|
1610 This function returns the setf-method for @var{place}, by
|
|
|
1611 invoking the definition previously recorded by @code{defsetf}
|
|
|
1612 or @code{define-setf-method}. The result is a list of five
|
|
|
1613 values as described above. You can use this function to build
|
|
|
1614 your own @code{incf}-like modify macros. (Actually, it is
|
|
|
1615 better to use the internal functions @code{cl-setf-do-modify}
|
|
|
1616 and @code{cl-setf-do-store}, which are a bit easier to use and
|
|
|
1617 which also do a number of optimizations; consult the source
|
|
|
1618 code for the @code{incf} function for a simple example.)
|
|
|
1619
|
|
|
1620 The argument @var{env} specifies the ``environment'' to be
|
|
|
1621 passed on to @code{macroexpand} if @code{get-setf-method} should
|
|
|
1622 need to expand a macro in @var{place}. It should come from
|
|
|
1623 an @code{&environment} argument to the macro or setf-method
|
|
|
1624 that called @code{get-setf-method}.
|
|
|
1625
|
|
|
1626 See also the source code for the setf-methods for @code{apply}
|
|
|
1627 and @code{substring}, each of which works by calling
|
|
|
1628 @code{get-setf-method} on a simpler case, then massaging
|
|
|
1629 the result in various ways.
|
|
|
1630 @end defun
|
|
|
1631
|
|
|
1632 Modern Common Lisp defines a second, independent way to specify
|
|
|
1633 the @code{setf} behavior of a function, namely ``@code{setf}
|
|
|
1634 functions'' whose names are lists @code{(setf @var{name})}
|
|
|
1635 rather than symbols. For example, @code{(defun (setf foo) @dots{})}
|
|
|
1636 defines the function that is used when @code{setf} is applied to
|
|
|
1637 @code{foo}. This package does not currently support @code{setf}
|
|
|
1638 functions. In particular, it is a compile-time error to use
|
|
|
1639 @code{setf} on a form which has not already been @code{defsetf}'d
|
|
|
1640 or otherwise declared; in newer Common Lisps, this would not be
|
|
|
1641 an error since the function @code{(setf @var{func})} might be
|
|
|
1642 defined later.
|
|
|
1643
|
|
|
1644 @iftex
|
|
|
1645 @secno=4
|
|
|
1646 @end iftex
|
|
|
1647
|
|
|
1648 @node Variable Bindings, Conditionals, Generalized Variables, Control Structure
|
|
|
1649 @section Variable Bindings
|
|
|
1650
|
|
|
1651 @noindent
|
|
|
1652 These Lisp forms make bindings to variables and function names,
|
|
|
1653 analogous to Lisp's built-in @code{let} form.
|
|
|
1654
|
|
|
1655 @xref{Modify Macros}, for the @code{letf} and @code{letf*} forms which
|
|
|
1656 are also related to variable bindings.
|
|
|
1657
|
|
|
1658 @menu
|
|
|
1659 * Dynamic Bindings:: The `progv' form
|
|
|
1660 * Lexical Bindings:: `lexical-let' and lexical closures
|
|
|
1661 * Function Bindings:: `flet' and `labels'
|
|
|
1662 * Macro Bindings:: `macrolet' and `symbol-macrolet'
|
|
|
1663 @end menu
|
|
|
1664
|
|
|
1665 @node Dynamic Bindings, Lexical Bindings, Variable Bindings, Variable Bindings
|
|
|
1666 @subsection Dynamic Bindings
|
|
|
1667
|
|
|
1668 @noindent
|
|
|
1669 The standard @code{let} form binds variables whose names are known
|
|
|
1670 at compile-time. The @code{progv} form provides an easy way to
|
|
|
1671 bind variables whose names are computed at run-time.
|
|
|
1672
|
|
|
1673 @defspec progv symbols values forms@dots{}
|
|
|
1674 This form establishes @code{let}-style variable bindings on a
|
|
|
1675 set of variables computed at run-time. The expressions
|
|
|
1676 @var{symbols} and @var{values} are evaluated, and must return lists
|
|
|
1677 of symbols and values, respectively. The symbols are bound to the
|
|
|
1678 corresponding values for the duration of the body @var{form}s.
|
|
|
1679 If @var{values} is shorter than @var{symbols}, the last few symbols
|
|
|
1680 are made unbound (as if by @code{makunbound}) inside the body.
|
|
|
1681 If @var{symbols} is shorter than @var{values}, the excess values
|
|
|
1682 are ignored.
|
|
|
1683 @end defspec
|
|
|
1684
|
|
|
1685 @node Lexical Bindings, Function Bindings, Dynamic Bindings, Variable Bindings
|
|
|
1686 @subsection Lexical Bindings
|
|
|
1687
|
|
|
1688 @noindent
|
|
|
1689 The @dfn{CL} package defines the following macro which
|
|
|
1690 more closely follows the Common Lisp @code{let} form:
|
|
|
1691
|
|
|
1692 @defspec lexical-let (bindings@dots{}) forms@dots{}
|
|
|
1693 This form is exactly like @code{let} except that the bindings it
|
|
|
1694 establishes are purely lexical. Lexical bindings are similar to
|
|
|
1695 local variables in a language like C: Only the code physically
|
|
|
1696 within the body of the @code{lexical-let} (after macro expansion)
|
|
|
1697 may refer to the bound variables.
|
|
|
1698
|
|
|
1699 @example
|
|
|
1700 (setq a 5)
|
|
|
1701 (defun foo (b) (+ a b))
|
|
|
1702 (let ((a 2)) (foo a))
|
|
|
1703 @result{} 4
|
|
|
1704 (lexical-let ((a 2)) (foo a))
|
|
|
1705 @result{} 7
|
|
|
1706 @end example
|
|
|
1707
|
|
|
1708 @noindent
|
|
|
1709 In this example, a regular @code{let} binding of @code{a} actually
|
|
|
1710 makes a temporary change to the global variable @code{a}, so @code{foo}
|
|
|
1711 is able to see the binding of @code{a} to 2. But @code{lexical-let}
|
|
|
1712 actually creates a distinct local variable @code{a} for use within its
|
|
|
1713 body, without any effect on the global variable of the same name.
|
|
|
1714
|
|
|
1715 The most important use of lexical bindings is to create @dfn{closures}.
|
|
|
1716 A closure is a function object that refers to an outside lexical
|
|
|
1717 variable. For example:
|
|
|
1718
|
|
|
1719 @example
|
|
|
1720 (defun make-adder (n)
|
|
|
1721 (lexical-let ((n n))
|
|
|
1722 (function (lambda (m) (+ n m)))))
|
|
|
1723 (setq add17 (make-adder 17))
|
|
|
1724 (funcall add17 4)
|
|
|
1725 @result{} 21
|
|
|
1726 @end example
|
|
|
1727
|
|
|
1728 @noindent
|
|
|
1729 The call @code{(make-adder 17)} returns a function object which adds
|
|
|
1730 17 to its argument. If @code{let} had been used instead of
|
|
|
1731 @code{lexical-let}, the function object would have referred to the
|
|
|
1732 global @code{n}, which would have been bound to 17 only during the
|
|
|
1733 call to @code{make-adder} itself.
|
|
|
1734
|
|
|
1735 @example
|
|
|
1736 (defun make-counter ()
|
|
|
1737 (lexical-let ((n 0))
|
|
|
1738 (function* (lambda (&optional (m 1)) (incf n m)))))
|
|
|
1739 (setq count-1 (make-counter))
|
|
|
1740 (funcall count-1 3)
|
|
|
1741 @result{} 3
|
|
|
1742 (funcall count-1 14)
|
|
|
1743 @result{} 17
|
|
|
1744 (setq count-2 (make-counter))
|
|
|
1745 (funcall count-2 5)
|
|
|
1746 @result{} 5
|
|
|
1747 (funcall count-1 2)
|
|
|
1748 @result{} 19
|
|
|
1749 (funcall count-2)
|
|
|
1750 @result{} 6
|
|
|
1751 @end example
|
|
|
1752
|
|
|
1753 @noindent
|
|
|
1754 Here we see that each call to @code{make-counter} creates a distinct
|
|
|
1755 local variable @code{n}, which serves as a private counter for the
|
|
|
1756 function object that is returned.
|
|
|
1757
|
|
|
1758 Closed-over lexical variables persist until the last reference to
|
|
|
1759 them goes away, just like all other Lisp objects. For example,
|
|
|
1760 @code{count-2} refers to a function object which refers to an
|
|
|
1761 instance of the variable @code{n}; this is the only reference
|
|
|
1762 to that variable, so after @code{(setq count-2 nil)} the garbage
|
|
|
1763 collector would be able to delete this instance of @code{n}.
|
|
|
1764 Of course, if a @code{lexical-let} does not actually create any
|
|
|
1765 closures, then the lexical variables are free as soon as the
|
|
|
1766 @code{lexical-let} returns.
|
|
|
1767
|
|
|
1768 Many closures are used only during the extent of the bindings they
|
|
|
1769 refer to; these are known as ``downward funargs'' in Lisp parlance.
|
|
|
1770 When a closure is used in this way, regular Emacs Lisp dynamic
|
|
|
1771 bindings suffice and will be more efficient than @code{lexical-let}
|
|
|
1772 closures:
|
|
|
1773
|
|
|
1774 @example
|
|
|
1775 (defun add-to-list (x list)
|
|
|
1776 (mapcar (function (lambda (y) (+ x y))) list))
|
|
|
1777 (add-to-list 7 '(1 2 5))
|
|
|
1778 @result{} (8 9 12)
|
|
|
1779 @end example
|
|
|
1780
|
|
|
1781 @noindent
|
|
|
1782 Since this lambda is only used while @code{x} is still bound,
|
|
|
1783 it is not necessary to make a true closure out of it.
|
|
|
1784
|
|
|
1785 You can use @code{defun} or @code{flet} inside a @code{lexical-let}
|
|
|
1786 to create a named closure. If several closures are created in the
|
|
|
1787 body of a single @code{lexical-let}, they all close over the same
|
|
|
1788 instance of the lexical variable.
|
|
|
1789
|
|
|
1790 The @code{lexical-let} form is an extension to Common Lisp. In
|
|
|
1791 true Common Lisp, all bindings are lexical unless declared otherwise.
|
|
|
1792 @end defspec
|
|
|
1793
|
|
|
1794 @defspec lexical-let* (bindings@dots{}) forms@dots{}
|
|
|
1795 This form is just like @code{lexical-let}, except that the bindings
|
|
|
1796 are made sequentially in the manner of @code{let*}.
|
|
|
1797 @end defspec
|
|
|
1798
|
|
|
1799 @node Function Bindings, Macro Bindings, Lexical Bindings, Variable Bindings
|
|
|
1800 @subsection Function Bindings
|
|
|
1801
|
|
|
1802 @noindent
|
|
|
1803 These forms make @code{let}-like bindings to functions instead
|
|
|
1804 of variables.
|
|
|
1805
|
|
|
1806 @defspec flet (bindings@dots{}) forms@dots{}
|
|
|
1807 This form establishes @code{let}-style bindings on the function
|
|
|
1808 cells of symbols rather than on the value cells. Each @var{binding}
|
|
|
1809 must be a list of the form @samp{(@var{name} @var{arglist}
|
|
|
1810 @var{forms}@dots{})}, which defines a function exactly as if
|
|
|
1811 it were a @code{defun*} form. The function @var{name} is defined
|
|
|
1812 accordingly for the duration of the body of the @code{flet}; then
|
|
|
1813 the old function definition, or lack thereof, is restored.
|
|
|
1814
|
|
|
1815 While @code{flet} in Common Lisp establishes a lexical binding of
|
|
|
1816 @var{name}, Emacs Lisp @code{flet} makes a dynamic binding. The
|
|
|
1817 result is that @code{flet} affects indirect calls to a function as
|
|
|
1818 well as calls directly inside the @code{flet} form itself.
|
|
|
1819
|
|
|
1820 You can use @code{flet} to disable or modify the behavior of a
|
|
|
1821 function in a temporary fashion. This will even work on Emacs
|
|
|
1822 primitives, although note that some calls to primitive functions
|
|
|
1823 internal to Emacs are made without going through the symbol's
|
|
|
1824 function cell, and so will not be affected by @code{flet}. For
|
|
|
1825 example,
|
|
|
1826
|
|
|
1827 @example
|
|
|
1828 (flet ((message (&rest args) (push args saved-msgs)))
|
|
|
1829 (do-something))
|
|
|
1830 @end example
|
|
|
1831
|
|
|
1832 This code attempts to replace the built-in function @code{message}
|
|
|
1833 with a function that simply saves the messages in a list rather
|
|
|
1834 than displaying them. The original definition of @code{message}
|
|
|
1835 will be restored after @code{do-something} exits. This code will
|
|
|
1836 work fine on messages generated by other Lisp code, but messages
|
|
|
1837 generated directly inside Emacs will not be caught since they make
|
|
|
1838 direct C-language calls to the message routines rather than going
|
|
|
1839 through the Lisp @code{message} function.
|
|
|
1840
|
|
|
1841 Functions defined by @code{flet} may use the full Common Lisp
|
|
|
1842 argument notation supported by @code{defun*}; also, the function
|
|
|
1843 body is enclosed in an implicit block as if by @code{defun*}.
|
|
|
1844 @xref{Program Structure}.
|
|
|
1845 @end defspec
|
|
|
1846
|
|
|
1847 @defspec labels (bindings@dots{}) forms@dots{}
|
|
|
1848 The @code{labels} form is a synonym for @code{flet}. (In Common
|
|
|
1849 Lisp, @code{labels} and @code{flet} differ in ways that depend on
|
|
|
1850 their lexical scoping; these distinctions vanish in dynamically
|
|
|
1851 scoped Emacs Lisp.)
|
|
|
1852 @end defspec
|
|
|
1853
|
|
|
1854 @node Macro Bindings, , Function Bindings, Variable Bindings
|
|
|
1855 @subsection Macro Bindings
|
|
|
1856
|
|
|
1857 @noindent
|
|
|
1858 These forms create local macros and ``symbol macros.''
|
|
|
1859
|
|
|
1860 @defspec macrolet (bindings@dots{}) forms@dots{}
|
|
|
1861 This form is analogous to @code{flet}, but for macros instead of
|
|
|
1862 functions. Each @var{binding} is a list of the same form as the
|
|
|
1863 arguments to @code{defmacro*} (i.e., a macro name, argument list,
|
|
|
1864 and macro-expander forms). The macro is defined accordingly for
|
|
|
1865 use within the body of the @code{macrolet}.
|
|
|
1866
|
|
|
1867 Because of the nature of macros, @code{macrolet} is lexically
|
|
|
1868 scoped even in Emacs Lisp: The @code{macrolet} binding will
|
|
|
1869 affect only calls that appear physically within the body
|
|
|
1870 @var{forms}, possibly after expansion of other macros in the
|
|
|
1871 body.
|
|
|
1872 @end defspec
|
|
|
1873
|
|
|
1874 @defspec symbol-macrolet (bindings@dots{}) forms@dots{}
|
|
|
1875 This form creates @dfn{symbol macros}, which are macros that look
|
|
|
1876 like variable references rather than function calls. Each
|
|
|
1877 @var{binding} is a list @samp{(@var{var} @var{expansion})};
|
|
|
1878 any reference to @var{var} within the body @var{forms} is
|
|
|
1879 replaced by @var{expansion}.
|
|
|
1880
|
|
|
1881 @example
|
|
|
1882 (setq bar '(5 . 9))
|
|
|
1883 (symbol-macrolet ((foo (car bar)))
|
|
|
1884 (incf foo))
|
|
|
1885 bar
|
|
|
1886 @result{} (6 . 9)
|
|
|
1887 @end example
|
|
|
1888
|
|
|
1889 A @code{setq} of a symbol macro is treated the same as a @code{setf}.
|
|
|
1890 I.e., @code{(setq foo 4)} in the above would be equivalent to
|
|
|
1891 @code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
|
|
|
1892
|
|
|
1893 Likewise, a @code{let} or @code{let*} binding a symbol macro is
|
|
|
1894 treated like a @code{letf} or @code{letf*}. This differs from true
|
|
|
1895 Common Lisp, where the rules of lexical scoping cause a @code{let}
|
|
|
1896 binding to shadow a @code{symbol-macrolet} binding. In this package,
|
|
|
1897 only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
|
|
|
1898 macro.
|
|
|
1899
|
|
|
1900 There is no analogue of @code{defmacro} for symbol macros; all symbol
|
|
|
1901 macros are local. A typical use of @code{symbol-macrolet} is in the
|
|
|
1902 expansion of another macro:
|
|
|
1903
|
|
|
1904 @example
|
|
|
1905 (defmacro* my-dolist ((x list) &rest body)
|
|
|
1906 (let ((var (gensym)))
|
|
|
1907 (list 'loop 'for var 'on list 'do
|
|
|
1908 (list* 'symbol-macrolet (list (list x (list 'car var)))
|
|
|
1909 body))))
|
|
|
1910
|
|
|
1911 (setq mylist '(1 2 3 4))
|
|
|
1912 (my-dolist (x mylist) (incf x))
|
|
|
1913 mylist
|
|
|
1914 @result{} (2 3 4 5)
|
|
|
1915 @end example
|
|
|
1916
|
|
|
1917 @noindent
|
|
|
1918 In this example, the @code{my-dolist} macro is similar to @code{dolist}
|
|
|
1919 (@pxref{Iteration}) except that the variable @code{x} becomes a true
|
|
|
1920 reference onto the elements of the list. The @code{my-dolist} call
|
|
|
1921 shown here expands to
|
|
|
1922
|
|
|
1923 @example
|
|
|
1924 (loop for G1234 on mylist do
|
|
|
1925 (symbol-macrolet ((x (car G1234)))
|
|
|
1926 (incf x)))
|
|
|
1927 @end example
|
|
|
1928
|
|
|
1929 @noindent
|
|
|
1930 which in turn expands to
|
|
|
1931
|
|
|
1932 @example
|
|
|
1933 (loop for G1234 on mylist do (incf (car G1234)))
|
|
|
1934 @end example
|
|
|
1935
|
|
|
1936 @xref{Loop Facility}, for a description of the @code{loop} macro.
|
|
|
1937 This package defines a nonstandard @code{in-ref} loop clause that
|
|
|
1938 works much like @code{my-dolist}.
|
|
|
1939 @end defspec
|
|
|
1940
|
|
|
1941 @node Conditionals, Blocks and Exits, Variable Bindings, Control Structure
|
|
|
1942 @section Conditionals
|
|
|
1943
|
|
|
1944 @noindent
|
|
|
1945 These conditional forms augment Emacs Lisp's simple @code{if},
|
|
|
1946 @code{and}, @code{or}, and @code{cond} forms.
|
|
|
1947
|
|
|
1948 @defspec when test forms@dots{}
|
|
|
1949 This is a variant of @code{if} where there are no ``else'' forms,
|
|
|
1950 and possibly several ``then'' forms. In particular,
|
|
|
1951
|
|
|
1952 @example
|
|
|
1953 (when @var{test} @var{a} @var{b} @var{c})
|
|
|
1954 @end example
|
|
|
1955
|
|
|
1956 @noindent
|
|
|
1957 is entirely equivalent to
|
|
|
1958
|
|
|
1959 @example
|
|
|
1960 (if @var{test} (progn @var{a} @var{b} @var{c}) nil)
|
|
|
1961 @end example
|
|
|
1962 @end defspec
|
|
|
1963
|
|
|
1964 @defspec unless test forms@dots{}
|
|
|
1965 This is a variant of @code{if} where there are no ``then'' forms,
|
|
|
1966 and possibly several ``else'' forms:
|
|
|
1967
|
|
|
1968 @example
|
|
|
1969 (unless @var{test} @var{a} @var{b} @var{c})
|
|
|
1970 @end example
|
|
|
1971
|
|
|
1972 @noindent
|
|
|
1973 is entirely equivalent to
|
|
|
1974
|
|
|
1975 @example
|
|
|
1976 (when (not @var{test}) @var{a} @var{b} @var{c})
|
|
|
1977 @end example
|
|
|
1978 @end defspec
|
|
|
1979
|
|
|
1980 @defspec case keyform clause@dots{}
|
|
|
1981 This macro evaluates @var{keyform}, then compares it with the key
|
|
|
1982 values listed in the various @var{clause}s. Whichever clause matches
|
|
|
1983 the key is executed; comparison is done by @code{eql}. If no clause
|
|
|
1984 matches, the @code{case} form returns @code{nil}. The clauses are
|
|
|
1985 of the form
|
|
|
1986
|
|
|
1987 @example
|
|
|
1988 (@var{keylist} @var{body-forms}@dots{})
|
|
|
1989 @end example
|
|
|
1990
|
|
|
1991 @noindent
|
|
|
1992 where @var{keylist} is a list of key values. If there is exactly
|
|
|
1993 one value, and it is not a cons cell or the symbol @code{nil} or
|
|
|
1994 @code{t}, then it can be used by itself as a @var{keylist} without
|
|
|
1995 being enclosed in a list. All key values in the @code{case} form
|
|
|
1996 must be distinct. The final clauses may use @code{t} in place of
|
|
|
1997 a @var{keylist} to indicate a default clause that should be taken
|
|
|
1998 if none of the other clauses match. (The symbol @code{otherwise}
|
|
|
1999 is also recognized in place of @code{t}. To make a clause that
|
|
|
2000 matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
|
|
|
2001 enclose the symbol in a list.)
|
|
|
2002
|
|
|
2003 For example, this expression reads a keystroke, then does one of
|
|
|
2004 four things depending on whether it is an @samp{a}, a @samp{b},
|
|
|
2005 a @key{RET} or @key{LFD}, or anything else.
|
|
|
2006
|
|
|
2007 @example
|
|
|
2008 (case (read-char)
|
|
|
2009 (?a (do-a-thing))
|
|
|
2010 (?b (do-b-thing))
|
|
|
2011 ((?\r ?\n) (do-ret-thing))
|
|
|
2012 (t (do-other-thing)))
|
|
|
2013 @end example
|
|
|
2014 @end defspec
|
|
|
2015
|
|
|
2016 @defspec ecase keyform clause@dots{}
|
|
|
2017 This macro is just like @code{case}, except that if the key does
|
|
|
2018 not match any of the clauses, an error is signalled rather than
|
|
|
2019 simply returning @code{nil}.
|
|
|
2020 @end defspec
|
|
|
2021
|
|
|
2022 @defspec typecase keyform clause@dots{}
|
|
|
2023 This macro is a version of @code{case} that checks for types
|
|
|
2024 rather than values. Each @var{clause} is of the form
|
|
|
2025 @samp{(@var{type} @var{body}...)}. @xref{Type Predicates},
|
|
|
2026 for a description of type specifiers. For example,
|
|
|
2027
|
|
|
2028 @example
|
|
|
2029 (typecase x
|
|
|
2030 (integer (munch-integer x))
|
|
|
2031 (float (munch-float x))
|
|
|
2032 (string (munch-integer (string-to-int x)))
|
|
|
2033 (t (munch-anything x)))
|
|
|
2034 @end example
|
|
|
2035
|
|
|
2036 The type specifier @code{t} matches any type of object; the word
|
|
|
2037 @code{otherwise} is also allowed. To make one clause match any of
|
|
|
2038 several types, use an @code{(or ...)} type specifier.
|
|
|
2039 @end defspec
|
|
|
2040
|
|
|
2041 @defspec etypecase keyform clause@dots{}
|
|
|
2042 This macro is just like @code{typecase}, except that if the key does
|
|
|
2043 not match any of the clauses, an error is signalled rather than
|
|
|
2044 simply returning @code{nil}.
|
|
|
2045 @end defspec
|
|
|
2046
|
|
|
2047 @node Blocks and Exits, Iteration, Conditionals, Control Structure
|
|
|
2048 @section Blocks and Exits
|
|
|
2049
|
|
|
2050 @noindent
|
|
|
2051 Common Lisp @dfn{blocks} provide a non-local exit mechanism very
|
|
|
2052 similar to @code{catch} and @code{throw}, but lexically rather than
|
|
|
2053 dynamically scoped. This package actually implements @code{block}
|
|
|
2054 in terms of @code{catch}; however, the lexical scoping allows the
|
|
|
2055 optimizing byte-compiler to omit the costly @code{catch} step if the
|
|
|
2056 body of the block does not actually @code{return-from} the block.
|
|
|
2057
|
|
|
2058 @defspec block name forms@dots{}
|
|
|
2059 The @var{forms} are evaluated as if by a @code{progn}. However,
|
|
|
2060 if any of the @var{forms} execute @code{(return-from @var{name})},
|
|
|
2061 they will jump out and return directly from the @code{block} form.
|
|
|
2062 The @code{block} returns the result of the last @var{form} unless
|
|
|
2063 a @code{return-from} occurs.
|
|
|
2064
|
|
|
2065 The @code{block}/@code{return-from} mechanism is quite similar to
|
|
|
2066 the @code{catch}/@code{throw} mechanism. The main differences are
|
|
|
2067 that block @var{name}s are unevaluated symbols, rather than forms
|
|
|
2068 (such as quoted symbols) which evaluate to a tag at run-time; and
|
|
|
2069 also that blocks are lexically scoped whereas @code{catch}/@code{throw}
|
|
|
2070 are dynamically scoped. This means that functions called from the
|
|
|
2071 body of a @code{catch} can also @code{throw} to the @code{catch},
|
|
|
2072 but the @code{return-from} referring to a block name must appear
|
|
|
2073 physically within the @var{forms} that make up the body of the block.
|
|
|
2074 They may not appear within other called functions, although they may
|
|
|
2075 appear within macro expansions or @code{lambda}s in the body. Block
|
|
|
2076 names and @code{catch} names form independent name-spaces.
|
|
|
2077
|
|
|
2078 In true Common Lisp, @code{defun} and @code{defmacro} surround
|
|
|
2079 the function or expander bodies with implicit blocks with the
|
|
|
2080 same name as the function or macro. This does not occur in Emacs
|
|
|
2081 Lisp, but this package provides @code{defun*} and @code{defmacro*}
|
|
|
2082 forms which do create the implicit block.
|
|
|
2083
|
|
|
2084 The Common Lisp looping constructs defined by this package,
|
|
|
2085 such as @code{loop} and @code{dolist}, also create implicit blocks
|
|
|
2086 just as in Common Lisp.
|
|
|
2087
|
|
|
2088 Because they are implemented in terms of Emacs Lisp @code{catch}
|
|
|
2089 and @code{throw}, blocks have the same overhead as actual
|
|
|
2090 @code{catch} constructs (roughly two function calls). However,
|
|
|
2091 Zawinski and Furuseth's optimizing byte compiler (standard in
|
|
|
2092 Emacs 19) will optimize away the @code{catch} if the block does
|
|
|
2093 not in fact contain any @code{return} or @code{return-from} calls
|
|
|
2094 that jump to it. This means that @code{do} loops and @code{defun*}
|
|
|
2095 functions which don't use @code{return} don't pay the overhead to
|
|
|
2096 support it.
|
|
|
2097 @end defspec
|
|
|
2098
|
|
|
2099 @defspec return-from name [result]
|
|
|
2100 This macro returns from the block named @var{name}, which must be
|
|
|
2101 an (unevaluated) symbol. If a @var{result} form is specified, it
|
|
|
2102 is evaluated to produce the result returned from the @code{block}.
|
|
|
2103 Otherwise, @code{nil} is returned.
|
|
|
2104 @end defspec
|
|
|
2105
|
|
|
2106 @defspec return [result]
|
|
|
2107 This macro is exactly like @code{(return-from nil @var{result})}.
|
|
|
2108 Common Lisp loops like @code{do} and @code{dolist} implicitly enclose
|
|
|
2109 themselves in @code{nil} blocks.
|
|
|
2110 @end defspec
|
|
|
2111
|
|
|
2112 @node Iteration, Loop Facility, Blocks and Exits, Control Structure
|
|
|
2113 @section Iteration
|
|
|
2114
|
|
|
2115 @noindent
|
|
|
2116 The macros described here provide more sophisticated, high-level
|
|
|
2117 looping constructs to complement Emacs Lisp's basic @code{while}
|
|
|
2118 loop.
|
|
|
2119
|
|
|
2120 @defspec loop forms@dots{}
|
|
|
2121 The @dfn{CL} package supports both the simple, old-style meaning of
|
|
|
2122 @code{loop} and the extremely powerful and flexible feature known as
|
|
|
2123 the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
|
|
|
2124 facility is discussed in the following section; @pxref{Loop Facility}.
|
|
|
2125 The simple form of @code{loop} is described here.
|
|
|
2126
|
|
|
2127 If @code{loop} is followed by zero or more Lisp expressions,
|
|
|
2128 then @code{(loop @var{exprs}@dots{})} simply creates an infinite
|
|
|
2129 loop executing the expressions over and over. The loop is
|
|
|
2130 enclosed in an implicit @code{nil} block. Thus,
|
|
|
2131
|
|
|
2132 @example
|
|
|
2133 (loop (foo) (if (no-more) (return 72)) (bar))
|
|
|
2134 @end example
|
|
|
2135
|
|
|
2136 @noindent
|
|
|
2137 is exactly equivalent to
|
|
|
2138
|
|
|
2139 @example
|
|
|
2140 (block nil (while t (foo) (if (no-more) (return 72)) (bar)))
|
|
|
2141 @end example
|
|
|
2142
|
|
|
2143 If any of the expressions are plain symbols, the loop is instead
|
|
|
2144 interpreted as a Loop Macro specification as described later.
