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4009494e | 1 | \input texinfo @c -*-texinfo-*- |
db78a8cb | 2 | @setfilename ../../info/cl |
4009494e | 3 | @settitle Common Lisp Extensions |
8d6510b9 | 4 | @include emacsver.texi |
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5 | |
6 | @copying | |
7 | This file documents the GNU Emacs Common Lisp emulation package. | |
8 | ||
44e97401 | 9 | Copyright @copyright{} 1993, 2001-2012 Free Software Foundation, Inc. |
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10 | |
11 | @quotation | |
12 | Permission is granted to copy, distribute and/or modify this document | |
6a2c4aec | 13 | under the terms of the GNU Free Documentation License, Version 1.3 or |
4009494e | 14 | any later version published by the Free Software Foundation; with no |
debf4439 GM |
15 | Invariant Sections, with the Front-Cover texts being ``A GNU Manual'', |
16 | and with the Back-Cover Texts as in (a) below. A copy of the license | |
17 | is included in the section entitled ``GNU Free Documentation License''. | |
4009494e | 18 | |
6f093307 GM |
19 | (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and |
20 | modify this GNU manual. Buying copies from the FSF supports it in | |
21 | developing GNU and promoting software freedom.'' | |
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22 | @end quotation |
23 | @end copying | |
24 | ||
0c973505 | 25 | @dircategory Emacs lisp libraries |
4009494e | 26 | @direntry |
9360256a | 27 | * CL: (cl). Partial Common Lisp support for Emacs Lisp. |
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28 | @end direntry |
29 | ||
30 | @finalout | |
31 | ||
32 | @titlepage | |
33 | @sp 6 | |
34 | @center @titlefont{Common Lisp Extensions} | |
35 | @sp 4 | |
36 | @center For GNU Emacs Lisp | |
37 | @sp 1 | |
8d6510b9 | 38 | @center as distributed with Emacs @value{EMACSVER} |
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39 | @sp 5 |
40 | @center Dave Gillespie | |
41 | @center daveg@@synaptics.com | |
42 | @page | |
43 | @vskip 0pt plus 1filll | |
44 | @insertcopying | |
45 | @end titlepage | |
46 | ||
5dc584b5 KB |
47 | @contents |
48 | ||
5dc584b5 | 49 | @ifnottex |
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50 | @node Top |
51 | @top GNU Emacs Common Lisp Emulation | |
52 | ||
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53 | @insertcopying |
54 | @end ifnottex | |
55 | ||
4009494e | 56 | @menu |
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57 | * Overview:: Basics, usage, etc. |
58 | * Program Structure:: Arglists, @code{cl-eval-when}, @code{defalias}. | |
59 | * Predicates:: @code{cl-typep} and @code{cl-equalp}. | |
5887564d | 60 | * Control Structure:: @code{cl-do}, @code{cl-loop}, etc. |
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61 | * Macros:: Destructuring, @code{cl-define-compiler-macro}. |
62 | * Declarations:: @code{cl-proclaim}, @code{cl-declare}, etc. | |
63 | * Symbols:: Property lists, @code{cl-gensym}. | |
64 | * Numbers:: Predicates, functions, random numbers. | |
65 | * Sequences:: Mapping, functions, searching, sorting. | |
66 | * Lists:: @code{cl-caddr}, @code{cl-sublis}, @code{cl-member}, @code{cl-assoc}, etc. | |
67 | * Structures:: @code{cl-defstruct}. | |
a6880551 | 68 | * Assertions:: @code{cl-check-type}, @code{cl-assert}. |
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69 | |
70 | * Efficiency Concerns:: Hints and techniques. | |
71 | * Common Lisp Compatibility:: All known differences with Steele. | |
8d6510b9 | 72 | * Porting Common Lisp:: Hints for porting Common Lisp code. |
3c0c6155 | 73 | * Obsolete Features:: Obsolete features. |
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74 | |
75 | * GNU Free Documentation License:: The license for this documentation. | |
76 | * Function Index:: | |
77 | * Variable Index:: | |
78 | @end menu | |
79 | ||
1d5b82ef | 80 | @node Overview |
4009494e | 81 | @chapter Overview |
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82 | |
83 | @noindent | |
1d5b82ef GM |
84 | This document describes a set of Emacs Lisp facilities borrowed from |
85 | Common Lisp. All the facilities are described here in detail. While | |
86 | this document does not assume any prior knowledge of Common Lisp, it | |
87 | does assume a basic familiarity with Emacs Lisp. | |
88 | ||
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89 | Common Lisp is a huge language, and Common Lisp systems tend to be |
90 | massive and extremely complex. Emacs Lisp, by contrast, is rather | |
91 | minimalist in the choice of Lisp features it offers the programmer. | |
92 | As Emacs Lisp programmers have grown in number, and the applications | |
93 | they write have grown more ambitious, it has become clear that Emacs | |
94 | Lisp could benefit from many of the conveniences of Common Lisp. | |
95 | ||
8d6510b9 | 96 | The @code{CL} package adds a number of Common Lisp functions and |
4009494e | 97 | control structures to Emacs Lisp. While not a 100% complete |
8d6510b9 | 98 | implementation of Common Lisp, @code{CL} adds enough functionality |
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99 | to make Emacs Lisp programming significantly more convenient. |
100 | ||
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101 | Some Common Lisp features have been omitted from this package |
102 | for various reasons: | |
103 | ||
104 | @itemize @bullet | |
105 | @item | |
106 | Some features are too complex or bulky relative to their benefit | |
107 | to Emacs Lisp programmers. CLOS and Common Lisp streams are fine | |
108 | examples of this group. | |
109 | ||
110 | @item | |
111 | Other features cannot be implemented without modification to the | |
112 | Emacs Lisp interpreter itself, such as multiple return values, | |
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113 | case-insensitive symbols, and complex numbers. |
114 | The @code{CL} package generally makes no attempt to emulate these | |
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115 | features. |
116 | ||
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117 | @end itemize |
118 | ||
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119 | This package was originally written by Dave Gillespie, |
120 | @file{daveg@@synaptics.com}, as a total rewrite of an earlier 1986 | |
121 | @file{cl.el} package by Cesar Quiroz. Care has been taken to ensure | |
122 | that each function is defined efficiently, concisely, and with minimal | |
123 | impact on the rest of the Emacs environment. Stefan Monnier added the | |
124 | file @file{cl-lib.el} and rationalized the namespace for Emacs 24.3. | |
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125 | |
126 | @menu | |
8d6510b9 | 127 | * Usage:: How to use the CL package. |
a05cb6e3 | 128 | * Organization:: The package's component files. |
8d6510b9 | 129 | * Naming Conventions:: Notes on CL function names. |
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130 | @end menu |
131 | ||
1d5b82ef | 132 | @node Usage |
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133 | @section Usage |
134 | ||
135 | @noindent | |
8d6510b9 GM |
136 | The @code{CL} package is distributed with Emacs, so there is no need |
137 | to install any additional files in order to start using it. Lisp code | |
138 | that uses features from the @code{CL} package should simply include at | |
139 | the beginning: | |
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140 | |
141 | @example | |
8d6510b9 | 142 | (require 'cl-lib) |
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143 | @end example |
144 | ||
145 | @noindent | |
8d6510b9 GM |
146 | You may wish to add such a statement to your init file, if you |
147 | make frequent use of CL features. | |
4009494e | 148 | |
1d5b82ef | 149 | @node Organization |
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150 | @section Organization |
151 | ||
152 | @noindent | |
8d6510b9 | 153 | The Common Lisp package is organized into four main files: |
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154 | |
155 | @table @file | |
8d6510b9 GM |
156 | @item cl-lib.el |
157 | This is the main file, which contains basic functions | |
158 | and information about the package. This file is relatively compact. | |
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159 | |
160 | @item cl-extra.el | |
161 | This file contains the larger, more complex or unusual functions. | |
162 | It is kept separate so that packages which only want to use Common | |
8d6510b9 | 163 | Lisp fundamentals like the @code{cl-incf} function won't need to pay |
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164 | the overhead of loading the more advanced functions. |
165 | ||
166 | @item cl-seq.el | |
167 | This file contains most of the advanced functions for operating | |
8d6510b9 | 168 | on sequences or lists, such as @code{cl-delete-if} and @code{cl-assoc}. |
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169 | |
170 | @item cl-macs.el | |
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171 | This file contains the features that are macros instead of functions. |
172 | Macros expand when the caller is compiled, not when it is run, so the | |
173 | macros generally only need to be present when the byte-compiler is | |
174 | running (or when the macros are used in uncompiled code). Most of the | |
175 | macros of this package are isolated in @file{cl-macs.el} so that they | |
176 | won't take up memory unless you are compiling. | |
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177 | @end table |
178 | ||
8d6510b9 | 179 | The file @file{cl-lib.el} includes all necessary @code{autoload} |
4009494e | 180 | commands for the functions and macros in the other three files. |
8d6510b9 | 181 | All you have to do is @code{(require 'cl-lib)}, and @file{cl-lib.el} |
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182 | will take care of pulling in the other files when they are |
183 | needed. | |
184 | ||
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185 | There is another file, @file{cl.el}, which was the main entry point to |
186 | the CL package prior to Emacs 24.3. Nowadays, it is replaced by | |
187 | @file{cl-lib.el}. The two provide the same features (in most cases), | |
188 | but use different function names (in fact, @file{cl.el} mainly just | |
189 | defines aliases to the @file{cl-lib.el} definitions). Where | |
190 | @file{cl-lib.el} defines a function called, for example, | |
191 | @code{cl-incf}, @file{cl.el} uses the same name but without the | |
192 | @samp{cl-} prefix, e.g. @code{incf} in this example. There are a few | |
193 | exceptions to this. First, functions such as @code{cl-defun} where | |
194 | the unprefixed version was already used for a standard Emacs Lisp | |
195 | function. In such cases, the @file{cl.el} version adds a @samp{*} | |
196 | suffix, e.g. @code{defun*}. Second, there are some obsolete features | |
197 | that are only implemented in @file{cl.el}, not in @file{cl-lib.el}, | |
198 | because they are replaced by other standard Emacs Lisp features. | |
199 | Finally, in a very few cases the old @file{cl.el} versions do not | |
200 | behave in exactly the same way as the @file{cl-lib.el} versions. | |
201 | @xref{Obsolete Features}. | |
202 | ||
203 | Since the old @file{cl.el} does not use a clean namespace, Emacs has a | |
204 | policy that packages distributed with Emacs must not load @code{cl} at | |
205 | run time. (It is ok for them to load @code{cl} at @emph{compile} | |
206 | time, with @code{eval-when-compile}, and use the macros it provides.) | |
207 | There is no such restriction on the use of @code{cl-lib}. New code | |
208 | should use @code{cl-lib} rather than @code{cl}. | |
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209 | |
210 | There is one more file, @file{cl-compat.el}, which defines some | |
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211 | routines from the older Quiroz CL package that are not otherwise |
212 | present in the new package. This file is obsolete and should not be | |
213 | used in new code. | |
4009494e | 214 | |
1d5b82ef | 215 | @node Naming Conventions |
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216 | @section Naming Conventions |
217 | ||
218 | @noindent | |
219 | Except where noted, all functions defined by this package have the | |
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220 | same calling conventions as their Common Lisp counterparts, and |
221 | names that are those of Common Lisp plus a @samp{cl-} prefix. | |
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222 | |
223 | Internal function and variable names in the package are prefixed | |
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224 | by @code{cl--}. Here is a complete list of functions prefixed by |
225 | @code{cl-} that were not taken from Common Lisp: | |
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226 | |
227 | @example | |
8d6510b9 GM |
228 | cl-callf cl-callf2 cl-defsubst |
229 | cl-floatp-safe cl-letf cl-letf* | |
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230 | @end example |
231 | ||
8d6510b9 | 232 | The following simple functions and macros are defined in @file{cl-lib.el}; |
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233 | they do not cause other components like @file{cl-extra} to be loaded. |
234 | ||
235 | @example | |
8d6510b9 GM |
236 | cl-floatp-safe cl-endp |
237 | cl-evenp cl-oddp cl-plusp cl-minusp | |
238 | cl-caaar .. cl-cddddr | |
239 | cl-list* cl-ldiff cl-rest cl-first .. cl-tenth | |
240 | cl-copy-list cl-subst cl-mapcar [2] | |
241 | cl-adjoin [3] cl-acons cl-pairlis | |
242 | cl-pushnew [3,4] cl-incf [4] cl-decf [4] | |
243 | cl-proclaim cl-declaim | |
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244 | @end example |
245 | ||
246 | @noindent | |
247 | [2] Only for one sequence argument or two list arguments. | |
248 | ||
249 | @noindent | |
250 | [3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified, | |
251 | and @code{:key} is not used. | |
252 | ||
253 | @noindent | |
254 | [4] Only when @var{place} is a plain variable name. | |
255 | ||
1d5b82ef | 256 | @node Program Structure |
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257 | @chapter Program Structure |
258 | ||
259 | @noindent | |
8d6510b9 | 260 | This section describes features of the @code{CL} package that have to |
4009494e | 261 | do with programs as a whole: advanced argument lists for functions, |
8d6510b9 | 262 | and the @code{cl-eval-when} construct. |
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263 | |
264 | @menu | |
8d6510b9 GM |
265 | * Argument Lists:: @code{&key}, @code{&aux}, @code{cl-defun}, @code{cl-defmacro}. |
266 | * Time of Evaluation:: The @code{cl-eval-when} construct. | |
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267 | @end menu |
268 | ||
1d5b82ef | 269 | @node Argument Lists |
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270 | @section Argument Lists |
271 | ||
272 | @noindent | |
273 | Emacs Lisp's notation for argument lists of functions is a subset of | |
274 | the Common Lisp notation. As well as the familiar @code{&optional} | |
275 | and @code{&rest} markers, Common Lisp allows you to specify default | |
276 | values for optional arguments, and it provides the additional markers | |
277 | @code{&key} and @code{&aux}. | |
278 | ||
279 | Since argument parsing is built-in to Emacs, there is no way for | |
280 | this package to implement Common Lisp argument lists seamlessly. | |
281 | Instead, this package defines alternates for several Lisp forms | |
282 | which you must use if you need Common Lisp argument lists. | |
283 | ||
e1117425 | 284 | @defmac cl-defun name arglist body... |
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285 | This form is identical to the regular @code{defun} form, except |
286 | that @var{arglist} is allowed to be a full Common Lisp argument | |
287 | list. Also, the function body is enclosed in an implicit block | |
288 | called @var{name}; @pxref{Blocks and Exits}. | |
e1117425 | 289 | @end defmac |
4009494e | 290 | |
e1117425 | 291 | @defmac cl-defsubst name arglist body... |
8d6510b9 | 292 | This is just like @code{cl-defun}, except that the function that |
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293 | is defined is automatically proclaimed @code{inline}, i.e., |
294 | calls to it may be expanded into in-line code by the byte compiler. | |
295 | This is analogous to the @code{defsubst} form; | |
8d6510b9 | 296 | @code{cl-defsubst} uses a different method (compiler macros) which |
da0bbbc4 | 297 | works in all versions of Emacs, and also generates somewhat more |
8d6510b9 | 298 | efficient inline expansions. In particular, @code{cl-defsubst} |
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299 | arranges for the processing of keyword arguments, default values, |
300 | etc., to be done at compile-time whenever possible. | |
e1117425 | 301 | @end defmac |
4009494e | 302 | |
e1117425 | 303 | @defmac cl-defmacro name arglist body... |
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304 | This is identical to the regular @code{defmacro} form, |
305 | except that @var{arglist} is allowed to be a full Common Lisp | |
306 | argument list. The @code{&environment} keyword is supported as | |
307 | described in Steele. The @code{&whole} keyword is supported only | |
308 | within destructured lists (see below); top-level @code{&whole} | |
309 | cannot be implemented with the current Emacs Lisp interpreter. | |
310 | The macro expander body is enclosed in an implicit block called | |
311 | @var{name}. | |
e1117425 | 312 | @end defmac |
4009494e | 313 | |
e1117425 | 314 | @defmac cl-function symbol-or-lambda |
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315 | This is identical to the regular @code{function} form, |
316 | except that if the argument is a @code{lambda} form then that | |
317 | form may use a full Common Lisp argument list. | |
e1117425 | 318 | @end defmac |
4009494e | 319 | |
8d6510b9 | 320 | Also, all forms (such as @code{cl-flet} and @code{cl-labels}) defined |
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321 | in this package that include @var{arglist}s in their syntax allow |
322 | full Common Lisp argument lists. | |
323 | ||
8d6510b9 GM |
324 | Note that it is @emph{not} necessary to use @code{cl-defun} in |
325 | order to have access to most @code{CL} features in your function. | |
326 | These features are always present; @code{cl-defun}'s only | |
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327 | difference from @code{defun} is its more flexible argument |
328 | lists and its implicit block. | |
329 | ||
330 | The full form of a Common Lisp argument list is | |
331 | ||
332 | @example | |
333 | (@var{var}... | |
334 | &optional (@var{var} @var{initform} @var{svar})... | |
335 | &rest @var{var} | |
336 | &key ((@var{keyword} @var{var}) @var{initform} @var{svar})... | |
337 | &aux (@var{var} @var{initform})...) | |
338 | @end example | |
339 | ||
340 | Each of the five argument list sections is optional. The @var{svar}, | |
341 | @var{initform}, and @var{keyword} parts are optional; if they are | |
342 | omitted, then @samp{(@var{var})} may be written simply @samp{@var{var}}. | |
343 | ||
344 | The first section consists of zero or more @dfn{required} arguments. | |
345 | These arguments must always be specified in a call to the function; | |
346 | there is no difference between Emacs Lisp and Common Lisp as far as | |
347 | required arguments are concerned. | |
348 | ||
349 | The second section consists of @dfn{optional} arguments. These | |
350 | arguments may be specified in the function call; if they are not, | |
351 | @var{initform} specifies the default value used for the argument. | |
352 | (No @var{initform} means to use @code{nil} as the default.) The | |
353 | @var{initform} is evaluated with the bindings for the preceding | |
354 | arguments already established; @code{(a &optional (b (1+ a)))} | |
355 | matches one or two arguments, with the second argument defaulting | |
356 | to one plus the first argument. If the @var{svar} is specified, | |
357 | it is an auxiliary variable which is bound to @code{t} if the optional | |
358 | argument was specified, or to @code{nil} if the argument was omitted. | |
359 | If you don't use an @var{svar}, then there will be no way for your | |
360 | function to tell whether it was called with no argument, or with | |
361 | the default value passed explicitly as an argument. | |
362 | ||
363 | The third section consists of a single @dfn{rest} argument. If | |
364 | more arguments were passed to the function than are accounted for | |
365 | by the required and optional arguments, those extra arguments are | |
366 | collected into a list and bound to the ``rest'' argument variable. | |
367 | Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp. | |
368 | Common Lisp accepts @code{&body} as a synonym for @code{&rest} in | |
369 | macro contexts; this package accepts it all the time. | |
370 | ||
371 | The fourth section consists of @dfn{keyword} arguments. These | |
372 | are optional arguments which are specified by name rather than | |
373 | positionally in the argument list. For example, | |
374 | ||
375 | @example | |
8d6510b9 | 376 | (cl-defun foo (a &optional b &key c d (e 17))) |
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377 | @end example |
378 | ||
379 | @noindent | |
380 | defines a function which may be called with one, two, or more | |
381 | arguments. The first two arguments are bound to @code{a} and | |
382 | @code{b} in the usual way. The remaining arguments must be | |
383 | pairs of the form @code{:c}, @code{:d}, or @code{:e} followed | |
384 | by the value to be bound to the corresponding argument variable. | |
385 | (Symbols whose names begin with a colon are called @dfn{keywords}, | |
386 | and they are self-quoting in the same way as @code{nil} and | |
387 | @code{t}.) | |
388 | ||
389 | For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five | |
390 | arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword | |
391 | appears more than once in the function call, the first occurrence | |
392 | takes precedence over the later ones. Note that it is not possible | |
393 | to specify keyword arguments without specifying the optional | |
394 | argument @code{b} as well, since @code{(foo 1 :c 2)} would bind | |
395 | @code{b} to the keyword @code{:c}, then signal an error because | |
396 | @code{2} is not a valid keyword. | |
397 | ||
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398 | You can also explicitly specify the keyword argument; it need not be |
399 | simply the variable name prefixed with a colon. For example, | |
400 | ||
401 | @example | |
8d6510b9 | 402 | (cl-defun bar (&key (a 1) ((baz b) 4))) |
09094f28 CY |
403 | @end example |
404 | ||
405 | @noindent | |
406 | ||
407 | specifies a keyword @code{:a} that sets the variable @code{a} with | |
408 | default value 1, as well as a keyword @code{baz} that sets the | |
409 | variable @code{b} with default value 4. In this case, because | |
410 | @code{baz} is not self-quoting, you must quote it explicitly in the | |
411 | function call, like this: | |
412 | ||
413 | @example | |
414 | (bar :a 10 'baz 42) | |
415 | @end example | |
416 | ||
417 | Ordinarily, it is an error to pass an unrecognized keyword to | |
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418 | a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask |
419 | Lisp to ignore unrecognized keywords, either by adding the | |
420 | marker @code{&allow-other-keys} after the keyword section | |
421 | of the argument list, or by specifying an @code{:allow-other-keys} | |
422 | argument in the call whose value is non-@code{nil}. If the | |
423 | function uses both @code{&rest} and @code{&key} at the same time, | |
424 | the ``rest'' argument is bound to the keyword list as it appears | |
425 | in the call. For example: | |
426 | ||
427 | @smallexample | |
8d6510b9 GM |
428 | (cl-defun find-thing (thing &rest rest &key need &allow-other-keys) |
429 | (or (apply 'cl-member thing thing-list :allow-other-keys t rest) | |
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430 | (if need (error "Thing not found")))) |
431 | @end smallexample | |
432 | ||
433 | @noindent | |
434 | This function takes a @code{:need} keyword argument, but also | |
435 | accepts other keyword arguments which are passed on to the | |
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436 | @code{cl-member} function. @code{allow-other-keys} is used to |
437 | keep both @code{find-thing} and @code{cl-member} from complaining | |
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438 | about each others' keywords in the arguments. |
439 | ||
440 | The fifth section of the argument list consists of @dfn{auxiliary | |
441 | variables}. These are not really arguments at all, but simply | |
442 | variables which are bound to @code{nil} or to the specified | |
443 | @var{initforms} during execution of the function. There is no | |
444 | difference between the following two functions, except for a | |
445 | matter of stylistic taste: | |
446 | ||
447 | @example | |
8d6510b9 | 448 | (cl-defun foo (a b &aux (c (+ a b)) d) |
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449 | @var{body}) |
450 | ||
8d6510b9 | 451 | (cl-defun foo (a b) |
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452 | (let ((c (+ a b)) d) |
453 | @var{body})) | |
454 | @end example | |
455 | ||
456 | Argument lists support @dfn{destructuring}. In Common Lisp, | |
457 | destructuring is only allowed with @code{defmacro}; this package | |
8d6510b9 | 458 | allows it with @code{cl-defun} and other argument lists as well. |
4009494e GM |
459 | In destructuring, any argument variable (@var{var} in the above |
460 | diagram) can be replaced by a list of variables, or more generally, | |
461 | a recursive argument list. The corresponding argument value must | |
462 | be a list whose elements match this recursive argument list. | |
463 | For example: | |
464 | ||
465 | @example | |
8d6510b9 | 466 | (cl-defmacro dolist ((var listform &optional resultform) |
4009494e GM |
467 | &rest body) |
468 | ...) | |
469 | @end example | |
470 | ||
471 | This says that the first argument of @code{dolist} must be a list | |
472 | of two or three items; if there are other arguments as well as this | |
473 | list, they are stored in @code{body}. All features allowed in | |
474 | regular argument lists are allowed in these recursive argument lists. | |
475 | In addition, the clause @samp{&whole @var{var}} is allowed at the | |
476 | front of a recursive argument list. It binds @var{var} to the | |
477 | whole list being matched; thus @code{(&whole all a b)} matches | |
478 | a list of two things, with @code{a} bound to the first thing, | |
479 | @code{b} bound to the second thing, and @code{all} bound to the | |
480 | list itself. (Common Lisp allows @code{&whole} in top-level | |
481 | @code{defmacro} argument lists as well, but Emacs Lisp does not | |
482 | support this usage.) | |
483 | ||
484 | One last feature of destructuring is that the argument list may be | |
485 | dotted, so that the argument list @code{(a b . c)} is functionally | |
486 | equivalent to @code{(a b &rest c)}. | |
487 | ||
488 | If the optimization quality @code{safety} is set to 0 | |
489 | (@pxref{Declarations}), error checking for wrong number of | |
490 | arguments and invalid keyword arguments is disabled. By default, | |
491 | argument lists are rigorously checked. | |
492 | ||
1d5b82ef | 493 | @node Time of Evaluation |
4009494e GM |
494 | @section Time of Evaluation |
495 | ||
496 | @noindent | |
497 | Normally, the byte-compiler does not actually execute the forms in | |
498 | a file it compiles. For example, if a file contains @code{(setq foo t)}, | |
499 | the act of compiling it will not actually set @code{foo} to @code{t}. | |
500 | This is true even if the @code{setq} was a top-level form (i.e., not | |
501 | enclosed in a @code{defun} or other form). Sometimes, though, you | |
502 | would like to have certain top-level forms evaluated at compile-time. | |
503 | For example, the compiler effectively evaluates @code{defmacro} forms | |
504 | at compile-time so that later parts of the file can refer to the | |
505 | macros that are defined. | |
506 | ||
e1117425 | 507 | @defmac cl-eval-when (situations...) forms... |
4009494e GM |
508 | This form controls when the body @var{forms} are evaluated. |
509 | The @var{situations} list may contain any set of the symbols | |
510 | @code{compile}, @code{load}, and @code{eval} (or their long-winded | |
511 | ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel}, | |
512 | and @code{:execute}). | |
513 | ||
8d6510b9 | 514 | The @code{cl-eval-when} form is handled differently depending on |
4009494e GM |
515 | whether or not it is being compiled as a top-level form. |
516 | Specifically, it gets special treatment if it is being compiled | |
517 | by a command such as @code{byte-compile-file} which compiles files | |
518 | or buffers of code, and it appears either literally at the | |
519 | top level of the file or inside a top-level @code{progn}. | |
520 | ||
8d6510b9 | 521 | For compiled top-level @code{cl-eval-when}s, the body @var{forms} are |
4009494e GM |
522 | executed at compile-time if @code{compile} is in the @var{situations} |
523 | list, and the @var{forms} are written out to the file (to be executed | |
524 | at load-time) if @code{load} is in the @var{situations} list. | |
525 | ||
526 | For non-compiled-top-level forms, only the @code{eval} situation is | |
527 | relevant. (This includes forms executed by the interpreter, forms | |
528 | compiled with @code{byte-compile} rather than @code{byte-compile-file}, | |
8d6510b9 | 529 | and non-top-level forms.) The @code{cl-eval-when} acts like a |
4009494e GM |
530 | @code{progn} if @code{eval} is specified, and like @code{nil} |
531 | (ignoring the body @var{forms}) if not. | |
532 | ||
8d6510b9 | 533 | The rules become more subtle when @code{cl-eval-when}s are nested; |
4009494e GM |
534 | consult Steele (second edition) for the gruesome details (and |
535 | some gruesome examples). | |
536 | ||
537 | Some simple examples: | |
538 | ||
539 | @example | |
540 | ;; Top-level forms in foo.el: | |
8d6510b9 GM |
541 | (cl-eval-when (compile) (setq foo1 'bar)) |
542 | (cl-eval-when (load) (setq foo2 'bar)) | |
543 | (cl-eval-when (compile load) (setq foo3 'bar)) | |
544 | (cl-eval-when (eval) (setq foo4 'bar)) | |
545 | (cl-eval-when (eval compile) (setq foo5 'bar)) | |
546 | (cl-eval-when (eval load) (setq foo6 'bar)) | |
547 | (cl-eval-when (eval compile load) (setq foo7 'bar)) | |
4009494e GM |
548 | @end example |
549 | ||
550 | When @file{foo.el} is compiled, these variables will be set during | |
551 | the compilation itself: | |
552 | ||
553 | @example | |
554 | foo1 foo3 foo5 foo7 ; `compile' | |
555 | @end example | |
556 | ||
557 | When @file{foo.elc} is loaded, these variables will be set: | |
558 | ||
559 | @example | |
560 | foo2 foo3 foo6 foo7 ; `load' | |
561 | @end example | |
562 | ||
563 | And if @file{foo.el} is loaded uncompiled, these variables will | |
564 | be set: | |
565 | ||
566 | @example | |
567 | foo4 foo5 foo6 foo7 ; `eval' | |
568 | @end example | |
569 | ||
8d6510b9 | 570 | If these seven @code{cl-eval-when}s had been, say, inside a @code{defun}, |
4009494e GM |
571 | then the first three would have been equivalent to @code{nil} and the |
572 | last four would have been equivalent to the corresponding @code{setq}s. | |
573 | ||
8d6510b9 | 574 | Note that @code{(cl-eval-when (load eval) @dots{})} is equivalent |
4009494e GM |
575 | to @code{(progn @dots{})} in all contexts. The compiler treats |
576 | certain top-level forms, like @code{defmacro} (sort-of) and | |
a05cb6e3 | 577 | @code{require}, as if they were wrapped in @code{(cl-eval-when |
4009494e | 578 | (compile load eval) @dots{})}. |
e1117425 | 579 | @end defmac |
4009494e | 580 | |
8d6510b9 | 581 | Emacs includes two special forms related to @code{cl-eval-when}. |
4009494e | 582 | One of these, @code{eval-when-compile}, is not quite equivalent to |
a05cb6e3 | 583 | any @code{cl-eval-when} construct and is described below. |
4009494e GM |
584 | |
585 | The other form, @code{(eval-and-compile @dots{})}, is exactly | |
a05cb6e3 | 586 | equivalent to @samp{(cl-eval-when (compile load eval) @dots{})} and |
4009494e GM |
587 | so is not itself defined by this package. |
588 | ||
e1117425 | 589 | @defmac eval-when-compile forms... |
4009494e GM |
590 | The @var{forms} are evaluated at compile-time; at execution time, |
591 | this form acts like a quoted constant of the resulting value. Used | |
592 | at top-level, @code{eval-when-compile} is just like @samp{eval-when | |
593 | (compile eval)}. In other contexts, @code{eval-when-compile} | |
594 | allows code to be evaluated once at compile-time for efficiency | |
595 | or other reasons. | |
596 | ||
597 | This form is similar to the @samp{#.} syntax of true Common Lisp. | |
e1117425 | 598 | @end defmac |
4009494e | 599 | |
e1117425 | 600 | @defmac cl-load-time-value form |
4009494e GM |
601 | The @var{form} is evaluated at load-time; at execution time, |
602 | this form acts like a quoted constant of the resulting value. | |
603 | ||
604 | Early Common Lisp had a @samp{#,} syntax that was similar to | |
605 | this, but ANSI Common Lisp replaced it with @code{load-time-value} | |
606 | and gave it more well-defined semantics. | |
607 | ||
8d6510b9 | 608 | In a compiled file, @code{cl-load-time-value} arranges for @var{form} |
4009494e GM |
609 | to be evaluated when the @file{.elc} file is loaded and then used |
610 | as if it were a quoted constant. In code compiled by | |
611 | @code{byte-compile} rather than @code{byte-compile-file}, the | |
612 | effect is identical to @code{eval-when-compile}. In uncompiled | |
8d6510b9 | 613 | code, both @code{eval-when-compile} and @code{cl-load-time-value} |
4009494e GM |
614 | act exactly like @code{progn}. |
615 | ||
616 | @example | |
617 | (defun report () | |
618 | (insert "This function was executed on: " | |
619 | (current-time-string) | |
620 | ", compiled on: " | |
621 | (eval-when-compile (current-time-string)) | |
622 | ;; or '#.(current-time-string) in real Common Lisp | |
623 | ", and loaded on: " | |
8d6510b9 | 624 | (cl-load-time-value (current-time-string)))) |
4009494e GM |
625 | @end example |