|
|
|
2145 (This is not a restriction in practice, since a plain symbol
|
|
|
2146 in the above notation would simply access and throw away the
|
|
|
2147 value of a variable.)
|
|
|
2148 @end defspec
|
|
|
2149
|
|
|
2150 @defspec do (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
|
|
|
2151 This macro creates a general iterative loop. Each @var{spec} is
|
|
|
2152 of the form
|
|
|
2153
|
|
|
2154 @example
|
|
|
2155 (@var{var} [@var{init} [@var{step}]])
|
|
|
2156 @end example
|
|
|
2157
|
|
|
2158 The loop works as follows: First, each @var{var} is bound to the
|
|
|
2159 associated @var{init} value as if by a @code{let} form. Then, in
|
|
|
2160 each iteration of the loop, the @var{end-test} is evaluated; if
|
|
|
2161 true, the loop is finished. Otherwise, the body @var{forms} are
|
|
|
2162 evaluated, then each @var{var} is set to the associated @var{step}
|
|
|
2163 expression (as if by a @code{psetq} form) and the next iteration
|
|
|
2164 begins. Once the @var{end-test} becomes true, the @var{result}
|
|
|
2165 forms are evaluated (with the @var{var}s still bound to their
|
|
|
2166 values) to produce the result returned by @code{do}.
|
|
|
2167
|
|
|
2168 The entire @code{do} loop is enclosed in an implicit @code{nil}
|
|
|
2169 block, so that you can use @code{(return)} to break out of the
|
|
|
2170 loop at any time.
|
|
|
2171
|
|
|
2172 If there are no @var{result} forms, the loop returns @code{nil}.
|
|
|
2173 If a given @var{var} has no @var{step} form, it is bound to its
|
|
|
2174 @var{init} value but not otherwise modified during the @code{do}
|
|
|
2175 loop (unless the code explicitly modifies it); this case is just
|
|
|
2176 a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
|
|
|
2177 around the loop. If @var{init} is also omitted it defaults to
|
|
|
2178 @code{nil}, and in this case a plain @samp{@var{var}} can be used
|
|
|
2179 in place of @samp{(@var{var})}, again following the analogy with
|
|
|
2180 @code{let}.
|
|
|
2181
|
|
|
2182 This example (from Steele) illustrates a loop which applies the
|
|
|
2183 function @code{f} to successive pairs of values from the lists
|
|
|
2184 @code{foo} and @code{bar}; it is equivalent to the call
|
|
|
2185 @code{(mapcar* 'f foo bar)}. Note that this loop has no body
|
|
|
2186 @var{forms} at all, performing all its work as side effects of
|
|
|
2187 the rest of the loop.
|
|
|
2188
|
|
|
2189 @example
|
|
|
2190 (do ((x foo (cdr x))
|
|
|
2191 (y bar (cdr y))
|
|
|
2192 (z nil (cons (f (car x) (car y)) z)))
|
|
|
2193 ((or (null x) (null y))
|
|
|
2194 (nreverse z)))
|
|
|
2195 @end example
|
|
|
2196 @end defspec
|
|
|
2197
|
|
|
2198 @defspec do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{}
|
|
|
2199 This is to @code{do} what @code{let*} is to @code{let}. In
|
|
|
2200 particular, the initial values are bound as if by @code{let*}
|
|
|
2201 rather than @code{let}, and the steps are assigned as if by
|
|
|
2202 @code{setq} rather than @code{psetq}.
|
|
|
2203
|
|
|
2204 Here is another way to write the above loop:
|
|
|
2205
|
|
|
2206 @example
|
|
|
2207 (do* ((xp foo (cdr xp))
|
|
|
2208 (yp bar (cdr yp))
|
|
|
2209 (x (car xp) (car xp))
|
|
|
2210 (y (car yp) (car yp))
|
|
|
2211 z)
|
|
|
2212 ((or (null xp) (null yp))
|
|
|
2213 (nreverse z))
|
|
|
2214 (push (f x y) z))
|
|
|
2215 @end example
|
|
|
2216 @end defspec
|
|
|
2217
|
|
|
2218 @defspec dolist (var list [result]) forms@dots{}
|
|
|
2219 This is a more specialized loop which iterates across the elements
|
|
|
2220 of a list. @var{list} should evaluate to a list; the body @var{forms}
|
|
|
2221 are executed with @var{var} bound to each element of the list in
|
|
|
2222 turn. Finally, the @var{result} form (or @code{nil}) is evaluated
|
|
|
2223 with @var{var} bound to @code{nil} to produce the result returned by
|
|
|
2224 the loop. The loop is surrounded by an implicit @code{nil} block.
|
|
|
2225 @end defspec
|
|
|
2226
|
|
|
2227 @defspec dotimes (var count [result]) forms@dots{}
|
|
|
2228 This is a more specialized loop which iterates a specified number
|
|
|
2229 of times. The body is executed with @var{var} bound to the integers
|
|
|
2230 from zero (inclusive) to @var{count} (exclusive), in turn. Then
|
|
|
2231 the @code{result} form is evaluated with @var{var} bound to the total
|
|
|
2232 number of iterations that were done (i.e., @code{(max 0 @var{count})})
|
|
|
2233 to get the return value for the loop form. The loop is surrounded
|
|
|
2234 by an implicit @code{nil} block.
|
|
|
2235 @end defspec
|
|
|
2236
|
|
|
2237 @defspec do-symbols (var [obarray [result]]) forms@dots{}
|
|
|
2238 This loop iterates over all interned symbols. If @var{obarray}
|
|
|
2239 is specified and is not @code{nil}, it loops over all symbols in
|
|
|
2240 that obarray. For each symbol, the body @var{forms} are evaluated
|
|
|
2241 with @var{var} bound to that symbol. The symbols are visited in
|
|
|
2242 an unspecified order. Afterward the @var{result} form, if any,
|
|
|
2243 is evaluated (with @var{var} bound to @code{nil}) to get the return
|
|
|
2244 value. The loop is surrounded by an implicit @code{nil} block.
|
|
|
2245 @end defspec
|
|
|
2246
|
|
|
2247 @defspec do-all-symbols (var [result]) forms@dots{}
|
|
|
2248 This is identical to @code{do-symbols} except that the @var{obarray}
|
|
|
2249 argument is omitted; it always iterates over the default obarray.
|
|
|
2250 @end defspec
|
|
|
2251
|
|
|
2252 @xref{Mapping over Sequences}, for some more functions for
|
|
|
2253 iterating over vectors or lists.
|
|
|
2254
|
|
|
2255 @node Loop Facility, Multiple Values, Iteration, Control Structure
|
|
|
2256 @section Loop Facility
|
|
|
2257
|
|
|
2258 @noindent
|
|
|
2259 A common complaint with Lisp's traditional looping constructs is
|
|
|
2260 that they are either too simple and limited, such as Common Lisp's
|
|
|
2261 @code{dotimes} or Emacs Lisp's @code{while}, or too unreadable and
|
|
|
2262 obscure, like Common Lisp's @code{do} loop.
|
|
|
2263
|
|
|
2264 To remedy this, recent versions of Common Lisp have added a new
|
|
|
2265 construct called the ``Loop Facility'' or ``@code{loop} macro,''
|
|
|
2266 with an easy-to-use but very powerful and expressive syntax.
|
|
|
2267
|
|
|
2268 @menu
|
|
|
2269 * Loop Basics:: `loop' macro, basic clause structure
|
|
|
2270 * Loop Examples:: Working examples of `loop' macro
|
|
|
2271 * For Clauses:: Clauses introduced by `for' or `as'
|
|
|
2272 * Iteration Clauses:: `repeat', `while', `thereis', etc.
|
|
|
2273 * Accumulation Clauses:: `collect', `sum', `maximize', etc.
|
|
|
2274 * Other Clauses:: `with', `if', `initially', `finally'
|
|
|
2275 @end menu
|
|
|
2276
|
|
|
2277 @node Loop Basics, Loop Examples, Loop Facility, Loop Facility
|
|
|
2278 @subsection Loop Basics
|
|
|
2279
|
|
|
2280 @noindent
|
|
|
2281 The @code{loop} macro essentially creates a mini-language within
|
|
|
2282 Lisp that is specially tailored for describing loops. While this
|
|
|
2283 language is a little strange-looking by the standards of regular Lisp,
|
|
|
2284 it turns out to be very easy to learn and well-suited to its purpose.
|
|
|
2285
|
|
|
2286 Since @code{loop} is a macro, all parsing of the loop language
|
|
|
2287 takes place at byte-compile time; compiled @code{loop}s are just
|
|
|
2288 as efficient as the equivalent @code{while} loops written longhand.
|
|
|
2289
|
|
|
2290 @defspec loop clauses@dots{}
|
|
|
2291 A loop construct consists of a series of @var{clause}s, each
|
|
|
2292 introduced by a symbol like @code{for} or @code{do}. Clauses
|
|
|
2293 are simply strung together in the argument list of @code{loop},
|
|
|
2294 with minimal extra parentheses. The various types of clauses
|
|
|
2295 specify initializations, such as the binding of temporary
|
|
|
2296 variables, actions to be taken in the loop, stepping actions,
|
|
|
2297 and final cleanup.
|
|
|
2298
|
|
|
2299 Common Lisp specifies a certain general order of clauses in a
|
|
|
2300 loop:
|
|
|
2301
|
|
|
2302 @example
|
|
|
2303 (loop @var{name-clause}
|
|
|
2304 @var{var-clauses}@dots{}
|
|
|
2305 @var{action-clauses}@dots{})
|
|
|
2306 @end example
|
|
|
2307
|
|
|
2308 The @var{name-clause} optionally gives a name to the implicit
|
|
|
2309 block that surrounds the loop. By default, the implicit block
|
|
|
2310 is named @code{nil}. The @var{var-clauses} specify what
|
|
|
2311 variables should be bound during the loop, and how they should
|
|
|
2312 be modified or iterated throughout the course of the loop. The
|
|
|
2313 @var{action-clauses} are things to be done during the loop, such
|
|
|
2314 as computing, collecting, and returning values.
|
|
|
2315
|
|
|
2316 The Emacs version of the @code{loop} macro is less restrictive about
|
|
|
2317 the order of clauses, but things will behave most predictably if
|
|
|
2318 you put the variable-binding clauses @code{with}, @code{for}, and
|
|
|
2319 @code{repeat} before the action clauses. As in Common Lisp,
|
|
|
2320 @code{initially} and @code{finally} clauses can go anywhere.
|
|
|
2321
|
|
|
2322 Loops generally return @code{nil} by default, but you can cause
|
|
|
2323 them to return a value by using an accumulation clause like
|
|
|
2324 @code{collect}, an end-test clause like @code{always}, or an
|
|
|
2325 explicit @code{return} clause to jump out of the implicit block.
|
|
|
2326 (Because the loop body is enclosed in an implicit block, you can
|
|
|
2327 also use regular Lisp @code{return} or @code{return-from} to
|
|
|
2328 break out of the loop.)
|
|
|
2329 @end defspec
|
|
|
2330
|
|
|
2331 The following sections give some examples of the Loop Macro in
|
|
|
2332 action, and describe the particular loop clauses in great detail.
|
|
|
2333 Consult the second edition of Steele's @dfn{Common Lisp, the Language},
|
|
|
2334 for additional discussion and examples of the @code{loop} macro.
|
|
|
2335
|
|
|
2336 @node Loop Examples, For Clauses, Loop Basics, Loop Facility
|
|
|
2337 @subsection Loop Examples
|
|
|
2338
|
|
|
2339 @noindent
|
|
|
2340 Before listing the full set of clauses that are allowed, let's
|
|
|
2341 look at a few example loops just to get a feel for the @code{loop}
|
|
|
2342 language.
|
|
|
2343
|
|
|
2344 @example
|
|
|
2345 (loop for buf in (buffer-list)
|
|
|
2346 collect (buffer-file-name buf))
|
|
|
2347 @end example
|
|
|
2348
|
|
|
2349 @noindent
|
|
|
2350 This loop iterates over all Emacs buffers, using the list
|
|
|
2351 returned by @code{buffer-list}. For each buffer @code{buf},
|
|
|
2352 it calls @code{buffer-file-name} and collects the results into
|
|
|
2353 a list, which is then returned from the @code{loop} construct.
|
|
|
2354 The result is a list of the file names of all the buffers in
|
|
|
2355 Emacs' memory. The words @code{for}, @code{in}, and @code{collect}
|
|
|
2356 are reserved words in the @code{loop} language.
|
|
|
2357
|
|
|
2358 @example
|
|
|
2359 (loop repeat 20 do (insert "Yowsa\n"))
|
|
|
2360 @end example
|
|
|
2361
|
|
|
2362 @noindent
|
|
|
2363 This loop inserts the phrase ``Yowsa'' twenty times in the
|
|
|
2364 current buffer.
|
|
|
2365
|
|
|
2366 @example
|
|
|
2367 (loop until (eobp) do (munch-line) (forward-line 1))
|
|
|
2368 @end example
|
|
|
2369
|
|
|
2370 @noindent
|
|
|
2371 This loop calls @code{munch-line} on every line until the end
|
|
|
2372 of the buffer. If point is already at the end of the buffer,
|
|
|
2373 the loop exits immediately.
|
|
|
2374
|
|
|
2375 @example
|
|
|
2376 (loop do (munch-line) until (eobp) do (forward-line 1))
|
|
|
2377 @end example
|
|
|
2378
|
|
|
2379 @noindent
|
|
|
2380 This loop is similar to the above one, except that @code{munch-line}
|
|
|
2381 is always called at least once.
|
|
|
2382
|
|
|
2383 @example
|
|
|
2384 (loop for x from 1 to 100
|
|
|
2385 for y = (* x x)
|
|
|
2386 until (>= y 729)
|
|
|
2387 finally return (list x (= y 729)))
|
|
|
2388 @end example
|
|
|
2389
|
|
|
2390 @noindent
|
|
|
2391 This more complicated loop searches for a number @code{x} whose
|
|
|
2392 square is 729. For safety's sake it only examines @code{x}
|
|
|
2393 values up to 100; dropping the phrase @samp{to 100} would
|
|
|
2394 cause the loop to count upwards with no limit. The second
|
|
|
2395 @code{for} clause defines @code{y} to be the square of @code{x}
|
|
|
2396 within the loop; the expression after the @code{=} sign is
|
|
|
2397 reevaluated each time through the loop. The @code{until}
|
|
|
2398 clause gives a condition for terminating the loop, and the
|
|
|
2399 @code{finally} clause says what to do when the loop finishes.
|
|
|
2400 (This particular example was written less concisely than it
|
|
|
2401 could have been, just for the sake of illustration.)
|
|
|
2402
|
|
|
2403 Note that even though this loop contains three clauses (two
|
|
|
2404 @code{for}s and an @code{until}) that would have been enough to
|
|
|
2405 define loops all by themselves, it still creates a single loop
|
|
|
2406 rather than some sort of triple-nested loop. You must explicitly
|
|
|
2407 nest your @code{loop} constructs if you want nested loops.
|
|
|
2408
|
|
|
2409 @node For Clauses, Iteration Clauses, Loop Examples, Loop Facility
|
|
|
2410 @subsection For Clauses
|
|
|
2411
|
|
|
2412 @noindent
|
|
|
2413 Most loops are governed by one or more @code{for} clauses.
|
|
|
2414 A @code{for} clause simultaneously describes variables to be
|
|
|
2415 bound, how those variables are to be stepped during the loop,
|
|
|
2416 and usually an end condition based on those variables.
|
|
|
2417
|
|
|
2418 The word @code{as} is a synonym for the word @code{for}. This
|
|
|
2419 word is followed by a variable name, then a word like @code{from}
|
|
|
2420 or @code{across} that describes the kind of iteration desired.
|
|
|
2421 In Common Lisp, the phrase @code{being the} sometimes precedes
|
|
|
2422 the type of iteration; in this package both @code{being} and
|
|
|
2423 @code{the} are optional. The word @code{each} is a synonym
|
|
|
2424 for @code{the}, and the word that follows it may be singular
|
|
|
2425 or plural: @samp{for x being the elements of y} or
|
|
|
2426 @samp{for x being each element of y}. Which form you use
|
|
|
2427 is purely a matter of style.
|
|
|
2428
|
|
|
2429 The variable is bound around the loop as if by @code{let}:
|
|
|
2430
|
|
|
2431 @example
|
|
|
2432 (setq i 'happy)
|
|
|
2433 (loop for i from 1 to 10 do (do-something-with i))
|
|
|
2434 i
|
|
|
2435 @result{} happy
|
|
|
2436 @end example
|
|
|
2437
|
|
|
2438 @table @code
|
|
|
2439 @item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
|
|
|
2440 This type of @code{for} clause creates a counting loop. Each of
|
|
|
2441 the three sub-terms is optional, though there must be at least one
|
|
|
2442 term so that the clause is marked as a counting clause.
|
|
|
2443
|
|
|
2444 The three expressions are the starting value, the ending value, and
|
|
|
2445 the step value, respectively, of the variable. The loop counts
|
|
|
2446 upwards by default (@var{expr3} must be positive), from @var{expr1}
|
|
|
2447 to @var{expr2} inclusively. If you omit the @code{from} term, the
|
|
|
2448 loop counts from zero; if you omit the @code{to} term, the loop
|
|
|
2449 counts forever without stopping (unless stopped by some other
|
|
|
2450 loop clause, of course); if you omit the @code{by} term, the loop
|
|
|
2451 counts in steps of one.
|
|
|
2452
|
|
|
2453 You can replace the word @code{from} with @code{upfrom} or
|
|
|
2454 @code{downfrom} to indicate the direction of the loop. Likewise,
|
|
|
2455 you can replace @code{to} with @code{upto} or @code{downto}.
|
|
|
2456 For example, @samp{for x from 5 downto 1} executes five times
|
|
|
2457 with @code{x} taking on the integers from 5 down to 1 in turn.
|
|
|
2458 Also, you can replace @code{to} with @code{below} or @code{above},
|
|
|
2459 which are like @code{upto} and @code{downto} respectively except
|
|
|
2460 that they are exclusive rather than inclusive limits:
|
|
|
2461
|
|
|
2462 @example
|
|
|
2463 (loop for x to 10 collect x)
|
|
|
2464 @result{} (0 1 2 3 4 5 6 7 8 9 10)
|
|
|
2465 (loop for x below 10 collect x)
|
|
|
2466 @result{} (0 1 2 3 4 5 6 7 8 9)
|
|
|
2467 @end example
|
|
|
2468
|
|
|
2469 The @code{by} value is always positive, even for downward-counting
|
|
|
2470 loops. Some sort of @code{from} value is required for downward
|
|
|
2471 loops; @samp{for x downto 5} is not a legal loop clause all by
|
|
|
2472 itself.
|
|
|
2473
|
|
|
2474 @item for @var{var} in @var{list} by @var{function}
|
|
|
2475 This clause iterates @var{var} over all the elements of @var{list},
|
|
|
2476 in turn. If you specify the @code{by} term, then @var{function}
|
|
|
2477 is used to traverse the list instead of @code{cdr}; it must be a
|
|
|
2478 function taking one argument. For example:
|
|
|
2479
|
|
|
2480 @example
|
|
|
2481 (loop for x in '(1 2 3 4 5 6) collect (* x x))
|
|
|
2482 @result{} (1 4 9 16 25 36)
|
|
|
2483 (loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
|
|
|
2484 @result{} (1 9 25)
|
|
|
2485 @end example
|
|
|
2486
|
|
|
2487 @item for @var{var} on @var{list} by @var{function}
|
|
|
2488 This clause iterates @var{var} over all the cons cells of @var{list}.
|
|
|
2489
|
|
|
2490 @example
|
|
|
2491 (loop for x on '(1 2 3 4) collect x)
|
|
|
2492 @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
|
|
|
2493 @end example
|
|
|
2494
|
|
|
2495 With @code{by}, there is no real reason that the @code{on} expression
|
|
|
2496 must be a list. For example:
|
|
|
2497
|
|
|
2498 @example
|
|
|
2499 (loop for x on first-animal by 'next-animal collect x)
|
|
|
2500 @end example
|
|
|
2501
|
|
|
2502 @noindent
|
|
|
2503 where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
|
|
|
2504 the next in the (assumed) sequence of animals, or @code{nil} if
|
|
|
2505 @var{x} was the last animal in the sequence.
|
|
|
2506
|
|
|
2507 @item for @var{var} in-ref @var{list} by @var{function}
|
|
|
2508 This is like a regular @code{in} clause, but @var{var} becomes
|
|
|
2509 a @code{setf}-able ``reference'' onto the elements of the list
|
|
|
2510 rather than just a temporary variable. For example,
|
|
|
2511
|
|
|
2512 @example
|
|
|
2513 (loop for x in-ref my-list do (incf x))
|
|
|
2514 @end example
|
|
|
2515
|
|
|
2516 @noindent
|
|
|
2517 increments every element of @code{my-list} in place. This clause
|
|
|
2518 is an extension to standard Common Lisp.
|
|
|
2519
|
|
|
2520 @item for @var{var} across @var{array}
|
|
|
2521 This clause iterates @var{var} over all the elements of @var{array},
|
|
|
2522 which may be a vector or a string.
|
|
|
2523
|
|
|
2524 @example
|
|
|
2525 (loop for x across "aeiou"
|
|
|
2526 do (use-vowel (char-to-string x)))
|
|
|
2527 @end example
|
|
|
2528
|
|
|
2529 @item for @var{var} across-ref @var{array}
|
|
|
2530 This clause iterates over an array, with @var{var} a @code{setf}-able
|
|
|
2531 reference onto the elements; see @code{in-ref} above.
|
|
|
2532
|
|
|
2533 @item for @var{var} being the elements of @var{sequence}
|
|
|
2534 This clause iterates over the elements of @var{sequence}, which may
|
|
|
2535 be a list, vector, or string. Since the type must be determined
|
|
|
2536 at run-time, this is somewhat less efficient than @code{in} or
|
|
|
2537 @code{across}. The clause may be followed by the additional term
|
|
|
2538 @samp{using (index @var{var2})} to cause @var{var2} to be bound to
|
|
|
2539 the successive indices (starting at 0) of the elements.
|
|
|
2540
|
|
|
2541 This clause type is taken from older versions of the @code{loop} macro,
|
|
|
2542 and is not present in modern Common Lisp. The @samp{using (sequence ...)}
|
|
|
2543 term of the older macros is not supported.
|
|
|
2544
|
|
|
2545 @item for @var{var} being the elements of-ref @var{sequence}
|
|
|
2546 This clause iterates over a sequence, with @var{var} a @code{setf}-able
|
|
|
2547 reference onto the elements; see @code{in-ref} above.
|
|
|
2548
|
|
|
2549 @item for @var{var} being the symbols [of @var{obarray}]
|
|
|
2550 This clause iterates over symbols, either over all interned symbols
|
|
|
2551 or over all symbols in @var{obarray}. The loop is executed with
|
|
|
2552 @var{var} bound to each symbol in turn. The symbols are visited in
|
|
|
2553 an unspecified order.
|
|
|
2554
|
|
|
2555 As an example,
|
|
|
2556
|
|
|
2557 @example
|
|
|
2558 (loop for sym being the symbols
|
|
|
2559 when (fboundp sym)
|
|
|
2560 when (string-match "^map" (symbol-name sym))
|
|
|
2561 collect sym)
|
|
|
2562 @end example
|
|
|
2563
|
|
|
2564 @noindent
|
|
|
2565 returns a list of all the functions whose names begin with @samp{map}.
|
|
|
2566
|
|
|
2567 The Common Lisp words @code{external-symbols} and @code{present-symbols}
|
|
|
2568 are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
|
|
|
2569
|
|
|
2570 Due to a minor implementation restriction, it will not work to have
|
|
|
2571 more than one @code{for} clause iterating over symbols, hash tables,
|
|
|
2572 keymaps, overlays, or intervals in a given @code{loop}. Fortunately,
|
|
|
2573 it would rarely if ever be useful to do so. It @emph{is} legal to mix
|
|
|
2574 one of these types of clauses with other clauses like @code{for ... to}
|
|
|
2575 or @code{while}.
|
|
|
2576
|
|
|
2577 @item for @var{var} being the hash-keys of @var{hash-table}
|
|
|
2578 This clause iterates over the entries in @var{hash-table}. For each
|
|
|
2579 hash table entry, @var{var} is bound to the entry's key. If you write
|
|
|
2580 @samp{the hash-values} instead, @var{var} is bound to the values
|
|
|
2581 of the entries. The clause may be followed by the additional
|
|
|
2582 term @samp{using (hash-values @var{var2})} (where @code{hash-values}
|
|
|
2583 is the opposite word of the word following @code{the}) to cause
|
|
|
2584 @var{var} and @var{var2} to be bound to the two parts of each
|
|
|
2585 hash table entry.
|
|
|
2586
|
|
|
2587 @item for @var{var} being the key-codes of @var{keymap}
|
|
|
2588 This clause iterates over the entries in @var{keymap}. In GNU Emacs 18
|
|
|
2589 and 19, keymaps are either alists or vectors, and key-codes are integers
|
|
|
2590 or symbols. In XEmacs, keymaps are a special new data type, and
|
|
|
2591 key-codes are symbols or lists of symbols. The iteration does not enter
|
|
|
2592 nested keymaps or inherited (parent) keymaps. You can use @samp{the
|
|
|
2593 key-bindings} to access the commands bound to the keys rather than the
|
|
|
2594 key codes, and you can add a @code{using} clause to access both the
|
|
|
2595 codes and the bindings together.
|
|
|
2596
|
|
|
2597 @item for @var{var} being the key-seqs of @var{keymap}
|
|
|
2598 This clause iterates over all key sequences defined by @var{keymap}
|
|
|
2599 and its nested keymaps, where @var{var} takes on values which are
|
|
|
2600 strings in Emacs 18 or vectors in Emacs 19. The strings or vectors
|
|
|
2601 are reused for each iteration, so you must copy them if you wish to keep
|
|
|
2602 them permanently. You can add a @samp{using (key-bindings ...)}
|
|
|
2603 clause to get the command bindings as well.
|
|
|
2604
|
|
|
2605 @item for @var{var} being the overlays [of @var{buffer}] @dots{}
|
|
|
2606 This clause iterates over the Emacs 19 ``overlays'' or XEmacs
|
|
|
2607 ``extents'' of a buffer (the clause @code{extents} is synonymous with
|
|
|
2608 @code{overlays}). Under Emacs 18, this clause iterates zero times. If
|
|
|
2609 the @code{of} term is omitted, the current buffer is used. This clause
|
|
|
2610 also accepts optional @samp{from @var{pos}} and @samp{to @var{pos}}
|
|
|
2611 terms, limiting the clause to overlays which overlap the specified
|
|
|
2612 region.
|
|
|
2613
|
|
|
2614 @item for @var{var} being the intervals [of @var{buffer}] @dots{}
|
|
|
2615 This clause iterates over all intervals of a buffer with constant
|
|
|
2616 text properties. The variable @var{var} will be bound to conses
|
|
|
2617 of start and end positions, where one start position is always equal
|
|
|
2618 to the previous end position. The clause allows @code{of},
|
|
|
2619 @code{from}, @code{to}, and @code{property} terms, where the latter
|
|
|
2620 term restricts the search to just the specified property. The
|
|
|
2621 @code{of} term may specify either a buffer or a string. This
|
|
|
2622 clause is useful only in GNU Emacs 19; in other versions, all
|
|
|
2623 buffers and strings consist of a single interval.
|
|
|
2624
|
|
|
2625 @item for @var{var} being the frames
|
|
|
2626 This clause iterates over all frames, i.e., X window system windows
|
|
|
2627 open on Emacs files. This clause works only under Emacs 19. The
|
|
|
2628 clause @code{screens} is a synonym for @code{frames}. The frames
|
|
|
2629 are visited in @code{next-frame} order starting from
|
|
|
2630 @code{selected-frame}.
|
|
|
2631
|
|
|
2632 @item for @var{var} being the windows [of @var{frame}]
|
|
|
2633 This clause iterates over the windows (in the Emacs sense) of
|
|
|
2634 the current frame, or of the specified @var{frame}. (In Emacs 18
|
|
|
2635 there is only ever one frame, and the @code{of} term is not
|
|
|
2636 allowed there.)
|
|
|
2637
|
|
|
2638 @item for @var{var} being the buffers
|
|
|
2639 This clause iterates over all buffers in Emacs. It is equivalent
|
|
|
2640 to @samp{for @var{var} in (buffer-list)}.
|
|
|
2641
|
|
|
2642 @item for @var{var} = @var{expr1} then @var{expr2}
|
|
|
2643 This clause does a general iteration. The first time through
|
|
|
2644 the loop, @var{var} will be bound to @var{expr1}. On the second
|
|
|
2645 and successive iterations it will be set by evaluating @var{expr2}
|
|
|
2646 (which may refer to the old value of @var{var}). For example,
|
|
|
2647 these two loops are effectively the same:
|
|
|
2648
|
|
|
2649 @example
|
|
|
2650 (loop for x on my-list by 'cddr do ...)
|
|
|
2651 (loop for x = my-list then (cddr x) while x do ...)
|
|
|
2652 @end example
|
|
|
2653
|
|
|
2654 Note that this type of @code{for} clause does not imply any sort
|
|
|
2655 of terminating condition; the above example combines it with a
|
|
|
2656 @code{while} clause to tell when to end the loop.
|
|
|
2657
|
|
|
2658 If you omit the @code{then} term, @var{expr1} is used both for
|
|
|
2659 the initial setting and for successive settings:
|
|
|
2660
|
|
|
2661 @example
|
|
|
2662 (loop for x = (random) when (> x 0) return x)
|
|
|
2663 @end example
|
|
|
2664
|
|
|
2665 @noindent
|
|
|
2666 This loop keeps taking random numbers from the @code{(random)}
|
|
|
2667 function until it gets a positive one, which it then returns.
|
|
|
2668 @end table
|
|
|
2669
|
|
|
2670 If you include several @code{for} clauses in a row, they are
|
|
|
2671 treated sequentially (as if by @code{let*} and @code{setq}).
|
|
|
2672 You can instead use the word @code{and} to link the clauses,
|
|
|
2673 in which case they are processed in parallel (as if by @code{let}
|
|
|
2674 and @code{psetq}).
|
|
|
2675
|
|
|
2676 @example
|
|
|
2677 (loop for x below 5 for y = nil then x collect (list x y))
|
|
|
2678 @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
|
|
|
2679 (loop for x below 5 and y = nil then x collect (list x y))
|
|
|
2680 @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
|
|
|
2681 @end example
|
|
|
2682
|
|
|
2683 @noindent
|
|
|
2684 In the first loop, @code{y} is set based on the value of @code{x}
|
|
|
2685 that was just set by the previous clause; in the second loop,
|
|
|
2686 @code{x} and @code{y} are set simultaneously so @code{y} is set
|
|
|
2687 based on the value of @code{x} left over from the previous time
|
|
|
2688 through the loop.
|
|
|
2689
|
|
|
2690 Another feature of the @code{loop} macro is @dfn{destructuring},
|
|
|
2691 similar in concept to the destructuring provided by @code{defmacro}.
|
|
|
2692 The @var{var} part of any @code{for} clause can be given as a list
|
|
|
2693 of variables instead of a single variable. The values produced
|
|
|
2694 during loop execution must be lists; the values in the lists are
|
|
|
2695 stored in the corresponding variables.
|
|
|
2696
|
|
|
2697 @example
|
|
|
2698 (loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
|
|
|
2699 @result{} (5 9 13)
|
|
|
2700 @end example
|
|
|
2701
|
|
|
2702 In loop destructuring, if there are more values than variables
|
|
|
2703 the trailing values are ignored, and if there are more variables
|
|
|
2704 than values the trailing variables get the value @code{nil}.
|
|
|
2705 If @code{nil} is used as a variable name, the corresponding
|
|
|
2706 values are ignored. Destructuring may be nested, and dotted
|
|
|
2707 lists of variables like @code{(x . y)} are allowed.
|
|
|
2708
|
|
|
2709 @node Iteration Clauses, Accumulation Clauses, For Clauses, Loop Facility
|
|
|
2710 @subsection Iteration Clauses
|
|
|
2711
|
|
|
2712 @noindent
|
|
|
2713 Aside from @code{for} clauses, there are several other loop clauses
|
|
|
2714 that control the way the loop operates. They might be used by
|
|
|
2715 themselves, or in conjunction with one or more @code{for} clauses.
|
|
|
2716
|
|
|
2717 @table @code
|
|
|
2718 @item repeat @var{integer}
|
|
|
2719 This clause simply counts up to the specified number using an
|
|
|
2720 internal temporary variable. The loops
|
|
|
2721
|
|
|
2722 @example
|
|
|
2723 (loop repeat n do ...)
|
|
|
2724 (loop for temp to n do ...)
|
|
|
2725 @end example
|
|
|
2726
|
|
|
2727 @noindent
|
|
|
2728 are identical except that the second one forces you to choose
|
|
|
2729 a name for a variable you aren't actually going to use.
|
|
|
2730
|
|
|
2731 @item while @var{condition}
|
|
|
2732 This clause stops the loop when the specified condition (any Lisp
|
|
|
2733 expression) becomes @code{nil}. For example, the following two
|
|
|
2734 loops are equivalent, except for the implicit @code{nil} block
|
|
|
2735 that surrounds the second one:
|
|
|
2736
|
|
|
2737 @example
|
|
|
2738 (while @var{cond} @var{forms}@dots{})
|
|
|
2739 (loop while @var{cond} do @var{forms}@dots{})
|
|
|
2740 @end example
|
|
|
2741
|
|
|
2742 @item until @var{condition}
|
|
|
2743 This clause stops the loop when the specified condition is true,
|
|
|
2744 i.e., non-@code{nil}.
|
|
|
2745
|
|
|
2746 @item always @var{condition}
|
|
|
2747 This clause stops the loop when the specified condition is @code{nil}.
|
|
|
2748 Unlike @code{while}, it stops the loop using @code{return nil} so that
|
|
|
2749 the @code{finally} clauses are not executed. If all the conditions
|
|
|
2750 were non-@code{nil}, the loop returns @code{t}:
|
|
|
2751
|
|
|
2752 @example
|
|
|
2753 (if (loop for size in size-list always (> size 10))
|
|
|
2754 (some-big-sizes)
|
|
|
2755 (no-big-sizes))
|
|
|
2756 @end example
|
|
|
2757
|
|
|
2758 @item never @var{condition}
|
|
|
2759 This clause is like @code{always}, except that the loop returns
|
|
|
2760 @code{t} if any conditions were false, or @code{nil} otherwise.
|
|
|
2761
|
|
|
2762 @item thereis @var{condition}
|
|
|
2763 This clause stops the loop when the specified form is non-@code{nil};
|
|
|
2764 in this case, it returns that non-@code{nil} value. If all the
|
|
|
2765 values were @code{nil}, the loop returns @code{nil}.
|
|
|
2766 @end table
|
|
|
2767
|
|
|
2768 @node Accumulation Clauses, Other Clauses, Iteration Clauses, Loop Facility
|
|
|
2769 @subsection Accumulation Clauses
|
|
|
2770
|
|
|
2771 @noindent
|
|
|
2772 These clauses cause the loop to accumulate information about the
|
|
|
2773 specified Lisp @var{form}. The accumulated result is returned
|
|
|
2774 from the loop unless overridden, say, by a @code{return} clause.
|
|
|
2775
|
|
|
2776 @table @code
|
|
|
2777 @item collect @var{form}
|
|
|
2778 This clause collects the values of @var{form} into a list. Several
|
|
|
2779 examples of @code{collect} appear elsewhere in this manual.
|
|
|
2780
|
|
|
2781 The word @code{collecting} is a synonym for @code{collect}, and
|
|
|
2782 likewise for the other accumulation clauses.
|
|
|
2783
|
|
|
2784 @item append @var{form}
|
|
|
2785 This clause collects lists of values into a result list using
|
|
|
2786 @code{append}.
|
|
|
2787
|
|
|
2788 @item nconc @var{form}
|
|
|
2789 This clause collects lists of values into a result list by
|
|
|
2790 destructively modifying the lists rather than copying them.
|
|
|
2791
|
|
|
2792 @item concat @var{form}
|
|
|
2793 This clause concatenates the values of the specified @var{form}
|
|
|
2794 into a string. (It and the following clause are extensions to
|
|
|
2795 standard Common Lisp.)
|
|
|
2796
|
|
|
2797 @item vconcat @var{form}
|
|
|
2798 This clause concatenates the values of the specified @var{form}
|
|
|
2799 into a vector.
|
|
|
2800
|
|
|
2801 @item count @var{form}
|
|
|
2802 This clause counts the number of times the specified @var{form}
|
|
|
2803 evaluates to a non-@code{nil} value.
|
|
|
2804
|
|
|
2805 @item sum @var{form}
|
|
|
2806 This clause accumulates the sum of the values of the specified
|
|
|
2807 @var{form}, which must evaluate to a number.
|
|
|
2808
|
|
|
2809 @item maximize @var{form}
|
|
|
2810 This clause accumulates the maximum value of the specified @var{form},
|
|
|
2811 which must evaluate to a number. The return value is undefined if
|
|
|
2812 @code{maximize} is executed zero times.
|
|
|
2813
|
|
|
2814 @item minimize @var{form}
|
|
|
2815 This clause accumulates the minimum value of the specified @var{form}.
|
|
|
2816 @end table
|
|
|
2817
|
|
|
2818 Accumulation clauses can be followed by @samp{into @var{var}} to
|
|
|
2819 cause the data to be collected into variable @var{var} (which is
|
|
|
2820 automatically @code{let}-bound during the loop) rather than an
|
|
|
2821 unnamed temporary variable. Also, @code{into} accumulations do
|
|
|
2822 not automatically imply a return value. The loop must use some
|
|
|
2823 explicit mechanism, such as @code{finally return}, to return
|
|
|
2824 the accumulated result.
|
|
|
2825
|
|
|
2826 It is legal for several accumulation clauses of the same type to
|
|
|
2827 accumulate into the same place. From Steele:
|
|
|
2828
|
|
|
2829 @example
|
|
|
2830 (loop for name in '(fred sue alice joe june)
|
|
|
2831 for kids in '((bob ken) () () (kris sunshine) ())
|
|
|
2832 collect name
|
|
|
2833 append kids)
|
|
|
2834 @result{} (fred bob ken sue alice joe kris sunshine june)
|
|
|
2835 @end example
|
|
|
2836
|
|
|
2837 @node Other Clauses, , Accumulation Clauses, Loop Facility
|
|
|
2838 @subsection Other Clauses
|
|
|
2839
|
|
|
2840 @noindent
|
|
|
2841 This section describes the remaining loop clauses.
|
|
|
2842
|
|
|
2843 @table @code
|
|
|
2844 @item with @var{var} = @var{value}
|
|
|
2845 This clause binds a variable to a value around the loop, but
|
|
|
2846 otherwise leaves the variable alone during the loop. The following
|
|
|
2847 loops are basically equivalent:
|
|
|
2848
|
|
|
2849 @example
|
|
|
2850 (loop with x = 17 do ...)
|
|
|
2851 (let ((x 17)) (loop do ...))
|
|
|
2852 (loop for x = 17 then x do ...)
|
|
|
2853 @end example
|
|
|
2854
|
|
|
2855 Naturally, the variable @var{var} might be used for some purpose
|
|
|
2856 in the rest of the loop. For example:
|
|
|
2857
|
|
|
2858 @example
|
|
|
2859 (loop for x in my-list with res = nil do (push x res)
|
|
|
2860 finally return res)
|
|
|
2861 @end example
|
|
|
2862
|
|
|
2863 This loop inserts the elements of @code{my-list} at the front of
|
|
|
2864 a new list being accumulated in @code{res}, then returns the
|
|
|
2865 list @code{res} at the end of the loop. The effect is similar
|
|
|
2866 to that of a @code{collect} clause, but the list gets reversed
|
|
|
2867 by virtue of the fact that elements are being pushed onto the
|
|
|
2868 front of @code{res} rather than the end.
|
|
|
2869
|
|
|
2870 If you omit the @code{=} term, the variable is initialized to
|
|
|
2871 @code{nil}. (Thus the @samp{= nil} in the above example is
|
|
|
2872 unnecessary.)
|
|
|
2873
|
|
|
2874 Bindings made by @code{with} are sequential by default, as if
|
|
|
2875 by @code{let*}. Just like @code{for} clauses, @code{with} clauses
|
|
|
2876 can be linked with @code{and} to cause the bindings to be made by
|
|
|
2877 @code{let} instead.
|
|
|
2878
|
|
|
2879 @item if @var{condition} @var{clause}
|
|
|
2880 This clause executes the following loop clause only if the specified
|
|
|
2881 condition is true. The following @var{clause} should be an accumulation,
|
|
|
2882 @code{do}, @code{return}, @code{if}, or @code{unless} clause.
|
|
|
2883 Several clauses may be linked by separating them with @code{and}.
|
|
|
2884 These clauses may be followed by @code{else} and a clause or clauses
|
|
|
2885 to execute if the condition was false. The whole construct may
|
|
|
2886 optionally be followed by the word @code{end} (which may be used to
|
|
|
2887 disambiguate an @code{else} or @code{and} in a nested @code{if}).
|
|
|
2888
|
|
|
2889 The actual non-@code{nil} value of the condition form is available
|
|
|
2890 by the name @code{it} in the ``then'' part. For example:
|
|
|
2891
|
|
|
2892 @example
|
|
|
2893 (setq funny-numbers '(6 13 -1))
|
|
|
2894 @result{} (6 13 -1)
|
|
|
2895 (loop for x below 10
|
|
|
2896 if (oddp x)
|
|
|
2897 collect x into odds
|
|
|
2898 and if (memq x funny-numbers) return (cdr it) end
|
|
|
2899 else
|
|
|
2900 collect x into evens
|
|
|
2901 finally return (vector odds evens))
|
|
|
2902 @result{} [(1 3 5 7 9) (0 2 4 6 8)]
|
|
|
2903 (setq funny-numbers '(6 7 13 -1))
|
|
|
2904 @result{} (6 7 13 -1)
|
|
|
2905 (loop <@r{same thing again}>)
|
|
|
2906 @result{} (13 -1)
|
|
|
2907 @end example
|
|
|
2908
|
|
|
2909 Note the use of @code{and} to put two clauses into the ``then''
|
|
|
2910 part, one of which is itself an @code{if} clause. Note also that
|
|
|
2911 @code{end}, while normally optional, was necessary here to make
|
|
|
2912 it clear that the @code{else} refers to the outermost @code{if}
|
|
|
2913 clause. In the first case, the loop returns a vector of lists
|
|
|
2914 of the odd and even values of @var{x}. In the second case, the
|
|
|
2915 odd number 7 is one of the @code{funny-numbers} so the loop
|
|
|
2916 returns early; the actual returned value is based on the result
|
|
|
2917 of the @code{memq} call.
|
|
|
2918
|
|
|
2919 @item when @var{condition} @var{clause}
|
|
|
2920 This clause is just a synonym for @code{if}.
|
|
|
2921
|
|
|
2922 @item unless @var{condition} @var{clause}
|
|
|
2923 The @code{unless} clause is just like @code{if} except that the
|
|
|
2924 sense of the condition is reversed.
|
|
|
2925
|
|
|
2926 @item named @var{name}
|
|
|
2927 This clause gives a name other than @code{nil} to the implicit
|
|
|
2928 block surrounding the loop. The @var{name} is the symbol to be
|
|
|
2929 used as the block name.
|
|
|
2930
|
|
|
2931 @item initially [do] @var{forms}...
|
|
|
2932 This keyword introduces one or more Lisp forms which will be
|
|
|
2933 executed before the loop itself begins (but after any variables
|
|
|
2934 requested by @code{for} or @code{with} have been bound to their
|
|
|
2935 initial values). @code{initially} clauses can appear anywhere;
|
|
|
2936 if there are several, they are executed in the order they appear
|
|
|
2937 in the loop. The keyword @code{do} is optional.
|
|
|
2938
|
|
|
2939 @item finally [do] @var{forms}...
|
|
|
2940 This introduces Lisp forms which will be executed after the loop
|
|
|
2941 finishes (say, on request of a @code{for} or @code{while}).
|
|
|
2942 @code{initially} and @code{finally} clauses may appear anywhere
|
|
|
2943 in the loop construct, but they are executed (in the specified
|
|
|
2944 order) at the beginning or end, respectively, of the loop.
|
|
|
2945
|
|
|
2946 @item finally return @var{form}
|
|
|
2947 This says that @var{form} should be executed after the loop
|
|
|
2948 is done to obtain a return value. (Without this, or some other
|
|
|
2949 clause like @code{collect} or @code{return}, the loop will simply
|
|
|
2950 return @code{nil}.) Variables bound by @code{for}, @code{with},
|
|
|
2951 or @code{into} will still contain their final values when @var{form}
|
|
|
2952 is executed.
|
|
|
2953
|
|
|
2954 @item do @var{forms}...
|
|
|
2955 The word @code{do} may be followed by any number of Lisp expressions
|
|
|
2956 which are executed as an implicit @code{progn} in the body of the
|
|
|
2957 loop. Many of the examples in this section illustrate the use of
|
|
|
2958 @code{do}.
|
|
|
2959
|
|
|
2960 @item return @var{form}
|
|
|
2961 This clause causes the loop to return immediately. The following
|
|
|
2962 Lisp form is evaluated to give the return value of the @code{loop}
|
|
|
2963 form. The @code{finally} clauses, if any, are not executed.
|
|
|
2964 Of course, @code{return} is generally used inside an @code{if} or
|
|
|
2965 @code{unless}, as its use in a top-level loop clause would mean
|
|
|
2966 the loop would never get to ``loop'' more than once.
|
|
|
2967
|
|
|
2968 The clause @samp{return @var{form}} is equivalent to
|
|
|
2969 @samp{do (return @var{form})} (or @code{return-from} if the loop
|
|
|
2970 was named). The @code{return} clause is implemented a bit more
|
|
|
2971 efficiently, though.
|
|
|
2972 @end table
|
|
|
2973
|
|
|
2974 While there is no high-level way to add user extensions to @code{loop}
|
|
|
2975 (comparable to @code{defsetf} for @code{setf}, say), this package
|
|
|
2976 does offer two properties called @code{cl-loop-handler} and
|
|
|
2977 @code{cl-loop-for-handler} which are functions to be called when
|
|
|
2978 a given symbol is encountered as a top-level loop clause or
|
|
|
2979 @code{for} clause, respectively. Consult the source code in
|
|
|
2980 file @file{cl-macs.el} for details.
|
|
|
2981
|
|
|
2982 This package's @code{loop} macro is compatible with that of Common
|
|
|
2983 Lisp, except that a few features are not implemented: @code{loop-finish}
|
|
|
2984 and data-type specifiers. Naturally, the @code{for} clauses which
|
|
|
2985 iterate over keymaps, overlays, intervals, frames, windows, and
|
|
|
2986 buffers are Emacs-specific extensions.
|
|
|
2987
|
|
|
2988 @node Multiple Values, , Loop Facility, Control Structure
|
|
|
2989 @section Multiple Values
|
|
|
2990
|
|
|
2991 @noindent
|
|
|
2992 Common Lisp functions can return zero or more results. Emacs Lisp
|
|
|
2993 functions, by contrast, always return exactly one result. This
|
|
|
2994 package makes no attempt to emulate Common Lisp multiple return
|
|
|
2995 values; Emacs versions of Common Lisp functions that return more
|
|
|
2996 than one value either return just the first value (as in
|
|
|
2997 @code{compiler-macroexpand}) or return a list of values (as in
|
|
|
2998 @code{get-setf-method}). This package @emph{does} define placeholders
|
|
|
2999 for the Common Lisp functions that work with multiple values, but
|
|
|
3000 in Emacs Lisp these functions simply operate on lists instead.
|
|
|
3001 The @code{values} form, for example, is a synonym for @code{list}
|
|
|
3002 in Emacs.
|
|
|
3003
|
|
|
3004 @defspec multiple-value-bind (var@dots{}) values-form forms@dots{}
|
|
|
3005 This form evaluates @var{values-form}, which must return a list of
|
|
|
3006 values. It then binds the @var{var}s to these respective values,
|
|
|
3007 as if by @code{let}, and then executes the body @var{forms}.
|
|
|
3008 If there are more @var{var}s than values, the extra @var{var}s
|
|
|
3009 are bound to @code{nil}. If there are fewer @var{var}s than
|
|
|
3010 values, the excess values are ignored.
|
|
|
3011 @end defspec
|
|
|
3012
|
|
|
3013 @defspec multiple-value-setq (var@dots{}) form
|
|
|
3014 This form evaluates @var{form}, which must return a list of values.
|
|
|
3015 It then sets the @var{var}s to these respective values, as if by
|
|
|
3016 @code{setq}. Extra @var{var}s or values are treated the same as
|
|
|
3017 in @code{multiple-value-bind}.
|
|
|
3018 @end defspec
|
|
|
3019
|
|
|
3020 The older Quiroz package attempted a more faithful (but still
|
|
|
3021 imperfect) emulation of Common Lisp multiple values. The old
|
|
|
3022 method ``usually'' simulated true multiple values quite well,
|
|
|
3023 but under certain circumstances would leave spurious return
|
|
|
3024 values in memory where a later, unrelated @code{multiple-value-bind}
|
|
|
3025 form would see them.
|
|
|
3026
|
|
|
3027 Since a perfect emulation is not feasible in Emacs Lisp, this
|
|
|
3028 package opts to keep it as simple and predictable as possible.
|
|
|
3029
|
|
|
3030 @node Macros, Declarations, Control Structure, Top
|
|
|
3031 @chapter Macros
|
|
|
3032
|
|
|
3033 @noindent
|
|
|
3034 This package implements the various Common Lisp features of
|
|
|
3035 @code{defmacro}, such as destructuring, @code{&environment},
|
|
|
3036 and @code{&body}. Top-level @code{&whole} is not implemented
|
|
|
3037 for @code{defmacro} due to technical difficulties.
|
|
|
3038 @xref{Argument Lists}.
|
|
|
3039
|
|
|
3040 Destructuring is made available to the user by way of the
|
|
|
3041 following macro:
|
|
|
3042
|
|
|
3043 @defspec destructuring-bind arglist expr forms@dots{}
|
|
|
3044 This macro expands to code which executes @var{forms}, with
|
|
|
3045 the variables in @var{arglist} bound to the list of values
|
|
|
3046 returned by @var{expr}. The @var{arglist} can include all
|
|
|
3047 the features allowed for @code{defmacro} argument lists,
|
|
|
3048 including destructuring. (The @code{&environment} keyword
|
|
|
3049 is not allowed.) The macro expansion will signal an error
|
|
|
3050 if @var{expr} returns a list of the wrong number of arguments
|
|
|
3051 or with incorrect keyword arguments.
|
|
|
3052 @end defspec
|
|
|
3053
|
|
|
3054 This package also includes the Common Lisp @code{define-compiler-macro}
|
|
|
3055 facility, which allows you to define compile-time expansions and
|
|
|
3056 optimizations for your functions.
|
|
|
3057
|
|
|
3058 @defspec define-compiler-macro name arglist forms@dots{}
|
|
|
3059 This form is similar to @code{defmacro}, except that it only expands
|
|
|
3060 calls to @var{name} at compile-time; calls processed by the Lisp
|
|
|
3061 interpreter are not expanded, nor are they expanded by the
|
|
|
3062 @code{macroexpand} function.
|
|
|
3063
|
|
|
3064 The argument list may begin with a @code{&whole} keyword and a
|
|
|
3065 variable. This variable is bound to the macro-call form itself,
|
|
|
3066 i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}.
|
|
|
3067 If the macro expander returns this form unchanged, then the
|
|
|
3068 compiler treats it as a normal function call. This allows
|
|
|
3069 compiler macros to work as optimizers for special cases of a
|
|
|
3070 function, leaving complicated cases alone.
|
|
|
3071
|
|
|
3072 For example, here is a simplified version of a definition that
|
|
|
3073 appears as a standard part of this package:
|
|
|
3074
|
|
|
3075 @example
|
|
|
3076 (define-compiler-macro member* (&whole form a list &rest keys)
|
|
|
3077 (if (and (null keys)
|
|
|
3078 (eq (car-safe a) 'quote)
|
|
|
3079 (not (floatp-safe (cadr a))))
|
|
|
3080 (list 'memq a list)
|
|
|
3081 form))
|
|
|
3082 @end example
|
|
|
3083
|
|
|
3084 @noindent
|
|
|
3085 This definition causes @code{(member* @var{a} @var{list})} to change
|
|
|
3086 to a call to the faster @code{memq} in the common case where @var{a}
|
|
|
3087 is a non-floating-point constant; if @var{a} is anything else, or
|
|
|
3088 if there are any keyword arguments in the call, then the original
|
|
|
3089 @code{member*} call is left intact. (The actual compiler macro
|
|
|
3090 for @code{member*} optimizes a number of other cases, including
|
|
|
3091 common @code{:test} predicates.)
|
|
|
3092 @end defspec
|
|
|
3093
|
|
|
3094 @defun compiler-macroexpand form
|
|
|
3095 This function is analogous to @code{macroexpand}, except that it
|
|
|
3096 expands compiler macros rather than regular macros. It returns
|
|
|
3097 @var{form} unchanged if it is not a call to a function for which
|
|
|
3098 a compiler macro has been defined, or if that compiler macro
|
|
|
3099 decided to punt by returning its @code{&whole} argument. Like
|
|
|
3100 @code{macroexpand}, it expands repeatedly until it reaches a form
|
|
|
3101 for which no further expansion is possible.
|
|
|
3102 @end defun
|
|
|
3103
|
|
|
3104 @xref{Macro Bindings}, for descriptions of the @code{macrolet}
|
|
|
3105 and @code{symbol-macrolet} forms for making ``local'' macro
|
|
|
3106 definitions.
|
|
|
3107
|
|
|
3108 @node Declarations, Symbols, Macros, Top
|
|
|
3109 @chapter Declarations
|
|
|
3110
|
|
|
3111 @noindent
|
|
|
3112 Common Lisp includes a complex and powerful ``declaration''
|
|
|
3113 mechanism that allows you to give the compiler special hints
|
|
|
3114 about the types of data that will be stored in particular variables,
|
|
|
3115 and about the ways those variables and functions will be used. This
|
|
|
3116 package defines versions of all the Common Lisp declaration forms:
|
|
|
3117 @code{declare}, @code{locally}, @code{proclaim}, @code{declaim},
|
|
|
3118 and @code{the}.
|
|
|
3119
|
|
|
3120 Most of the Common Lisp declarations are not currently useful in
|
|
|
3121 Emacs Lisp, as the byte-code system provides little opportunity
|
|
|
3122 to benefit from type information, and @code{special} declarations
|
|
|
3123 are redundant in a fully dynamically-scoped Lisp. A few
|
|
|
3124 declarations are meaningful when the optimizing Emacs 19 byte
|
|
|
3125 compiler is being used, however. Under the earlier non-optimizing
|
|
|
3126 compiler, these declarations will effectively be ignored.
|
|
|
3127
|
|
|
3128 @defun proclaim decl-spec
|
|
|
3129 This function records a ``global'' declaration specified by
|
|
|
3130 @var{decl-spec}. Since @code{proclaim} is a function, @var{decl-spec}
|
|
|
3131 is evaluated and thus should normally be quoted.
|
|
|
3132 @end defun
|
|
|
3133
|
|
|
3134 @defspec declaim decl-specs@dots{}
|
|
|
3135 This macro is like @code{proclaim}, except that it takes any number
|
|
|
3136 of @var{decl-spec} arguments, and the arguments are unevaluated and
|
|
|
3137 unquoted. The @code{declaim} macro also puts an @code{(eval-when
|
|
|
3138 (compile load eval) ...)} around the declarations so that they will
|
|
|
3139 be registered at compile-time as well as at run-time. (This is vital,
|
|
|
3140 since normally the declarations are meant to influence the way the
|
|
|
3141 compiler treats the rest of the file that contains the @code{declaim}
|
|
|
3142 form.)
|
|
|
3143 @end defspec
|
|
|
3144
|
|
|
3145 @defspec declare decl-specs@dots{}
|
|
|
3146 This macro is used to make declarations within functions and other
|
|
|
3147 code. Common Lisp allows declarations in various locations, generally
|
|
|
3148 at the beginning of any of the many ``implicit @code{progn}s''
|
|
|
3149 throughout Lisp syntax, such as function bodies, @code{let} bodies,
|
|
|
3150 etc. Currently the only declaration understood by @code{declare}
|
|
|
3151 is @code{special}.
|
|
|
3152 @end defspec
|
|
|
3153
|
|
|
3154 @defspec locally declarations@dots{} forms@dots{}
|
|
|
3155 In this package, @code{locally} is no different from @code{progn}.
|
|
|
3156 @end defspec
|
|
|
3157
|
|
|
3158 @defspec the type form
|
|
|
3159 Type information provided by @code{the} is ignored in this package;
|
|
|
3160 in other words, @code{(the @var{type} @var{form})} is equivalent
|
|
|
3161 to @var{form}. Future versions of the optimizing byte-compiler may
|
|
|
3162 make use of this information.
|
|
|
3163
|
|
|
3164 For example, @code{mapcar} can map over both lists and arrays. It is
|
|
|
3165 hard for the compiler to expand @code{mapcar} into an in-line loop
|
|
|
3166 unless it knows whether the sequence will be a list or an array ahead
|
|
|
3167 of time. With @code{(mapcar 'car (the vector foo))}, a future
|
|
|
3168 compiler would have enough information to expand the loop in-line.
|
|
|
3169 For now, Emacs Lisp will treat the above code as exactly equivalent
|
|
|
3170 to @code{(mapcar 'car foo)}.
|
|
|
3171 @end defspec
|
|
|
3172
|
|
|
3173 Each @var{decl-spec} in a @code{proclaim}, @code{declaim}, or
|
|
|
3174 @code{declare} should be a list beginning with a symbol that says
|
|
|
3175 what kind of declaration it is. This package currently understands
|
|
|
3176 @code{special}, @code{inline}, @code{notinline}, @code{optimize},
|
|
|
3177 and @code{warn} declarations. (The @code{warn} declaration is an
|
|
|
3178 extension of standard Common Lisp.) Other Common Lisp declarations,
|
|
|
3179 such as @code{type} and @code{ftype}, are silently ignored.