626 | ||
627 | @noindent | |
628 | Byte-compiled, the above defun will result in the following code | |
629 | (or its compiled equivalent, of course) in the @file{.elc} file: | |
630 | ||
631 | @example | |
632 | (setq --temp-- (current-time-string)) | |
633 | (defun report () | |
634 | (insert "This function was executed on: " | |
635 | (current-time-string) | |
636 | ", compiled on: " | |
637 | '"Wed Jun 23 18:33:43 1993" | |
638 | ", and loaded on: " | |
639 | --temp--)) | |
640 | @end example | |
e1117425 | 641 | @end defmac |
4009494e | 642 | |
1d5b82ef | 643 | @node Predicates |
4009494e GM |
644 | @chapter Predicates |
645 | ||
646 | @noindent | |
647 | This section describes functions for testing whether various | |
648 | facts are true or false. | |
649 | ||
650 | @menu | |
8d6510b9 GM |
651 | * Type Predicates:: @code{cl-typep}, @code{cl-deftype}, and @code{cl-coerce}. |
652 | * Equality Predicates:: @code{cl-equalp}. | |
4009494e GM |
653 | @end menu |
654 | ||
1d5b82ef | 655 | @node Type Predicates |
4009494e GM |
656 | @section Type Predicates |
657 | ||
8d6510b9 | 658 | @defun cl-typep object type |
4009494e GM |
659 | Check if @var{object} is of type @var{type}, where @var{type} is a |
660 | (quoted) type name of the sort used by Common Lisp. For example, | |
8d6510b9 | 661 | @code{(cl-typep foo 'integer)} is equivalent to @code{(integerp foo)}. |
4009494e GM |
662 | @end defun |
663 | ||
664 | The @var{type} argument to the above function is either a symbol | |
665 | or a list beginning with a symbol. | |
666 | ||
667 | @itemize @bullet | |
668 | @item | |
669 | If the type name is a symbol, Emacs appends @samp{-p} to the | |
670 | symbol name to form the name of a predicate function for testing | |
671 | the type. (Built-in predicates whose names end in @samp{p} rather | |
672 | than @samp{-p} are used when appropriate.) | |
673 | ||
674 | @item | |
675 | The type symbol @code{t} stands for the union of all types. | |
8d6510b9 | 676 | @code{(cl-typep @var{object} t)} is always true. Likewise, the |
4009494e | 677 | type symbol @code{nil} stands for nothing at all, and |
8d6510b9 | 678 | @code{(cl-typep @var{object} nil)} is always false. |
4009494e GM |
679 | |
680 | @item | |
681 | The type symbol @code{null} represents the symbol @code{nil}. | |
8d6510b9 | 682 | Thus @code{(cl-typep @var{object} 'null)} is equivalent to |
4009494e GM |
683 | @code{(null @var{object})}. |
684 | ||
685 | @item | |
686 | The type symbol @code{atom} represents all objects that are not cons | |
8d6510b9 | 687 | cells. Thus @code{(cl-typep @var{object} 'atom)} is equivalent to |
4009494e GM |
688 | @code{(atom @var{object})}. |
689 | ||
690 | @item | |
691 | The type symbol @code{real} is a synonym for @code{number}, and | |
692 | @code{fixnum} is a synonym for @code{integer}. | |
693 | ||
694 | @item | |
695 | The type symbols @code{character} and @code{string-char} match | |
696 | integers in the range from 0 to 255. | |
697 | ||
698 | @item | |
8d6510b9 | 699 | The type symbol @code{float} uses the @code{cl-floatp-safe} predicate |
4009494e GM |
700 | defined by this package rather than @code{floatp}, so it will work |
701 | correctly even in Emacs versions without floating-point support. | |
702 | ||
703 | @item | |
704 | The type list @code{(integer @var{low} @var{high})} represents all | |
705 | integers between @var{low} and @var{high}, inclusive. Either bound | |
706 | may be a list of a single integer to specify an exclusive limit, | |
707 | or a @code{*} to specify no limit. The type @code{(integer * *)} | |
708 | is thus equivalent to @code{integer}. | |
709 | ||
710 | @item | |
711 | Likewise, lists beginning with @code{float}, @code{real}, or | |
712 | @code{number} represent numbers of that type falling in a particular | |
713 | range. | |
714 | ||
715 | @item | |
716 | Lists beginning with @code{and}, @code{or}, and @code{not} form | |
717 | combinations of types. For example, @code{(or integer (float 0 *))} | |
718 | represents all objects that are integers or non-negative floats. | |
719 | ||
720 | @item | |
8d6510b9 | 721 | Lists beginning with @code{member} or @code{cl-member} represent |
4009494e GM |
722 | objects @code{eql} to any of the following values. For example, |
723 | @code{(member 1 2 3 4)} is equivalent to @code{(integer 1 4)}, | |
724 | and @code{(member nil)} is equivalent to @code{null}. | |
725 | ||
726 | @item | |
727 | Lists of the form @code{(satisfies @var{predicate})} represent | |
728 | all objects for which @var{predicate} returns true when called | |
729 | with that object as an argument. | |
730 | @end itemize | |
731 | ||
732 | The following function and macro (not technically predicates) are | |
8d6510b9 | 733 | related to @code{cl-typep}. |
4009494e | 734 | |
8d6510b9 | 735 | @defun cl-coerce object type |
4009494e GM |
736 | This function attempts to convert @var{object} to the specified |
737 | @var{type}. If @var{object} is already of that type as determined by | |
a05cb6e3 | 738 | @code{cl-typep}, it is simply returned. Otherwise, certain types of |
4009494e GM |
739 | conversions will be made: If @var{type} is any sequence type |
740 | (@code{string}, @code{list}, etc.) then @var{object} will be | |
741 | converted to that type if possible. If @var{type} is | |
742 | @code{character}, then strings of length one and symbols with | |
743 | one-character names can be coerced. If @var{type} is @code{float}, | |
744 | then integers can be coerced in versions of Emacs that support | |
8d6510b9 | 745 | floats. In all other circumstances, @code{cl-coerce} signals an |
4009494e GM |
746 | error. |
747 | @end defun | |
748 | ||
e1117425 | 749 | @defmac cl-deftype name arglist forms... |
4009494e GM |
750 | This macro defines a new type called @var{name}. It is similar |
751 | to @code{defmacro} in many ways; when @var{name} is encountered | |
752 | as a type name, the body @var{forms} are evaluated and should | |
753 | return a type specifier that is equivalent to the type. The | |
754 | @var{arglist} is a Common Lisp argument list of the sort accepted | |
8d6510b9 | 755 | by @code{cl-defmacro}. The type specifier @samp{(@var{name} @var{args}...)} |
4009494e GM |
756 | is expanded by calling the expander with those arguments; the type |
757 | symbol @samp{@var{name}} is expanded by calling the expander with | |
758 | no arguments. The @var{arglist} is processed the same as for | |
8d6510b9 | 759 | @code{cl-defmacro} except that optional arguments without explicit |
4009494e GM |
760 | defaults use @code{*} instead of @code{nil} as the ``default'' |
761 | default. Some examples: | |
762 | ||
763 | @example | |
8d6510b9 GM |
764 | (cl-deftype null () '(satisfies null)) ; predefined |
765 | (cl-deftype list () '(or null cons)) ; predefined | |
766 | (cl-deftype unsigned-byte (&optional bits) | |
4009494e GM |
767 | (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits))))) |
768 | (unsigned-byte 8) @equiv{} (integer 0 255) | |
769 | (unsigned-byte) @equiv{} (integer 0 *) | |
770 | unsigned-byte @equiv{} (integer 0 *) | |
771 | @end example | |
772 | ||
773 | @noindent | |
774 | The last example shows how the Common Lisp @code{unsigned-byte} | |
775 | type specifier could be implemented if desired; this package does | |
776 | not implement @code{unsigned-byte} by default. | |
e1117425 | 777 | @end defmac |
4009494e | 778 | |
8d6510b9 GM |
779 | The @code{cl-typecase} and @code{cl-check-type} macros also use type |
780 | names. @xref{Conditionals}. @xref{Assertions}. The @code{cl-map}, | |
781 | @code{cl-concatenate}, and @code{cl-merge} functions take type-name | |
4009494e GM |
782 | arguments to specify the type of sequence to return. @xref{Sequences}. |
783 | ||
1d5b82ef | 784 | @node Equality Predicates |
4009494e GM |
785 | @section Equality Predicates |
786 | ||
787 | @noindent | |
8d6510b9 | 788 | This package defines the Common Lisp predicate @code{cl-equalp}. |
4009494e | 789 | |
8d6510b9 | 790 | @defun cl-equalp a b |
4009494e GM |
791 | This function is a more flexible version of @code{equal}. In |
792 | particular, it compares strings case-insensitively, and it compares | |
8d6510b9 | 793 | numbers without regard to type (so that @code{(cl-equalp 3 3.0)} is |
4009494e GM |
794 | true). Vectors and conses are compared recursively. All other |
795 | objects are compared as if by @code{equal}. | |
796 | ||
797 | This function differs from Common Lisp @code{equalp} in several | |
798 | respects. First, Common Lisp's @code{equalp} also compares | |
799 | @emph{characters} case-insensitively, which would be impractical | |
800 | in this package since Emacs does not distinguish between integers | |
801 | and characters. In keeping with the idea that strings are less | |
8d6510b9 | 802 | vector-like in Emacs Lisp, this package's @code{cl-equalp} also will |
4009494e GM |
803 | not compare strings against vectors of integers. |
804 | @end defun | |
805 | ||
806 | Also note that the Common Lisp functions @code{member} and @code{assoc} | |
807 | use @code{eql} to compare elements, whereas Emacs Lisp follows the | |
808 | MacLisp tradition and uses @code{equal} for these two functions. | |
8d6510b9 GM |
809 | In Emacs, use @code{memq} (or @code{cl-member}) and @code{assq} (or |
810 | @code{cl-assoc}) to get functions which use @code{eql} for comparisons. | |
4009494e | 811 | |
1d5b82ef | 812 | @node Control Structure |
4009494e GM |
813 | @chapter Control Structure |
814 | ||
815 | @noindent | |
816 | The features described in the following sections implement | |
5887564d GM |
817 | various advanced control structures, including extensions to the |
818 | standard @code{setf} facility, and a number of looping and conditional | |
4009494e GM |
819 | constructs. |
820 | ||
5887564d | 821 | @c FIXME |
f94b04fc | 822 | @c flet is not cl-flet. |
4009494e | 823 | @menu |
8d6510b9 | 824 | * Assignment:: The @code{cl-psetq} form. |
5887564d | 825 | * Generalized Variables:: Extensions to generalized variables. |
3c0c6155 | 826 | * Variable Bindings:: @code{cl-progv}, @code{flet}, @code{cl-macrolet}. |
8d6510b9 GM |
827 | * Conditionals:: @code{cl-case}, @code{cl-typecase}. |
828 | * Blocks and Exits:: @code{cl-block}, @code{cl-return}, @code{cl-return-from}. | |
829 | * Iteration:: @code{cl-do}, @code{cl-dotimes}, @code{cl-dolist}, @code{cl-do-symbols}. | |
830 | * Loop Facility:: The Common Lisp @code{cl-loop} macro. | |
f94b04fc | 831 | * Multiple Values:: @code{cl-values}, @code{cl-multiple-value-bind}, etc. |
4009494e GM |
832 | @end menu |
833 | ||
1d5b82ef | 834 | @node Assignment |
4009494e GM |
835 | @section Assignment |
836 | ||
837 | @noindent | |
8d6510b9 | 838 | The @code{cl-psetq} form is just like @code{setq}, except that multiple |
4009494e GM |
839 | assignments are done in parallel rather than sequentially. |
840 | ||
e1117425 | 841 | @defmac cl-psetq [symbol form]@dots{} |
4009494e GM |
842 | This special form (actually a macro) is used to assign to several |
843 | variables simultaneously. Given only one @var{symbol} and @var{form}, | |
844 | it has the same effect as @code{setq}. Given several @var{symbol} | |
845 | and @var{form} pairs, it evaluates all the @var{form}s in advance | |
846 | and then stores the corresponding variables afterwards. | |
847 | ||
848 | @example | |
849 | (setq x 2 y 3) | |
850 | (setq x (+ x y) y (* x y)) | |
851 | x | |
852 | @result{} 5 | |
853 | y ; @r{@code{y} was computed after @code{x} was set.} | |
854 | @result{} 15 | |
855 | (setq x 2 y 3) | |
8d6510b9 | 856 | (cl-psetq x (+ x y) y (* x y)) |
4009494e GM |
857 | x |
858 | @result{} 5 | |
859 | y ; @r{@code{y} was computed before @code{x} was set.} | |
860 | @result{} 6 | |
861 | @end example | |
862 | ||
8d6510b9 GM |
863 | The simplest use of @code{cl-psetq} is @code{(cl-psetq x y y x)}, which |
864 | exchanges the values of two variables. (The @code{cl-rotatef} form | |
4009494e GM |
865 | provides an even more convenient way to swap two variables; |
866 | @pxref{Modify Macros}.) | |
867 | ||
8d6510b9 | 868 | @code{cl-psetq} always returns @code{nil}. |
e1117425 | 869 | @end defmac |
4009494e | 870 | |
1d5b82ef | 871 | @node Generalized Variables |
4009494e GM |
872 | @section Generalized Variables |
873 | ||
5887564d GM |
874 | A @dfn{generalized variable} or @dfn{place form} is one of the many |
875 | places in Lisp memory where values can be stored. The simplest place | |
876 | form is a regular Lisp variable. But the cars and cdrs of lists, | |
877 | elements of arrays, properties of symbols, and many other locations | |
878 | are also places where Lisp values are stored. For basic information, | |
879 | @pxref{Generalized Variables,,,elisp,GNU Emacs Lisp Reference Manual}. | |
880 | This package provides several additional features related to | |
881 | generalized variables. | |
4009494e GM |
882 | |
883 | @menu | |
5887564d | 884 | * Setf Extensions:: Additional @code{setf} places. |
4ddedf94 | 885 | * Modify Macros:: @code{cl-incf}, @code{cl-rotatef}, @code{cl-letf}, @code{cl-callf}, etc. |
4009494e GM |
886 | @end menu |
887 | ||
5887564d GM |
888 | @node Setf Extensions |
889 | @subsection Setf Extensions | |
4009494e | 890 | |
5887564d GM |
891 | Several standard (e.g. @code{car}) and Emacs-specific |
892 | (e.g. @code{window-point}) Lisp functions are @code{setf}-able by default. | |
893 | This package defines @code{setf} handlers for several additional functions: | |
4009494e | 894 | |
5887564d | 895 | @itemize |
4009494e | 896 | @item |
5887564d | 897 | Functions from @code{CL} itself: |
4009494e | 898 | @smallexample |
5887564d GM |
899 | cl-caaar .. cl-cddddr cl-first .. cl-tenth |
900 | cl-rest cl-get cl-getf cl-subseq | |
4009494e GM |
901 | @end smallexample |
902 | ||
516e1a08 GM |
903 | @noindent |
904 | Note that for @code{cl-getf} (as for @code{nthcdr}), the list argument | |
905 | of the function must itself be a valid @var{place} form. | |
906 | ||
4009494e | 907 | @item |
5887564d | 908 | General Emacs Lisp functions: |
4009494e | 909 | @smallexample |
5887564d GM |
910 | buffer-file-name getenv |
911 | buffer-modified-p global-key-binding | |
912 | buffer-name local-key-binding | |
913 | buffer-string mark | |
914 | buffer-substring mark-marker | |
915 | current-buffer marker-position | |
916 | current-case-table mouse-position | |
917 | current-column point | |
918 | current-global-map point-marker | |
919 | current-input-mode point-max | |
920 | current-local-map point-min | |
921 | current-window-configuration read-mouse-position | |
922 | default-file-modes screen-height | |
923 | documentation-property screen-width | |
924 | face-background selected-window | |
925 | face-background-pixmap selected-screen | |
926 | face-font selected-frame | |
927 | face-foreground standard-case-table | |
928 | face-underline-p syntax-table | |
929 | file-modes visited-file-modtime | |
930 | frame-height window-height | |
931 | frame-parameters window-width | |
932 | frame-visible-p x-get-secondary-selection | |
933 | frame-width x-get-selection | |
934 | get-register | |
4009494e GM |
935 | @end smallexample |
936 | ||
937 | Most of these have directly corresponding ``set'' functions, like | |
938 | @code{use-local-map} for @code{current-local-map}, or @code{goto-char} | |
939 | for @code{point}. A few, like @code{point-min}, expand to longer | |
5887564d GM |
940 | sequences of code when they are used with @code{setf} |
941 | (@code{(narrow-to-region x (point-max))} in this case). | |
4009494e GM |
942 | |
943 | @item | |
944 | A call of the form @code{(substring @var{subplace} @var{n} [@var{m}])}, | |
945 | where @var{subplace} is itself a valid generalized variable whose | |
946 | current value is a string, and where the value stored is also a | |
947 | string. The new string is spliced into the specified part of the | |
948 | destination string. For example: | |
949 | ||
950 | @example | |
951 | (setq a (list "hello" "world")) | |
952 | @result{} ("hello" "world") | |
953 | (cadr a) | |
954 | @result{} "world" | |
955 | (substring (cadr a) 2 4) | |
956 | @result{} "rl" | |
957 | (setf (substring (cadr a) 2 4) "o") | |
958 | @result{} "o" | |
959 | (cadr a) | |
960 | @result{} "wood" | |
961 | a | |
962 | @result{} ("hello" "wood") | |
963 | @end example | |
964 | ||
965 | The generalized variable @code{buffer-substring}, listed above, | |
966 | also works in this way by replacing a portion of the current buffer. | |
967 | ||
5887564d GM |
968 | @c FIXME? Also `eq'? (see cl-lib.el) |
969 | ||
a3c5b619 GM |
970 | @c Currently commented out in cl.el. |
971 | @ignore | |
4009494e GM |
972 | @item |
973 | A call of the form @code{(apply '@var{func} @dots{})} or | |
974 | @code{(apply (function @var{func}) @dots{})}, where @var{func} | |
975 | is a @code{setf}-able function whose store function is ``suitable'' | |
976 | in the sense described in Steele's book; since none of the standard | |
977 | Emacs place functions are suitable in this sense, this feature is | |
978 | only interesting when used with places you define yourself with | |
979 | @code{define-setf-method} or the long form of @code{defsetf}. | |
d55911cf | 980 | @xref{Obsolete Setf Customization}. |
a3c5b619 | 981 | @end ignore |
4009494e GM |
982 | |
983 | @item | |
984 | A macro call, in which case the macro is expanded and @code{setf} | |
985 | is applied to the resulting form. | |
986 | ||
987 | @item | |
988 | Any form for which a @code{defsetf} or @code{define-setf-method} | |
a3c5b619 | 989 | has been made. @xref{Obsolete Setf Customization}. |
4009494e GM |
990 | @end itemize |
991 | ||
5887564d GM |
992 | @c FIXME should this be in lispref? It seems self-evident. |
993 | @c Contrast with the cl-incf example later on. | |
994 | @c Here it really only serves as a constrast to wrong-order. | |
4009494e GM |
995 | The @code{setf} macro takes care to evaluate all subforms in |
996 | the proper left-to-right order; for example, | |
997 | ||
998 | @example | |
39a58b5b | 999 | (setf (aref vec (cl-incf i)) i) |
4009494e GM |
1000 | @end example |
1001 | ||
1002 | @noindent | |
39a58b5b | 1003 | looks like it will evaluate @code{(cl-incf i)} exactly once, before the |
4009494e GM |
1004 | following access to @code{i}; the @code{setf} expander will insert |
1005 | temporary variables as necessary to ensure that it does in fact work | |
1006 | this way no matter what setf-method is defined for @code{aref}. | |
1007 | (In this case, @code{aset} would be used and no such steps would | |
1008 | be necessary since @code{aset} takes its arguments in a convenient | |
1009 | order.) | |
1010 | ||
1011 | However, if the @var{place} form is a macro which explicitly | |
1012 | evaluates its arguments in an unusual order, this unusual order | |
1013 | will be preserved. Adapting an example from Steele, given | |
1014 | ||
1015 | @example | |
1016 | (defmacro wrong-order (x y) (list 'aref y x)) | |
1017 | @end example | |
1018 | ||
1019 | @noindent | |
1020 | the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will | |
1021 | evaluate @var{b} first, then @var{a}, just as in an actual call | |
1022 | to @code{wrong-order}. | |
4009494e | 1023 | |
1d5b82ef | 1024 | @node Modify Macros |
4009494e GM |
1025 | @subsection Modify Macros |
1026 | ||
1027 | @noindent | |
5887564d GM |
1028 | This package defines a number of macros that operate on generalized |
1029 | variables. Many are interesting and useful even when the @var{place} | |
1030 | is just a variable name. | |
4009494e | 1031 | |
e1117425 | 1032 | @defmac cl-psetf [place form]@dots{} |
8d6510b9 | 1033 | This macro is to @code{setf} what @code{cl-psetq} is to @code{setq}: |
4009494e GM |
1034 | When several @var{place}s and @var{form}s are involved, the |
1035 | assignments take place in parallel rather than sequentially. | |
1036 | Specifically, all subforms are evaluated from left to right, then | |
1037 | all the assignments are done (in an undefined order). | |
e1117425 | 1038 | @end defmac |
4009494e | 1039 | |
e1117425 | 1040 | @defmac cl-incf place &optional x |
4009494e GM |
1041 | This macro increments the number stored in @var{place} by one, or |
1042 | by @var{x} if specified. The incremented value is returned. For | |
39a58b5b GM |
1043 | example, @code{(cl-incf i)} is equivalent to @code{(setq i (1+ i))}, and |
1044 | @code{(cl-incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x) 2))}. | |
4009494e | 1045 | |
5887564d GM |
1046 | As with @code{setf}, care is taken to preserve the ``apparent'' order |
1047 | of evaluation. For example, | |
4009494e GM |
1048 | |
1049 | @example | |
39a58b5b | 1050 | (cl-incf (aref vec (cl-incf i))) |
4009494e GM |
1051 | @end example |
1052 | ||
1053 | @noindent | |
1054 | appears to increment @code{i} once, then increment the element of | |
1055 | @code{vec} addressed by @code{i}; this is indeed exactly what it | |
1056 | does, which means the above form is @emph{not} equivalent to the | |
1057 | ``obvious'' expansion, | |
1058 | ||
1059 | @example | |
a05cb6e3 GM |
1060 | (setf (aref vec (cl-incf i)) |
1061 | (1+ (aref vec (cl-incf i)))) ; wrong! | |
4009494e GM |
1062 | @end example |
1063 | ||
1064 | @noindent | |
1065 | but rather to something more like | |
1066 | ||
1067 | @example | |
39a58b5b | 1068 | (let ((temp (cl-incf i))) |
4009494e GM |
1069 | (setf (aref vec temp) (1+ (aref vec temp)))) |
1070 | @end example | |
1071 | ||
1072 | @noindent | |
39a58b5b | 1073 | Again, all of this is taken care of automatically by @code{cl-incf} and |
4009494e GM |
1074 | the other generalized-variable macros. |
1075 | ||
39a58b5b GM |
1076 | As a more Emacs-specific example of @code{cl-incf}, the expression |
1077 | @code{(cl-incf (point) @var{n})} is essentially equivalent to | |
4009494e | 1078 | @code{(forward-char @var{n})}. |
e1117425 | 1079 | @end defmac |
4009494e | 1080 | |
e1117425 | 1081 | @defmac cl-decf place &optional x |
4009494e GM |
1082 | This macro decrements the number stored in @var{place} by one, or |
1083 | by @var{x} if specified. | |
e1117425 | 1084 | @end defmac |
4009494e | 1085 | |
e1117425 | 1086 | @defmac cl-pushnew x place @t{&key :test :test-not :key} |
4009494e GM |
1087 | This macro inserts @var{x} at the front of the list stored in |
1088 | @var{place}, but only if @var{x} was not @code{eql} to any | |
1089 | existing element of the list. The optional keyword arguments | |
a05cb6e3 | 1090 | are interpreted in the same way as for @code{cl-adjoin}. |
4009494e | 1091 | @xref{Lists as Sets}. |
e1117425 | 1092 | @end defmac |
4009494e | 1093 | |
e1117425 | 1094 | @defmac cl-shiftf place@dots{} newvalue |
4009494e GM |
1095 | This macro shifts the @var{place}s left by one, shifting in the |
1096 | value of @var{newvalue} (which may be any Lisp expression, not just | |
1097 | a generalized variable), and returning the value shifted out of | |
5887564d | 1098 | the first @var{place}. Thus, @code{(cl-shiftf @var{a} @var{b} @var{c} |
4009494e GM |
1099 | @var{d})} is equivalent to |
1100 | ||
1101 | @example | |
1102 | (prog1 | |
1103 | @var{a} | |
5887564d GM |
1104 | (cl-psetf @var{a} @var{b} |
1105 | @var{b} @var{c} | |
1106 | @var{c} @var{d})) | |
4009494e GM |
1107 | @end example |
1108 | ||
1109 | @noindent | |
1110 | except that the subforms of @var{a}, @var{b}, and @var{c} are actually | |
1111 | evaluated only once each and in the apparent order. | |
e1117425 | 1112 | @end defmac |
4009494e | 1113 | |
e1117425 | 1114 | @defmac cl-rotatef place@dots{} |
4009494e | 1115 | This macro rotates the @var{place}s left by one in circular fashion. |
a05cb6e3 | 1116 | Thus, @code{(cl-rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to |
4009494e GM |
1117 | |
1118 | @example | |
5887564d GM |
1119 | (cl-psetf @var{a} @var{b} |
1120 | @var{b} @var{c} | |
1121 | @var{c} @var{d} | |
1122 | @var{d} @var{a}) | |
4009494e GM |
1123 | @end example |
1124 | ||
1125 | @noindent | |
a05cb6e3 GM |
1126 | except for the evaluation of subforms. @code{cl-rotatef} always |
1127 | returns @code{nil}. Note that @code{(cl-rotatef @var{a} @var{b})} | |
4009494e | 1128 | conveniently exchanges @var{a} and @var{b}. |
e1117425 | 1129 | @end defmac |
4009494e GM |
1130 | |
1131 | The following macros were invented for this package; they have no | |
1132 | analogues in Common Lisp. | |
1133 | ||
4ddedf94 | 1134 | @defmac cl-letf (bindings@dots{}) forms@dots{} |
4009494e GM |
1135 | This macro is analogous to @code{let}, but for generalized variables |
1136 | rather than just symbols. Each @var{binding} should be of the form | |
1137 | @code{(@var{place} @var{value})}; the original contents of the | |
1138 | @var{place}s are saved, the @var{value}s are stored in them, and | |
1139 | then the body @var{form}s are executed. Afterwards, the @var{places} | |
1140 | are set back to their original saved contents. This cleanup happens | |
1141 | even if the @var{form}s exit irregularly due to a @code{throw} or an | |
1142 | error. | |
1143 | ||
1144 | For example, | |
1145 | ||
1146 | @example | |
4ddedf94 GM |
1147 | (cl-letf (((point) (point-min)) |
1148 | (a 17)) | |
1149 | ...) | |
4009494e GM |
1150 | @end example |
1151 | ||
1152 | @noindent | |
4ddedf94 | 1153 | moves point in the current buffer to the beginning of the buffer, |
4009494e GM |
1154 | and also binds @code{a} to 17 (as if by a normal @code{let}, since |
1155 | @code{a} is just a regular variable). After the body exits, @code{a} | |
1156 | is set back to its original value and point is moved back to its | |
1157 | original position. | |
1158 | ||
4ddedf94 | 1159 | Note that @code{cl-letf} on @code{(point)} is not quite like a |
4009494e GM |
1160 | @code{save-excursion}, as the latter effectively saves a marker |
1161 | which tracks insertions and deletions in the buffer. Actually, | |
4ddedf94 | 1162 | a @code{cl-letf} of @code{(point-marker)} is much closer to this |
4009494e GM |
1163 | behavior. (@code{point} and @code{point-marker} are equivalent |
1164 | as @code{setf} places; each will accept either an integer or a | |
1165 | marker as the stored value.) | |
1166 | ||
1167 | Since generalized variables look like lists, @code{let}'s shorthand | |
1168 | of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would | |
4ddedf94 | 1169 | be ambiguous in @code{cl-letf} and is not allowed. |
4009494e GM |
1170 | |
1171 | However, a @var{binding} specifier may be a one-element list | |
1172 | @samp{(@var{place})}, which is similar to @samp{(@var{place} | |
1173 | @var{place})}. In other words, the @var{place} is not disturbed | |
4ddedf94 GM |
1174 | on entry to the body, and the only effect of the @code{cl-letf} is |
1175 | to restore the original value of @var{place} afterwards. | |
1176 | @c I suspect this may no longer be true; either way it's | |
1177 | @c implementation detail and so not essential to document. | |
1178 | @ignore | |
1179 | (The redundant access-and-store suggested by the @code{(@var{place} | |
4009494e | 1180 | @var{place})} example does not actually occur.) |
4ddedf94 | 1181 | @end ignore |
4009494e | 1182 | |
4ddedf94 GM |
1183 | Note that in this case, and in fact almost every case, @var{place} |
1184 | must have a well-defined value outside the @code{cl-letf} body. | |
1185 | There is essentially only one exception to this, which is @var{place} | |
1186 | a plain variable with a specified @var{value} (such as @code{(a 17)} | |
1187 | in the above example). | |
1188 | @c See http://debbugs.gnu.org/12758 | |
1189 | @c Some or all of this was true for cl.el, but not for cl-lib.el. | |
1190 | @ignore | |
1191 | The only exceptions are plain variables and calls to | |
1192 | @code{symbol-value} and @code{symbol-function}. If the symbol is not | |
1193 | bound on entry, it is simply made unbound by @code{makunbound} or | |
1194 | @code{fmakunbound} on exit. | |
1195 | @end ignore | |
e1117425 | 1196 | @end defmac |
4009494e | 1197 | |
e1117425 | 1198 | @defmac cl-letf* (bindings@dots{}) forms@dots{} |
4ddedf94 | 1199 | This macro is to @code{cl-letf} what @code{let*} is to @code{let}: |
4009494e | 1200 | It does the bindings in sequential rather than parallel order. |
e1117425 | 1201 | @end defmac |
4009494e | 1202 | |
e1117425 | 1203 | @defmac cl-callf @var{function} @var{place} @var{args}@dots{} |
4009494e GM |
1204 | This is the ``generic'' modify macro. It calls @var{function}, |
1205 | which should be an unquoted function name, macro name, or lambda. | |
1206 | It passes @var{place} and @var{args} as arguments, and assigns the | |
39a58b5b | 1207 | result back to @var{place}. For example, @code{(cl-incf @var{place} |
a05cb6e3 | 1208 | @var{n})} is the same as @code{(cl-callf + @var{place} @var{n})}. |
4009494e GM |
1209 | Some more examples: |
1210 | ||
1211 | @example | |
a05cb6e3 GM |
1212 | (cl-callf abs my-number) |
1213 | (cl-callf concat (buffer-name) "<" (number-to-string n) ">") | |
1214 | (cl-callf cl-union happy-people (list joe bob) :test 'same-person) | |
4009494e GM |
1215 | @end example |
1216 | ||
d571e9c3 | 1217 | Note again that @code{cl-callf} is an extension to standard Common Lisp. |
e1117425 | 1218 | @end defmac |
4009494e | 1219 | |
e1117425 | 1220 | @defmac cl-callf2 @var{function} @var{arg1} @var{place} @var{args}@dots{} |
a05cb6e3 | 1221 | This macro is like @code{cl-callf}, except that @var{place} is |
4009494e GM |
1222 | the @emph{second} argument of @var{function} rather than the |
1223 | first. For example, @code{(push @var{x} @var{place})} is | |
a05cb6e3 | 1224 | equivalent to @code{(cl-callf2 cons @var{x} @var{place})}. |
e1117425 | 1225 | @end defmac |
4009494e | 1226 | |
a05cb6e3 | 1227 | The @code{cl-callf} and @code{cl-callf2} macros serve as building |
d55911cf | 1228 | blocks for other macros like @code{cl-incf}, and @code{cl-pushnew}. |
4ddedf94 | 1229 | The @code{cl-letf} and @code{cl-letf*} macros are used in the processing |
d55911cf | 1230 | of symbol macros; @pxref{Macro Bindings}. |
4009494e | 1231 | |
4009494e | 1232 | |
1d5b82ef | 1233 | @node Variable Bindings |
4009494e GM |
1234 | @section Variable Bindings |
1235 | ||
1236 | @noindent | |
1237 | These Lisp forms make bindings to variables and function names, | |
1238 | analogous to Lisp's built-in @code{let} form. | |
1239 | ||
4ddedf94 | 1240 | @xref{Modify Macros}, for the @code{cl-letf} and @code{cl-letf*} forms which |
4009494e GM |
1241 | are also related to variable bindings. |
1242 | ||
1243 | @menu | |
39a58b5b | 1244 | * Dynamic Bindings:: The @code{cl-progv} form. |
8d6510b9 | 1245 | * Function Bindings:: @code{flet} and @code{labels}. |
39a58b5b | 1246 | * Macro Bindings:: @code{cl-macrolet} and @code{cl-symbol-macrolet}. |
4009494e GM |
1247 | @end menu |
1248 | ||
1d5b82ef | 1249 | @node Dynamic Bindings |
4009494e GM |
1250 | @subsection Dynamic Bindings |
1251 | ||
1252 | @noindent | |
1253 | The standard @code{let} form binds variables whose names are known | |
39a58b5b | 1254 | at compile-time. The @code{cl-progv} form provides an easy way to |
4009494e GM |
1255 | bind variables whose names are computed at run-time. |
1256 | ||
e1117425 | 1257 | @defmac cl-progv symbols values forms@dots{} |
4009494e GM |
1258 | This form establishes @code{let}-style variable bindings on a |
1259 | set of variables computed at run-time. The expressions | |
1260 | @var{symbols} and @var{values} are evaluated, and must return lists | |
1261 | of symbols and values, respectively. The symbols are bound to the | |
1262 | corresponding values for the duration of the body @var{form}s. | |
1263 | If @var{values} is shorter than @var{symbols}, the last few symbols | |
a05cb6e3 | 1264 | are bound to @code{nil}. |
4009494e GM |
1265 | If @var{symbols} is shorter than @var{values}, the excess values |
1266 | are ignored. | |
e1117425 | 1267 | @end defmac |
4009494e | 1268 | |
1d5b82ef | 1269 | @node Function Bindings |
4009494e GM |
1270 | @subsection Function Bindings |
1271 | ||
1272 | @noindent | |
1273 | These forms make @code{let}-like bindings to functions instead | |
1274 | of variables. | |
1275 | ||
e1117425 | 1276 | @defmac flet (bindings@dots{}) forms@dots{} |
4009494e GM |
1277 | This form establishes @code{let}-style bindings on the function |
1278 | cells of symbols rather than on the value cells. Each @var{binding} | |
1279 | must be a list of the form @samp{(@var{name} @var{arglist} | |
1280 | @var{forms}@dots{})}, which defines a function exactly as if | |
a05cb6e3 | 1281 | it were a @code{cl-defun} form. The function @var{name} is defined |
4009494e GM |
1282 | accordingly for the duration of the body of the @code{flet}; then |
1283 | the old function definition, or lack thereof, is restored. | |
1284 | ||
1285 | While @code{flet} in Common Lisp establishes a lexical binding of | |
1286 | @var{name}, Emacs Lisp @code{flet} makes a dynamic binding. The | |
1287 | result is that @code{flet} affects indirect calls to a function as | |
1288 | well as calls directly inside the @code{flet} form itself. | |
1289 | ||
1290 | You can use @code{flet} to disable or modify the behavior of a | |
1291 | function in a temporary fashion. This will even work on Emacs | |
1292 | primitives, although note that some calls to primitive functions | |
1293 | internal to Emacs are made without going through the symbol's | |
1294 | function cell, and so will not be affected by @code{flet}. For | |
1295 | example, | |
1296 | ||
1297 | @example | |
1298 | (flet ((message (&rest args) (push args saved-msgs))) | |
1299 | (do-something)) | |
1300 | @end example | |
1301 | ||
1302 | This code attempts to replace the built-in function @code{message} | |
1303 | with a function that simply saves the messages in a list rather | |
1304 | than displaying them. The original definition of @code{message} | |
1305 | will be restored after @code{do-something} exits. This code will | |
1306 | work fine on messages generated by other Lisp code, but messages | |
1307 | generated directly inside Emacs will not be caught since they make | |
1308 | direct C-language calls to the message routines rather than going | |
1309 | through the Lisp @code{message} function. | |
1310 | ||
3c4be1f2 GM |
1311 | @c Bug#411. |
1312 | Also note that many primitives (e.g. @code{+}) have special byte-compile | |
1313 | handling. Attempts to redefine such functions using @code{flet} will | |
1314 | fail if byte-compiled. In such cases, use @code{labels} instead. | |
1315 | ||
4009494e | 1316 | Functions defined by @code{flet} may use the full Common Lisp |
39a58b5b GM |
1317 | argument notation supported by @code{cl-defun}; also, the function |