|
|
|
3180
|
|
|
3181 @table @code
|
|
|
3182 @item special
|
|
|
3183 Since all variables in Emacs Lisp are ``special'' (in the Common
|
|
|
3184 Lisp sense), @code{special} declarations are only advisory. They
|
|
|
3185 simply tell the optimizing byte compiler that the specified
|
|
|
3186 variables are intentionally being referred to without being
|
|
|
3187 bound in the body of the function. The compiler normally emits
|
|
|
3188 warnings for such references, since they could be typographical
|
|
|
3189 errors for references to local variables.
|
|
|
3190
|
|
|
3191 The declaration @code{(declare (special @var{var1} @var{var2}))} is
|
|
|
3192 equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
|
|
|
3193 optimizing compiler, or to nothing at all in older compilers (which
|
|
|
3194 do not warn for non-local references).
|
|
|
3195
|
|
|
3196 In top-level contexts, it is generally better to write
|
|
|
3197 @code{(defvar @var{var})} than @code{(declaim (special @var{var}))},
|
|
|
3198 since @code{defvar} makes your intentions clearer. But the older
|
|
|
3199 byte compilers can not handle @code{defvar}s appearing inside of
|
|
|
3200 functions, while @code{(declare (special @var{var}))} takes care
|
|
|
3201 to work correctly with all compilers.
|
|
|
3202
|
|
|
3203 @item inline
|
|
|
3204 The @code{inline} @var{decl-spec} lists one or more functions
|
|
|
3205 whose bodies should be expanded ``in-line'' into calling functions
|
|
|
3206 whenever the compiler is able to arrange for it. For example,
|
|
|
3207 the Common Lisp function @code{cadr} is declared @code{inline}
|
|
|
3208 by this package so that the form @code{(cadr @var{x})} will
|
|
|
3209 expand directly into @code{(car (cdr @var{x}))} when it is called
|
|
|
3210 in user functions, for a savings of one (relatively expensive)
|
|
|
3211 function call.
|
|
|
3212
|
|
|
3213 The following declarations are all equivalent. Note that the
|
|
|
3214 @code{defsubst} form is a convenient way to define a function
|
|
|
3215 and declare it inline all at once, but it is available only in
|
|
|
3216 Emacs 19.
|
|
|
3217
|
|
|
3218 @example
|
|
|
3219 (declaim (inline foo bar))
|
|
|
3220 (eval-when (compile load eval) (proclaim '(inline foo bar)))
|
|
442
|
3221 (proclaim-inline foo bar) ; XEmacs only
|
|
|
3222 (defsubst foo (...) ...) ; instead of defun; Emacs 19 only
|
|
428
|
3223 @end example
|
|
|
3224
|
|
|
3225 @strong{Please note:} This declaration remains in effect after the
|
|
|
3226 containing source file is done. It is correct to use it to
|
|
|
3227 request that a function you have defined should be inlined,
|
|
|
3228 but it is impolite to use it to request inlining of an external
|
|
|
3229 function.
|
|
|
3230
|
|
|
3231 In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
|
|
|
3232 before a particular call to a function to cause just that call to
|
|
|
3233 be inlined; the current byte compilers provide no way to implement
|
|
|
3234 this, so @code{(declare (inline @dots{}))} is currently ignored by
|
|
|
3235 this package.
|
|
|
3236
|
|
|
3237 @item notinline
|
|
|
3238 The @code{notinline} declaration lists functions which should
|
|
|
3239 not be inlined after all; it cancels a previous @code{inline}
|
|
|
3240 declaration.
|
|
|
3241
|
|
|
3242 @item optimize
|
|
|
3243 This declaration controls how much optimization is performed by
|
|
|
3244 the compiler. Naturally, it is ignored by the earlier non-optimizing
|
|
|
3245 compilers.
|
|
|
3246
|
|
|
3247 The word @code{optimize} is followed by any number of lists like
|
|
|
3248 @code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several
|
|
|
3249 optimization ``qualities''; this package ignores all but @code{speed}
|
|
|
3250 and @code{safety}. The value of a quality should be an integer from
|
|
|
3251 0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important.''
|
|
|
3252 The default level for both qualities is 1.
|
|
|
3253
|
|
|
3254 In this package, with the Emacs 19 optimizing compiler, the
|
|
|
3255 @code{speed} quality is tied to the @code{byte-compile-optimize}
|
|
|
3256 flag, which is set to @code{nil} for @code{(speed 0)} and to
|
|
|
3257 @code{t} for higher settings; and the @code{safety} quality is
|
|
|
3258 tied to the @code{byte-compile-delete-errors} flag, which is
|
|
|
3259 set to @code{t} for @code{(safety 3)} and to @code{nil} for all
|
|
|
3260 lower settings. (The latter flag controls whether the compiler
|
|
|
3261 is allowed to optimize out code whose only side-effect could
|
|
|
3262 be to signal an error, e.g., rewriting @code{(progn foo bar)} to
|
|
|
3263 @code{bar} when it is not known whether @code{foo} will be bound
|
|
|
3264 at run-time.)
|
|
|
3265
|
|
|
3266 Note that even compiling with @code{(safety 0)}, the Emacs
|
|
|
3267 byte-code system provides sufficient checking to prevent real
|
|
|
3268 harm from being done. For example, barring serious bugs in
|
|
|
3269 Emacs itself, Emacs will not crash with a segmentation fault
|
|
|
3270 just because of an error in a fully-optimized Lisp program.
|
|
|
3271
|
|
|
3272 The @code{optimize} declaration is normally used in a top-level
|
|
|
3273 @code{proclaim} or @code{declaim} in a file; Common Lisp allows
|
|
|
3274 it to be used with @code{declare} to set the level of optimization
|
|
|
3275 locally for a given form, but this will not work correctly with the
|
|
|
3276 current version of the optimizing compiler. (The @code{declare}
|
|
|
3277 will set the new optimization level, but that level will not
|
|
|
3278 automatically be unset after the enclosing form is done.)
|
|
|
3279
|
|
|
3280 @item warn
|
|
|
3281 This declaration controls what sorts of warnings are generated
|
|
|
3282 by the byte compiler. Again, only the optimizing compiler
|
|
|
3283 generates warnings. The word @code{warn} is followed by any
|
|
|
3284 number of ``warning qualities,'' similar in form to optimization
|
|
|
3285 qualities. The currently supported warning types are
|
|
|
3286 @code{redefine}, @code{callargs}, @code{unresolved}, and
|
|
|
3287 @code{free-vars}; in the current system, a value of 0 will
|
|
|
3288 disable these warnings and any higher value will enable them.
|
|
|
3289 See the documentation for the optimizing byte compiler for details.
|
|
|
3290 @end table
|
|
|
3291
|
|
|
3292 @node Symbols, Numbers, Declarations, Top
|
|
|
3293 @chapter Symbols
|
|
|
3294
|
|
|
3295 @noindent
|
|
|
3296 This package defines several symbol-related features that were
|
|
|
3297 missing from Emacs Lisp.
|
|
|
3298
|
|
|
3299 @menu
|
|
442
|
3300 * Property Lists:: `getf', `remf'
|
|
428
|
3301 * Creating Symbols:: `gensym', `gentemp'
|
|
|
3302 @end menu
|
|
|
3303
|
|
|
3304 @node Property Lists, Creating Symbols, Symbols, Symbols
|
|
|
3305 @section Property Lists
|
|
|
3306
|
|
|
3307 @noindent
|
|
|
3308 These functions augment the standard Emacs Lisp functions @code{get}
|
|
442
|
3309 and @code{put} for operating on properties attached to objects.
|
|
428
|
3310 There are also functions for working with property lists as
|
|
442
|
3311 first-class data structures not attached to particular objects.
|
|
428
|
3312
|
|
|
3313 @defun getf place property &optional default
|
|
|
3314 This function scans the list @var{place} as if it were a property
|
|
|
3315 list, i.e., a list of alternating property names and values. If
|
|
|
3316 an even-numbered element of @var{place} is found which is @code{eq}
|
|
|
3317 to @var{property}, the following odd-numbered element is returned.
|
|
|
3318 Otherwise, @var{default} is returned (or @code{nil} if no default
|
|
|
3319 is given).
|
|
|
3320
|
|
|
3321 In particular,
|
|
|
3322
|
|
|
3323 @example
|
|
|
3324 (get sym prop) @equiv{} (getf (symbol-plist sym) prop)
|
|
|
3325 @end example
|
|
|
3326
|
|
|
3327 It is legal to use @code{getf} as a @code{setf} place, in which case
|
|
|
3328 its @var{place} argument must itself be a legal @code{setf} place.
|
|
|
3329 The @var{default} argument, if any, is ignored in this context.
|
|
|
3330 The effect is to change (via @code{setcar}) the value cell in the
|
|
|
3331 list that corresponds to @var{property}, or to cons a new property-value
|
|
|
3332 pair onto the list if the property is not yet present.
|
|
|
3333
|
|
|
3334 @example
|
|
|
3335 (put sym prop val) @equiv{} (setf (getf (symbol-plist sym) prop) val)
|
|
|
3336 @end example
|
|
|
3337
|
|
440
|
3338 The @code{get} function is also @code{setf}-able. The fact that
|
|
|
3339 @code{default} is ignored can sometimes be useful:
|
|
428
|
3340
|
|
|
3341 @example
|
|
440
|
3342 (incf (get 'foo 'usage-count 0))
|
|
428
|
3343 @end example
|
|
|
3344
|
|
|
3345 Here, symbol @code{foo}'s @code{usage-count} property is incremented
|
|
|
3346 if it exists, or set to 1 (an incremented 0) otherwise.
|
|
|
3347
|
|
|
3348 When not used as a @code{setf} form, @code{getf} is just a regular
|
|
|
3349 function and its @var{place} argument can actually be any Lisp
|
|
|
3350 expression.
|
|
|
3351 @end defun
|
|
|
3352
|
|
|
3353 @defspec remf place property
|
|
|
3354 This macro removes the property-value pair for @var{property} from
|
|
|
3355 the property list stored at @var{place}, which is any @code{setf}-able
|
|
|
3356 place expression. It returns true if the property was found. Note
|
|
|
3357 that if @var{property} happens to be first on the list, this will
|
|
|
3358 effectively do a @code{(setf @var{place} (cddr @var{place}))},
|
|
|
3359 whereas if it occurs later, this simply uses @code{setcdr} to splice
|
|
|
3360 out the property and value cells.
|
|
|
3361 @end defspec
|
|
|
3362
|
|
|
3363 @iftex
|
|
|
3364 @secno=2
|
|
|
3365 @end iftex
|
|
|
3366
|
|
|
3367 @node Creating Symbols, , Property Lists, Symbols
|
|
|
3368 @section Creating Symbols
|
|
|
3369
|
|
|
3370 @noindent
|
|
|
3371 These functions create unique symbols, typically for use as
|
|
|
3372 temporary variables.
|
|
|
3373
|
|
|
3374 @defun gensym &optional x
|
|
|
3375 This function creates a new, uninterned symbol (using @code{make-symbol})
|
|
|
3376 with a unique name. (The name of an uninterned symbol is relevant
|
|
|
3377 only if the symbol is printed.) By default, the name is generated
|
|
|
3378 from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
|
|
|
3379 @samp{G1002}, etc. If the optional argument @var{x} is a string, that
|
|
|
3380 string is used as a prefix instead of @samp{G}. Uninterned symbols
|
|
|
3381 are used in macro expansions for temporary variables, to ensure that
|
|
|
3382 their names will not conflict with ``real'' variables in the user's
|
|
|
3383 code.
|
|
|
3384 @end defun
|
|
|
3385
|
|
|
3386 @defvar *gensym-counter*
|
|
|
3387 This variable holds the counter used to generate @code{gensym} names.
|
|
|
3388 It is incremented after each use by @code{gensym}. In Common Lisp
|
|
|
3389 this is initialized with 0, but this package initializes it with a
|
|
|
3390 random (time-dependent) value to avoid trouble when two files that
|
|
|
3391 each used @code{gensym} in their compilation are loaded together.
|
|
|
3392
|
|
|
3393 @strong{XEmacs note:} As of XEmacs 21.0, an uninterned symbol remains
|
|
|
3394 uninterned even after being dumped to bytecode. Older versions of Emacs
|
|
|
3395 didn't distinguish the printed representation of interned and uninterned
|
|
|
3396 symbols, so their names had to be treated more carefully.
|
|
|
3397 @end defvar
|
|
|
3398
|
|
|
3399 @defun gentemp &optional x
|
|
|
3400 This function is like @code{gensym}, except that it produces a new
|
|
|
3401 @emph{interned} symbol. If the symbol that is generated already
|
|
|
3402 exists, the function keeps incrementing the counter and trying
|
|
|
3403 again until a new symbol is generated.
|
|
|
3404 @end defun
|
|
|
3405
|
|
|
3406 The Quiroz @file{cl.el} package also defined a @code{defkeyword}
|
|
|
3407 form for creating self-quoting keyword symbols. This package
|
|
|
3408 automatically creates all keywords that are called for by
|
|
|
3409 @code{&key} argument specifiers, and discourages the use of
|
|
|
3410 keywords as data unrelated to keyword arguments, so the
|
|
|
3411 @code{defkeyword} form has been discontinued.
|
|
|
3412
|
|
|
3413 @iftex
|
|
|
3414 @chapno=11
|
|
|
3415 @end iftex
|
|
|
3416
|
|
|
3417 @node Numbers, Sequences, Symbols, Top
|
|
|
3418 @chapter Numbers
|
|
|
3419
|
|
|
3420 @noindent
|
|
|
3421 This section defines a few simple Common Lisp operations on numbers
|
|
|
3422 which were left out of Emacs Lisp.
|
|
|
3423
|
|
|
3424 @menu
|
|
|
3425 * Predicates on Numbers:: `plusp', `oddp', `floatp-safe', etc.
|
|
|
3426 * Numerical Functions:: `abs', `expt', `floor*', etc.
|
|
|
3427 * Random Numbers:: `random*', `make-random-state'
|
|
|
3428 * Implementation Parameters:: `most-positive-fixnum', `most-positive-float'
|
|
|
3429 @end menu
|
|
|
3430
|
|
|
3431 @iftex
|
|
|
3432 @secno=1
|
|
|
3433 @end iftex
|
|
|
3434
|
|
|
3435 @node Predicates on Numbers, Numerical Functions, Numbers, Numbers
|
|
|
3436 @section Predicates on Numbers
|
|
|
3437
|
|
|
3438 @noindent
|
|
|
3439 These functions return @code{t} if the specified condition is
|
|
|
3440 true of the numerical argument, or @code{nil} otherwise.
|
|
|
3441
|
|
|
3442 @defun plusp number
|
|
|
3443 This predicate tests whether @var{number} is positive. It is an
|
|
|
3444 error if the argument is not a number.
|
|
|
3445 @end defun
|
|
|
3446
|
|
|
3447 @defun minusp number
|
|
|
3448 This predicate tests whether @var{number} is negative. It is an
|
|
|
3449 error if the argument is not a number.
|
|
|
3450 @end defun
|
|
|
3451
|
|
|
3452 @defun oddp integer
|
|
|
3453 This predicate tests whether @var{integer} is odd. It is an
|
|
|
3454 error if the argument is not an integer.
|
|
|
3455 @end defun
|
|
|
3456
|
|
|
3457 @defun evenp integer
|
|
|
3458 This predicate tests whether @var{integer} is even. It is an
|
|
|
3459 error if the argument is not an integer.
|
|
|
3460 @end defun
|
|
|
3461
|
|
|
3462 @defun floatp-safe object
|
|
|
3463 This predicate tests whether @var{object} is a floating-point
|
|
|
3464 number. On systems that support floating-point, this is equivalent
|
|
|
3465 to @code{floatp}. On other systems, this always returns @code{nil}.
|
|
|
3466 @end defun
|
|
|
3467
|
|
|
3468 @iftex
|
|
|
3469 @secno=3
|
|
|
3470 @end iftex
|
|
|
3471
|
|
|
3472 @node Numerical Functions, Random Numbers, Predicates on Numbers, Numbers
|
|
|
3473 @section Numerical Functions
|
|
|
3474
|
|
|
3475 @noindent
|
|
|
3476 These functions perform various arithmetic operations on numbers.
|
|
|
3477
|
|
|
3478 @defun abs number
|
|
|
3479 This function returns the absolute value of @var{number}. (Newer
|
|
|
3480 versions of Emacs provide this as a built-in function; this package
|
|
|
3481 defines @code{abs} only for Emacs 18 versions which don't provide
|
|
|
3482 it as a primitive.)
|
|
|
3483 @end defun
|
|
|
3484
|
|
|
3485 @defun expt base power
|
|
|
3486 This function returns @var{base} raised to the power of @var{number}.
|
|
|
3487 (Newer versions of Emacs provide this as a built-in function; this
|
|
|
3488 package defines @code{expt} only for Emacs 18 versions which don't
|
|
|
3489 provide it as a primitive.)
|
|
|
3490 @end defun
|
|
|
3491
|
|
|
3492 @defun gcd &rest integers
|
|
|
3493 This function returns the Greatest Common Divisor of the arguments.
|
|
|
3494 For one argument, it returns the absolute value of that argument.
|
|
|
3495 For zero arguments, it returns zero.
|
|
|
3496 @end defun
|
|
|
3497
|
|
|
3498 @defun lcm &rest integers
|
|
|
3499 This function returns the Least Common Multiple of the arguments.
|
|
|
3500 For one argument, it returns the absolute value of that argument.
|
|
|
3501 For zero arguments, it returns one.
|
|
|
3502 @end defun
|
|
|
3503
|
|
|
3504 @defun isqrt integer
|
|
|
3505 This function computes the ``integer square root'' of its integer
|
|
|
3506 argument, i.e., the greatest integer less than or equal to the true
|
|
|
3507 square root of the argument.
|
|
|
3508 @end defun
|
|
|
3509
|
|
|
3510 @defun floor* number &optional divisor
|
|
|
3511 This function implements the Common Lisp @code{floor} function.
|
|
|
3512 It is called @code{floor*} to avoid name conflicts with the
|
|
|
3513 simpler @code{floor} function built-in to Emacs 19.
|
|
|
3514
|
|
|
3515 With one argument, @code{floor*} returns a list of two numbers:
|
|
|
3516 The argument rounded down (toward minus infinity) to an integer,
|
|
|
3517 and the ``remainder'' which would have to be added back to the
|
|
|
3518 first return value to yield the argument again. If the argument
|
|
|
3519 is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
|
|
|
3520 If the argument is an Emacs 19 floating-point number, the first
|
|
|
3521 result is a Lisp integer and the second is a Lisp float between
|
|
|
3522 0 (inclusive) and 1 (exclusive).
|
|
|
3523
|
|
|
3524 With two arguments, @code{floor*} divides @var{number} by
|
|
|
3525 @var{divisor}, and returns the floor of the quotient and the
|
|
|
3526 corresponding remainder as a list of two numbers. If
|
|
|
3527 @code{(floor* @var{x} @var{y})} returns @code{(@var{q} @var{r})},
|
|
|
3528 then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r}
|
|
|
3529 between 0 (inclusive) and @var{r} (exclusive). Also, note
|
|
|
3530 that @code{(floor* @var{x})} is exactly equivalent to
|
|
|
3531 @code{(floor* @var{x} 1)}.
|
|
|
3532
|
|
|
3533 This function is entirely compatible with Common Lisp's @code{floor}
|
|
|
3534 function, except that it returns the two results in a list since
|
|
|
3535 Emacs Lisp does not support multiple-valued functions.
|
|
|
3536 @end defun
|
|
|
3537
|
|
|
3538 @defun ceiling* number &optional divisor
|
|
|
3539 This function implements the Common Lisp @code{ceiling} function,
|
|
|
3540 which is analogous to @code{floor} except that it rounds the
|
|
|
3541 argument or quotient of the arguments up toward plus infinity.
|
|
|
3542 The remainder will be between 0 and minus @var{r}.
|
|
|
3543 @end defun
|
|
|
3544
|
|
|
3545 @defun truncate* number &optional divisor
|
|
|
3546 This function implements the Common Lisp @code{truncate} function,
|
|
|
3547 which is analogous to @code{floor} except that it rounds the
|
|
|
3548 argument or quotient of the arguments toward zero. Thus it is
|
|
|
3549 equivalent to @code{floor*} if the argument or quotient is
|
|
|
3550 positive, or to @code{ceiling*} otherwise. The remainder has
|
|
|
3551 the same sign as @var{number}.
|
|
|
3552 @end defun
|
|
|
3553
|
|
|
3554 @defun round* number &optional divisor
|
|
|
3555 This function implements the Common Lisp @code{round} function,
|
|
|
3556 which is analogous to @code{floor} except that it rounds the
|
|
|
3557 argument or quotient of the arguments to the nearest integer.
|
|
|
3558 In the case of a tie (the argument or quotient is exactly
|
|
|
3559 halfway between two integers), it rounds to the even integer.
|
|
|
3560 @end defun
|
|
|
3561
|
|
|
3562 @defun mod* number divisor
|
|
|
3563 This function returns the same value as the second return value
|
|
|
3564 of @code{floor}.
|
|
|
3565 @end defun
|
|
|
3566
|
|
|
3567 @defun rem* number divisor
|
|
|
3568 This function returns the same value as the second return value
|
|
|
3569 of @code{truncate}.
|
|
|
3570 @end defun
|
|
|
3571
|
|
|
3572 These definitions are compatible with those in the Quiroz
|
|
|
3573 @file{cl.el} package, except that this package appends @samp{*}
|
|
|
3574 to certain function names to avoid conflicts with existing
|
|
|
3575 Emacs 19 functions, and that the mechanism for returning
|
|
|
3576 multiple values is different.
|
|
|
3577
|
|
|
3578 @iftex
|
|
|
3579 @secno=8
|
|
|
3580 @end iftex
|
|
|
3581
|
|
|
3582 @node Random Numbers, Implementation Parameters, Numerical Functions, Numbers
|
|
|
3583 @section Random Numbers
|
|
|
3584
|
|
|
3585 @noindent
|
|
|
3586 This package also provides an implementation of the Common Lisp
|
|
|
3587 random number generator. It uses its own additive-congruential
|
|
|
3588 algorithm, which is much more likely to give statistically clean
|
|
|
3589 random numbers than the simple generators supplied by many
|
|
|
3590 operating systems.
|
|
|
3591
|
|
|
3592 @defun random* number &optional state
|
|
|
3593 This function returns a random nonnegative number less than
|
|
|
3594 @var{number}, and of the same type (either integer or floating-point).
|
|
|
3595 The @var{state} argument should be a @code{random-state} object
|
|
|
3596 which holds the state of the random number generator. The
|
|
|
3597 function modifies this state object as a side effect. If
|
|
|
3598 @var{state} is omitted, it defaults to the variable
|
|
|
3599 @code{*random-state*}, which contains a pre-initialized
|
|
|
3600 @code{random-state} object.
|
|
|
3601 @end defun
|
|
|
3602
|
|
|
3603 @defvar *random-state*
|
|
|
3604 This variable contains the system ``default'' @code{random-state}
|
|
|
3605 object, used for calls to @code{random*} that do not specify an
|
|
|
3606 alternative state object. Since any number of programs in the
|
|
|
3607 Emacs process may be accessing @code{*random-state*} in interleaved
|
|
|
3608 fashion, the sequence generated from this variable will be
|
|
|
3609 irreproducible for all intents and purposes.
|
|
|
3610 @end defvar
|
|
|
3611
|
|
|
3612 @defun make-random-state &optional state
|
|
|
3613 This function creates or copies a @code{random-state} object.
|
|
|
3614 If @var{state} is omitted or @code{nil}, it returns a new copy of
|
|
|
3615 @code{*random-state*}. This is a copy in the sense that future
|
|
|
3616 sequences of calls to @code{(random* @var{n})} and
|
|
|
3617 @code{(random* @var{n} @var{s})} (where @var{s} is the new
|
|
|
3618 random-state object) will return identical sequences of random
|
|
|
3619 numbers.
|
|
|
3620
|
|
|
3621 If @var{state} is a @code{random-state} object, this function
|
|
|
3622 returns a copy of that object. If @var{state} is @code{t}, this
|
|
|
3623 function returns a new @code{random-state} object seeded from the
|
|
|
3624 date and time. As an extension to Common Lisp, @var{state} may also
|
|
|
3625 be an integer in which case the new object is seeded from that
|
|
|
3626 integer; each different integer seed will result in a completely
|
|
|
3627 different sequence of random numbers.
|
|
|
3628
|
|
|
3629 It is legal to print a @code{random-state} object to a buffer or
|
|
|
3630 file and later read it back with @code{read}. If a program wishes
|
|
|
3631 to use a sequence of pseudo-random numbers which can be reproduced
|
|
|
3632 later for debugging, it can call @code{(make-random-state t)} to
|
|
|
3633 get a new sequence, then print this sequence to a file. When the
|
|
|
3634 program is later rerun, it can read the original run's random-state
|
|
|
3635 from the file.
|
|
|
3636 @end defun
|
|
|
3637
|
|
|
3638 @defun random-state-p object
|
|
|
3639 This predicate returns @code{t} if @var{object} is a
|
|
|
3640 @code{random-state} object, or @code{nil} otherwise.
|
|
|
3641 @end defun
|
|
|
3642
|
|
|
3643 @node Implementation Parameters, , Random Numbers, Numbers
|
|
|
3644 @section Implementation Parameters
|
|
|
3645
|
|
|
3646 @noindent
|
|
|
3647 This package defines several useful constants having to with numbers.
|
|
|
3648
|
|
|
3649 @defvar most-positive-fixnum
|
|
|
3650 This constant equals the largest value a Lisp integer can hold.
|
|
|
3651 It is typically @code{2^23-1} or @code{2^25-1}.
|
|
|
3652 @end defvar
|
|
|
3653
|
|
|
3654 @defvar most-negative-fixnum
|
|
|
3655 This constant equals the smallest (most negative) value a Lisp
|
|
|
3656 integer can hold.
|
|
|
3657 @end defvar
|
|
|
3658
|
|
|
3659 The following parameters have to do with floating-point numbers.
|
|
|
3660 This package determines their values by exercising the computer's
|
|
|
3661 floating-point arithmetic in various ways. Because this operation
|
|
|
3662 might be slow, the code for initializing them is kept in a separate
|
|
|
3663 function that must be called before the parameters can be used.
|
|
|
3664
|
|
|
3665 @defun cl-float-limits
|
|
|
3666 This function makes sure that the Common Lisp floating-point
|
|
|
3667 parameters like @code{most-positive-float} have been initialized.
|
|
|
3668 Until it is called, these parameters will be @code{nil}. If this
|
|
|
3669 version of Emacs does not support floats (e.g., most versions of
|
|
|
3670 Emacs 18), the parameters will remain @code{nil}. If the parameters
|
|
|
3671 have already been initialized, the function returns immediately.
|
|
|
3672
|
|
|
3673 The algorithm makes assumptions that will be valid for most modern
|
|
|
3674 machines, but will fail if the machine's arithmetic is extremely
|
|
|
3675 unusual, e.g., decimal.
|
|
|
3676 @end defun
|
|
|
3677
|
|
|
3678 Since true Common Lisp supports up to four different floating-point
|
|
|
3679 precisions, it has families of constants like
|
|
|
3680 @code{most-positive-single-float}, @code{most-positive-double-float},
|
|
|
3681 @code{most-positive-long-float}, and so on. Emacs has only one
|
|
|
3682 floating-point precision, so this package omits the precision word
|
|
|
3683 from the constants' names.
|
|
|
3684
|
|
|
3685 @defvar most-positive-float
|
|
|
3686 This constant equals the largest value a Lisp float can hold.
|
|
|
3687 For those systems whose arithmetic supports infinities, this is
|
|
|
3688 the largest @emph{finite} value. For IEEE machines, the value
|
|
|
3689 is approximately @code{1.79e+308}.
|
|
|
3690 @end defvar
|
|
|
3691
|
|
|
3692 @defvar most-negative-float
|
|
|
3693 This constant equals the most-negative value a Lisp float can hold.
|
|
|
3694 (It is assumed to be equal to @code{(- most-positive-float)}.)
|
|
|
3695 @end defvar
|
|
|
3696
|
|
|
3697 @defvar least-positive-float
|
|
|
3698 This constant equals the smallest Lisp float value greater than zero.
|
|
|
3699 For IEEE machines, it is about @code{4.94e-324} if denormals are
|
|
|
3700 supported or @code{2.22e-308} if not.
|
|
|
3701 @end defvar
|
|
|
3702
|
|
|
3703 @defvar least-positive-normalized-float
|
|
|
3704 This constant equals the smallest @emph{normalized} Lisp float greater
|
|
|
3705 than zero, i.e., the smallest value for which IEEE denormalization
|
|
|
3706 will not result in a loss of precision. For IEEE machines, this
|
|
|
3707 value is about @code{2.22e-308}. For machines that do not support
|
|
|
3708 the concept of denormalization and gradual underflow, this constant
|
|
|
3709 will always equal @code{least-positive-float}.
|
|
|
3710 @end defvar
|
|
|
3711
|
|
|
3712 @defvar least-negative-float
|
|
|
3713 This constant is the negative counterpart of @code{least-positive-float}.
|
|
|
3714 @end defvar
|
|
|
3715
|
|
|
3716 @defvar least-negative-normalized-float
|
|
|
3717 This constant is the negative counterpart of
|
|
|
3718 @code{least-positive-normalized-float}.
|
|
|
3719 @end defvar
|
|
|
3720
|
|
|
3721 @defvar float-epsilon
|
|
|
3722 This constant is the smallest positive Lisp float that can be added
|
|
|
3723 to 1.0 to produce a distinct value. Adding a smaller number to 1.0
|
|
|
3724 will yield 1.0 again due to roundoff. For IEEE machines, epsilon
|
|
|
3725 is about @code{2.22e-16}.
|
|
|
3726 @end defvar
|
|
|
3727
|
|
|
3728 @defvar float-negative-epsilon
|
|
|
3729 This is the smallest positive value that can be subtracted from
|
|
|
3730 1.0 to produce a distinct value. For IEEE machines, it is about
|
|
|
3731 @code{1.11e-16}.
|
|
|
3732 @end defvar
|
|
|
3733
|
|
|
3734 @iftex
|
|
|
3735 @chapno=13
|
|
|
3736 @end iftex
|
|
|
3737
|
|
|
3738 @node Sequences, Lists, Numbers, Top
|
|
|
3739 @chapter Sequences
|
|
|
3740
|
|
|
3741 @noindent
|
|
|
3742 Common Lisp defines a number of functions that operate on
|
|
|
3743 @dfn{sequences}, which are either lists, strings, or vectors.
|
|
|
3744 Emacs Lisp includes a few of these, notably @code{elt} and
|
|
|
3745 @code{length}; this package defines most of the rest.
|
|
|
3746
|
|
|
3747 @menu
|
|
|
3748 * Sequence Basics:: Arguments shared by all sequence functions
|
|
|
3749 * Mapping over Sequences:: `mapcar*', `mapcan', `map', `every', etc.
|
|
|
3750 * Sequence Functions:: `subseq', `remove*', `substitute', etc.
|
|
|
3751 * Searching Sequences:: `find', `position', `count', `search', etc.
|
|
|
3752 * Sorting Sequences:: `sort*', `stable-sort', `merge'
|
|
|
3753 @end menu
|
|
|
3754
|
|
|
3755 @node Sequence Basics, Mapping over Sequences, Sequences, Sequences
|
|
|
3756 @section Sequence Basics
|
|
|
3757
|
|
778
|
3758 @noindent Many of the sequence functions take keyword arguments;
|
|
|
3759 @pxref{Argument Lists}. All keyword arguments are optional and, if
|
|
|
3760 specified, may appear in any order.
|
|
428
|
3761
|
|
|
3762 The @code{:key} argument should be passed either @code{nil}, or a
|
|
|
3763 function of one argument. This key function is used as a filter
|
|
|
3764 through which the elements of the sequence are seen; for example,
|
|
|
3765 @code{(find x y :key 'car)} is similar to @code{(assoc* x y)}:
|
|
|
3766 It searches for an element of the list whose @code{car} equals
|
|
|
3767 @code{x}, rather than for an element which equals @code{x} itself.
|
|
|
3768 If @code{:key} is omitted or @code{nil}, the filter is effectively
|
|
|
3769 the identity function.
|
|
|
3770
|
|
|
3771 The @code{:test} and @code{:test-not} arguments should be either
|
|
|
3772 @code{nil}, or functions of two arguments. The test function is
|
|
|
3773 used to compare two sequence elements, or to compare a search value
|
|
|
3774 with sequence elements. (The two values are passed to the test
|
|
|
3775 function in the same order as the original sequence function
|
|
|
3776 arguments from which they are derived, or, if they both come from
|
|
|
3777 the same sequence, in the same order as they appear in that sequence.)
|
|
|
3778 The @code{:test} argument specifies a function which must return
|
|
|
3779 true (non-@code{nil}) to indicate a match; instead, you may use
|
|
|
3780 @code{:test-not} to give a function which returns @emph{false} to
|
|
|
3781 indicate a match. The default test function is @code{:test 'eql}.
|
|
|
3782
|
|
|
3783 Many functions which take @var{item} and @code{:test} or @code{:test-not}
|
|
|
3784 arguments also come in @code{-if} and @code{-if-not} varieties,
|
|
|
3785 where a @var{predicate} function is passed instead of @var{item},
|
|
|
3786 and sequence elements match if the predicate returns true on them
|
|
|
3787 (or false in the case of @code{-if-not}). For example:
|
|
|
3788
|
|
|
3789 @example
|
|
|
3790 (remove* 0 seq :test '=) @equiv{} (remove-if 'zerop seq)
|
|
|
3791 @end example
|
|
|
3792
|
|
|
3793 @noindent
|
|
|
3794 to remove all zeros from sequence @code{seq}.
|
|
|
3795
|
|
|
3796 Some operations can work on a subsequence of the argument sequence;
|
|
|
3797 these function take @code{:start} and @code{:end} arguments which
|
|
|
3798 default to zero and the length of the sequence, respectively.
|
|
|
3799 Only elements between @var{start} (inclusive) and @var{end}
|
|
|
3800 (exclusive) are affected by the operation. The @var{end} argument
|
|
|
3801 may be passed @code{nil} to signify the length of the sequence;
|
|
|
3802 otherwise, both @var{start} and @var{end} must be integers, with
|
|
|
3803 @code{0 <= @var{start} <= @var{end} <= (length @var{seq})}.
|
|
|
3804 If the function takes two sequence arguments, the limits are
|
|
|
3805 defined by keywords @code{:start1} and @code{:end1} for the first,
|
|
|
3806 and @code{:start2} and @code{:end2} for the second.
|
|
|
3807
|
|
|
3808 A few functions accept a @code{:from-end} argument, which, if
|
|
|
3809 non-@code{nil}, causes the operation to go from right-to-left
|
|
|
3810 through the sequence instead of left-to-right, and a @code{:count}
|
|
|
3811 argument, which specifies an integer maximum number of elements
|
|
|
3812 to be removed or otherwise processed.
|
|
|
3813
|
|
|
3814 The sequence functions make no guarantees about the order in
|
|
|
3815 which the @code{:test}, @code{:test-not}, and @code{:key} functions
|
|
|
3816 are called on various elements. Therefore, it is a bad idea to depend
|
|
|
3817 on side effects of these functions. For example, @code{:from-end}
|
|
|
3818 may cause the sequence to be scanned actually in reverse, or it may
|
|
|
3819 be scanned forwards but computing a result ``as if'' it were scanned
|
|
|
3820 backwards. (Some functions, like @code{mapcar*} and @code{every},
|
|
|
3821 @emph{do} specify exactly the order in which the function is called
|
|
|
3822 so side effects are perfectly acceptable in those cases.)
|
|
|
3823
|
|
|
3824 Strings in GNU Emacs 19 may contain ``text properties'' as well
|
|
|
3825 as character data. Except as noted, it is undefined whether or
|
|
|
3826 not text properties are preserved by sequence functions. For
|
|
|
3827 example, @code{(remove* ?A @var{str})} may or may not preserve
|
|
|
3828 the properties of the characters copied from @var{str} into the
|
|
|
3829 result.
|
|
|
3830
|
|
|
3831 @node Mapping over Sequences, Sequence Functions, Sequence Basics, Sequences
|
|
|
3832 @section Mapping over Sequences
|
|
|
3833
|
|
|
3834 @noindent
|
|
|
3835 These functions ``map'' the function you specify over the elements
|
|
|
3836 of lists or arrays. They are all variations on the theme of the
|
|
|
3837 built-in function @code{mapcar}.
|
|
|
3838
|
|
|
3839 @defun mapcar* function seq &rest more-seqs
|
|
|
3840 This function calls @var{function} on successive parallel sets of
|
|
|
3841 elements from its argument sequences. Given a single @var{seq}
|
|
|
3842 argument it is equivalent to @code{mapcar}; given @var{n} sequences,
|
|
|
3843 it calls the function with the first elements of each of the sequences
|
|
|
3844 as the @var{n} arguments to yield the first element of the result
|
|
|
3845 list, then with the second elements, and so on. The mapping stops as
|
|
|
3846 soon as the shortest sequence runs out. The argument sequences may
|
|
|
3847 be any mixture of lists, strings, and vectors; the return sequence
|
|
|
3848 is always a list.
|
|
|
3849
|
|
|
3850 Common Lisp's @code{mapcar} accepts multiple arguments but works
|
|
|
3851 only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
|
|
|
3852 argument. This package's @code{mapcar*} works as a compatible
|
|
|
3853 superset of both.
|
|
|
3854 @end defun
|
|
|
3855
|
|
|
3856 @defun map result-type function seq &rest more-seqs
|
|
|
3857 This function maps @var{function} over the argument sequences,
|
|
|
3858 just like @code{mapcar*}, but it returns a sequence of type
|
|
|
3859 @var{result-type} rather than a list. @var{result-type} must
|
|
|
3860 be one of the following symbols: @code{vector}, @code{string},
|
|
|
3861 @code{list} (in which case the effect is the same as for
|
|
|
3862 @code{mapcar*}), or @code{nil} (in which case the results are
|
|
|
3863 thrown away and @code{map} returns @code{nil}).
|
|
|
3864 @end defun
|
|
|
3865
|
|
|
3866 @defun maplist function list &rest more-lists
|
|
|
3867 This function calls @var{function} on each of its argument lists,
|
|
|
3868 then on the @code{cdr}s of those lists, and so on, until the
|
|
|
3869 shortest list runs out. The results are returned in the form
|
|
|
3870 of a list. Thus, @code{maplist} is like @code{mapcar*} except
|
|
|
3871 that it passes in the list pointers themselves rather than the
|
|
|
3872 @code{car}s of the advancing pointers.
|
|
|
3873 @end defun
|
|
|
3874
|
|
|
3875 @defun mapc function seq &rest more-seqs
|
|
|
3876 This function is like @code{mapcar*}, except that the values
|
|
|
3877 returned by @var{function} are ignored and thrown away rather
|
|
|
3878 than being collected into a list. The return value of @code{mapc}
|
|
|
3879 is @var{seq}, the first sequence.
|
|
|
3880 @end defun
|
|
|
3881
|
|
|
3882 @defun mapl function list &rest more-lists
|
|
|
3883 This function is like @code{maplist}, except that it throws away
|
|
|
3884 the values returned by @var{function}.
|
|
|
3885 @end defun
|
|
|
3886
|
|
|
3887 @defun mapcan function seq &rest more-seqs
|
|
|
3888 This function is like @code{mapcar*}, except that it concatenates
|
|
|
3889 the return values (which must be lists) using @code{nconc},
|
|
|
3890 rather than simply collecting them into a list.
|
|
|
3891 @end defun
|
|
|
3892
|
|
|
3893 @defun mapcon function list &rest more-lists
|
|
|
3894 This function is like @code{maplist}, except that it concatenates
|
|
|
3895 the return values using @code{nconc}.
|
|
|
3896 @end defun
|
|
|
3897
|
|
|
3898 @defun some predicate seq &rest more-seqs
|
|
|
3899 This function calls @var{predicate} on each element of @var{seq}
|
|
|
3900 in turn; if @var{predicate} returns a non-@code{nil} value,
|
|
|
3901 @code{some} returns that value, otherwise it returns @code{nil}.
|
|
|
3902 Given several sequence arguments, it steps through the sequences
|
|
|
3903 in parallel until the shortest one runs out, just as in
|
|
|
3904 @code{mapcar*}. You can rely on the left-to-right order in which
|
|
|
3905 the elements are visited, and on the fact that mapping stops
|
|
|
3906 immediately as soon as @var{predicate} returns non-@code{nil}.
|
|
|
3907 @end defun
|
|
|
3908
|
|
|
3909 @defun every predicate seq &rest more-seqs
|
|
|
3910 This function calls @var{predicate} on each element of the sequence(s)
|
|
|
3911 in turn; it returns @code{nil} as soon as @var{predicate} returns
|
|
|
3912 @code{nil} for any element, or @code{t} if the predicate was true
|
|
|
3913 for all elements.
|
|
|
3914 @end defun
|
|
|
3915
|
|
|
3916 @defun notany predicate seq &rest more-seqs
|
|
|
3917 This function calls @var{predicate} on each element of the sequence(s)
|
|
|
3918 in turn; it returns @code{nil} as soon as @var{predicate} returns
|
|
|
3919 a non-@code{nil} value for any element, or @code{t} if the predicate
|
|
|
3920 was @code{nil} for all elements.
|
|
|
3921 @end defun
|
|
|
3922
|
|
|
3923 @defun notevery predicate seq &rest more-seqs
|
|
|
3924 This function calls @var{predicate} on each element of the sequence(s)
|
|
|
3925 in turn; it returns a non-@code{nil} value as soon as @var{predicate}
|
|
|
3926 returns @code{nil} for any element, or @code{t} if the predicate was
|
|
|
3927 true for all elements.
|
|
|
3928 @end defun
|
|
|
3929
|
|
|
3930 @defun reduce function seq @t{&key :from-end :start :end :initial-value :key}
|
|
|
3931 This function combines the elements of @var{seq} using an associative
|
|
|
3932 binary operation. Suppose @var{function} is @code{*} and @var{seq} is
|
|
|
3933 the list @code{(2 3 4 5)}. The first two elements of the list are
|
|
|
3934 combined with @code{(* 2 3) = 6}; this is combined with the next
|
|
|
3935 element, @code{(* 6 4) = 24}, and that is combined with the final
|
|
|
3936 element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
|
|
|
3937 to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
|
|
|
3938 an explicit call to @code{reduce}.
|
|
|
3939
|
|
|
3940 If @code{:from-end} is true, the reduction is right-associative instead
|
|
|
3941 of left-associative:
|
|
|
3942
|
|
|
3943 @example
|
|
|
3944 (reduce '- '(1 2 3 4))
|
|
|
3945 @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
|
|
|
3946 (reduce '- '(1 2 3 4) :from-end t)
|
|
|
3947 @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
|
|
|
3948 @end example
|
|
|
3949
|
|
|
3950 If @code{:key} is specified, it is a function of one argument which
|
|
|
3951 is called on each of the sequence elements in turn.
|
|
|
3952
|
|
|
3953 If @code{:initial-value} is specified, it is effectively added to the
|
|
|
3954 front (or rear in the case of @code{:from-end}) of the sequence.
|
|
|
3955 The @code{:key} function is @emph{not} applied to the initial value.
|
|
|
3956
|
|
|
3957 If the sequence, including the initial value, has exactly one element
|
|
|
3958 then that element is returned without ever calling @var{function}.
|
|
|
3959 If the sequence is empty (and there is no initial value), then
|
|
|
3960 @var{function} is called with no arguments to obtain the return value.
|
|
|
3961 @end defun
|
|
|
3962
|
|
|
3963 All of these mapping operations can be expressed conveniently in
|
|
|
3964 terms of the @code{loop} macro. In compiled code, @code{loop} will
|
|
|
3965 be faster since it generates the loop as in-line code with no
|
|
|
3966 function calls.
|
|
|
3967
|
|
|
3968 @node Sequence Functions, Searching Sequences, Mapping over Sequences, Sequences
|
|
|
3969 @section Sequence Functions
|
|
|
3970
|
|
|
3971 @noindent
|
|
|
3972 This section describes a number of Common Lisp functions for
|
|
|
3973 operating on sequences.
|
|
|
3974
|
|
|
3975 @defun subseq sequence start &optional end
|
|
|
3976 This function returns a given subsequence of the argument
|
|
|
3977 @var{sequence}, which may be a list, string, or vector.
|
|
|
3978 The indices @var{start} and @var{end} must be in range, and
|
|
|
3979 @var{start} must be no greater than @var{end}. If @var{end}
|
|
|
3980 is omitted, it defaults to the length of the sequence. The
|
|
|
3981 return value is always a copy; it does not share structure
|
|
|
3982 with @var{sequence}.
|
|
|
3983
|
|
|
3984 As an extension to Common Lisp, @var{start} and/or @var{end}
|
|
|
3985 may be negative, in which case they represent a distance back
|
|
|
3986 from the end of the sequence. This is for compatibility with
|
|
|
3987 Emacs' @code{substring} function. Note that @code{subseq} is
|
|
|
3988 the @emph{only} sequence function that allows negative
|
|
|
3989 @var{start} and @var{end}.
|
|
|
3990
|
|
|
3991 You can use @code{setf} on a @code{subseq} form to replace a
|
|
|
3992 specified range of elements with elements from another sequence.
|
|
|
3993 The replacement is done as if by @code{replace}, described below.
|
|
|
3994 @end defun
|
|
|
3995
|
|
|
3996 @defun concatenate result-type &rest seqs
|
|
|
3997 This function concatenates the argument sequences together to
|
|
|
3998 form a result sequence of type @var{result-type}, one of the
|
|
|
3999 symbols @code{vector}, @code{string}, or @code{list}. The
|
|
|
4000 arguments are always copied, even in cases such as
|
|
|
4001 @code{(concatenate 'list '(1 2 3))} where the result is
|
|
|
4002 identical to an argument.
|
|
|
4003 @end defun
|
|
|
4004
|
|
|
4005 @defun fill seq item @t{&key :start :end}
|
|
|
4006 This function fills the elements of the sequence (or the specified
|
|
|
4007 part of the sequence) with the value @var{item}.
|
|
|
4008 @end defun
|
|
|
4009
|
|
|
4010 @defun replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
|
|
|
4011 This function copies part of @var{seq2} into part of @var{seq1}.
|
|
|
4012 The sequence @var{seq1} is not stretched or resized; the amount
|
|
|
4013 of data copied is simply the shorter of the source and destination
|
|
|
4014 (sub)sequences. The function returns @var{seq1}.
|
|
|
4015
|
|
|
4016 If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
|
|
|
4017 will work correctly even if the regions indicated by the start
|
|
|
4018 and end arguments overlap. However, if @var{seq1} and @var{seq2}
|
|
|
4019 are lists which share storage but are not @code{eq}, and the
|
|
|
4020 start and end arguments specify overlapping regions, the effect
|
|
|
4021 is undefined.
|
|
|
4022 @end defun
|
|
|
4023
|
|
|
4024 @defun remove* item seq @t{&key :test :test-not :key :count :start :end :from-end}
|
|
|
4025 This returns a copy of @var{seq} with all elements matching
|
|
|
4026 @var{item} removed. The result may share storage with or be
|
|
|
4027 @code{eq} to @var{seq} in some circumstances, but the original
|
|
|
4028 @var{seq} will not be modified. The @code{:test}, @code{:test-not},
|
|
|
4029 and @code{:key} arguments define the matching test that is used;
|
|
|
4030 by default, elements @code{eql} to @var{item} are removed. The
|
|
|
4031 @code{:count} argument specifies the maximum number of matching
|
|
|
4032 elements that can be removed (only the leftmost @var{count} matches
|
|
|
4033 are removed). The @code{:start} and @code{:end} arguments specify
|
|
|
4034 a region in @var{seq} in which elements will be removed; elements
|
|
|
4035 outside that region are not matched or removed. The @code{:from-end}
|
|
|
4036 argument, if true, says that elements should be deleted from the
|
|
|
4037 end of the sequence rather than the beginning (this matters only
|
|
|
4038 if @var{count} was also specified).
|
|
|
4039 @end defun
|
|
|
4040
|
|
|
4041 @defun delete* item seq @t{&key :test :test-not :key :count :start :end :from-end}
|
|
|
4042 This deletes all elements of @var{seq} which match @var{item}.
|
|
|
4043 It is a destructive operation. Since Emacs Lisp does not support
|
|
|
4044 stretchable strings or vectors, this is the same as @code{remove*}
|
|
|
4045 for those sequence types. On lists, @code{remove*} will copy the
|
|
|
4046 list if necessary to preserve the original list, whereas
|
|
|
4047 @code{delete*} will splice out parts of the argument list.
|
|
|
4048 Compare @code{append} and @code{nconc}, which are analogous
|
|
|
4049 non-destructive and destructive list operations in Emacs Lisp.
|
|
|
4050 @end defun
|
|
|
4051
|
|
|
4052 @findex remove-if
|
|
|
4053 @findex remove-if-not
|
|
|
4054 @findex delete-if
|
|
|
4055 @findex delete-if-not
|
|
|
4056 The predicate-oriented functions @code{remove-if}, @code{remove-if-not},
|
|
|
4057 @code{delete-if}, and @code{delete-if-not} are defined similarly.
|
|
|
4058
|
|
|
4059 @defun delete item list
|
|
|
4060 This MacLisp-compatible function deletes from @var{list} all elements
|
|
|
4061 which are @code{equal} to @var{item}. The @code{delete} function is
|
|
|
4062 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
|
|
|
4063 @end defun
|
|
|
4064
|
|
|
4065 @defun remove item list
|
|
|
4066 This function removes from @var{list} all elements which are
|
|
|
4067 @code{equal} to @var{item}. This package defines it for symmetry
|
|
|
4068 with @code{delete}, even though @code{remove} is not built-in to
|
|
|
4069 Emacs 19.
|
|
|
4070 @end defun
|
|
|
4071
|
|
|
4072 @defun remq item list
|
|
|
4073 This function removes from @var{list} all elements which are
|
|
|
4074 @code{eq} to @var{item}. This package defines it for symmetry
|
|
|
4075 with @code{delq}, even though @code{remq} is not built-in to
|
|
|
4076 Emacs 19.
|
|
|
4077 @end defun
|
|
|
4078
|
|
|
4079 @defun remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
|
|
|
4080 This function returns a copy of @var{seq} with duplicate elements
|
|
|
4081 removed. Specifically, if two elements from the sequence match
|
|
|
4082 according to the @code{:test}, @code{:test-not}, and @code{:key}
|
|
|
4083 arguments, only the rightmost one is retained. If @code{:from-end}
|
|
|
4084 is true, the leftmost one is retained instead. If @code{:start} or
|
|
|
4085 @code{:end} is specified, only elements within that subsequence are
|
|
|
4086 examined or removed.
|
|
|
4087 @end defun
|
|
|
4088
|
|
|
4089 @defun delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end}
|
|
|
4090 This function deletes duplicate elements from @var{seq}. It is
|
|
|
4091 a destructive version of @code{remove-duplicates}.
|
|
|
4092 @end defun
|
|
|
4093
|
|
|
4094 @defun substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
|
|
|
4095 This function returns a copy of @var{seq}, with all elements
|
|
|
4096 matching @var{old} replaced with @var{new}. The @code{:count},
|
|
|
4097 @code{:start}, @code{:end}, and @code{:from-end} arguments may be
|
|
|
4098 used to limit the number of substitutions made.
|
|
|
4099 @end defun
|
|
|
4100
|
|
|
4101 @defun nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end}
|
|
|
4102 This is a destructive version of @code{substitute}; it performs
|
|
|
4103 the substitution using @code{setcar} or @code{aset} rather than
|
|
|
4104 by returning a changed copy of the sequence.
|
|
|
4105 @end defun
|
|
|
4106
|
|
|
4107 @findex substitute-if
|
|
|
4108 @findex substitute-if-not
|
|
|
4109 @findex nsubstitute-if
|
|
|
4110 @findex nsubstitute-if-not
|
|
|
4111 The @code{substitute-if}, @code{substitute-if-not}, @code{nsubstitute-if},
|
|
|
4112 and @code{nsubstitute-if-not} functions are defined similarly. For
|
|
|
4113 these, a @var{predicate} is given in place of the @var{old} argument.
|
|
|
4114
|
|
|
4115 @node Searching Sequences, Sorting Sequences, Sequence Functions, Sequences
|
|
|
4116 @section Searching Sequences
|
|
|
4117
|
|
|
4118 @noindent
|
|
|
4119 These functions search for elements or subsequences in a sequence.
|
|
|
4120 (See also @code{member*} and @code{assoc*}; @pxref{Lists}.)
|
|
|
4121
|
|
|
4122 @defun find item seq @t{&key :test :test-not :key :start :end :from-end}
|
|
|
4123 This function searches @var{seq} for an element matching @var{item}.
|
|
|
4124 If it finds a match, it returns the matching element. Otherwise,
|
|
|
4125 it returns @code{nil}. It returns the leftmost match, unless
|
|
|
4126 @code{:from-end} is true, in which case it returns the rightmost
|
|
|
4127 match. The @code{:start} and @code{:end} arguments may be used to
|
|
|
4128 limit the range of elements that are searched.
|
|
|
4129 @end defun
|
|
|
4130
|
|
|
4131 @defun position item seq @t{&key :test :test-not :key :start :end :from-end}
|
|
|
4132 This function is like @code{find}, except that it returns the
|
|
|
4133 integer position in the sequence of the matching item rather than
|
|
|
4134 the item itself. The position is relative to the start of the
|
|
|
4135 sequence as a whole, even if @code{:start} is non-zero. The function
|
|
|
4136 returns @code{nil} if no matching element was found.
|
|
|
4137 @end defun
|
|
|
4138
|
|
|
4139 @defun count item seq @t{&key :test :test-not :key :start :end}
|
|
|
4140 This function returns the number of elements of @var{seq} which
|
|
|
4141 match @var{item}. The result is always a nonnegative integer.
|
|
|
4142 @end defun
|
|
|
4143
|
|
|
4144 @findex find-if
|
|
|
4145 @findex find-if-not
|
|
|
4146 @findex position-if
|
|
|
4147 @findex position-if-not
|
|
|
4148 @findex count-if
|
|
|
4149 @findex count-if-not
|
|
|
4150 The @code{find-if}, @code{find-if-not}, @code{position-if},
|
|
|
4151 @code{position-if-not}, @code{count-if}, and @code{count-if-not}
|
|
|
4152 functions are defined similarly.
|
|
|
4153
|
|
|
4154 @defun mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end}
|
|
|
4155 This function compares the specified parts of @var{seq1} and
|
|
|
4156 @var{seq2}. If they are the same length and the corresponding
|
|
|
4157 elements match (according to @code{:test}, @code{:test-not},
|
|
|
4158 and @code{:key}), the function returns @code{nil}. If there is
|
|
|
4159 a mismatch, the function returns the index (relative to @var{seq1})
|
|
|
4160 of the first mismatching element. This will be the leftmost pair of
|
|
|
4161 elements which do not match, or the position at which the shorter of
|
|
|
4162 the two otherwise-matching sequences runs out.
|
|
|
4163
|
|
|
4164 If @code{:from-end} is true, then the elements are compared from right
|
|
|
4165 to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
|
|
|
4166 If the sequences differ, then one plus the index of the rightmost
|
|
|
4167 difference (relative to @var{seq1}) is returned.
|
|
|
4168
|
|
|
4169 An interesting example is @code{(mismatch str1 str2 :key 'upcase)},
|
|
|
4170 which compares two strings case-insensitively.
|
|
|
4171 @end defun
|
|
|
4172
|
|
|
4173 @defun search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
|
|
|
4174 This function searches @var{seq2} for a subsequence that matches
|
|
|
4175 @var{seq1} (or part of it specified by @code{:start1} and
|
|
|
4176 @code{:end1}.) Only matches which fall entirely within the region
|
|
|
4177 defined by @code{:start2} and @code{:end2} will be considered.
|
|
|
4178 The return value is the index of the leftmost element of the
|
|
|
4179 leftmost match, relative to the start of @var{seq2}, or @code{nil}
|
|
|
4180 if no matches were found. If @code{:from-end} is true, the
|
|
|
4181 function finds the @emph{rightmost} matching subsequence.
|
|
|
4182 @end defun
|
|
|
4183
|
|
|
4184 @node Sorting Sequences, , Searching Sequences, Sequences
|
|
|
4185 @section Sorting Sequences
|
|
|
4186
|
|
|
4187 @defun sort* seq predicate @t{&key :key}
|
|
|
4188 This function sorts @var{seq} into increasing order as determined
|
|
|
4189 by using @var{predicate} to compare pairs of elements. @var{predicate}
|
|
|
4190 should return true (non-@code{nil}) if and only if its first argument
|
|
|
4191 is less than (not equal to) its second argument. For example,
|
|
|
4192 @code{<} and @code{string-lessp} are suitable predicate functions
|
|
|
4193 for sorting numbers and strings, respectively; @code{>} would sort
|
|
|
4194 numbers into decreasing rather than increasing order.
|
|
|
4195
|
|
|
4196 This function differs from Emacs' built-in @code{sort} in that it
|
|
|
4197 can operate on any type of sequence, not just lists. Also, it
|
|
|
4198 accepts a @code{:key} argument which is used to preprocess data
|
|
|
4199 fed to the @var{predicate} function. For example,
|
|
|
4200
|
|
|
4201 @example
|
|
|
4202 (setq data (sort data 'string-lessp :key 'downcase))
|
|
|
4203 @end example
|
|
|
4204
|
|
|
4205 @noindent
|
|
|
4206 sorts @var{data}, a sequence of strings, into increasing alphabetical
|
|
|
4207 order without regard to case. A @code{:key} function of @code{car}
|
|
|
4208 would be useful for sorting association lists.
|
|
|
4209
|
|
|
4210 The @code{sort*} function is destructive; it sorts lists by actually
|
|
|
4211 rearranging the @code{cdr} pointers in suitable fashion.