1318 | body is enclosed in an implicit block as if by @code{cl-defun}. | |
4009494e | 1319 | @xref{Program Structure}. |
e1117425 | 1320 | @end defmac |
4009494e | 1321 | |
e1117425 | 1322 | @defmac labels (bindings@dots{}) forms@dots{} |
4009494e GM |
1323 | The @code{labels} form is like @code{flet}, except that it |
1324 | makes lexical bindings of the function names rather than | |
1325 | dynamic bindings. (In true Common Lisp, both @code{flet} and | |
1326 | @code{labels} make lexical bindings of slightly different sorts; | |
1327 | since Emacs Lisp is dynamically bound by default, it seemed | |
1328 | more appropriate for @code{flet} also to use dynamic binding. | |
1329 | The @code{labels} form, with its lexical binding, is fully | |
1330 | compatible with Common Lisp.) | |
1331 | ||
1332 | Lexical scoping means that all references to the named | |
1333 | functions must appear physically within the body of the | |
1334 | @code{labels} form. References may appear both in the body | |
1335 | @var{forms} of @code{labels} itself, and in the bodies of | |
1336 | the functions themselves. Thus, @code{labels} can define | |
1337 | local recursive functions, or mutually-recursive sets of | |
1338 | functions. | |
1339 | ||
1340 | A ``reference'' to a function name is either a call to that | |
1341 | function, or a use of its name quoted by @code{quote} or | |
1342 | @code{function} to be passed on to, say, @code{mapcar}. | |
e1117425 | 1343 | @end defmac |
4009494e | 1344 | |
1d5b82ef | 1345 | @node Macro Bindings |
4009494e GM |
1346 | @subsection Macro Bindings |
1347 | ||
1348 | @noindent | |
a05cb6e3 | 1349 | These forms create local macros and ``symbol macros''. |
4009494e | 1350 | |
e1117425 | 1351 | @defmac cl-macrolet (bindings@dots{}) forms@dots{} |
4009494e GM |
1352 | This form is analogous to @code{flet}, but for macros instead of |
1353 | functions. Each @var{binding} is a list of the same form as the | |
39a58b5b | 1354 | arguments to @code{cl-defmacro} (i.e., a macro name, argument list, |
4009494e | 1355 | and macro-expander forms). The macro is defined accordingly for |
39a58b5b | 1356 | use within the body of the @code{cl-macrolet}. |
4009494e | 1357 | |
3c0c6155 GM |
1358 | @c FIXME this should be modified to say ``even when lexical-binding |
1359 | @c is code{nil}'', but is that true? The doc of cl-macrolet just | |
1360 | @c refers us to cl-flet, which refers to cl-labels, which says that it | |
1361 | @c behaves differently according to whether l-b is true or not. | |
39a58b5b GM |
1362 | Because of the nature of macros, @code{cl-macrolet} is lexically |
1363 | scoped even in Emacs Lisp: The @code{cl-macrolet} binding will | |
4009494e GM |
1364 | affect only calls that appear physically within the body |
1365 | @var{forms}, possibly after expansion of other macros in the | |
1366 | body. | |
e1117425 | 1367 | @end defmac |
4009494e | 1368 | |
e1117425 | 1369 | @defmac cl-symbol-macrolet (bindings@dots{}) forms@dots{} |
4009494e GM |
1370 | This form creates @dfn{symbol macros}, which are macros that look |
1371 | like variable references rather than function calls. Each | |
1372 | @var{binding} is a list @samp{(@var{var} @var{expansion})}; | |
1373 | any reference to @var{var} within the body @var{forms} is | |
1374 | replaced by @var{expansion}. | |
1375 | ||
1376 | @example | |
1377 | (setq bar '(5 . 9)) | |
39a58b5b GM |
1378 | (cl-symbol-macrolet ((foo (car bar))) |
1379 | (cl-incf foo)) | |
4009494e GM |
1380 | bar |
1381 | @result{} (6 . 9) | |
1382 | @end example | |
1383 | ||
1384 | A @code{setq} of a symbol macro is treated the same as a @code{setf}. | |
1385 | I.e., @code{(setq foo 4)} in the above would be equivalent to | |
1386 | @code{(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}. | |
1387 | ||
1388 | Likewise, a @code{let} or @code{let*} binding a symbol macro is | |
4ddedf94 | 1389 | treated like a @code{cl-letf} or @code{cl-letf*}. This differs from true |
3c0c6155 | 1390 | @c FIXME does it work like this in Emacs with lexical-binding = t? |
4009494e | 1391 | Common Lisp, where the rules of lexical scoping cause a @code{let} |
39a58b5b | 1392 | binding to shadow a @code{cl-symbol-macrolet} binding. In this package, |
3c0c6155 | 1393 | @c FIXME obsolete. |
4009494e GM |
1394 | only @code{lexical-let} and @code{lexical-let*} will shadow a symbol |
1395 | macro. | |
1396 | ||
1397 | There is no analogue of @code{defmacro} for symbol macros; all symbol | |
39a58b5b | 1398 | macros are local. A typical use of @code{cl-symbol-macrolet} is in the |
4009494e GM |
1399 | expansion of another macro: |
1400 | ||
1401 | @example | |
39a58b5b | 1402 | (cl-defmacro my-dolist ((x list) &rest body) |
4009494e | 1403 | (let ((var (gensym))) |
39a58b5b | 1404 | (list 'cl-loop 'for var 'on list 'do |
a05cb6e3 GM |
1405 | (cl-list* 'cl-symbol-macrolet |
1406 | (list (list x (list 'car var))) | |
1407 | body)))) | |
4009494e GM |
1408 | |
1409 | (setq mylist '(1 2 3 4)) | |
39a58b5b | 1410 | (my-dolist (x mylist) (cl-incf x)) |
4009494e GM |
1411 | mylist |
1412 | @result{} (2 3 4 5) | |
1413 | @end example | |
1414 | ||
1415 | @noindent | |
1416 | In this example, the @code{my-dolist} macro is similar to @code{dolist} | |
1417 | (@pxref{Iteration}) except that the variable @code{x} becomes a true | |
1418 | reference onto the elements of the list. The @code{my-dolist} call | |
1419 | shown here expands to | |
1420 | ||
1421 | @example | |
39a58b5b GM |
1422 | (cl-loop for G1234 on mylist do |
1423 | (cl-symbol-macrolet ((x (car G1234))) | |
1424 | (cl-incf x))) | |
4009494e GM |
1425 | @end example |
1426 | ||
1427 | @noindent | |
1428 | which in turn expands to | |
1429 | ||
1430 | @example | |
39a58b5b | 1431 | (cl-loop for G1234 on mylist do (cl-incf (car G1234))) |
4009494e GM |
1432 | @end example |
1433 | ||
39a58b5b | 1434 | @xref{Loop Facility}, for a description of the @code{cl-loop} macro. |
4009494e GM |
1435 | This package defines a nonstandard @code{in-ref} loop clause that |
1436 | works much like @code{my-dolist}. | |
e1117425 | 1437 | @end defmac |
4009494e | 1438 | |
1d5b82ef | 1439 | @node Conditionals |
4009494e GM |
1440 | @section Conditionals |
1441 | ||
1442 | @noindent | |
1443 | These conditional forms augment Emacs Lisp's simple @code{if}, | |
1444 | @code{and}, @code{or}, and @code{cond} forms. | |
1445 | ||
e1117425 | 1446 | @defmac cl-case keyform clause@dots{} |
4009494e GM |
1447 | This macro evaluates @var{keyform}, then compares it with the key |
1448 | values listed in the various @var{clause}s. Whichever clause matches | |
1449 | the key is executed; comparison is done by @code{eql}. If no clause | |
39a58b5b | 1450 | matches, the @code{cl-case} form returns @code{nil}. The clauses are |
4009494e GM |
1451 | of the form |
1452 | ||
1453 | @example | |
1454 | (@var{keylist} @var{body-forms}@dots{}) | |
1455 | @end example | |
1456 | ||
1457 | @noindent | |
1458 | where @var{keylist} is a list of key values. If there is exactly | |
1459 | one value, and it is not a cons cell or the symbol @code{nil} or | |
1460 | @code{t}, then it can be used by itself as a @var{keylist} without | |
a05cb6e3 | 1461 | being enclosed in a list. All key values in the @code{cl-case} form |
4009494e GM |
1462 | must be distinct. The final clauses may use @code{t} in place of |
1463 | a @var{keylist} to indicate a default clause that should be taken | |
1464 | if none of the other clauses match. (The symbol @code{otherwise} | |
1465 | is also recognized in place of @code{t}. To make a clause that | |
1466 | matches the actual symbol @code{t}, @code{nil}, or @code{otherwise}, | |
1467 | enclose the symbol in a list.) | |
1468 | ||
1469 | For example, this expression reads a keystroke, then does one of | |
1470 | four things depending on whether it is an @samp{a}, a @samp{b}, | |
1471 | a @key{RET} or @kbd{C-j}, or anything else. | |
1472 | ||
1473 | @example | |
39a58b5b | 1474 | (cl-case (read-char) |
4009494e GM |
1475 | (?a (do-a-thing)) |
1476 | (?b (do-b-thing)) | |
1477 | ((?\r ?\n) (do-ret-thing)) | |
1478 | (t (do-other-thing))) | |
1479 | @end example | |
e1117425 | 1480 | @end defmac |
4009494e | 1481 | |
e1117425 | 1482 | @defmac cl-ecase keyform clause@dots{} |
39a58b5b | 1483 | This macro is just like @code{cl-case}, except that if the key does |
4009494e GM |
1484 | not match any of the clauses, an error is signaled rather than |
1485 | simply returning @code{nil}. | |
e1117425 | 1486 | @end defmac |
4009494e | 1487 | |
e1117425 | 1488 | @defmac cl-typecase keyform clause@dots{} |
39a58b5b | 1489 | This macro is a version of @code{cl-case} that checks for types |
4009494e GM |
1490 | rather than values. Each @var{clause} is of the form |
1491 | @samp{(@var{type} @var{body}...)}. @xref{Type Predicates}, | |
1492 | for a description of type specifiers. For example, | |
1493 | ||
1494 | @example | |
39a58b5b | 1495 | (cl-typecase x |
4009494e GM |
1496 | (integer (munch-integer x)) |
1497 | (float (munch-float x)) | |
1498 | (string (munch-integer (string-to-int x))) | |
1499 | (t (munch-anything x))) | |
1500 | @end example | |
1501 | ||
1502 | The type specifier @code{t} matches any type of object; the word | |
1503 | @code{otherwise} is also allowed. To make one clause match any of | |
1504 | several types, use an @code{(or ...)} type specifier. | |
e1117425 | 1505 | @end defmac |
4009494e | 1506 | |
e1117425 | 1507 | @defmac cl-etypecase keyform clause@dots{} |
39a58b5b | 1508 | This macro is just like @code{cl-typecase}, except that if the key does |
4009494e GM |
1509 | not match any of the clauses, an error is signaled rather than |
1510 | simply returning @code{nil}. | |
e1117425 | 1511 | @end defmac |
4009494e | 1512 | |
1d5b82ef | 1513 | @node Blocks and Exits |
4009494e GM |
1514 | @section Blocks and Exits |
1515 | ||
1516 | @noindent | |
1517 | Common Lisp @dfn{blocks} provide a non-local exit mechanism very | |
1518 | similar to @code{catch} and @code{throw}, but lexically rather than | |
39a58b5b | 1519 | dynamically scoped. This package actually implements @code{cl-block} |
4009494e GM |
1520 | in terms of @code{catch}; however, the lexical scoping allows the |
1521 | optimizing byte-compiler to omit the costly @code{catch} step if the | |
39a58b5b | 1522 | body of the block does not actually @code{cl-return-from} the block. |
4009494e | 1523 | |
e1117425 | 1524 | @defmac cl-block name forms@dots{} |
4009494e | 1525 | The @var{forms} are evaluated as if by a @code{progn}. However, |
39a58b5b GM |
1526 | if any of the @var{forms} execute @code{(cl-return-from @var{name})}, |
1527 | they will jump out and return directly from the @code{cl-block} form. | |
1528 | The @code{cl-block} returns the result of the last @var{form} unless | |
1529 | a @code{cl-return-from} occurs. | |
4009494e | 1530 | |
39a58b5b | 1531 | The @code{cl-block}/@code{cl-return-from} mechanism is quite similar to |
4009494e GM |
1532 | the @code{catch}/@code{throw} mechanism. The main differences are |
1533 | that block @var{name}s are unevaluated symbols, rather than forms | |
1534 | (such as quoted symbols) which evaluate to a tag at run-time; and | |
1535 | also that blocks are lexically scoped whereas @code{catch}/@code{throw} | |
1536 | are dynamically scoped. This means that functions called from the | |
1537 | body of a @code{catch} can also @code{throw} to the @code{catch}, | |
39a58b5b | 1538 | but the @code{cl-return-from} referring to a block name must appear |
4009494e GM |
1539 | physically within the @var{forms} that make up the body of the block. |
1540 | They may not appear within other called functions, although they may | |
1541 | appear within macro expansions or @code{lambda}s in the body. Block | |
1542 | names and @code{catch} names form independent name-spaces. | |
1543 | ||
1544 | In true Common Lisp, @code{defun} and @code{defmacro} surround | |
1545 | the function or expander bodies with implicit blocks with the | |
1546 | same name as the function or macro. This does not occur in Emacs | |
39a58b5b | 1547 | Lisp, but this package provides @code{cl-defun} and @code{cl-defmacro} |
4009494e GM |
1548 | forms which do create the implicit block. |
1549 | ||
1550 | The Common Lisp looping constructs defined by this package, | |
39a58b5b | 1551 | such as @code{cl-loop} and @code{cl-dolist}, also create implicit blocks |
4009494e GM |
1552 | just as in Common Lisp. |
1553 | ||
1554 | Because they are implemented in terms of Emacs Lisp @code{catch} | |
1555 | and @code{throw}, blocks have the same overhead as actual | |
1556 | @code{catch} constructs (roughly two function calls). However, | |
1557 | the optimizing byte compiler will optimize away the @code{catch} | |
1558 | if the block does | |
39a58b5b GM |
1559 | not in fact contain any @code{cl-return} or @code{cl-return-from} calls |
1560 | that jump to it. This means that @code{cl-do} loops and @code{cl-defun} | |
1561 | functions which don't use @code{cl-return} don't pay the overhead to | |
4009494e | 1562 | support it. |
e1117425 | 1563 | @end defmac |
4009494e | 1564 | |
e1117425 | 1565 | @defmac cl-return-from name [result] |
4009494e GM |
1566 | This macro returns from the block named @var{name}, which must be |
1567 | an (unevaluated) symbol. If a @var{result} form is specified, it | |
1568 | is evaluated to produce the result returned from the @code{block}. | |
1569 | Otherwise, @code{nil} is returned. | |
e1117425 | 1570 | @end defmac |
4009494e | 1571 | |
e1117425 | 1572 | @defmac cl-return [result] |
39a58b5b GM |
1573 | This macro is exactly like @code{(cl-return-from nil @var{result})}. |
1574 | Common Lisp loops like @code{cl-do} and @code{cl-dolist} implicitly enclose | |
4009494e | 1575 | themselves in @code{nil} blocks. |
e1117425 | 1576 | @end defmac |
4009494e | 1577 | |
1d5b82ef | 1578 | @node Iteration |
4009494e GM |
1579 | @section Iteration |
1580 | ||
1581 | @noindent | |
1582 | The macros described here provide more sophisticated, high-level | |
1583 | looping constructs to complement Emacs Lisp's basic @code{while} | |
1584 | loop. | |
1585 | ||
e1117425 | 1586 | @defmac cl-loop forms@dots{} |
8d6510b9 | 1587 | The @code{CL} package supports both the simple, old-style meaning of |
4009494e GM |
1588 | @code{loop} and the extremely powerful and flexible feature known as |
1589 | the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced | |
1590 | facility is discussed in the following section; @pxref{Loop Facility}. | |
1591 | The simple form of @code{loop} is described here. | |
1592 | ||
39a58b5b GM |
1593 | If @code{cl-loop} is followed by zero or more Lisp expressions, |
1594 | then @code{(cl-loop @var{exprs}@dots{})} simply creates an infinite | |
4009494e GM |
1595 | loop executing the expressions over and over. The loop is |
1596 | enclosed in an implicit @code{nil} block. Thus, | |
1597 | ||
1598 | @example | |
39a58b5b | 1599 | (cl-loop (foo) (if (no-more) (return 72)) (bar)) |
4009494e GM |
1600 | @end example |
1601 | ||
1602 | @noindent | |
1603 | is exactly equivalent to | |
1604 | ||
1605 | @example | |
39a58b5b | 1606 | (cl-block nil (while t (foo) (if (no-more) (return 72)) (bar))) |
4009494e GM |
1607 | @end example |
1608 | ||
1609 | If any of the expressions are plain symbols, the loop is instead | |
1610 | interpreted as a Loop Macro specification as described later. | |
1611 | (This is not a restriction in practice, since a plain symbol | |
1612 | in the above notation would simply access and throw away the | |
1613 | value of a variable.) | |
e1117425 | 1614 | @end defmac |
4009494e | 1615 | |
e1117425 | 1616 | @defmac cl-do (spec@dots{}) (end-test [result@dots{}]) forms@dots{} |
4009494e GM |
1617 | This macro creates a general iterative loop. Each @var{spec} is |
1618 | of the form | |
1619 | ||
1620 | @example | |
1621 | (@var{var} [@var{init} [@var{step}]]) | |
1622 | @end example | |
1623 | ||
1624 | The loop works as follows: First, each @var{var} is bound to the | |
1625 | associated @var{init} value as if by a @code{let} form. Then, in | |
1626 | each iteration of the loop, the @var{end-test} is evaluated; if | |
1627 | true, the loop is finished. Otherwise, the body @var{forms} are | |
1628 | evaluated, then each @var{var} is set to the associated @var{step} | |
8d6510b9 | 1629 | expression (as if by a @code{cl-psetq} form) and the next iteration |
4009494e GM |
1630 | begins. Once the @var{end-test} becomes true, the @var{result} |
1631 | forms are evaluated (with the @var{var}s still bound to their | |
a05cb6e3 | 1632 | values) to produce the result returned by @code{cl-do}. |
4009494e | 1633 | |
39a58b5b GM |
1634 | The entire @code{cl-do} loop is enclosed in an implicit @code{nil} |
1635 | block, so that you can use @code{(cl-return)} to break out of the | |
4009494e GM |
1636 | loop at any time. |
1637 | ||
1638 | If there are no @var{result} forms, the loop returns @code{nil}. | |
1639 | If a given @var{var} has no @var{step} form, it is bound to its | |
a05cb6e3 | 1640 | @var{init} value but not otherwise modified during the @code{cl-do} |
4009494e GM |
1641 | loop (unless the code explicitly modifies it); this case is just |
1642 | a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})} | |