|
|
|
4212 @end defun
|
|
|
4213
|
|
|
4214 @defun stable-sort seq predicate @t{&key :key}
|
|
|
4215 This function sorts @var{seq} @dfn{stably}, meaning two elements
|
|
|
4216 which are equal in terms of @var{predicate} are guaranteed not to
|
|
|
4217 be rearranged out of their original order by the sort.
|
|
|
4218
|
|
|
4219 In practice, @code{sort*} and @code{stable-sort} are equivalent
|
|
|
4220 in Emacs Lisp because the underlying @code{sort} function is
|
|
|
4221 stable by default. However, this package reserves the right to
|
|
|
4222 use non-stable methods for @code{sort*} in the future.
|
|
|
4223 @end defun
|
|
|
4224
|
|
|
4225 @defun merge type seq1 seq2 predicate @t{&key :key}
|
|
|
4226 This function merges two sequences @var{seq1} and @var{seq2} by
|
|
|
4227 interleaving their elements. The result sequence, of type @var{type}
|
|
|
4228 (in the sense of @code{concatenate}), has length equal to the sum
|
|
|
4229 of the lengths of the two input sequences. The sequences may be
|
|
|
4230 modified destructively. Order of elements within @var{seq1} and
|
|
|
4231 @var{seq2} is preserved in the interleaving; elements of the two
|
|
|
4232 sequences are compared by @var{predicate} (in the sense of
|
|
|
4233 @code{sort}) and the lesser element goes first in the result.
|
|
|
4234 When elements are equal, those from @var{seq1} precede those from
|
|
|
4235 @var{seq2} in the result. Thus, if @var{seq1} and @var{seq2} are
|
|
|
4236 both sorted according to @var{predicate}, then the result will be
|
|
|
4237 a merged sequence which is (stably) sorted according to
|
|
|
4238 @var{predicate}.
|
|
|
4239 @end defun
|
|
|
4240
|
|
|
4241 @node Lists, Hash Tables, Sequences, Top
|
|
|
4242 @chapter Lists
|
|
|
4243
|
|
|
4244 @noindent
|
|
|
4245 The functions described here operate on lists.
|
|
|
4246
|
|
|
4247 @menu
|
|
|
4248 * List Functions:: `caddr', `first', `last', `list*', etc.
|
|
|
4249 * Substitution of Expressions:: `subst', `sublis', etc.
|
|
|
4250 * Lists as Sets:: `member*', `adjoin', `union', etc.
|
|
|
4251 * Association Lists:: `assoc*', `rassoc*', `acons', `pairlis'
|
|
|
4252 @end menu
|
|
|
4253
|
|
|
4254 @node List Functions, Substitution of Expressions, Lists, Lists
|
|
|
4255 @section List Functions
|
|
|
4256
|
|
|
4257 @noindent
|
|
|
4258 This section describes a number of simple operations on lists,
|
|
|
4259 i.e., chains of cons cells.
|
|
|
4260
|
|
|
4261 @defun caddr x
|
|
|
4262 This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
|
|
|
4263 Likewise, this package defines all 28 @code{c@var{xxx}r} functions
|
|
|
4264 where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
|
|
|
4265 All of these functions are @code{setf}-able, and calls to them
|
|
|
4266 are expanded inline by the byte-compiler for maximum efficiency.
|
|
|
4267 @end defun
|
|
|
4268
|
|
|
4269 @defun first x
|
|
|
4270 This function is a synonym for @code{(car @var{x})}. Likewise,
|
|
|
4271 the functions @code{second}, @code{third}, @dots{}, through
|
|
|
4272 @code{tenth} return the given element of the list @var{x}.
|
|
|
4273 @end defun
|
|
|
4274
|
|
|
4275 @defun rest x
|
|
|
4276 This function is a synonym for @code{(cdr @var{x})}.
|
|
|
4277 @end defun
|
|
|
4278
|
|
|
4279 @defun endp x
|
|
|
4280 Common Lisp defines this function to act like @code{null}, but
|
|
|
4281 signalling an error if @code{x} is neither a @code{nil} nor a
|
|
|
4282 cons cell. This package simply defines @code{endp} as a synonym
|
|
|
4283 for @code{null}.
|
|
|
4284 @end defun
|
|
|
4285
|
|
|
4286 @defun list-length x
|
|
|
4287 This function returns the length of list @var{x}, exactly like
|
|
|
4288 @code{(length @var{x})}, except that if @var{x} is a circular
|
|
|
4289 list (where the cdr-chain forms a loop rather than terminating
|
|
|
4290 with @code{nil}), this function returns @code{nil}. (The regular
|
|
|
4291 @code{length} function would get stuck if given a circular list.)
|
|
|
4292 @end defun
|
|
|
4293
|
|
|
4294 @defun last x &optional n
|
|
|
4295 This function returns the last cons, or the @var{n}th-to-last cons,
|
|
|
4296 of the list @var{x}. If @var{n} is omitted it defaults to 1.
|
|
|
4297 The ``last cons'' means the first cons cell of the list whose
|
|
|
4298 @code{cdr} is not another cons cell. (For normal lists, the
|
|
|
4299 @code{cdr} of the last cons will be @code{nil}.) This function
|
|
|
4300 returns @code{nil} if @var{x} is @code{nil} or shorter than
|
|
|
4301 @var{n}. Note that the last @emph{element} of the list is
|
|
|
4302 @code{(car (last @var{x}))}.
|
|
|
4303 @end defun
|
|
|
4304
|
|
|
4305 @defun butlast x &optional n
|
|
|
4306 This function returns the list @var{x} with the last element,
|
|
|
4307 or the last @var{n} elements, removed. If @var{n} is greater
|
|
|
4308 than zero it makes a copy of the list so as not to damage the
|
|
|
4309 original list. In general, @code{(append (butlast @var{x} @var{n})
|
|
|
4310 (last @var{x} @var{n}))} will return a list equal to @var{x}.
|
|
|
4311 @end defun
|
|
|
4312
|
|
|
4313 @defun nbutlast x &optional n
|
|
|
4314 This is a version of @code{butlast} that works by destructively
|
|
|
4315 modifying the @code{cdr} of the appropriate element, rather than
|
|
|
4316 making a copy of the list.
|
|
|
4317 @end defun
|
|
|
4318
|
|
|
4319 @defun list* arg &rest others
|
|
|
4320 This function constructs a list of its arguments. The final
|
|
|
4321 argument becomes the @code{cdr} of the last cell constructed.
|
|
|
4322 Thus, @code{(list* @var{a} @var{b} @var{c})} is equivalent to
|
|
|
4323 @code{(cons @var{a} (cons @var{b} @var{c}))}, and
|
|
|
4324 @code{(list* @var{a} @var{b} nil)} is equivalent to
|
|
|
4325 @code{(list @var{a} @var{b})}.
|
|
|
4326
|
|
|
4327 (Note that this function really is called @code{list*} in Common
|
|
|
4328 Lisp; it is not a name invented for this package like @code{member*}
|
|
|
4329 or @code{defun*}.)
|
|
|
4330 @end defun
|
|
|
4331
|
|
|
4332 @defun ldiff list sublist
|
|
|
4333 If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to
|
|
|
4334 one of the cons cells of @var{list}, then this function returns
|
|
|
4335 a copy of the part of @var{list} up to but not including
|
|
|
4336 @var{sublist}. For example, @code{(ldiff x (cddr x))} returns
|
|
|
4337 the first two elements of the list @code{x}. The result is a
|
|
|
4338 copy; the original @var{list} is not modified. If @var{sublist}
|
|
|
4339 is not a sublist of @var{list}, a copy of the entire @var{list}
|
|
|
4340 is returned.
|
|
|
4341 @end defun
|
|
|
4342
|
|
|
4343 @defun copy-list list
|
|
|
4344 This function returns a copy of the list @var{list}. It copies
|
|
|
4345 dotted lists like @code{(1 2 . 3)} correctly.
|
|
|
4346 @end defun
|
|
|
4347
|
|
|
4348 @defun copy-tree x &optional vecp
|
|
|
4349 This function returns a copy of the tree of cons cells @var{x}.
|
|
|
4350 Unlike @code{copy-sequence} (and its alias @code{copy-list}),
|
|
|
4351 which copies only along the @code{cdr} direction, this function
|
|
|
4352 copies (recursively) along both the @code{car} and the @code{cdr}
|
|
|
4353 directions. If @var{x} is not a cons cell, the function simply
|
|
|
4354 returns @var{x} unchanged. If the optional @var{vecp} argument
|
|
|
4355 is true, this function copies vectors (recursively) as well as
|
|
|
4356 cons cells.
|
|
|
4357 @end defun
|
|
|
4358
|
|
|
4359 @defun tree-equal x y @t{&key :test :test-not :key}
|
|
|
4360 This function compares two trees of cons cells. If @var{x} and
|
|
|
4361 @var{y} are both cons cells, their @code{car}s and @code{cdr}s are
|
|
|
4362 compared recursively. If neither @var{x} nor @var{y} is a cons
|
|
|
4363 cell, they are compared by @code{eql}, or according to the
|
|
|
4364 specified test. The @code{:key} function, if specified, is
|
|
|
4365 applied to the elements of both trees. @xref{Sequences}.
|
|
|
4366 @end defun
|
|
|
4367
|
|
|
4368 @iftex
|
|
|
4369 @secno=3
|
|
|
4370 @end iftex
|
|
|
4371
|
|
|
4372 @node Substitution of Expressions, Lists as Sets, List Functions, Lists
|
|
|
4373 @section Substitution of Expressions
|
|
|
4374
|
|
|
4375 @noindent
|
|
|
4376 These functions substitute elements throughout a tree of cons
|
|
|
4377 cells. (@xref{Sequence Functions}, for the @code{substitute}
|
|
|
4378 function, which works on just the top-level elements of a list.)
|
|
|
4379
|
|
|
4380 @defun subst new old tree @t{&key :test :test-not :key}
|
|
|
4381 This function substitutes occurrences of @var{old} with @var{new}
|
|
|
4382 in @var{tree}, a tree of cons cells. It returns a substituted
|
|
|
4383 tree, which will be a copy except that it may share storage with
|
|
|
4384 the argument @var{tree} in parts where no substitutions occurred.
|
|
|
4385 The original @var{tree} is not modified. This function recurses
|
|
|
4386 on, and compares against @var{old}, both @code{car}s and @code{cdr}s
|
|
|
4387 of the component cons cells. If @var{old} is itself a cons cell,
|
|
|
4388 then matching cells in the tree are substituted as usual without
|
|
|
4389 recursively substituting in that cell. Comparisons with @var{old}
|
|
|
4390 are done according to the specified test (@code{eql} by default).
|
|
|
4391 The @code{:key} function is applied to the elements of the tree
|
|
|
4392 but not to @var{old}.
|
|
|
4393 @end defun
|
|
|
4394
|
|
|
4395 @defun nsubst new old tree @t{&key :test :test-not :key}
|
|
|
4396 This function is like @code{subst}, except that it works by
|
|
|
4397 destructive modification (by @code{setcar} or @code{setcdr})
|
|
|
4398 rather than copying.
|
|
|
4399 @end defun
|
|
|
4400
|
|
|
4401 @findex subst-if
|
|
|
4402 @findex subst-if-not
|
|
|
4403 @findex nsubst-if
|
|
|
4404 @findex nsubst-if-not
|
|
|
4405 The @code{subst-if}, @code{subst-if-not}, @code{nsubst-if}, and
|
|
|
4406 @code{nsubst-if-not} functions are defined similarly.
|
|
|
4407
|
|
|
4408 @defun sublis alist tree @t{&key :test :test-not :key}
|
|
|
4409 This function is like @code{subst}, except that it takes an
|
|
|
4410 association list @var{alist} of @var{old}-@var{new} pairs.
|
|
|
4411 Each element of the tree (after applying the @code{:key}
|
|
|
4412 function, if any), is compared with the @code{car}s of
|
|
|
4413 @var{alist}; if it matches, it is replaced by the corresponding
|
|
|
4414 @code{cdr}.
|
|
|
4415 @end defun
|
|
|
4416
|
|
|
4417 @defun nsublis alist tree @t{&key :test :test-not :key}
|
|
|
4418 This is a destructive version of @code{sublis}.
|
|
|
4419 @end defun
|
|
|
4420
|
|
|
4421 @node Lists as Sets, Association Lists, Substitution of Expressions, Lists
|
|
|
4422 @section Lists as Sets
|
|
|
4423
|
|
|
4424 @noindent
|
|
|
4425 These functions perform operations on lists which represent sets
|
|
|
4426 of elements.
|
|
|
4427
|
|
|
4428 @defun member item list
|
|
|
4429 This MacLisp-compatible function searches @var{list} for an element
|
|
|
4430 which is @code{equal} to @var{item}. The @code{member} function is
|
|
|
4431 built-in to Emacs 19; this package defines it equivalently in Emacs 18.
|
|
|
4432 See the following function for a Common-Lisp compatible version.
|
|
|
4433 @end defun
|
|
|
4434
|
|
|
4435 @defun member* item list @t{&key :test :test-not :key}
|
|
|
4436 This function searches @var{list} for an element matching @var{item}.
|
|
|
4437 If a match is found, it returns the cons cell whose @code{car} was
|
|
|
4438 the matching element. Otherwise, it returns @code{nil}. Elements
|
|
|
4439 are compared by @code{eql} by default; you can use the @code{:test},
|
|
|
4440 @code{:test-not}, and @code{:key} arguments to modify this behavior.
|
|
|
4441 @xref{Sequences}.
|
|
|
4442
|
|
|
4443 Note that this function's name is suffixed by @samp{*} to avoid
|
|
|
4444 the incompatible @code{member} function defined in Emacs 19.
|
|
|
4445 (That function uses @code{equal} for comparisons; it is equivalent
|
|
|
4446 to @code{(member* @var{item} @var{list} :test 'equal)}.)
|
|
|
4447 @end defun
|
|
|
4448
|
|
|
4449 @findex member-if
|
|
|
4450 @findex member-if-not
|
|
|
4451 The @code{member-if} and @code{member-if-not} functions
|
|
|
4452 analogously search for elements which satisfy a given predicate.
|
|
|
4453
|
|
|
4454 @defun tailp sublist list
|
|
|
4455 This function returns @code{t} if @var{sublist} is a sublist of
|
|
|
4456 @var{list}, i.e., if @var{sublist} is @code{eql} to @var{list} or to
|
|
|
4457 any of its @code{cdr}s.
|
|
|
4458 @end defun
|
|
|
4459
|
|
|
4460 @defun adjoin item list @t{&key :test :test-not :key}
|
|
|
4461 This function conses @var{item} onto the front of @var{list},
|
|
|
4462 like @code{(cons @var{item} @var{list})}, but only if @var{item}
|
|
|
4463 is not already present on the list (as determined by @code{member*}).
|
|
|
4464 If a @code{:key} argument is specified, it is applied to
|
|
|
4465 @var{item} as well as to the elements of @var{list} during
|
|
|
4466 the search, on the reasoning that @var{item} is ``about'' to
|
|
|
4467 become part of the list.
|
|
|
4468 @end defun
|
|
|
4469
|
|
|
4470 @defun union list1 list2 @t{&key :test :test-not :key}
|
|
|
4471 This function combines two lists which represent sets of items,
|
|
|
4472 returning a list that represents the union of those two sets.
|
|
|
4473 The result list will contain all items which appear in @var{list1}
|
|
|
4474 or @var{list2}, and no others. If an item appears in both
|
|
|
4475 @var{list1} and @var{list2} it will be copied only once. If
|
|
|
4476 an item is duplicated in @var{list1} or @var{list2}, it is
|
|
|
4477 undefined whether or not that duplication will survive in the
|
|
|
4478 result list. The order of elements in the result list is also
|
|
|
4479 undefined.
|
|
|
4480 @end defun
|
|
|
4481
|
|
|
4482 @defun nunion list1 list2 @t{&key :test :test-not :key}
|
|
|
4483 This is a destructive version of @code{union}; rather than copying,
|
|
|
4484 it tries to reuse the storage of the argument lists if possible.
|
|
|
4485 @end defun
|
|
|
4486
|
|
|
4487 @defun intersection list1 list2 @t{&key :test :test-not :key}
|
|
|
4488 This function computes the intersection of the sets represented
|
|
|
4489 by @var{list1} and @var{list2}. It returns the list of items
|
|
|
4490 which appear in both @var{list1} and @var{list2}.
|
|
|
4491 @end defun
|
|
|
4492
|
|
|
4493 @defun nintersection list1 list2 @t{&key :test :test-not :key}
|
|
|
4494 This is a destructive version of @code{intersection}. It
|
|
|
4495 tries to reuse storage of @var{list1} rather than copying.
|
|
|
4496 It does @emph{not} reuse the storage of @var{list2}.
|
|
|
4497 @end defun
|
|
|
4498
|
|
|
4499 @defun set-difference list1 list2 @t{&key :test :test-not :key}
|
|
|
4500 This function computes the ``set difference'' of @var{list1}
|
|
|
4501 and @var{list2}, i.e., the set of elements that appear in
|
|
|
4502 @var{list1} but @emph{not} in @var{list2}.
|
|
|
4503 @end defun
|
|
|
4504
|
|
|
4505 @defun nset-difference list1 list2 @t{&key :test :test-not :key}
|
|
|
4506 This is a destructive @code{set-difference}, which will try
|
|
|
4507 to reuse @var{list1} if possible.
|
|
|
4508 @end defun
|
|
|
4509
|
|
|
4510 @defun set-exclusive-or list1 list2 @t{&key :test :test-not :key}
|
|
|
4511 This function computes the ``set exclusive or'' of @var{list1}
|
|
|
4512 and @var{list2}, i.e., the set of elements that appear in
|
|
|
4513 exactly one of @var{list1} and @var{list2}.
|
|
|
4514 @end defun
|
|
|
4515
|
|
|
4516 @defun nset-exclusive-or list1 list2 @t{&key :test :test-not :key}
|
|
|
4517 This is a destructive @code{set-exclusive-or}, which will try
|
|
|
4518 to reuse @var{list1} and @var{list2} if possible.
|
|
|
4519 @end defun
|
|
|
4520
|
|
|
4521 @defun subsetp list1 list2 @t{&key :test :test-not :key}
|
|
|
4522 This function checks whether @var{list1} represents a subset
|
|
|
4523 of @var{list2}, i.e., whether every element of @var{list1}
|
|
|
4524 also appears in @var{list2}.
|
|
|
4525 @end defun
|
|
|
4526
|
|
|
4527 @node Association Lists, , Lists as Sets, Lists
|
|
|
4528 @section Association Lists
|
|
|
4529
|
|
|
4530 @noindent
|
|
|
4531 An @dfn{association list} is a list representing a mapping from
|
|
|
4532 one set of values to another; any list whose elements are cons
|
|
|
4533 cells is an association list.
|
|
|
4534
|
|
|
4535 @defun assoc* item a-list @t{&key :test :test-not :key}
|
|
|
4536 This function searches the association list @var{a-list} for an
|
|
|
4537 element whose @code{car} matches (in the sense of @code{:test},
|
|
|
4538 @code{:test-not}, and @code{:key}, or by comparison with @code{eql})
|
|
|
4539 a given @var{item}. It returns the matching element, if any,
|
|
|
4540 otherwise @code{nil}. It ignores elements of @var{a-list} which
|
|
|
4541 are not cons cells. (This corresponds to the behavior of
|
|
|
4542 @code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's
|
|
|
4543 @code{assoc} ignores @code{nil}s but considers any other non-cons
|
|
|
4544 elements of @var{a-list} to be an error.)
|
|
|
4545 @end defun
|
|
|
4546
|
|
|
4547 @defun rassoc* item a-list @t{&key :test :test-not :key}
|
|
|
4548 This function searches for an element whose @code{cdr} matches
|
|
|
4549 @var{item}. If @var{a-list} represents a mapping, this applies
|
|
|
4550 the inverse of the mapping to @var{item}.
|
|
|
4551 @end defun
|
|
|
4552
|
|
|
4553 @defun rassoc item a-list
|
|
|
4554 This function searches like @code{rassoc*} with a @code{:test}
|
|
|
4555 argument of @code{equal}. It is analogous to Emacs Lisp's
|
|
|
4556 standard @code{assoc} function, which derives from the MacLisp
|
|
|
4557 rather than the Common Lisp tradition.
|
|
|
4558 @end defun
|
|
|
4559
|
|
|
4560 @findex assoc-if
|
|
|
4561 @findex assoc-if-not
|
|
|
4562 @findex rassoc-if
|
|
|
4563 @findex rassoc-if-not
|
|
|
4564 The @code{assoc-if}, @code{assoc-if-not}, @code{rassoc-if},
|
|
|
4565 and @code{rassoc-if-not} functions are defined similarly.
|
|
|
4566
|
|
|
4567 Two simple functions for constructing association lists are:
|
|
|
4568
|
|
|
4569 @defun acons key value alist
|
|
|
4570 This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}.
|
|
|
4571 @end defun
|
|
|
4572
|
|
|
4573 @defun pairlis keys values &optional alist
|
|
|
4574 This is equivalent to @code{(nconc (mapcar* 'cons @var{keys} @var{values})
|
|
|
4575 @var{alist})}.
|
|
|
4576 @end defun
|
|
|
4577
|
|
|
4578 @node Hash Tables, Structures, Lists, Top
|
|
|
4579 @chapter Hash Tables
|
|
|
4580
|
|
|
4581 @noindent
|
|
|
4582 Hash tables are now implemented directly in the C code and documented in
|
|
446
|
4583 @ref{Hash Tables,,, lispref, XEmacs Lisp Reference Manual}.
|
|
428
|
4584
|
|
|
4585 @ignore
|
|
|
4586 A @dfn{hash table} is a data structure that maps ``keys'' onto
|
|
|
4587 ``values.'' Keys and values can be arbitrary Lisp data objects.
|
|
|
4588 Hash tables have the property that the time to search for a given
|
|
|
4589 key is roughly constant; simpler data structures like association
|
|
|
4590 lists take time proportional to the number of entries in the list.
|
|
|
4591
|
|
|
4592 @defun make-hash-table @t{&key :test :size}
|
|
|
4593 This function creates and returns a hash-table object whose
|
|
|
4594 function for comparing elements is @code{:test} (@code{eql}
|
|
|
4595 by default), and which is allocated to fit about @code{:size}
|
|
|
4596 elements. The @code{:size} argument is purely advisory; the
|
|
|
4597 table will stretch automatically if you store more elements in
|
|
|
4598 it. If @code{:size} is omitted, a reasonable default is used.
|
|
|
4599
|
|
|
4600 Common Lisp allows only @code{eq}, @code{eql}, @code{equal},
|
|
|
4601 and @code{equalp} as legal values for the @code{:test} argument.
|
|
|
4602 In this package, any reasonable predicate function will work,
|
|
|
4603 though if you use something else you should check the details of
|
|
|
4604 the hashing function described below to make sure it is suitable
|
|
|
4605 for your predicate.
|
|
|
4606
|
|
|
4607 Some versions of Emacs (like XEmacs) include a built-in hash
|
|
|
4608 table type; in these versions, @code{make-hash-table} with a test of
|
|
|
4609 @code{eq}, @code{eql}, or @code{equal} will use these built-in hash
|
|
|
4610 tables. In all other cases, it will return a hash-table object which
|
|
|
4611 takes the form of a list with an identifying ``tag'' symbol at the
|
|
|
4612 front. All of the hash table functions in this package can operate on
|
|
|
4613 both types of hash table; normally you will never know which type is
|
|
|
4614 being used.
|
|
|
4615
|
|
|
4616 This function accepts the additional Common Lisp keywords
|
|
|
4617 @code{:rehash-size} and @code{:rehash-threshold}, but it ignores
|
|
|
4618 their values.
|
|
|
4619 @end defun
|
|
|
4620
|
|
|
4621 @defun gethash key table &optional default
|
|
|
4622 This function looks up @var{key} in @var{table}. If @var{key}
|
|
|
4623 exists in the table, in the sense that it matches any of the existing
|
|
|
4624 keys according to the table's test function, then the associated value
|
|
|
4625 is returned. Otherwise, @var{default} (or @code{nil}) is returned.
|
|
|
4626
|
|
|
4627 To store new data in the hash table, use @code{setf} on a call to
|
|
|
4628 @code{gethash}. If @var{key} already exists in the table, the
|
|
|
4629 corresponding value is changed to the stored value. If @var{key}
|
|
|
4630 does not already exist, a new entry is added to the table and the
|
|
|
4631 table is reallocated to a larger size if necessary. The @var{default}
|
|
|
4632 argument is allowed but ignored in this case. The situation is
|
|
440
|
4633 exactly analogous to that of @code{get}; @pxref{Property Lists}.
|
|
428
|
4634 @end defun
|
|
|
4635
|
|
|
4636 @defun remhash key table
|
|
|
4637 This function removes the entry for @var{key} from @var{table}.
|
|
|
4638 If an entry was removed, it returns @code{t}. If @var{key} does
|
|
|
4639 not appear in the table, it does nothing and returns @code{nil}.
|
|
|
4640 @end defun
|
|
|
4641
|
|
|
4642 @defun clrhash table
|
|
|
4643 This function removes all the entries from @var{table}, leaving
|
|
|
4644 an empty hash table.
|
|
|
4645 @end defun
|
|
|
4646
|
|
|
4647 @defun maphash function table
|
|
|
4648 This function calls @var{function} for each entry in @var{table}.
|
|
|
4649 It passes two arguments to @var{function}, the key and the value
|
|
|
4650 of the given entry. The return value of @var{function} is ignored;
|
|
|
4651 @var{maphash} itself returns @code{nil}. @xref{Loop Facility}, for
|
|
|
4652 an alternate way of iterating over hash tables.
|
|
|
4653 @end defun
|
|
|
4654
|
|
|
4655 @defun hash-table-count table This function returns the number of
|
|
|
4656 entries in @var{table}. @strong{Warning:} The current implementation of
|
|
|
4657 XEmacs hash-tables does not decrement the stored @code{count}
|
|
|
4658 when @code{remhash} removes an entry. Therefore, the return value of
|
|
|
4659 this function is not dependable if you have used @code{remhash} on the
|
|
|
4660 table and the table's test is @code{eq}, @code{eql}, or @code{equal}.
|
|
|
4661 A slower, but reliable, way to count the entries is
|
|
|
4662 @code{(loop for x being the hash-keys of @var{table} count t)}.
|
|
|
4663 @end defun
|
|
|
4664
|
|
|
4665 @defun hash-table-p object This function returns @code{t} if
|
|
|
4666 @var{object} is a hash table, @code{nil} otherwise. It recognizes both
|
|
|
4667 types of hash tables (both XEmacs built-in tables and tables implemented
|
|
|
4668 with special lists.)
|
|
|
4669 @end defun
|
|
|
4670
|
|
|
4671 Sometimes when dealing with hash tables it is useful to know the
|
|
|
4672 exact ``hash function'' that is used. This package implements
|
|
|
4673 hash tables using Emacs Lisp ``obarrays,'' which are the same
|
|
|
4674 data structure that Emacs Lisp uses to keep track of symbols.
|
|
|
4675 Each hash table includes an embedded obarray. Key values given
|
|
|
4676 to @code{gethash} are converted by various means into strings,
|
|
|
4677 which are then looked up in the obarray using @code{intern} and
|
|
|
4678 @code{intern-soft}. The symbol, or ``bucket,'' corresponding to
|
|
|
4679 a given key string includes as its @code{symbol-value} an association
|
|
|
4680 list of all key-value pairs which hash to that string. Depending
|
|
|
4681 on the test function, it is possible for many entries to hash to
|
|
|
4682 the same bucket. For example, if the test is @code{eql}, then the
|
|
|
4683 symbol @code{foo} and two separately built strings @code{"foo"} will
|
|
|
4684 create three entries in the same bucket. Search time is linear
|
|
|
4685 within buckets, so hash tables will be most effective if you arrange
|
|
|
4686 not to store too many things that hash the same.
|
|
|
4687
|
|
|
4688 The following algorithm is used to convert Lisp objects to hash
|
|
|
4689 strings:
|
|
|
4690
|
|
|
4691 @itemize @bullet
|
|
|
4692 @item
|
|
|
4693 Strings are used directly as hash strings. (However, if the test
|
|
|
4694 function is @code{equalp}, strings are @code{downcase}d first.)
|
|
|
4695
|
|
|
4696 @item
|
|
|
4697 Symbols are hashed according to their @code{symbol-name}.
|
|
|
4698
|
|
|
4699 @item
|
|
|
4700 Integers are hashed into one of 16 buckets depending on their value
|
|
|
4701 modulo 16. Floating-point numbers are truncated to integers and
|
|
|
4702 hashed modulo 16.
|
|
|
4703
|
|
|
4704 @item
|
|
|
4705 Cons cells are hashed according to their @code{car}s; nonempty vectors
|
|
|
4706 are hashed according to their first element.
|
|
|
4707
|
|
|
4708 @item
|
|
|
4709 All other types of objects hash into a single bucket named @code{"*"}.
|
|
|
4710 @end itemize
|
|
|
4711
|
|
|
4712 @noindent
|
|
|
4713 Thus, for example, searching among many buffer objects in a hash table
|
|
|
4714 will devolve to a (still fairly fast) linear-time search through a
|
|
|
4715 single bucket, whereas searching for different symbols will be very
|
|
|
4716 fast since each symbol will, in general, hash into its own bucket.