1643 | around the loop. If @var{init} is also omitted it defaults to | |
1644 | @code{nil}, and in this case a plain @samp{@var{var}} can be used | |
1645 | in place of @samp{(@var{var})}, again following the analogy with | |
1646 | @code{let}. | |
1647 | ||
1648 | This example (from Steele) illustrates a loop which applies the | |
1649 | function @code{f} to successive pairs of values from the lists | |
1650 | @code{foo} and @code{bar}; it is equivalent to the call | |
39a58b5b | 1651 | @code{(cl-mapcar 'f foo bar)}. Note that this loop has no body |
4009494e GM |
1652 | @var{forms} at all, performing all its work as side effects of |
1653 | the rest of the loop. | |
1654 | ||
1655 | @example | |
39a58b5b GM |
1656 | (cl-do ((x foo (cdr x)) |
1657 | (y bar (cdr y)) | |
1658 | (z nil (cons (f (car x) (car y)) z))) | |
1659 | ((or (null x) (null y)) | |
1660 | (nreverse z))) | |
4009494e | 1661 | @end example |
e1117425 | 1662 | @end defmac |
4009494e | 1663 | |
e1117425 | 1664 | @defmac cl-do* (spec@dots{}) (end-test [result@dots{}]) forms@dots{} |
39a58b5b | 1665 | This is to @code{cl-do} what @code{let*} is to @code{let}. In |
4009494e GM |
1666 | particular, the initial values are bound as if by @code{let*} |
1667 | rather than @code{let}, and the steps are assigned as if by | |
8d6510b9 | 1668 | @code{setq} rather than @code{cl-psetq}. |
4009494e GM |
1669 | |
1670 | Here is another way to write the above loop: | |
1671 | ||
1672 | @example | |
39a58b5b GM |
1673 | (cl-do* ((xp foo (cdr xp)) |
1674 | (yp bar (cdr yp)) | |
1675 | (x (car xp) (car xp)) | |
1676 | (y (car yp) (car yp)) | |
1677 | z) | |
4009494e GM |
1678 | ((or (null xp) (null yp)) |
1679 | (nreverse z)) | |
1680 | (push (f x y) z)) | |
1681 | @end example | |
e1117425 | 1682 | @end defmac |
4009494e | 1683 | |
e1117425 | 1684 | @defmac cl-dolist (var list [result]) forms@dots{} |
4009494e GM |
1685 | This is a more specialized loop which iterates across the elements |
1686 | of a list. @var{list} should evaluate to a list; the body @var{forms} | |
1687 | are executed with @var{var} bound to each element of the list in | |
1688 | turn. Finally, the @var{result} form (or @code{nil}) is evaluated | |
1689 | with @var{var} bound to @code{nil} to produce the result returned by | |
677c1109 | 1690 | the loop. Unlike with Emacs's built in @code{dolist}, the loop is |
4009494e | 1691 | surrounded by an implicit @code{nil} block. |
e1117425 | 1692 | @end defmac |
4009494e | 1693 | |
e1117425 | 1694 | @defmac cl-dotimes (var count [result]) forms@dots{} |
4009494e GM |
1695 | This is a more specialized loop which iterates a specified number |
1696 | of times. The body is executed with @var{var} bound to the integers | |
1697 | from zero (inclusive) to @var{count} (exclusive), in turn. Then | |
1698 | the @code{result} form is evaluated with @var{var} bound to the total | |
1699 | number of iterations that were done (i.e., @code{(max 0 @var{count})}) | |
677c1109 | 1700 | to get the return value for the loop form. Unlike with Emacs's built in |
4009494e | 1701 | @code{dolist}, the loop is surrounded by an implicit @code{nil} block. |
e1117425 | 1702 | @end defmac |
4009494e | 1703 | |
e1117425 | 1704 | @defmac cl-do-symbols (var [obarray [result]]) forms@dots{} |
4009494e GM |
1705 | This loop iterates over all interned symbols. If @var{obarray} |
1706 | is specified and is not @code{nil}, it loops over all symbols in | |
1707 | that obarray. For each symbol, the body @var{forms} are evaluated | |
1708 | with @var{var} bound to that symbol. The symbols are visited in | |
1709 | an unspecified order. Afterward the @var{result} form, if any, | |
1710 | is evaluated (with @var{var} bound to @code{nil}) to get the return | |
1711 | value. The loop is surrounded by an implicit @code{nil} block. | |
e1117425 | 1712 | @end defmac |
4009494e | 1713 | |
e1117425 | 1714 | @defmac cl-do-all-symbols (var [result]) forms@dots{} |
39a58b5b | 1715 | This is identical to @code{cl-do-symbols} except that the @var{obarray} |
4009494e | 1716 | argument is omitted; it always iterates over the default obarray. |
e1117425 | 1717 | @end defmac |
4009494e GM |
1718 | |
1719 | @xref{Mapping over Sequences}, for some more functions for | |
1720 | iterating over vectors or lists. | |
1721 | ||
1d5b82ef | 1722 | @node Loop Facility |
4009494e GM |
1723 | @section Loop Facility |
1724 | ||
1725 | @noindent | |
1726 | A common complaint with Lisp's traditional looping constructs is | |
1727 | that they are either too simple and limited, such as Common Lisp's | |
1728 | @code{dotimes} or Emacs Lisp's @code{while}, or too unreadable and | |
1729 | obscure, like Common Lisp's @code{do} loop. | |
1730 | ||
1731 | To remedy this, recent versions of Common Lisp have added a new | |
a05cb6e3 | 1732 | construct called the ``Loop Facility'' or ``@code{loop} macro'', |
4009494e GM |
1733 | with an easy-to-use but very powerful and expressive syntax. |
1734 | ||
1735 | @menu | |
39a58b5b GM |
1736 | * Loop Basics:: @code{cl-loop} macro, basic clause structure. |
1737 | * Loop Examples:: Working examples of @code{cl-loop} macro. | |
8d6510b9 | 1738 | * For Clauses:: Clauses introduced by @code{for} or @code{as}. |
53eced6d GM |
1739 | * Iteration Clauses:: @code{repeat}, @code{while}, @code{thereis}, etc. |
1740 | * Accumulation Clauses:: @code{collect}, @code{sum}, @code{maximize}, etc. | |
8d6510b9 | 1741 | * Other Clauses:: @code{with}, @code{if}, @code{initially}, @code{finally}. |
4009494e GM |
1742 | @end menu |
1743 | ||
1d5b82ef | 1744 | @node Loop Basics |
4009494e GM |
1745 | @subsection Loop Basics |
1746 | ||
1747 | @noindent | |
39a58b5b | 1748 | The @code{cl-loop} macro essentially creates a mini-language within |
4009494e GM |
1749 | Lisp that is specially tailored for describing loops. While this |
1750 | language is a little strange-looking by the standards of regular Lisp, | |
1751 | it turns out to be very easy to learn and well-suited to its purpose. | |
1752 | ||
39a58b5b GM |
1753 | Since @code{cl-loop} is a macro, all parsing of the loop language |
1754 | takes place at byte-compile time; compiled @code{cl-loop}s are just | |
4009494e GM |
1755 | as efficient as the equivalent @code{while} loops written longhand. |
1756 | ||
e1117425 | 1757 | @defmac cl-loop clauses@dots{} |
4009494e GM |
1758 | A loop construct consists of a series of @var{clause}s, each |
1759 | introduced by a symbol like @code{for} or @code{do}. Clauses | |
39a58b5b | 1760 | are simply strung together in the argument list of @code{cl-loop}, |
4009494e GM |
1761 | with minimal extra parentheses. The various types of clauses |
1762 | specify initializations, such as the binding of temporary | |
1763 | variables, actions to be taken in the loop, stepping actions, | |
1764 | and final cleanup. | |
1765 | ||
1766 | Common Lisp specifies a certain general order of clauses in a | |
1767 | loop: | |
1768 | ||
1769 | @example | |
39a58b5b GM |
1770 | (cl-loop @var{name-clause} |
1771 | @var{var-clauses}@dots{} | |
1772 | @var{action-clauses}@dots{}) | |
4009494e GM |
1773 | @end example |
1774 | ||
1775 | The @var{name-clause} optionally gives a name to the implicit | |
1776 | block that surrounds the loop. By default, the implicit block | |
1777 | is named @code{nil}. The @var{var-clauses} specify what | |
1778 | variables should be bound during the loop, and how they should | |
1779 | be modified or iterated throughout the course of the loop. The | |
1780 | @var{action-clauses} are things to be done during the loop, such | |
1781 | as computing, collecting, and returning values. | |
1782 | ||
39a58b5b | 1783 | The Emacs version of the @code{cl-loop} macro is less restrictive about |
4009494e GM |
1784 | the order of clauses, but things will behave most predictably if |
1785 | you put the variable-binding clauses @code{with}, @code{for}, and | |
1786 | @code{repeat} before the action clauses. As in Common Lisp, | |
1787 | @code{initially} and @code{finally} clauses can go anywhere. | |
1788 | ||
1789 | Loops generally return @code{nil} by default, but you can cause | |
1790 | them to return a value by using an accumulation clause like | |
1791 | @code{collect}, an end-test clause like @code{always}, or an | |
1792 | explicit @code{return} clause to jump out of the implicit block. | |
1793 | (Because the loop body is enclosed in an implicit block, you can | |
a05cb6e3 | 1794 | also use regular Lisp @code{cl-return} or @code{cl-return-from} to |
4009494e | 1795 | break out of the loop.) |
e1117425 | 1796 | @end defmac |
4009494e GM |
1797 | |
1798 | The following sections give some examples of the Loop Macro in | |
1799 | action, and describe the particular loop clauses in great detail. | |
1800 | Consult the second edition of Steele's @dfn{Common Lisp, the Language}, | |
1801 | for additional discussion and examples of the @code{loop} macro. | |
1802 | ||
1d5b82ef | 1803 | @node Loop Examples |
4009494e GM |
1804 | @subsection Loop Examples |
1805 | ||
1806 | @noindent | |
1807 | Before listing the full set of clauses that are allowed, let's | |
39a58b5b | 1808 | look at a few example loops just to get a feel for the @code{cl-loop} |
4009494e GM |
1809 | language. |
1810 | ||
1811 | @example | |
39a58b5b GM |
1812 | (cl-loop for buf in (buffer-list) |
1813 | collect (buffer-file-name buf)) | |
4009494e GM |
1814 | @end example |
1815 | ||
1816 | @noindent | |
1817 | This loop iterates over all Emacs buffers, using the list | |
a05cb6e3 | 1818 | returned by @code{buffer-list}. For each buffer @var{buf}, |
4009494e | 1819 | it calls @code{buffer-file-name} and collects the results into |
39a58b5b | 1820 | a list, which is then returned from the @code{cl-loop} construct. |
4009494e | 1821 | The result is a list of the file names of all the buffers in |
44e97401 | 1822 | Emacs's memory. The words @code{for}, @code{in}, and @code{collect} |
39a58b5b | 1823 | are reserved words in the @code{cl-loop} language. |
4009494e GM |
1824 | |
1825 | @example | |
39a58b5b | 1826 | (cl-loop repeat 20 do (insert "Yowsa\n")) |
4009494e GM |
1827 | @end example |
1828 | ||
1829 | @noindent | |
1830 | This loop inserts the phrase ``Yowsa'' twenty times in the | |
1831 | current buffer. | |
1832 | ||
1833 | @example | |
39a58b5b | 1834 | (cl-loop until (eobp) do (munch-line) (forward-line 1)) |
4009494e GM |
1835 | @end example |
1836 | ||
1837 | @noindent | |
1838 | This loop calls @code{munch-line} on every line until the end | |
1839 | of the buffer. If point is already at the end of the buffer, | |
1840 | the loop exits immediately. | |
1841 | ||
1842 | @example | |
39a58b5b | 1843 | (cl-loop do (munch-line) until (eobp) do (forward-line 1)) |
4009494e GM |
1844 | @end example |
1845 | ||
1846 | @noindent | |
1847 | This loop is similar to the above one, except that @code{munch-line} | |
1848 | is always called at least once. | |
1849 | ||
1850 | @example | |
39a58b5b GM |
1851 | (cl-loop for x from 1 to 100 |
1852 | for y = (* x x) | |
1853 | until (>= y 729) | |
1854 | finally return (list x (= y 729))) | |
4009494e GM |
1855 | @end example |
1856 | ||
1857 | @noindent | |
1858 | This more complicated loop searches for a number @code{x} whose | |
1859 | square is 729. For safety's sake it only examines @code{x} | |
1860 | values up to 100; dropping the phrase @samp{to 100} would | |
1861 | cause the loop to count upwards with no limit. The second | |
1862 | @code{for} clause defines @code{y} to be the square of @code{x} | |
1863 | within the loop; the expression after the @code{=} sign is | |
1864 | reevaluated each time through the loop. The @code{until} | |
1865 | clause gives a condition for terminating the loop, and the | |
1866 | @code{finally} clause says what to do when the loop finishes. | |
1867 | (This particular example was written less concisely than it | |
1868 | could have been, just for the sake of illustration.) | |
1869 | ||
1870 | Note that even though this loop contains three clauses (two | |
1871 | @code{for}s and an @code{until}) that would have been enough to | |
1872 | define loops all by themselves, it still creates a single loop | |
1873 | rather than some sort of triple-nested loop. You must explicitly | |
39a58b5b | 1874 | nest your @code{cl-loop} constructs if you want nested loops. |
4009494e | 1875 | |
1d5b82ef | 1876 | @node For Clauses |
4009494e GM |
1877 | @subsection For Clauses |
1878 | ||
1879 | @noindent | |
1880 | Most loops are governed by one or more @code{for} clauses. | |
1881 | A @code{for} clause simultaneously describes variables to be | |
1882 | bound, how those variables are to be stepped during the loop, | |
1883 | and usually an end condition based on those variables. | |
1884 | ||
1885 | The word @code{as} is a synonym for the word @code{for}. This | |
1886 | word is followed by a variable name, then a word like @code{from} | |
1887 | or @code{across} that describes the kind of iteration desired. | |
1888 | In Common Lisp, the phrase @code{being the} sometimes precedes | |
1889 | the type of iteration; in this package both @code{being} and | |
1890 | @code{the} are optional. The word @code{each} is a synonym | |
1891 | for @code{the}, and the word that follows it may be singular | |
1892 | or plural: @samp{for x being the elements of y} or | |
1893 | @samp{for x being each element of y}. Which form you use | |
1894 | is purely a matter of style. | |
1895 | ||
1896 | The variable is bound around the loop as if by @code{let}: | |
1897 | ||
1898 | @example | |
1899 | (setq i 'happy) | |
39a58b5b | 1900 | (cl-loop for i from 1 to 10 do (do-something-with i)) |
4009494e GM |
1901 | i |
1902 | @result{} happy | |
1903 | @end example | |
1904 | ||
1905 | @table @code | |
1906 | @item for @var{var} from @var{expr1} to @var{expr2} by @var{expr3} | |
1907 | This type of @code{for} clause creates a counting loop. Each of | |
1908 | the three sub-terms is optional, though there must be at least one | |
1909 | term so that the clause is marked as a counting clause. | |
1910 | ||
1911 | The three expressions are the starting value, the ending value, and | |
1912 | the step value, respectively, of the variable. The loop counts | |
1913 | upwards by default (@var{expr3} must be positive), from @var{expr1} | |
1914 | to @var{expr2} inclusively. If you omit the @code{from} term, the | |
1915 | loop counts from zero; if you omit the @code{to} term, the loop | |
1916 | counts forever without stopping (unless stopped by some other | |
1917 | loop clause, of course); if you omit the @code{by} term, the loop | |
1918 | counts in steps of one. | |
1919 | ||
1920 | You can replace the word @code{from} with @code{upfrom} or | |
1921 | @code{downfrom} to indicate the direction of the loop. Likewise, | |
1922 | you can replace @code{to} with @code{upto} or @code{downto}. | |
1923 | For example, @samp{for x from 5 downto 1} executes five times | |
1924 | with @code{x} taking on the integers from 5 down to 1 in turn. | |
1925 | Also, you can replace @code{to} with @code{below} or @code{above}, | |
1926 | which are like @code{upto} and @code{downto} respectively except | |
1927 | that they are exclusive rather than inclusive limits: | |
1928 | ||
1929 | @example | |
39a58b5b GM |
1930 | (cl-loop for x to 10 collect x) |
1931 | @result{} (0 1 2 3 4 5 6 7 8 9 10) | |
1932 | (cl-loop for x below 10 collect x) | |
1933 | @result{} (0 1 2 3 4 5 6 7 8 9) | |
4009494e GM |
1934 | @end example |
1935 | ||
1936 | The @code{by} value is always positive, even for downward-counting | |
1937 | loops. Some sort of @code{from} value is required for downward | |
1938 | loops; @samp{for x downto 5} is not a valid loop clause all by | |
1939 | itself. | |
1940 | ||
1941 | @item for @var{var} in @var{list} by @var{function} | |
1942 | This clause iterates @var{var} over all the elements of @var{list}, | |
1943 | in turn. If you specify the @code{by} term, then @var{function} | |
1944 | is used to traverse the list instead of @code{cdr}; it must be a | |
1945 | function taking one argument. For example: | |
1946 | ||
1947 | @example | |
39a58b5b GM |
1948 | (cl-loop for x in '(1 2 3 4 5 6) collect (* x x)) |
1949 | @result{} (1 4 9 16 25 36) | |
1950 | (cl-loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x)) | |
1951 | @result{} (1 9 25) | |
4009494e GM |
1952 | @end example |
1953 | ||
1954 | @item for @var{var} on @var{list} by @var{function} | |
1955 | This clause iterates @var{var} over all the cons cells of @var{list}. | |
1956 | ||
1957 | @example | |
39a58b5b GM |
1958 | (cl-loop for x on '(1 2 3 4) collect x) |
1959 | @result{} ((1 2 3 4) (2 3 4) (3 4) (4)) | |
4009494e GM |
1960 | @end example |
1961 | ||
1962 | With @code{by}, there is no real reason that the @code{on} expression | |
1963 | must be a list. For example: | |
1964 | ||
1965 | @example | |
39a58b5b | 1966 | (cl-loop for x on first-animal by 'next-animal collect x) |
4009494e GM |
1967 | @end example |
1968 | ||
1969 | @noindent | |
1970 | where @code{(next-animal x)} takes an ``animal'' @var{x} and returns | |
1971 | the next in the (assumed) sequence of animals, or @code{nil} if | |
1972 | @var{x} was the last animal in the sequence. | |
1973 | ||
1974 | @item for @var{var} in-ref @var{list} by @var{function} | |
1975 | This is like a regular @code{in} clause, but @var{var} becomes | |
1976 | a @code{setf}-able ``reference'' onto the elements of the list | |
1977 | rather than just a temporary variable. For example, | |
1978 | ||
1979 | @example | |
39a58b5b | 1980 | (cl-loop for x in-ref my-list do (cl-incf x)) |
4009494e GM |
1981 | @end example |
1982 | ||
1983 | @noindent | |
1984 | increments every element of @code{my-list} in place. This clause | |
1985 | is an extension to standard Common Lisp. | |
1986 | ||
1987 | @item for @var{var} across @var{array} | |
1988 | This clause iterates @var{var} over all the elements of @var{array}, | |
1989 | which may be a vector or a string. | |
1990 | ||
1991 | @example | |
39a58b5b GM |
1992 | (cl-loop for x across "aeiou" |
1993 | do (use-vowel (char-to-string x))) | |
4009494e GM |
1994 | @end example |
1995 | ||
1996 | @item for @var{var} across-ref @var{array} | |
1997 | This clause iterates over an array, with @var{var} a @code{setf}-able | |
1998 | reference onto the elements; see @code{in-ref} above. | |
1999 | ||
2000 | @item for @var{var} being the elements of @var{sequence} | |
2001 | This clause iterates over the elements of @var{sequence}, which may | |
2002 | be a list, vector, or string. Since the type must be determined | |
2003 | at run-time, this is somewhat less efficient than @code{in} or | |
2004 | @code{across}. The clause may be followed by the additional term | |
2005 | @samp{using (index @var{var2})} to cause @var{var2} to be bound to | |
2006 | the successive indices (starting at 0) of the elements. | |
2007 | ||
2008 | This clause type is taken from older versions of the @code{loop} macro, | |
2009 | and is not present in modern Common Lisp. The @samp{using (sequence ...)} | |
2010 | term of the older macros is not supported. | |
2011 | ||
2012 | @item for @var{var} being the elements of-ref @var{sequence} | |
2013 | This clause iterates over a sequence, with @var{var} a @code{setf}-able | |
2014 | reference onto the elements; see @code{in-ref} above. | |
2015 | ||
2016 | @item for @var{var} being the symbols [of @var{obarray}] | |
2017 | This clause iterates over symbols, either over all interned symbols | |
2018 | or over all symbols in @var{obarray}. The loop is executed with | |
2019 | @var{var} bound to each symbol in turn. The symbols are visited in | |
2020 | an unspecified order. | |
2021 | ||
2022 | As an example, | |
2023 | ||
2024 | @example | |
39a58b5b GM |
2025 | (cl-loop for sym being the symbols |
2026 | when (fboundp sym) | |
2027 | when (string-match "^map" (symbol-name sym)) | |
2028 | collect sym) | |
4009494e GM |
2029 | @end example |
2030 | ||
2031 | @noindent | |
2032 | returns a list of all the functions whose names begin with @samp{map}. | |
2033 | ||
2034 | The Common Lisp words @code{external-symbols} and @code{present-symbols} | |
2035 | are also recognized but are equivalent to @code{symbols} in Emacs Lisp. | |
2036 | ||
2037 | Due to a minor implementation restriction, it will not work to have | |
2038 | more than one @code{for} clause iterating over symbols, hash tables, | |
39a58b5b | 2039 | keymaps, overlays, or intervals in a given @code{cl-loop}. Fortunately, |
4009494e GM |
2040 | it would rarely if ever be useful to do so. It @emph{is} valid to mix |
2041 | one of these types of clauses with other clauses like @code{for ... to} | |
2042 | or @code{while}. | |
2043 | ||
2044 | @item for @var{var} being the hash-keys of @var{hash-table} | |
79414ae4 KR |
2045 | @itemx for @var{var} being the hash-values of @var{hash-table} |
2046 | This clause iterates over the entries in @var{hash-table} with | |
2047 | @var{var} bound to each key, or value. A @samp{using} clause can bind | |
2048 | a second variable to the opposite part. | |
2049 | ||
2050 | @example | |
39a58b5b GM |
2051 | (cl-loop for k being the hash-keys of h |
2052 | using (hash-values v) | |
2053 | do | |
2054 | (message "key %S -> value %S" k v)) | |
79414ae4 | 2055 | @end example |
4009494e GM |
2056 | |
2057 | @item for @var{var} being the key-codes of @var{keymap} | |
79414ae4 | 2058 | @itemx for @var{var} being the key-bindings of @var{keymap} |
4009494e | 2059 | This clause iterates over the entries in @var{keymap}. |
36374111 SM |
2060 | The iteration does not enter nested keymaps but does enter inherited |
2061 | (parent) keymaps. | |
79414ae4 KR |
2062 | A @code{using} clause can access both the codes and the bindings |
2063 | together. | |
2064 | ||
2065 | @example | |
39a58b5b GM |
2066 | (cl-loop for c being the key-codes of (current-local-map) |
2067 | using (key-bindings b) | |
2068 | do | |
2069 | (message "key %S -> binding %S" c b)) | |
79414ae4 KR |
2070 | @end example |
2071 | ||
4009494e GM |
2072 | |
2073 | @item for @var{var} being the key-seqs of @var{keymap} | |
2074 | This clause iterates over all key sequences defined by @var{keymap} | |
2075 | and its nested keymaps, where @var{var} takes on values which are | |
2076 | vectors. The strings or vectors | |
2077 | are reused for each iteration, so you must copy them if you wish to keep | |
2078 | them permanently. You can add a @samp{using (key-bindings ...)} | |
2079 | clause to get the command bindings as well. | |
2080 | ||
2081 | @item for @var{var} being the overlays [of @var{buffer}] @dots{} | |
2082 | This clause iterates over the ``overlays'' of a buffer | |
2083 | (the clause @code{extents} is synonymous | |
2084 | with @code{overlays}). If the @code{of} term is omitted, the current | |
2085 | buffer is used. | |
2086 | This clause also accepts optional @samp{from @var{pos}} and | |
2087 | @samp{to @var{pos}} terms, limiting the clause to overlays which | |
2088 | overlap the specified region. | |
2089 | ||
2090 | @item for @var{var} being the intervals [of @var{buffer}] @dots{} | |
2091 | This clause iterates over all intervals of a buffer with constant | |
2092 | text properties. The variable @var{var} will be bound to conses | |
2093 | of start and end positions, where one start position is always equal | |
2094 | to the previous end position. The clause allows @code{of}, | |
2095 | @code{from}, @code{to}, and @code{property} terms, where the latter | |
2096 | term restricts the search to just the specified property. The | |
2097 | @code{of} term may specify either a buffer or a string. | |
2098 | ||
2099 | @item for @var{var} being the frames | |
7dde1a86 GM |
2100 | This clause iterates over all Emacs frames. The clause @code{screens} is |
2101 | a synonym for @code{frames}. The frames are visited in | |
2102 | @code{next-frame} order starting from @code{selected-frame}. | |
4009494e GM |
2103 | |
2104 | @item for @var{var} being the windows [of @var{frame}] | |
2105 | This clause iterates over the windows (in the Emacs sense) of | |
7dde1a86 GM |
2106 | the current frame, or of the specified @var{frame}. It visits windows |
2107 | in @code{next-window} order starting from @code{selected-window} | |
2108 | (or @code{frame-selected-window} if you specify @var{frame}). | |
2109 | This clause treats the minibuffer window in the same way as | |
2110 | @code{next-window} does. For greater flexibility, consider using | |
2111 | @code{walk-windows} instead. | |
4009494e GM |
2112 | |
2113 | @item for @var{var} being the buffers | |
2114 | This clause iterates over all buffers in Emacs. It is equivalent | |
2115 | to @samp{for @var{var} in (buffer-list)}. | |
2116 | ||
2117 | @item for @var{var} = @var{expr1} then @var{expr2} | |
2118 | This clause does a general iteration. The first time through | |
2119 | the loop, @var{var} will be bound to @var{expr1}. On the second | |
2120 | and successive iterations it will be set by evaluating @var{expr2} | |
2121 | (which may refer to the old value of @var{var}). For example, | |
2122 | these two loops are effectively the same: | |
2123 | ||
2124 | @example | |
39a58b5b GM |
2125 | (cl-loop for x on my-list by 'cddr do ...) |
2126 | (cl-loop for x = my-list then (cddr x) while x do ...) | |
4009494e GM |
2127 | @end example |
2128 | ||
2129 | Note that this type of @code{for} clause does not imply any sort | |
2130 | of terminating condition; the above example combines it with a | |
2131 | @code{while} clause to tell when to end the loop. | |
2132 | ||
2133 | If you omit the @code{then} term, @var{expr1} is used both for | |
2134 | the initial setting and for successive settings: | |
2135 | ||
2136 | @example | |
39a58b5b | 2137 | (cl-loop for x = (random) when (> x 0) return x) |
4009494e GM |
2138 | @end example |
2139 | ||
2140 | @noindent | |
2141 | This loop keeps taking random numbers from the @code{(random)} | |
2142 | function until it gets a positive one, which it then returns. | |
2143 | @end table | |
2144 | ||
2145 | If you include several @code{for} clauses in a row, they are | |
2146 | treated sequentially (as if by @code{let*} and @code{setq}). | |
2147 | You can instead use the word @code{and} to link the clauses, | |
2148 | in which case they are processed in parallel (as if by @code{let} | |
8d6510b9 | 2149 | and @code{cl-psetq}). |
4009494e GM |
2150 | |
2151 | @example | |
39a58b5b GM |
2152 | (cl-loop for x below 5 for y = nil then x collect (list x y)) |
2153 | @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4)) | |
2154 | (cl-loop for x below 5 and y = nil then x collect (list x y)) | |
2155 | @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3)) | |
4009494e GM |
2156 | @end example |
2157 | ||
2158 | @noindent | |
2159 | In the first loop, @code{y} is set based on the value of @code{x} | |
2160 | that was just set by the previous clause; in the second loop, | |
2161 | @code{x} and @code{y} are set simultaneously so @code{y} is set | |
2162 | based on the value of @code{x} left over from the previous time | |
2163 | through the loop. | |
2164 | ||
39a58b5b | 2165 | Another feature of the @code{cl-loop} macro is @dfn{destructuring}, |
4009494e GM |
2166 | similar in concept to the destructuring provided by @code{defmacro}. |
2167 | The @var{var} part of any @code{for} clause can be given as a list | |
2168 | of variables instead of a single variable. The values produced | |
2169 | during loop execution must be lists; the values in the lists are | |
2170 | stored in the corresponding variables. | |
2171 | ||
2172 | @example | |
39a58b5b GM |
2173 | (cl-loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y)) |
2174 | @result{} (5 9 13) | |
4009494e GM |
2175 | @end example |
2176 | ||
2177 | In loop destructuring, if there are more values than variables | |
2178 | the trailing values are ignored, and if there are more variables | |
2179 | than values the trailing variables get the value @code{nil}. | |
2180 | If @code{nil} is used as a variable name, the corresponding | |
2181 | values are ignored. Destructuring may be nested, and dotted | |
c0a8ae95 KR |
2182 | lists of variables like @code{(x . y)} are allowed, so for example |
2183 | to process an alist | |
2184 | ||
2185 | @example | |
39a58b5b GM |
2186 | (cl-loop for (key . value) in '((a . 1) (b . 2)) |
2187 | collect value) | |
2188 | @result{} (1 2) | |
c0a8ae95 | 2189 | @end example |
4009494e | 2190 | |
1d5b82ef | 2191 | @node Iteration Clauses |
4009494e GM |
2192 | @subsection Iteration Clauses |
2193 | ||
2194 | @noindent | |
2195 | Aside from @code{for} clauses, there are several other loop clauses | |
2196 | that control the way the loop operates. They might be used by | |
2197 | themselves, or in conjunction with one or more @code{for} clauses. | |
2198 | ||
2199 | @table @code | |
2200 | @item repeat @var{integer} | |
2201 | This clause simply counts up to the specified number using an | |
2202 | internal temporary variable. The loops | |
2203 | ||
2204 | @example | |
39a58b5b GM |
2205 | (cl-loop repeat (1+ n) do ...) |
2206 | (cl-loop for temp to n do ...) | |
4009494e GM |
2207 | @end example |
2208 | ||
2209 | @noindent | |
2210 | are identical except that the second one forces you to choose | |
2211 | a name for a variable you aren't actually going to use. | |
2212 | ||
2213 | @item while @var{condition} | |
2214 | This clause stops the loop when the specified condition (any Lisp | |
2215 | expression) becomes @code{nil}. For example, the following two | |
2216 | loops are equivalent, except for the implicit @code{nil} block | |
2217 | that surrounds the second one: | |
2218 | ||
2219 | @example | |
2220 | (while @var{cond} @var{forms}@dots{}) | |
39a58b5b | 2221 | (cl-loop while @var{cond} do @var{forms}@dots{}) |
4009494e GM |
2222 | @end example |
2223 | ||
2224 | @item until @var{condition} | |
2225 | This clause stops the loop when the specified condition is true, | |
2226 | i.e., non-@code{nil}. | |
2227 | ||
2228 | @item always @var{condition} | |
2229 | This clause stops the loop when the specified condition is @code{nil}. | |
2230 | Unlike @code{while}, it stops the loop using @code{return nil} so that | |
2231 | the @code{finally} clauses are not executed. If all the conditions | |
2232 | were non-@code{nil}, the loop returns @code{t}: | |
2233 | ||
2234 | @example | |
39a58b5b | 2235 | (if (cl-loop for size in size-list always (> size 10)) |
4009494e GM |
2236 | (some-big-sizes) |
2237 | (no-big-sizes)) | |
2238 | @end example | |
2239 | ||
2240 | @item never @var{condition} | |
2241 | This clause is like @code{always}, except that the loop returns | |
2242 | @code{t} if any conditions were false, or @code{nil} otherwise. | |
2243 | ||
2244 | @item thereis @var{condition} | |
2245 | This clause stops the loop when the specified form is non-@code{nil}; | |
2246 | in this case, it returns that non-@code{nil} value. If all the | |
2247 | values were @code{nil}, the loop returns @code{nil}. | |
2248 | @end table | |
2249 | ||
1d5b82ef | 2250 | @node Accumulation Clauses |
4009494e GM |
2251 | @subsection Accumulation Clauses |
2252 | ||
2253 | @noindent | |
2254 | These clauses cause the loop to accumulate information about the | |
2255 | specified Lisp @var{form}. The accumulated result is returned | |
2256 | from the loop unless overridden, say, by a @code{return} clause. | |
2257 | ||
2258 | @table @code | |
2259 | @item collect @var{form} | |
2260 | This clause collects the values of @var{form} into a list. Several | |
2261 | examples of @code{collect} appear elsewhere in this manual. | |
2262 | ||
2263 | The word @code{collecting} is a synonym for @code{collect}, and | |
2264 | likewise for the other accumulation clauses. | |
2265 | ||
2266 | @item append @var{form} | |
2267 | This clause collects lists of values into a result list using | |
2268 | @code{append}. | |
2269 | ||
2270 | @item nconc @var{form} | |
2271 | This clause collects lists of values into a result list by | |
2272 | destructively modifying the lists rather than copying them. | |
2273 | ||
2274 | @item concat @var{form} | |
2275 | This clause concatenates the values of the specified @var{form} | |
2276 | into a string. (It and the following clause are extensions to | |
2277 | standard Common Lisp.) | |
2278 | ||
2279 | @item vconcat @var{form} | |
2280 | This clause concatenates the values of the specified @var{form} | |
2281 | into a vector. | |
2282 | ||
2283 | @item count @var{form} | |
2284 | This clause counts the number of times the specified @var{form} | |
2285 | evaluates to a non-@code{nil} value. | |
2286 | ||
2287 | @item sum @var{form} | |
2288 | This clause accumulates the sum of the values of the specified | |
2289 | @var{form}, which must evaluate to a number. | |
2290 | ||
2291 | @item maximize @var{form} | |
2292 | This clause accumulates the maximum value of the specified @var{form}, | |
2293 | which must evaluate to a number. The return value is undefined if | |
2294 | @code{maximize} is executed zero times. | |
2295 | ||
2296 | @item minimize @var{form} | |
2297 | This clause accumulates the minimum value of the specified @var{form}. | |
2298 | @end table | |
2299 | ||
2300 | Accumulation clauses can be followed by @samp{into @var{var}} to | |
2301 | cause the data to be collected into variable @var{var} (which is | |
2302 | automatically @code{let}-bound during the loop) rather than an | |
2303 | unnamed temporary variable. Also, @code{into} accumulations do | |
2304 | not automatically imply a return value. The loop must use some | |
2305 | explicit mechanism, such as @code{finally return}, to return | |
2306 | the accumulated result. | |
2307 | ||
2308 | It is valid for several accumulation clauses of the same type to | |
2309 | accumulate into the same place. From Steele: | |
2310 | ||
2311 | @example | |
39a58b5b GM |
2312 | (cl-loop for name in '(fred sue alice joe june) |
2313 | for kids in '((bob ken) () () (kris sunshine) ()) | |
2314 | collect name | |
2315 | append kids) | |
2316 | @result{} (fred bob ken sue alice joe kris sunshine june) | |
4009494e GM |
2317 | @end example |
2318 | ||
1d5b82ef | 2319 | @node Other Clauses |
4009494e GM |
2320 | @subsection Other Clauses |
2321 | ||
2322 | @noindent | |
2323 | This section describes the remaining loop clauses. | |
2324 | ||
2325 | @table @code | |
2326 | @item with @var{var} = @var{value} | |
2327 | This clause binds a variable to a value around the loop, but | |
2328 | otherwise leaves the variable alone during the loop. The following | |
2329 | loops are basically equivalent: | |