|
|
|
4717
|
|
|
4718 The size of the obarray in a hash table is automatically adjusted
|
|
|
4719 as the number of elements increases.
|
|
|
4720
|
|
|
4721 As a special case, @code{make-hash-table} with a @code{:size} argument
|
|
|
4722 of 0 or 1 will create a hash-table object that uses a single association
|
|
|
4723 list rather than an obarray of many lists. For very small tables this
|
|
|
4724 structure will be more efficient since lookup does not require
|
|
|
4725 converting the key to a string or looking it up in an obarray.
|
|
|
4726 However, such tables are guaranteed to take time proportional to
|
|
|
4727 their size to do a search.
|
|
|
4728 @end ignore
|
|
|
4729
|
|
|
4730 @iftex
|
|
|
4731 @chapno=18
|
|
|
4732 @end iftex
|
|
|
4733
|
|
|
4734 @node Structures, Assertions, Hash Tables, Top
|
|
|
4735 @chapter Structures
|
|
|
4736
|
|
|
4737 @noindent
|
|
|
4738 The Common Lisp @dfn{structure} mechanism provides a general way
|
|
|
4739 to define data types similar to C's @code{struct} types. A
|
|
|
4740 structure is a Lisp object containing some number of @dfn{slots},
|
|
|
4741 each of which can hold any Lisp data object. Functions are
|
|
|
4742 provided for accessing and setting the slots, creating or copying
|
|
|
4743 structure objects, and recognizing objects of a particular structure
|
|
|
4744 type.
|
|
|
4745
|
|
|
4746 In true Common Lisp, each structure type is a new type distinct
|
|
|
4747 from all existing Lisp types. Since the underlying Emacs Lisp
|
|
|
4748 system provides no way to create new distinct types, this package
|
|
|
4749 implements structures as vectors (or lists upon request) with a
|
|
|
4750 special ``tag'' symbol to identify them.
|
|
|
4751
|
|
|
4752 @defspec defstruct name slots@dots{}
|
|
|
4753 The @code{defstruct} form defines a new structure type called
|
|
|
4754 @var{name}, with the specified @var{slots}. (The @var{slots}
|
|
|
4755 may begin with a string which documents the structure type.)
|
|
|
4756 In the simplest case, @var{name} and each of the @var{slots}
|
|
|
4757 are symbols. For example,
|
|
|
4758
|
|
|
4759 @example
|
|
|
4760 (defstruct person name age sex)
|
|
|
4761 @end example
|
|
|
4762
|
|
|
4763 @noindent
|
|
|
4764 defines a struct type called @code{person} which contains three
|
|
|
4765 slots. Given a @code{person} object @var{p}, you can access those
|
|
|
4766 slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
|
|
|
4767 and @code{(person-sex @var{p})}. You can also change these slots by
|
|
|
4768 using @code{setf} on any of these place forms:
|
|
|
4769
|
|
|
4770 @example
|
|
|
4771 (incf (person-age birthday-boy))
|
|
|
4772 @end example
|
|
|
4773
|
|
|
4774 You can create a new @code{person} by calling @code{make-person},
|
|
|
4775 which takes keyword arguments @code{:name}, @code{:age}, and
|
|
|
4776 @code{:sex} to specify the initial values of these slots in the
|
|
|
4777 new object. (Omitting any of these arguments leaves the corresponding
|
|
|
4778 slot ``undefined,'' according to the Common Lisp standard; in Emacs
|
|
|
4779 Lisp, such uninitialized slots are filled with @code{nil}.)
|
|
|
4780
|
|
|
4781 Given a @code{person}, @code{(copy-person @var{p})} makes a new
|
|
|
4782 object of the same type whose slots are @code{eq} to those of @var{p}.
|
|
|
4783
|
|
|
4784 Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
|
|
|
4785 true if @var{x} looks like a @code{person}, false otherwise. (Again,
|
|
|
4786 in Common Lisp this predicate would be exact; in Emacs Lisp the
|
|
|
4787 best it can do is verify that @var{x} is a vector of the correct
|
|
|
4788 length which starts with the correct tag symbol.)
|
|
|
4789
|
|
|
4790 Accessors like @code{person-name} normally check their arguments
|
|
|
4791 (effectively using @code{person-p}) and signal an error if the
|
|
|
4792 argument is the wrong type. This check is affected by
|
|
|
4793 @code{(optimize (safety @dots{}))} declarations. Safety level 1,
|
|
|
4794 the default, uses a somewhat optimized check that will detect all
|
|
|
4795 incorrect arguments, but may use an uninformative error message
|
|
|
4796 (e.g., ``expected a vector'' instead of ``expected a @code{person}'').
|
|
|
4797 Safety level 0 omits all checks except as provided by the underlying
|
|
|
4798 @code{aref} call; safety levels 2 and 3 do rigorous checking that will
|
|
|
4799 always print a descriptive error message for incorrect inputs.
|
|
|
4800 @xref{Declarations}.
|
|
|
4801
|
|
|
4802 @example
|
|
|
4803 (setq dave (make-person :name "Dave" :sex 'male))
|
|
|
4804 @result{} [cl-struct-person "Dave" nil male]
|
|
|
4805 (setq other (copy-person dave))
|
|
|
4806 @result{} [cl-struct-person "Dave" nil male]
|
|
|
4807 (eq dave other)
|
|
|
4808 @result{} nil
|
|
|
4809 (eq (person-name dave) (person-name other))
|
|
|
4810 @result{} t
|
|
|
4811 (person-p dave)
|
|
|
4812 @result{} t
|
|
|
4813 (person-p [1 2 3 4])
|
|
|
4814 @result{} nil
|
|
|
4815 (person-p "Bogus")
|
|
|
4816 @result{} nil
|
|
|
4817 (person-p '[cl-struct-person counterfeit person object])
|
|
|
4818 @result{} t
|
|
|
4819 @end example
|
|
|
4820
|
|
|
4821 In general, @var{name} is either a name symbol or a list of a name
|
|
|
4822 symbol followed by any number of @dfn{struct options}; each @var{slot}
|
|
|
4823 is either a slot symbol or a list of the form @samp{(@var{slot-name}
|
|
|
4824 @var{default-value} @var{slot-options}@dots{})}. The @var{default-value}
|
|
|
4825 is a Lisp form which is evaluated any time an instance of the
|
|
|
4826 structure type is created without specifying that slot's value.
|
|
|
4827
|
|
|
4828 Common Lisp defines several slot options, but the only one
|
|
|
4829 implemented in this package is @code{:read-only}. A non-@code{nil}
|
|
|
4830 value for this option means the slot should not be @code{setf}-able;
|
|
|
4831 the slot's value is determined when the object is created and does
|
|
|
4832 not change afterward.
|
|
|
4833
|
|
|
4834 @example
|
|
|
4835 (defstruct person
|
|
|
4836 (name nil :read-only t)
|
|
|
4837 age
|
|
|
4838 (sex 'unknown))
|
|
|
4839 @end example
|
|
|
4840
|
|
|
4841 Any slot options other than @code{:read-only} are ignored.
|
|
|
4842
|
|
|
4843 For obscure historical reasons, structure options take a different
|
|
|
4844 form than slot options. A structure option is either a keyword
|
|
|
4845 symbol, or a list beginning with a keyword symbol possibly followed
|
|
|
4846 by arguments. (By contrast, slot options are key-value pairs not
|
|
|
4847 enclosed in lists.)
|
|
|
4848
|
|
|
4849 @example
|
|
|
4850 (defstruct (person (:constructor create-person)
|
|
|
4851 (:type list)
|
|
|
4852 :named)
|
|
|
4853 name age sex)
|
|
|
4854 @end example
|
|
|
4855
|
|
|
4856 The following structure options are recognized.
|
|
|
4857
|
|
|
4858 @table @code
|
|
|
4859 @iftex
|
|
|
4860 @itemmax=0 in
|
|
|
4861 @advance@leftskip-.5@tableindent
|
|
|
4862 @end iftex
|
|
|
4863 @item :conc-name
|
|
|
4864 The argument is a symbol whose print name is used as the prefix for
|
|
|
4865 the names of slot accessor functions. The default is the name of
|
|
|
4866 the struct type followed by a hyphen. The option @code{(:conc-name p-)}
|
|
|
4867 would change this prefix to @code{p-}. Specifying @code{nil} as an
|
|
|
4868 argument means no prefix, so that the slot names themselves are used
|
|
|
4869 to name the accessor functions.
|
|
|
4870
|
|
|
4871 @item :constructor
|
|
|
4872 In the simple case, this option takes one argument which is an
|
|
|
4873 alternate name to use for the constructor function. The default
|
|
|
4874 is @code{make-@var{name}}, e.g., @code{make-person}. The above
|
|
|
4875 example changes this to @code{create-person}. Specifying @code{nil}
|
|
|
4876 as an argument means that no standard constructor should be
|
|
|
4877 generated at all.
|
|
|
4878
|
|
|
4879 In the full form of this option, the constructor name is followed
|
|
|
4880 by an arbitrary argument list. @xref{Program Structure}, for a
|
|
|
4881 description of the format of Common Lisp argument lists. All
|
|
|
4882 options, such as @code{&rest} and @code{&key}, are supported.
|
|
|
4883 The argument names should match the slot names; each slot is
|
|
|
4884 initialized from the corresponding argument. Slots whose names
|
|
|
4885 do not appear in the argument list are initialized based on the
|
|
|
4886 @var{default-value} in their slot descriptor. Also, @code{&optional}
|
|
|
4887 and @code{&key} arguments which don't specify defaults take their
|
|
|
4888 defaults from the slot descriptor. It is legal to include arguments
|
|
|
4889 which don't correspond to slot names; these are useful if they are
|
|
|
4890 referred to in the defaults for optional, keyword, or @code{&aux}
|
|
|
4891 arguments which @emph{do} correspond to slots.
|
|
|
4892
|
|
|
4893 You can specify any number of full-format @code{:constructor}
|
|
|
4894 options on a structure. The default constructor is still generated
|
|
|
4895 as well unless you disable it with a simple-format @code{:constructor}
|
|
|
4896 option.
|
|
|
4897
|
|
|
4898 @example
|
|
|
4899 (defstruct
|
|
|
4900 (person
|
|
|
4901 (:constructor nil) ; no default constructor
|
|
|
4902 (:constructor new-person (name sex &optional (age 0)))
|
|
|
4903 (:constructor new-hound (&key (name "Rover")
|
|
|
4904 (dog-years 0)
|
|
|
4905 &aux (age (* 7 dog-years))
|
|
|
4906 (sex 'canine))))
|
|
|
4907 name age sex)
|
|
|
4908 @end example
|
|
|
4909
|
|
|
4910 The first constructor here takes its arguments positionally rather
|
|
|
4911 than by keyword. (In official Common Lisp terminology, constructors
|
|
|
4912 that work By Order of Arguments instead of by keyword are called
|
|
|
4913 ``BOA constructors.'' No, I'm not making this up.) For example,
|
|
|
4914 @code{(new-person "Jane" 'female)} generates a person whose slots
|
|
|
4915 are @code{"Jane"}, 0, and @code{female}, respectively.
|
|
|
4916
|
|
|
4917 The second constructor takes two keyword arguments, @code{:name},
|
|
|
4918 which initializes the @code{name} slot and defaults to @code{"Rover"},
|
|
|
4919 and @code{:dog-years}, which does not itself correspond to a slot
|
|
|
4920 but which is used to initialize the @code{age} slot. The @code{sex}
|
|
|
4921 slot is forced to the symbol @code{canine} with no syntax for
|
|
|
4922 overriding it.
|
|
|
4923
|
|
|
4924 @item :copier
|
|
|
4925 The argument is an alternate name for the copier function for
|
|
|
4926 this type. The default is @code{copy-@var{name}}. @code{nil}
|
|
|
4927 means not to generate a copier function. (In this implementation,
|
|
|
4928 all copier functions are simply synonyms for @code{copy-sequence}.)
|
|
|
4929
|
|
|
4930 @item :predicate
|
|
|
4931 The argument is an alternate name for the predicate which recognizes
|
|
|
4932 objects of this type. The default is @code{@var{name}-p}. @code{nil}
|
|
|
4933 means not to generate a predicate function. (If the @code{:type}
|
|
|
4934 option is used without the @code{:named} option, no predicate is
|
|
|
4935 ever generated.)
|
|
|
4936
|
|
|
4937 In true Common Lisp, @code{typep} is always able to recognize a
|
|
|
4938 structure object even if @code{:predicate} was used. In this
|
|
|
4939 package, @code{typep} simply looks for a function called
|
|
|
4940 @code{@var{typename}-p}, so it will work for structure types
|
|
|
4941 only if they used the default predicate name.
|
|
|
4942
|
|
|
4943 @item :include
|
|
|
4944 This option implements a very limited form of C++-style inheritance.
|
|
|
4945 The argument is the name of another structure type previously
|
|
|
4946 created with @code{defstruct}. The effect is to cause the new
|
|
|
4947 structure type to inherit all of the included structure's slots
|
|
|
4948 (plus, of course, any new slots described by this struct's slot
|
|
|
4949 descriptors). The new structure is considered a ``specialization''
|
|
|
4950 of the included one. In fact, the predicate and slot accessors
|
|
|
4951 for the included type will also accept objects of the new type.
|
|
|
4952
|
|
|
4953 If there are extra arguments to the @code{:include} option after
|
|
|
4954 the included-structure name, these options are treated as replacement
|
|
|
4955 slot descriptors for slots in the included structure, possibly with
|
|
|
4956 modified default values. Borrowing an example from Steele:
|
|
|
4957
|
|
|
4958 @example
|
|
|
4959 (defstruct person name (age 0) sex)
|
|
|
4960 @result{} person
|
|
|
4961 (defstruct (astronaut (:include person (age 45)))
|
|
|
4962 helmet-size
|
|
|
4963 (favorite-beverage 'tang))
|
|
|
4964 @result{} astronaut
|
|
|
4965
|
|
|
4966 (setq joe (make-person :name "Joe"))
|
|
|
4967 @result{} [cl-struct-person "Joe" 0 nil]
|
|
|
4968 (setq buzz (make-astronaut :name "Buzz"))
|
|
|
4969 @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang]
|
|
|
4970
|
|
|
4971 (list (person-p joe) (person-p buzz))
|
|
|
4972 @result{} (t t)
|
|
|
4973 (list (astronaut-p joe) (astronaut-p buzz))
|
|
|
4974 @result{} (nil t)
|
|
|
4975
|
|
|
4976 (person-name buzz)
|
|
|
4977 @result{} "Buzz"
|
|
|
4978 (astronaut-name joe)
|
|
|
4979 @result{} error: "astronaut-name accessing a non-astronaut"
|
|
|
4980 @end example
|
|
|
4981
|
|
|
4982 Thus, if @code{astronaut} is a specialization of @code{person},
|
|
|
4983 then every @code{astronaut} is also a @code{person} (but not the
|
|
|
4984 other way around). Every @code{astronaut} includes all the slots
|
|
|
4985 of a @code{person}, plus extra slots that are specific to
|
|
|
4986 astronauts. Operations that work on people (like @code{person-name})
|
|
|
4987 work on astronauts just like other people.
|
|
|
4988
|
|
|
4989 @item :print-function
|
|
|
4990 In full Common Lisp, this option allows you to specify a function
|
|
|
4991 which is called to print an instance of the structure type. The
|
|
|
4992 Emacs Lisp system offers no hooks into the Lisp printer which would
|
|
|
4993 allow for such a feature, so this package simply ignores
|
|
|
4994 @code{:print-function}.
|
|
|
4995
|
|
|
4996 @item :type
|
|
|
4997 The argument should be one of the symbols @code{vector} or @code{list}.
|
|
|
4998 This tells which underlying Lisp data type should be used to implement
|
|
|
4999 the new structure type. Vectors are used by default, but
|
|
|
5000 @code{(:type list)} will cause structure objects to be stored as
|
|
|
5001 lists instead.
|
|
|
5002
|
|
|
5003 The vector representation for structure objects has the advantage
|
|
|
5004 that all structure slots can be accessed quickly, although creating
|
|
|
5005 vectors is a bit slower in Emacs Lisp. Lists are easier to create,
|
|
|
5006 but take a relatively long time accessing the later slots.
|
|
|
5007
|
|
|
5008 @item :named
|
|
|
5009 This option, which takes no arguments, causes a characteristic ``tag''
|
|
|
5010 symbol to be stored at the front of the structure object. Using
|
|
|
5011 @code{:type} without also using @code{:named} will result in a
|
|
|
5012 structure type stored as plain vectors or lists with no identifying
|
|
|
5013 features.
|
|
|
5014
|
|
|
5015 The default, if you don't specify @code{:type} explicitly, is to
|
|
|
5016 use named vectors. Therefore, @code{:named} is only useful in
|
|
|
5017 conjunction with @code{:type}.
|
|
|
5018
|
|
|
5019 @example
|
|
|
5020 (defstruct (person1) name age sex)
|
|
|
5021 (defstruct (person2 (:type list) :named) name age sex)
|
|
|
5022 (defstruct (person3 (:type list)) name age sex)
|
|
|
5023
|
|
|
5024 (setq p1 (make-person1))
|
|
|
5025 @result{} [cl-struct-person1 nil nil nil]
|
|
|
5026 (setq p2 (make-person2))
|
|
|
5027 @result{} (person2 nil nil nil)
|
|
|
5028 (setq p3 (make-person3))
|
|
|
5029 @result{} (nil nil nil)
|
|
|
5030
|
|
|
5031 (person1-p p1)
|
|
|
5032 @result{} t
|
|
|
5033 (person2-p p2)
|
|
|
5034 @result{} t
|
|
|
5035 (person3-p p3)
|
|
|
5036 @result{} error: function person3-p undefined
|
|
|
5037 @end example
|
|
|
5038
|
|
|
5039 Since unnamed structures don't have tags, @code{defstruct} is not
|
|
|
5040 able to make a useful predicate for recognizing them. Also,
|
|
|
5041 accessors like @code{person3-name} will be generated but they
|
|
|
5042 will not be able to do any type checking. The @code{person3-name}
|
|
|
5043 function, for example, will simply be a synonym for @code{car} in
|
|
|
5044 this case. By contrast, @code{person2-name} is able to verify
|
|
|
5045 that its argument is indeed a @code{person2} object before
|
|
|
5046 proceeding.
|
|
|
5047
|
|
|
5048 @item :initial-offset
|
|
|
5049 The argument must be a nonnegative integer. It specifies a
|
|
|
5050 number of slots to be left ``empty'' at the front of the
|
|
|
5051 structure. If the structure is named, the tag appears at the
|
|
|
5052 specified position in the list or vector; otherwise, the first
|
|
|
5053 slot appears at that position. Earlier positions are filled
|
|
|
5054 with @code{nil} by the constructors and ignored otherwise. If
|
|
|
5055 the type @code{:include}s another type, then @code{:initial-offset}
|
|
|
5056 specifies a number of slots to be skipped between the last slot
|
|
|
5057 of the included type and the first new slot.
|
|
|
5058 @end table
|
|
|
5059 @end defspec
|
|
|
5060
|
|
|
5061 Except as noted, the @code{defstruct} facility of this package is
|
|
|
5062 entirely compatible with that of Common Lisp.
|
|
|
5063
|
|
|
5064 @iftex
|
|
|
5065 @chapno=23
|
|
|
5066 @end iftex
|
|
|
5067
|
|
|
5068 @node Assertions, Efficiency Concerns, Structures, Top
|
|
|
5069 @chapter Assertions and Errors
|
|
|
5070
|
|
|
5071 @noindent
|
|
|
5072 This section describes two macros that test @dfn{assertions}, i.e.,
|
|
|
5073 conditions which must be true if the program is operating correctly.
|
|
|
5074 Assertions never add to the behavior of a Lisp program; they simply
|
|
|
5075 make ``sanity checks'' to make sure everything is as it should be.
|
|
|
5076
|
|
|
5077 If the optimization property @code{speed} has been set to 3, and
|
|
|
5078 @code{safety} is less than 3, then the byte-compiler will optimize
|
|
|
5079 away the following assertions. Because assertions might be optimized
|
|
|
5080 away, it is a bad idea for them to include side-effects.
|
|
|
5081
|
|
|
5082 @defspec assert test-form [show-args string args@dots{}]
|
|
|
5083 This form verifies that @var{test-form} is true (i.e., evaluates to
|
|
|
5084 a non-@code{nil} value). If so, it returns @code{nil}. If the test
|
|
|
5085 is not satisfied, @code{assert} signals an error.
|
|
|
5086
|
|
|
5087 A default error message will be supplied which includes @var{test-form}.
|
|
|
5088 You can specify a different error message by including a @var{string}
|
|
|
5089 argument plus optional extra arguments. Those arguments are simply
|
|
|
5090 passed to @code{error} to signal the error.
|
|
|
5091
|
|
|
5092 If the optional second argument @var{show-args} is @code{t} instead
|
|
|
5093 of @code{nil}, then the error message (with or without @var{string})
|
|
|
5094 will also include all non-constant arguments of the top-level
|
|
|
5095 @var{form}. For example:
|
|
|
5096
|
|
|
5097 @example
|
|
|
5098 (assert (> x 10) t "x is too small: %d")
|
|
|
5099 @end example
|
|
|
5100
|
|
446
|
5101 This usage of @var{show-args} is a change to Common Lisp. In
|
|
428
|
5102 true Common Lisp, the second argument gives a list of @var{places}
|
|
|
5103 which can be @code{setf}'d by the user before continuing from the
|
|
446
|
5104 error.
|
|
428
|
5105 @end defspec
|
|
|
5106
|
|
446
|
5107 @defspec check-type place type &optional string
|
|
|
5108 This form verifies that @var{place} evaluates to a value of type
|
|
428
|
5109 @var{type}. If so, it returns @code{nil}. If not, @code{check-type}
|
|
446
|
5110 signals a continuable @code{wrong-type-argument} error. The default
|
|
|
5111 error message lists the erroneous value along with @var{type} and
|
|
|
5112 @var{place} themselves. If @var{string} is specified, it is included in
|
|
|
5113 the error message in place of @var{type}. For example:
|
|
428
|
5114
|
|
|
5115 @example
|
|
|
5116 (check-type x (integer 1 *) "a positive integer")
|
|
|
5117 @end example
|
|
|
5118
|
|
|
5119 @xref{Type Predicates}, for a description of the type specifiers
|
|
|
5120 that may be used for @var{type}.
|
|
|
5121
|
|
446
|
5122 Note that as in Common Lisp, the first argument to @code{check-type}
|
|
|
5123 should be a @var{place} suitable for use by @code{setf}, because
|
|
|
5124 @code{check-type} signals a continuable error that allows the user to
|
|
|
5125 modify @var{place}, most simply by returning a value from the debugger.
|
|
428
|
5126 @end defspec
|
|
|
5127
|
|
|
5128 The following error-related macro is also defined:
|
|
|
5129
|
|
|
5130 @defspec ignore-errors forms@dots{}
|
|
|
5131 This executes @var{forms} exactly like a @code{progn}, except that
|
|
|
5132 errors are ignored during the @var{forms}. More precisely, if
|
|
|
5133 an error is signalled then @code{ignore-errors} immediately
|
|
|
5134 aborts execution of the @var{forms} and returns @code{nil}.
|
|
|
5135 If the @var{forms} complete successfully, @code{ignore-errors}
|
|
|
5136 returns the result of the last @var{form}.
|
|
|
5137 @end defspec
|
|
|
5138
|
|
|
5139 @node Efficiency Concerns, Common Lisp Compatibility, Assertions, Top
|
|
|
5140 @appendix Efficiency Concerns
|
|
|
5141
|
|
|
5142 @appendixsec Macros
|
|
|
5143
|
|
|
5144 @noindent
|
|
|
5145 Many of the advanced features of this package, such as @code{defun*},
|
|
|
5146 @code{loop}, and @code{setf}, are implemented as Lisp macros. In
|
|
|
5147 byte-compiled code, these complex notations will be expanded into
|
|
|
5148 equivalent Lisp code which is simple and efficient. For example,
|
|
|
5149 the forms
|
|
|
5150
|
|
|
5151 @example
|
|
|
5152 (incf i n)
|
|
|
5153 (push x (car p))
|
|
|
5154 @end example
|
|
|
5155
|
|
|
5156 @noindent
|
|
|
5157 are expanded at compile-time to the Lisp forms
|
|
|
5158
|
|
|
5159 @example
|
|
|
5160 (setq i (+ i n))
|
|
|
5161 (setcar p (cons x (car p)))
|
|
|
5162 @end example
|
|
|
5163
|
|
|
5164 @noindent
|
|
|
5165 which are the most efficient ways of doing these respective operations
|
|
|
5166 in Lisp. Thus, there is no performance penalty for using the more
|
|
|
5167 readable @code{incf} and @code{push} forms in your compiled code.
|
|
|
5168
|
|
|
5169 @emph{Interpreted} code, on the other hand, must expand these macros
|
|
|
5170 every time they are executed. For this reason it is strongly
|
|
|
5171 recommended that code making heavy use of macros be compiled.
|
|
|
5172 (The features labelled ``Special Form'' instead of ``Function'' in
|
|
|
5173 this manual are macros.) A loop using @code{incf} a hundred times
|
|
|
5174 will execute considerably faster if compiled, and will also
|
|
|
5175 garbage-collect less because the macro expansion will not have
|
|
|
5176 to be generated, used, and thrown away a hundred times.
|
|
|
5177
|
|
|
5178 You can find out how a macro expands by using the
|
|
|
5179 @code{cl-prettyexpand} function.
|
|
|
5180
|
|
|
5181 @defun cl-prettyexpand form &optional full
|
|
|
5182 This function takes a single Lisp form as an argument and inserts
|
|
|
5183 a nicely formatted copy of it in the current buffer (which must be
|
|
|
5184 in Lisp mode so that indentation works properly). It also expands
|
|
|
5185 all Lisp macros which appear in the form. The easiest way to use
|
|
|
5186 this function is to go to the @code{*scratch*} buffer and type, say,
|
|
|
5187
|
|
|
5188 @example
|
|
|
5189 (cl-prettyexpand '(loop for x below 10 collect x))
|
|
|
5190 @end example
|
|
|
5191
|
|
|
5192 @noindent
|
|
|
5193 and type @kbd{C-x C-e} immediately after the closing parenthesis;
|
|
|
5194 the expansion
|
|
|
5195
|
|
|
5196 @example
|
|
|
5197 (block nil
|
|
|
5198 (let* ((x 0)
|
|
|
5199 (G1004 nil))
|
|
|
5200 (while (< x 10)
|
|
|
5201 (setq G1004 (cons x G1004))
|
|
|
5202 (setq x (+ x 1)))
|
|
|
5203 (nreverse G1004)))
|
|
|
5204 @end example
|
|
|
5205
|
|
|
5206 @noindent
|
|
|
5207 will be inserted into the buffer. (The @code{block} macro is
|
|
|
5208 expanded differently in the interpreter and compiler, so
|
|
|
5209 @code{cl-prettyexpand} just leaves it alone. The temporary
|
|
|
5210 variable @code{G1004} was created by @code{gensym}.)
|
|
|
5211
|
|
|
5212 If the optional argument @var{full} is true, then @emph{all}
|
|
|
5213 macros are expanded, including @code{block}, @code{eval-when},
|
|
|
5214 and compiler macros. Expansion is done as if @var{form} were
|
|
|
5215 a top-level form in a file being compiled. For example,
|
|
|
5216
|
|
|
5217 @example
|
|
|
5218 (cl-prettyexpand '(pushnew 'x list))
|
|
|
5219 @print{} (setq list (adjoin 'x list))
|
|
|
5220 (cl-prettyexpand '(pushnew 'x list) t)
|
|
|
5221 @print{} (setq list (if (memq 'x list) list (cons 'x list)))
|
|
|
5222 (cl-prettyexpand '(caddr (member* 'a list)) t)
|
|
|
5223 @print{} (car (cdr (cdr (memq 'a list))))
|
|
|
5224 @end example
|
|
|
5225
|
|
|
5226 Note that @code{adjoin}, @code{caddr}, and @code{member*} all
|
|
|
5227 have built-in compiler macros to optimize them in common cases.
|
|
|
5228 @end defun
|
|
|
5229
|
|
|
5230 @ifinfo
|
|
|
5231 @example
|
|
|
5232
|
|
|
5233 @end example
|
|
|
5234 @end ifinfo
|
|
|
5235 @appendixsec Error Checking
|
|
|
5236
|
|
|
5237 @noindent
|
|
|
5238 Common Lisp compliance has in general not been sacrificed for the
|
|
|
5239 sake of efficiency. A few exceptions have been made for cases
|
|
|
5240 where substantial gains were possible at the expense of marginal
|
|
|
5241 incompatibility. One example is the use of @code{memq} (which is
|
|
|
5242 treated very efficiently by the byte-compiler) to scan for keyword
|
|
|
5243 arguments; this can become confused in rare cases when keyword
|
|
|
5244 symbols are used as both keywords and data values at once. This
|
|
|
5245 is extremely unlikely to occur in practical code, and the use of
|
|
|
5246 @code{memq} allows functions with keyword arguments to be nearly
|
|
|
5247 as fast as functions that use @code{&optional} arguments.
|
|
|
5248
|
|
|
5249 The Common Lisp standard (as embodied in Steele's book) uses the
|
|
|
5250 phrase ``it is an error if'' to indicate a situation which is not
|
|
|
5251 supposed to arise in complying programs; implementations are strongly
|
|
|
5252 encouraged but not required to signal an error in these situations.
|
|
|
5253 This package sometimes omits such error checking in the interest of
|
|
|
5254 compactness and efficiency. For example, @code{do} variable
|
|
|
5255 specifiers are supposed to be lists of one, two, or three forms;
|
|
|
5256 extra forms are ignored by this package rather than signalling a
|
|
|
5257 syntax error. The @code{endp} function is simply a synonym for
|
|
|
5258 @code{null} in this package. Functions taking keyword arguments
|
|
|
5259 will accept an odd number of arguments, treating the trailing
|
|
|
5260 keyword as if it were followed by the value @code{nil}.
|
|
|
5261
|
|
|
5262 Argument lists (as processed by @code{defun*} and friends)
|
|
|
5263 @emph{are} checked rigorously except for the minor point just
|
|
|
5264 mentioned; in particular, keyword arguments are checked for
|
|
|
5265 validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
|
|
|
5266 are fully implemented. Keyword validity checking is slightly
|
|
|
5267 time consuming (though not too bad in byte-compiled code);
|
|
|
5268 you can use @code{&allow-other-keys} to omit this check. Functions
|
|
|
5269 defined in this package such as @code{find} and @code{member*}
|
|
|
5270 do check their keyword arguments for validity.
|
|
|
5271
|
|
|
5272 @ifinfo
|
|
|
5273 @example
|
|
|
5274
|
|
|
5275 @end example
|
|
|
5276 @end ifinfo
|
|
|
5277 @appendixsec Optimizing Compiler
|
|
|
5278
|
|
|
5279 @noindent
|
|
|
5280 The byte-compiler that comes with Emacs 18 normally fails to expand
|
|
|
5281 macros that appear in top-level positions in the file (i.e., outside
|
|
|
5282 of @code{defun}s or other enclosing forms). This would have
|
|
|
5283 disastrous consequences to programs that used such top-level macros
|
|
|
5284 as @code{defun*}, @code{eval-when}, and @code{defstruct}. To
|
|
|
5285 work around this problem, the @dfn{CL} package patches the Emacs
|
|
|
5286 18 compiler to expand top-level macros. This patch will apply to
|
|
|
5287 your own macros, too, if they are used in a top-level context.
|
|
|
5288 The patch will not harm versions of the Emacs 18 compiler which
|
|
|
5289 have already had a similar patch applied, nor will it affect the
|
|
|
5290 optimizing Emacs 19 byte-compiler written by Jamie Zawinski and
|
|
|
5291 Hallvard Furuseth. The patch is applied to the byte compiler's
|
|
|
5292 code in Emacs' memory, @emph{not} to the @file{bytecomp.elc} file
|
|
|
5293 stored on disk.
|
|
|
5294
|
|
|
5295 The Emacs 19 compiler (for Emacs 18) is available from various
|
|
|
5296 Emacs Lisp archive sites such as @code{archive.cis.ohio-state.edu}.
|
|
|
5297 Its use is highly recommended; many of the Common Lisp macros emit
|
|
|
5298 code which can be improved by optimization. In particular,
|
|
|
5299 @code{block}s (whether explicit or implicit in constructs like
|
|
|
5300 @code{defun*} and @code{loop}) carry a fair run-time penalty; the
|
|
|
5301 optimizing compiler removes @code{block}s which are not actually
|
|
|
5302 referenced by @code{return} or @code{return-from} inside the block.
|
|
|
5303
|
|
|
5304 @node Common Lisp Compatibility, Old CL Compatibility, Efficiency Concerns, Top
|
|
|
5305 @appendix Common Lisp Compatibility
|
|
|
5306
|
|
|
5307 @noindent
|
|
|
5308 Following is a list of all known incompatibilities between this
|
|
|
5309 package and Common Lisp as documented in Steele (2nd edition).
|
|
|
5310
|
|
|
5311 Certain function names, such as @code{member}, @code{assoc}, and
|
|
|
5312 @code{floor}, were already taken by (incompatible) Emacs Lisp
|
|
|
5313 functions; this package appends @samp{*} to the names of its
|
|
|
5314 Common Lisp versions of these functions.
|
|
|
5315
|
|
|
5316 The word @code{defun*} is required instead of @code{defun} in order
|
|
|
5317 to use extended Common Lisp argument lists in a function. Likewise,
|
|
|
5318 @code{defmacro*} and @code{function*} are versions of those forms
|
|
|
5319 which understand full-featured argument lists. The @code{&whole}
|
|
|
5320 keyword does not work in @code{defmacro} argument lists (except
|
|
|
5321 inside recursive argument lists).
|
|
|
5322
|
|
|
5323 In order to allow an efficient implementation, keyword arguments use
|
|
|
5324 a slightly cheesy parser which may be confused if a keyword symbol
|
|
|
5325 is passed as the @emph{value} of another keyword argument.
|
|
|
5326 (Specifically, @code{(memq :@var{keyword} @var{rest-of-arguments})}
|
|
|
5327 is used to scan for @code{:@var{keyword}} among the supplied
|
|
|
5328 keyword arguments.)
|
|
|
5329
|
|
|
5330 The @code{eql} and @code{equal} predicates do not distinguish
|
|
|
5331 between IEEE floating-point plus and minus zero. The @code{equalp}
|
|
|
5332 predicate has several differences with Common Lisp; @pxref{Predicates}.
|
|
|
5333
|
|
|
5334 The @code{setf} mechanism is entirely compatible, except that
|
|
|
5335 setf-methods return a list of five values rather than five
|
|
|
5336 values directly. Also, the new ``@code{setf} function'' concept
|
|
|
5337 (typified by @code{(defun (setf foo) @dots{})}) is not implemented.
|
|
|
5338
|
|
|
5339 The @code{do-all-symbols} form is the same as @code{do-symbols}
|
|
|
5340 with no @var{obarray} argument. In Common Lisp, this form would
|
|
|
5341 iterate over all symbols in all packages. Since Emacs obarrays
|
|
|
5342 are not a first-class package mechanism, there is no way for
|
|
|
5343 @code{do-all-symbols} to locate any but the default obarray.
|
|
|
5344
|
|
|
5345 The @code{loop} macro is complete except that @code{loop-finish}
|
|
|
5346 and type specifiers are unimplemented.
|
|
|
5347
|
|
|
5348 The multiple-value return facility treats lists as multiple
|
|
|
5349 values, since Emacs Lisp cannot support multiple return values
|
|
|
5350 directly. The macros will be compatible with Common Lisp if
|
|
|
5351 @code{values} or @code{values-list} is always used to return to
|
|
|
5352 a @code{multiple-value-bind} or other multiple-value receiver;
|
|
|
5353 if @code{values} is used without @code{multiple-value-@dots{}}
|
|
|
5354 or vice-versa the effect will be different from Common Lisp.
|
|
|
5355
|
|
|
5356 Many Common Lisp declarations are ignored, and others match
|
|
|
5357 the Common Lisp standard in concept but not in detail. For
|
|
|
5358 example, local @code{special} declarations, which are purely
|
|
|
5359 advisory in Emacs Lisp, do not rigorously obey the scoping rules
|
|
|
5360 set down in Steele's book.
|
|
|
5361
|
|
|
5362 The variable @code{*gensym-counter*} starts out with a pseudo-random
|
|
|
5363 value rather than with zero. This is to cope with the fact that
|
|
|
5364 generated symbols become interned when they are written to and
|
|
|
5365 loaded back from a file.
|
|
|
5366
|
|
|
5367 The @code{defstruct} facility is compatible, except that structures
|
|
|
5368 are of type @code{:type vector :named} by default rather than some
|
|
|
5369 special, distinct type. Also, the @code{:type} slot option is ignored.
|
|
|
5370
|
|
|
5371 The second argument of @code{check-type} is treated differently.
|
|
|
5372
|
|
|
5373 @node Old CL Compatibility, Porting Common Lisp, Common Lisp Compatibility, Top
|
|
|
5374 @appendix Old CL Compatibility
|
|
|
5375
|
|
|
5376 @noindent
|
|
|
5377 Following is a list of all known incompatibilities between this package
|
|
|
5378 and the older Quiroz @file{cl.el} package.
|
|
|
5379
|
|
|
5380 This package's emulation of multiple return values in functions is
|
|
|
5381 incompatible with that of the older package. That package attempted
|
|
|
5382 to come as close as possible to true Common Lisp multiple return
|
|
|
5383 values; unfortunately, it could not be 100% reliable and so was prone
|
|
|
5384 to occasional surprises if used freely. This package uses a simpler
|
|
|
5385 method, namely replacing multiple values with lists of values, which
|
|
|
5386 is more predictable though more noticeably different from Common Lisp.
|
|
|
5387
|
|
|
5388 The @code{defkeyword} form and @code{keywordp} function are not
|
|
|
5389 implemented in this package.
|
|
|
5390
|
|
|
5391 The @code{member}, @code{floor}, @code{ceiling}, @code{truncate},
|
|
|
5392 @code{round}, @code{mod}, and @code{rem} functions are suffixed
|
|
|
5393 by @samp{*} in this package to avoid collision with existing
|
|
|
5394 functions in Emacs 18 or Emacs 19. The older package simply
|
|
|
5395 redefined these functions, overwriting the built-in meanings and
|
|
|
5396 causing serious portability problems with Emacs 19. (Some more
|
|
|
5397 recent versions of the Quiroz package changed the names to
|
|
|
5398 @code{cl-member}, etc.; this package defines the latter names as
|
|
|
5399 aliases for @code{member*}, etc.)
|
|
|
5400
|
|
|
5401 Certain functions in the old package which were buggy or inconsistent
|
|
|
5402 with the Common Lisp standard are incompatible with the conforming
|
|
|
5403 versions in this package. For example, @code{eql} and @code{member}
|
|
|
5404 were synonyms for @code{eq} and @code{memq} in that package, @code{setf}
|
|
|
5405 failed to preserve correct order of evaluation of its arguments, etc.
|
|
|
5406
|
|
|
5407 Finally, unlike the older package, this package is careful to
|
|
|
5408 prefix all of its internal names with @code{cl-}. Except for a
|
|
|
5409 few functions which are explicitly defined as additional features
|
|
|
5410 (such as @code{floatp-safe} and @code{letf}), this package does not
|
|
|
5411 export any non-@samp{cl-} symbols which are not also part of Common
|
|
|
5412 Lisp.
|
|
|
5413
|
|
|
5414 @ifinfo
|
|
|
5415 @example
|
|
|
5416
|
|
|
5417 @end example
|
|
|
5418 @end ifinfo
|
|
|
5419 @appendixsec The @code{cl-compat} package
|
|
|
5420
|
|
|
5421 @noindent
|
|
|
5422 The @dfn{CL} package includes emulations of some features of the
|
|
|
5423 old @file{cl.el}, in the form of a compatibility package
|
|
|
5424 @code{cl-compat}. To use it, put @code{(require 'cl-compat)} in
|
|
|
5425 your program.
|
|
|
5426
|
|
|
5427 The old package defined a number of internal routines without
|
|
|
5428 @code{cl-} prefixes or other annotations. Call to these routines
|
|
|
5429 may have crept into existing Lisp code. @code{cl-compat}
|
|
|
5430 provides emulations of the following internal routines:
|
|
|
5431 @code{pair-with-newsyms}, @code{zip-lists}, @code{unzip-lists},
|
|
|
5432 @code{reassemble-arglists}, @code{duplicate-symbols-p},
|
|
|
5433 @code{safe-idiv}.
|
|
|
5434
|
|
|
5435 Some @code{setf} forms translated into calls to internal
|
|
|
5436 functions that user code might call directly. The functions
|
|
|
5437 @code{setnth}, @code{setnthcdr}, and @code{setelt} fall in
|
|
|
5438 this category; they are defined by @code{cl-compat}, but the
|
|
|
5439 best fix is to change to use @code{setf} properly.
|
|
|
5440
|
|
|
5441 The @code{cl-compat} file defines the keyword functions
|
|
|
5442 @code{keywordp}, @code{keyword-of}, and @code{defkeyword},
|
|
|
5443 which are not defined by the new @dfn{CL} package because the
|
|
|
5444 use of keywords as data is discouraged.
|
|
|
5445
|
|
|
5446 The @code{build-klist} mechanism for parsing keyword arguments
|
|
|
5447 is emulated by @code{cl-compat}; the @code{with-keyword-args}
|
|
|
5448 macro is not, however, and in any case it's best to change to
|
|
|
5449 use the more natural keyword argument processing offered by
|
|
|
5450 @code{defun*}.
|
|
|
5451
|
|
|
5452 Multiple return values are treated differently by the two
|
|
|
5453 Common Lisp packages. The old package's method was more
|
|
|
5454 compatible with true Common Lisp, though it used heuristics
|
|
|
5455 that caused it to report spurious multiple return values in
|
|
|
5456 certain cases. The @code{cl-compat} package defines a set
|
|
|
5457 of multiple-value macros that are compatible with the old
|
|
|
5458 CL package; again, they are heuristic in nature, but they
|
|
|
5459 are guaranteed to work in any case where the old package's
|
|
|
5460 macros worked. To avoid name collision with the ``official''
|
|
|
5461 multiple-value facilities, the ones in @code{cl-compat} have
|
|
|
5462 capitalized names: @code{Values}, @code{Values-list},
|
|
|
5463 @code{Multiple-value-bind}, etc.
|
|
|
5464
|
|
|
5465 The functions @code{cl-floor}, @code{cl-ceiling}, @code{cl-truncate},
|
|
|
5466 and @code{cl-round} are defined by @code{cl-compat} to use the
|
|
|
5467 old-style multiple-value mechanism, just as they did in the old
|
|
|
5468 package. The newer @code{floor*} and friends return their two
|
|
|
5469 results in a list rather than as multiple values. Note that
|
|
|
5470 older versions of the old package used the unadorned names
|
|
|
5471 @code{floor}, @code{ceiling}, etc.; @code{cl-compat} cannot use
|
|
|
5472 these names because they conflict with Emacs 19 built-ins.
|
|
|
5473
|
|
|
5474 @node Porting Common Lisp, Function Index, Old CL Compatibility, Top
|
|
|
5475 @appendix Porting Common Lisp
|
|
|
5476
|
|
|
5477 @noindent
|
|
|
5478 This package is meant to be used as an extension to Emacs Lisp,
|
|
|
5479 not as an Emacs implementation of true Common Lisp. Some of the
|
|
|
5480 remaining differences between Emacs Lisp and Common Lisp make it
|
|
|
5481 difficult to port large Common Lisp applications to Emacs. For
|
|
|
5482 one, some of the features in this package are not fully compliant
|
|
|
5483 with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
|
|
|
5484 are also quite a few features that this package does not provide
|
|
|
5485 at all. Here are some major omissions that you will want watch out
|
|
|
5486 for when bringing Common Lisp code into Emacs.
|
|
|
5487
|
|
|
5488 @itemize @bullet
|
|
|
5489 @item
|
|
|
5490 Case-insensitivity. Symbols in Common Lisp are case-insensitive
|
|
|
5491 by default. Some programs refer to a function or variable as
|
|
|
5492 @code{foo} in one place and @code{Foo} or @code{FOO} in another.
|
|
|
5493 Emacs Lisp will treat these as three distinct symbols.
|
|
|
5494
|
|
|
5495 Some Common Lisp code is written in all upper-case. While Emacs
|
|
|
5496 is happy to let the program's own functions and variables use
|
|
|
5497 this convention, calls to Lisp builtins like @code{if} and
|
|
|
5498 @code{defun} will have to be changed to lower-case.
|
|
|
5499
|
|
|
5500 @item
|
|
|
5501 Lexical scoping. In Common Lisp, function arguments and @code{let}
|
|
|
5502 bindings apply only to references physically within their bodies
|
|
|
5503 (or within macro expansions in their bodies). Emacs Lisp, by
|
|
|
5504 contrast, uses @dfn{dynamic scoping} wherein a binding to a
|
|
|
5505 variable is visible even inside functions called from the body.
|
|
|
5506
|
|
|
5507 Variables in Common Lisp can be made dynamically scoped by
|
|
|
5508 declaring them @code{special} or using @code{defvar}. In Emacs
|
|
|
5509 Lisp it is as if all variables were declared @code{special}.
|
|
|
5510
|
|
|
5511 Often you can use code that was written for lexical scoping
|
|
|
5512 even in a dynamically scoped Lisp, but not always. Here is
|
|
|
5513 an example of a Common Lisp code fragment that would fail in
|
|
|
5514 Emacs Lisp:
|
|
|
5515
|
|
|
5516 @example
|
|
|
5517 (defun map-odd-elements (func list)
|
|
|
5518 (loop for x in list
|
|
|
5519 for flag = t then (not flag)
|
|
|
5520 collect (if flag x (funcall func x))))
|
|
|
5521
|
|
|
5522 (defun add-odd-elements (list x)
|
|
|
5523 (map-odd-elements (function (lambda (a) (+ a x))) list))
|
|
|
5524 @end example
|
|
|
5525
|
|
|
5526 @noindent
|
|
|
5527 In Common Lisp, the two functions' usages of @code{x} are completely
|
|
|
5528 independent. In Emacs Lisp, the binding to @code{x} made by
|
|
|
5529 @code{add-odd-elements} will have been hidden by the binding
|
|
|
5530 in @code{map-odd-elements} by the time the @code{(+ a x)} function
|
|
|
5531 is called.
|
|
|
5532
|
|
|
5533 (This package avoids such problems in its own mapping functions
|
|
|
5534 by using names like @code{cl-x} instead of @code{x} internally;
|
|
|
5535 as long as you don't use the @code{cl-} prefix for your own
|
|
|
5536 variables no collision can occur.)
|
|
|
5537
|
|
|
5538 @xref{Lexical Bindings}, for a description of the @code{lexical-let}
|
|
|
5539 form which establishes a Common Lisp-style lexical binding, and some
|
|
|
5540 examples of how it differs from Emacs' regular @code{let}.
|
|
|
5541
|
|
|
5542 @item
|
|
|
5543 Common Lisp allows the shorthand @code{#'x} to stand for
|
|
|
5544 @code{(function x)}, just as @code{'x} stands for @code{(quote x)}.
|
|
|
5545 In Common Lisp, one traditionally uses @code{#'} notation when
|
|
|
5546 referring to the name of a function. In Emacs Lisp, it works
|
|
|
5547 just as well to use a regular quote:
|
|
|
5548
|
|
|
5549 @example
|
|
442
|
5550 (loop for x in y by #'cddr collect (mapcar #'plusp x)) ; Common Lisp
|
|
|
5551 (loop for x in y by 'cddr collect (mapcar 'plusp x)) ; Emacs Lisp
|
|
428
|
5552 @end example
|
|
|
5553
|
|
|
5554 When @code{#'} introduces a @code{lambda} form, it is best to
|
|
|
5555 write out @code{(function ...)} longhand in Emacs Lisp. You can
|
|
|
5556 use a regular quote, but then the byte-compiler won't know that
|
|
|
5557 the @code{lambda} expression is code that can be compiled.
|
|
|
5558
|
|
|
5559 @example
|
|
|
5560 (mapcar #'(lambda (x) (* x 2)) list) ; Common Lisp
|
|
|
5561 (mapcar (function (lambda (x) (* x 2))) list) ; Emacs Lisp
|
|
|
5562 @end example
|
|
|
5563
|
|
|
5564 XEmacs supports @code{#'} notation starting with version 19.8.
|
|
|
5565
|
|
|
5566 @item
|
|
|
5567 Reader macros. Common Lisp includes a second type of macro that
|
|
|
5568 works at the level of individual characters. For example, Common
|
|
|
5569 Lisp implements the quote notation by a reader macro called @code{'},
|
|
|
5570 whereas Emacs Lisp's parser just treats quote as a special case.
|
|
|
5571 Some Lisp packages use reader macros to create special syntaxes
|
|
|
5572 for themselves, which the Emacs parser is incapable of reading.
|
|
|
5573
|
|
|
5574 @item
|
|
|
5575 Other syntactic features. Common Lisp provides a number of
|
|
|
5576 notations beginning with @code{#} that the Emacs Lisp parser
|
|
|
5577 won't understand. For example, @samp{#| ... |#} is an
|
|
|
5578 alternate comment notation, and @samp{#+lucid (foo)} tells
|
|
|
5579 the parser to ignore the @code{(foo)} except in Lucid Common
|
|
|
5580 Lisp.
|
|
|
5581
|
|
|
5582 The number prefixes `#b', `#o', and `#x', however, are supported
|
|
|
5583 by the Emacs Lisp parser to represent numbers in binary, octal,
|
|
|
5584 and hexadecimal notation (or radix), just like in Common Lisp.
|
|
|
5585
|
|
|
5586 @item
|
|
|
5587 Packages. In Common Lisp, symbols are divided into @dfn{packages}.
|
|
|
5588 Symbols that are Lisp built-ins are typically stored in one package;
|
|
|
5589 symbols that are vendor extensions are put in another, and each
|
|
|
5590 application program would have a package for its own symbols.
|
|
|
5591 Certain symbols are ``exported'' by a package and others are
|
|
|
5592 internal; certain packages ``use'' or import the exported symbols
|
|
|
5593 of other packages. To access symbols that would not normally be
|
|
|
5594 visible due to this importing and exporting, Common Lisp provides
|
|
|
5595 a syntax like @code{package:symbol} or @code{package::symbol}.
|
|
|
5596
|
|
|
5597 Emacs Lisp has a single namespace for all interned symbols, and
|
|
|
5598 then uses a naming convention of putting a prefix like @code{cl-}
|
|
|
5599 in front of the name. Some Emacs packages adopt the Common Lisp-like
|
|
|
5600 convention of using @code{cl:} or @code{cl::} as the prefix.
|
|
|
5601 However, the Emacs parser does not understand colons and just
|
|
|
5602 treats them as part of the symbol name. Thus, while @code{mapcar}
|
|
|
5603 and @code{lisp:mapcar} may refer to the same symbol in Common
|
|
|
5604 Lisp, they are totally distinct in Emacs Lisp. Common Lisp
|
|
|
5605 programs which refer to a symbol by the full name sometimes
|
|
|
5606 and the short name other times will not port cleanly to Emacs.
|
|
|
5607
|
|
|
5608 Emacs Lisp does have a concept of ``obarrays,'' which are
|
|
|
5609 package-like collections of symbols, but this feature is not
|
|
|
5610 strong enough to be used as a true package mechanism.
|
|
|
5611
|
|
|
5612 @item
|
|
|
5613 Keywords. The notation @code{:test-not} in Common Lisp really
|
|
|
5614 is a shorthand for @code{keyword:test-not}; keywords are just
|
|
|
5615 symbols in a built-in @code{keyword} package with the special
|
|
|
5616 property that all its symbols are automatically self-evaluating.
|
|
|
5617 Common Lisp programs often use keywords liberally to avoid
|
|
|
5618 having to use quotes.
|
|
|
5619
|
|
|
5620 In Emacs Lisp a keyword is just a symbol whose name begins with
|
|
|
5621 a colon; since the Emacs parser does not treat them specially,
|
|
|
5622 they have to be explicitly made self-evaluating by a statement
|
|
|
5623 like @code{(setq :test-not ':test-not)}. This package arranges
|
|
|
5624 to execute such a statement whenever @code{defun*} or some
|
|
|
5625 other form sees a keyword being used as an argument. Common
|
|
|
5626 Lisp code that assumes that a symbol @code{:mumble} will be
|
|
|
5627 self-evaluating even though it was never introduced by a
|
|
|
5628 @code{defun*} will have to be fixed.
|
|
|
5629
|
|
|
5630 @item
|
|
|
5631 The @code{format} function is quite different between Common
|
|
|
5632 Lisp and Emacs Lisp. It takes an additional ``destination''
|
|
|
5633 argument before the format string. A destination of @code{nil}
|
|
|
5634 means to format to a string as in Emacs Lisp; a destination
|
|
|
5635 of @code{t} means to write to the terminal (similar to
|
|
|
5636 @code{message} in Emacs). Also, format control strings are
|
|
|
5637 utterly different; @code{~} is used instead of @code{%} to
|
|
|
5638 introduce format codes, and the set of available codes is
|
|
|
5639 much richer. There are no notations like @code{\n} for
|
|
|
5640 string literals; instead, @code{format} is used with the
|
|
|
5641 ``newline'' format code, @code{~%}. More advanced formatting
|
|
|
5642 codes provide such features as paragraph filling, case
|
|
|
5643 conversion, and even loops and conditionals.
|
|
|
5644
|
|
|
5645 While it would have been possible to implement most of Common
|
|
|
5646 Lisp @code{format} in this package (under the name @code{format*},
|
|
|
5647 of course), it was not deemed worthwhile. It would have required
|
|
|
5648 a huge amount of code to implement even a decent subset of
|
|
|
5649 @code{format*}, yet the functionality it would provide over
|
|
|
5650 Emacs Lisp's @code{format} would rarely be useful.
|
|
|
5651
|
|
|
5652 @item
|
|
|
5653 Vector constants use square brackets in Emacs Lisp, but
|
|
|
5654 @code{#(a b c)} notation in Common Lisp. To further complicate
|
|
|
5655 matters, Emacs 19 introduces its own @code{#(} notation for
|
|
|
5656 something entirely different---strings with properties.
|
|
|
5657
|
|
|
5658 @item
|
|
|
5659 Characters are distinct from integers in Common Lisp. The
|
|
|
5660 notation for character constants is also different: @code{#\A}
|
|
|
5661 instead of @code{?A}. Also, @code{string=} and @code{string-equal}
|
|
|
5662 are synonyms in Emacs Lisp whereas the latter is case-insensitive
|
|
|
5663 in Common Lisp.
|
|
|
5664
|
|
|
5665 @item
|
|
|
5666 Data types. Some Common Lisp data types do not exist in Emacs
|
|
|
5667 Lisp. Rational numbers and complex numbers are not present,
|
|
|
5668 nor are large integers (all integers are ``fixnums''). All
|
|
|
5669 arrays are one-dimensional. There are no readtables or pathnames;
|
|
|
5670 streams are a set of existing data types rather than a new data
|
|
|
5671 type of their own. Hash tables, random-states, structures, and
|
|
|
5672 packages (obarrays) are built from Lisp vectors or lists rather
|
|
|
5673 than being distinct types.
|
|
|
5674
|
|
|
5675 @item
|
|
|
5676 The Common Lisp Object System (CLOS) is not implemented,
|
|
|
5677 nor is the Common Lisp Condition System.
|
|
|
5678
|
|
|
5679 @item
|
|
|
5680 Common Lisp features that are completely redundant with Emacs
|
|
|
5681 Lisp features of a different name generally have not been
|
|
|
5682 implemented. For example, Common Lisp writes @code{defconstant}
|
|
|
5683 where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
|
|
|
5684 takes its arguments in different ways in the two Lisps but does
|
|
|
5685 exactly the same thing, so this package has not bothered to
|
|
|
5686 implement a Common Lisp-style @code{make-list}.
|
|
|
5687
|
|
|
5688 @item
|
|
|
5689 A few more notable Common Lisp features not included in this
|
|
|
5690 package: @code{compiler-let}, @code{tagbody}, @code{prog},
|
|
|
5691 @code{ldb/dpb}, @code{parse-integer}, @code{cerror}.
|
|
|
5692
|
|
|
5693 @item
|
|
|
5694 Recursion. While recursion works in Emacs Lisp just like it
|
|
|
5695 does in Common Lisp, various details of the Emacs Lisp system
|
|
|
5696 and compiler make recursion much less efficient than it is in
|
|
|
5697 most Lisps. Some schools of thought prefer to use recursion
|
|
|
5698 in Lisp over other techniques; they would sum a list of
|
|
|
5699 numbers using something like
|
|
|
5700
|
|
|
5701 @example
|
|
|
5702 (defun sum-list (list)
|
|
|
5703 (if list
|
|
|
5704 (+ (car list) (sum-list (cdr list)))
|
|
|
5705 0))
|
|
|
5706 @end example
|
|
|
5707
|
|
|
5708 @noindent
|
|
|
5709 where a more iteratively-minded programmer might write one of
|
|
|
5710 these forms:
|
|
|
5711
|
|
|
5712 @example
|
|
|
5713 (let ((total 0)) (dolist (x my-list) (incf total x)) total)
|
|
|
5714 (loop for x in my-list sum x)
|
|
|
5715 @end example
|
|
|
5716
|
|
|
5717 While this would be mainly a stylistic choice in most Common Lisps,
|
|
|
5718 in Emacs Lisp you should be aware that the iterative forms are
|
|
|
5719 much faster than recursion. Also, Lisp programmers will want to
|
|
|
5720 note that the current Emacs Lisp compiler does not optimize tail
|
|
|
5721 recursion.
|
|
|
5722 @end itemize
|
|
|
5723
|
|
|
5724 @node Function Index, Variable Index, Porting Common Lisp, Top
|
|
|
5725 @unnumbered Function Index
|
|
|
5726
|
|
|
5727 @printindex fn
|
|
|
5728
|
|
|
5729 @node Variable Index, , Function Index, Top
|
|
|
5730 @unnumbered Variable Index
|
|
|
5731
|
|
|
5732 @printindex vr
|
|
|
5733
|
|
|
5734 @contents
|
|
|
5735 @bye
|