2330 | ||
2331 | @example | |
39a58b5b GM |
2332 | (cl-loop with x = 17 do ...) |
2333 | (let ((x 17)) (cl-loop do ...)) | |
2334 | (cl-loop for x = 17 then x do ...) | |
4009494e GM |
2335 | @end example |
2336 | ||
2337 | Naturally, the variable @var{var} might be used for some purpose | |
2338 | in the rest of the loop. For example: | |
2339 | ||
2340 | @example | |
39a58b5b GM |
2341 | (cl-loop for x in my-list with res = nil do (push x res) |
2342 | finally return res) | |
4009494e GM |
2343 | @end example |
2344 | ||
2345 | This loop inserts the elements of @code{my-list} at the front of | |
2346 | a new list being accumulated in @code{res}, then returns the | |
2347 | list @code{res} at the end of the loop. The effect is similar | |
2348 | to that of a @code{collect} clause, but the list gets reversed | |
2349 | by virtue of the fact that elements are being pushed onto the | |
2350 | front of @code{res} rather than the end. | |
2351 | ||
2352 | If you omit the @code{=} term, the variable is initialized to | |
2353 | @code{nil}. (Thus the @samp{= nil} in the above example is | |
2354 | unnecessary.) | |
2355 | ||
2356 | Bindings made by @code{with} are sequential by default, as if | |
2357 | by @code{let*}. Just like @code{for} clauses, @code{with} clauses | |
2358 | can be linked with @code{and} to cause the bindings to be made by | |
2359 | @code{let} instead. | |
2360 | ||
2361 | @item if @var{condition} @var{clause} | |
2362 | This clause executes the following loop clause only if the specified | |
2363 | condition is true. The following @var{clause} should be an accumulation, | |
2364 | @code{do}, @code{return}, @code{if}, or @code{unless} clause. | |
2365 | Several clauses may be linked by separating them with @code{and}. | |
2366 | These clauses may be followed by @code{else} and a clause or clauses | |
2367 | to execute if the condition was false. The whole construct may | |
2368 | optionally be followed by the word @code{end} (which may be used to | |
2369 | disambiguate an @code{else} or @code{and} in a nested @code{if}). | |
2370 | ||
2371 | The actual non-@code{nil} value of the condition form is available | |
2372 | by the name @code{it} in the ``then'' part. For example: | |
2373 | ||
2374 | @example | |
2375 | (setq funny-numbers '(6 13 -1)) | |
2376 | @result{} (6 13 -1) | |
39a58b5b GM |
2377 | (cl-loop for x below 10 |
2378 | if (oddp x) | |
2379 | collect x into odds | |
2380 | and if (memq x funny-numbers) return (cdr it) end | |
2381 | else | |
2382 | collect x into evens | |
2383 | finally return (vector odds evens)) | |
2384 | @result{} [(1 3 5 7 9) (0 2 4 6 8)] | |
4009494e GM |
2385 | (setq funny-numbers '(6 7 13 -1)) |
2386 | @result{} (6 7 13 -1) | |
39a58b5b GM |
2387 | (cl-loop <@r{same thing again}>) |
2388 | @result{} (13 -1) | |
4009494e GM |
2389 | @end example |
2390 | ||
2391 | Note the use of @code{and} to put two clauses into the ``then'' | |
2392 | part, one of which is itself an @code{if} clause. Note also that | |
2393 | @code{end}, while normally optional, was necessary here to make | |
2394 | it clear that the @code{else} refers to the outermost @code{if} | |
2395 | clause. In the first case, the loop returns a vector of lists | |
2396 | of the odd and even values of @var{x}. In the second case, the | |
2397 | odd number 7 is one of the @code{funny-numbers} so the loop | |
2398 | returns early; the actual returned value is based on the result | |
2399 | of the @code{memq} call. | |
2400 | ||
2401 | @item when @var{condition} @var{clause} | |
2402 | This clause is just a synonym for @code{if}. | |
2403 | ||
2404 | @item unless @var{condition} @var{clause} | |
2405 | The @code{unless} clause is just like @code{if} except that the | |
2406 | sense of the condition is reversed. | |
2407 | ||
2408 | @item named @var{name} | |
2409 | This clause gives a name other than @code{nil} to the implicit | |
2410 | block surrounding the loop. The @var{name} is the symbol to be | |
2411 | used as the block name. | |
2412 | ||
2413 | @item initially [do] @var{forms}... | |
2414 | This keyword introduces one or more Lisp forms which will be | |
2415 | executed before the loop itself begins (but after any variables | |
2416 | requested by @code{for} or @code{with} have been bound to their | |
2417 | initial values). @code{initially} clauses can appear anywhere; | |
2418 | if there are several, they are executed in the order they appear | |
2419 | in the loop. The keyword @code{do} is optional. | |
2420 | ||
2421 | @item finally [do] @var{forms}... | |
2422 | This introduces Lisp forms which will be executed after the loop | |
2423 | finishes (say, on request of a @code{for} or @code{while}). | |
2424 | @code{initially} and @code{finally} clauses may appear anywhere | |
2425 | in the loop construct, but they are executed (in the specified | |
2426 | order) at the beginning or end, respectively, of the loop. | |
2427 | ||
2428 | @item finally return @var{form} | |
2429 | This says that @var{form} should be executed after the loop | |
2430 | is done to obtain a return value. (Without this, or some other | |
2431 | clause like @code{collect} or @code{return}, the loop will simply | |
2432 | return @code{nil}.) Variables bound by @code{for}, @code{with}, | |
2433 | or @code{into} will still contain their final values when @var{form} | |
2434 | is executed. | |
2435 | ||
2436 | @item do @var{forms}... | |
2437 | The word @code{do} may be followed by any number of Lisp expressions | |
2438 | which are executed as an implicit @code{progn} in the body of the | |
2439 | loop. Many of the examples in this section illustrate the use of | |
2440 | @code{do}. | |
2441 | ||
2442 | @item return @var{form} | |
2443 | This clause causes the loop to return immediately. The following | |
2444 | Lisp form is evaluated to give the return value of the @code{loop} | |
2445 | form. The @code{finally} clauses, if any, are not executed. | |
2446 | Of course, @code{return} is generally used inside an @code{if} or | |
2447 | @code{unless}, as its use in a top-level loop clause would mean | |
2448 | the loop would never get to ``loop'' more than once. | |
2449 | ||
2450 | The clause @samp{return @var{form}} is equivalent to | |
a05cb6e3 | 2451 | @c FIXME cl-do, cl-return? |
4009494e GM |
2452 | @samp{do (return @var{form})} (or @code{return-from} if the loop |
2453 | was named). The @code{return} clause is implemented a bit more | |
2454 | efficiently, though. | |
2455 | @end table | |
2456 | ||
d55911cf GM |
2457 | While there is no high-level way to add user extensions to @code{cl-loop}, |
2458 | this package does offer two properties called @code{cl-loop-handler} | |
2459 | and @code{cl-loop-for-handler} which are functions to be called when a | |
2460 | given symbol is encountered as a top-level loop clause or @code{for} | |
2461 | clause, respectively. Consult the source code in file | |
2462 | @file{cl-macs.el} for details. | |
4009494e | 2463 | |
39a58b5b | 2464 | This package's @code{cl-loop} macro is compatible with that of Common |
4009494e GM |
2465 | Lisp, except that a few features are not implemented: @code{loop-finish} |
2466 | and data-type specifiers. Naturally, the @code{for} clauses which | |
2467 | iterate over keymaps, overlays, intervals, frames, windows, and | |
2468 | buffers are Emacs-specific extensions. | |
2469 | ||
1d5b82ef | 2470 | @node Multiple Values |
4009494e GM |
2471 | @section Multiple Values |
2472 | ||
2473 | @noindent | |
2474 | Common Lisp functions can return zero or more results. Emacs Lisp | |
2475 | functions, by contrast, always return exactly one result. This | |
2476 | package makes no attempt to emulate Common Lisp multiple return | |
2477 | values; Emacs versions of Common Lisp functions that return more | |
2478 | than one value either return just the first value (as in | |
d571e9c3 GM |
2479 | @code{cl-compiler-macroexpand}) or return a list of values. |
2480 | This package @emph{does} define placeholders | |
4009494e GM |
2481 | for the Common Lisp functions that work with multiple values, but |
2482 | in Emacs Lisp these functions simply operate on lists instead. | |
f94b04fc | 2483 | The @code{cl-values} form, for example, is a synonym for @code{list} |
4009494e GM |
2484 | in Emacs. |
2485 | ||
e1117425 | 2486 | @defmac cl-multiple-value-bind (var@dots{}) values-form forms@dots{} |
4009494e GM |
2487 | This form evaluates @var{values-form}, which must return a list of |
2488 | values. It then binds the @var{var}s to these respective values, | |
2489 | as if by @code{let}, and then executes the body @var{forms}. | |
2490 | If there are more @var{var}s than values, the extra @var{var}s | |
2491 | are bound to @code{nil}. If there are fewer @var{var}s than | |
2492 | values, the excess values are ignored. | |
e1117425 | 2493 | @end defmac |
4009494e | 2494 | |
e1117425 | 2495 | @defmac cl-multiple-value-setq (var@dots{}) form |
4009494e GM |
2496 | This form evaluates @var{form}, which must return a list of values. |
2497 | It then sets the @var{var}s to these respective values, as if by | |
2498 | @code{setq}. Extra @var{var}s or values are treated the same as | |
39a58b5b | 2499 | in @code{cl-multiple-value-bind}. |
e1117425 | 2500 | @end defmac |
4009494e | 2501 | |
4009494e GM |
2502 | Since a perfect emulation is not feasible in Emacs Lisp, this |
2503 | package opts to keep it as simple and predictable as possible. | |
2504 | ||
1d5b82ef | 2505 | @node Macros |
4009494e GM |
2506 | @chapter Macros |
2507 | ||
2508 | @noindent | |
2509 | This package implements the various Common Lisp features of | |
2510 | @code{defmacro}, such as destructuring, @code{&environment}, | |
2511 | and @code{&body}. Top-level @code{&whole} is not implemented | |
2512 | for @code{defmacro} due to technical difficulties. | |
2513 | @xref{Argument Lists}. | |
2514 | ||
2515 | Destructuring is made available to the user by way of the | |
2516 | following macro: | |
2517 | ||
e1117425 | 2518 | @defmac cl-destructuring-bind arglist expr forms@dots{} |
4009494e GM |
2519 | This macro expands to code which executes @var{forms}, with |
2520 | the variables in @var{arglist} bound to the list of values | |
2521 | returned by @var{expr}. The @var{arglist} can include all | |
2522 | the features allowed for @code{defmacro} argument lists, | |
2523 | including destructuring. (The @code{&environment} keyword | |
2524 | is not allowed.) The macro expansion will signal an error | |
2525 | if @var{expr} returns a list of the wrong number of arguments | |
2526 | or with incorrect keyword arguments. | |
e1117425 | 2527 | @end defmac |
4009494e | 2528 | |
39a58b5b | 2529 | This package also includes the Common Lisp @code{cl-define-compiler-macro} |
4009494e GM |
2530 | facility, which allows you to define compile-time expansions and |
2531 | optimizations for your functions. | |
2532 | ||
e1117425 | 2533 | @defmac cl-define-compiler-macro name arglist forms@dots{} |
4009494e GM |
2534 | This form is similar to @code{defmacro}, except that it only expands |
2535 | calls to @var{name} at compile-time; calls processed by the Lisp | |
2536 | interpreter are not expanded, nor are they expanded by the | |
2537 | @code{macroexpand} function. | |
2538 | ||
2539 | The argument list may begin with a @code{&whole} keyword and a | |
2540 | variable. This variable is bound to the macro-call form itself, | |
2541 | i.e., to a list of the form @samp{(@var{name} @var{args}@dots{})}. | |
2542 | If the macro expander returns this form unchanged, then the | |
2543 | compiler treats it as a normal function call. This allows | |
2544 | compiler macros to work as optimizers for special cases of a | |
2545 | function, leaving complicated cases alone. | |
2546 | ||
2547 | For example, here is a simplified version of a definition that | |
2548 | appears as a standard part of this package: | |
2549 | ||
2550 | @example | |
39a58b5b GM |
2551 | (cl-define-compiler-macro cl-member (&whole form a list &rest keys) |
2552 | (if (and (null keys) | |
2553 | (eq (car-safe a) 'quote) | |
2554 | (not (floatp-safe (cadr a)))) | |
2555 | (list 'memq a list) | |
2556 | form)) | |
4009494e GM |
2557 | @end example |
2558 | ||
2559 | @noindent | |
39a58b5b | 2560 | This definition causes @code{(cl-member @var{a} @var{list})} to change |
4009494e GM |
2561 | to a call to the faster @code{memq} in the common case where @var{a} |
2562 | is a non-floating-point constant; if @var{a} is anything else, or | |
2563 | if there are any keyword arguments in the call, then the original | |
39a58b5b GM |
2564 | @code{cl-member} call is left intact. (The actual compiler macro |
2565 | for @code{cl-member} optimizes a number of other cases, including | |
4009494e | 2566 | common @code{:test} predicates.) |
e1117425 | 2567 | @end defmac |
4009494e | 2568 | |
39a58b5b | 2569 | @defun cl-compiler-macroexpand form |
4009494e GM |
2570 | This function is analogous to @code{macroexpand}, except that it |
2571 | expands compiler macros rather than regular macros. It returns | |
2572 | @var{form} unchanged if it is not a call to a function for which | |
2573 | a compiler macro has been defined, or if that compiler macro | |
2574 | decided to punt by returning its @code{&whole} argument. Like | |
2575 | @code{macroexpand}, it expands repeatedly until it reaches a form | |
2576 | for which no further expansion is possible. | |
2577 | @end defun | |
2578 | ||
39a58b5b GM |
2579 | @xref{Macro Bindings}, for descriptions of the @code{cl-macrolet} |
2580 | and @code{cl-symbol-macrolet} forms for making ``local'' macro | |
4009494e GM |
2581 | definitions. |
2582 | ||
1d5b82ef | 2583 | @node Declarations |
4009494e GM |
2584 | @chapter Declarations |
2585 | ||
2586 | @noindent | |
2587 | Common Lisp includes a complex and powerful ``declaration'' | |
2588 | mechanism that allows you to give the compiler special hints | |
2589 | about the types of data that will be stored in particular variables, | |
2590 | and about the ways those variables and functions will be used. This | |
2591 | package defines versions of all the Common Lisp declaration forms: | |
39a58b5b GM |
2592 | @code{cl-declare}, @code{cl-locally}, @code{cl-proclaim}, @code{cl-declaim}, |
2593 | and @code{cl-the}. | |
4009494e GM |
2594 | |
2595 | Most of the Common Lisp declarations are not currently useful in | |
2596 | Emacs Lisp, as the byte-code system provides little opportunity | |
2597 | to benefit from type information, and @code{special} declarations | |
2598 | are redundant in a fully dynamically-scoped Lisp. A few | |
2599 | declarations are meaningful when the optimizing byte | |
2600 | compiler is being used, however. Under the earlier non-optimizing | |
2601 | compiler, these declarations will effectively be ignored. | |
2602 | ||
39a58b5b | 2603 | @defun cl-proclaim decl-spec |
4009494e | 2604 | This function records a ``global'' declaration specified by |
39a58b5b | 2605 | @var{decl-spec}. Since @code{cl-proclaim} is a function, @var{decl-spec} |
4009494e GM |
2606 | is evaluated and thus should normally be quoted. |
2607 | @end defun | |
2608 | ||
e1117425 | 2609 | @defmac cl-declaim decl-specs@dots{} |
39a58b5b | 2610 | This macro is like @code{cl-proclaim}, except that it takes any number |
4009494e | 2611 | of @var{decl-spec} arguments, and the arguments are unevaluated and |
39a58b5b | 2612 | unquoted. The @code{cl-declaim} macro also puts an @code{(cl-eval-when |
4009494e GM |
2613 | (compile load eval) ...)} around the declarations so that they will |
2614 | be registered at compile-time as well as at run-time. (This is vital, | |
2615 | since normally the declarations are meant to influence the way the | |
39a58b5b | 2616 | compiler treats the rest of the file that contains the @code{cl-declaim} |
4009494e | 2617 | form.) |
e1117425 | 2618 | @end defmac |
4009494e | 2619 | |
e1117425 | 2620 | @defmac cl-declare decl-specs@dots{} |
4009494e GM |
2621 | This macro is used to make declarations within functions and other |
2622 | code. Common Lisp allows declarations in various locations, generally | |
2623 | at the beginning of any of the many ``implicit @code{progn}s'' | |
2624 | throughout Lisp syntax, such as function bodies, @code{let} bodies, | |
39a58b5b | 2625 | etc. Currently the only declaration understood by @code{cl-declare} |
4009494e | 2626 | is @code{special}. |
e1117425 | 2627 | @end defmac |
4009494e | 2628 | |
e1117425 | 2629 | @defmac cl-locally declarations@dots{} forms@dots{} |
39a58b5b | 2630 | In this package, @code{cl-locally} is no different from @code{progn}. |
e1117425 | 2631 | @end defmac |
4009494e | 2632 | |
e1117425 | 2633 | @defmac cl-the type form |
39a58b5b GM |
2634 | Type information provided by @code{cl-the} is ignored in this package; |
2635 | in other words, @code{(cl-the @var{type} @var{form})} is equivalent | |
4009494e GM |
2636 | to @var{form}. Future versions of the optimizing byte-compiler may |
2637 | make use of this information. | |
2638 | ||
2639 | For example, @code{mapcar} can map over both lists and arrays. It is | |
2640 | hard for the compiler to expand @code{mapcar} into an in-line loop | |
2641 | unless it knows whether the sequence will be a list or an array ahead | |
39a58b5b | 2642 | of time. With @code{(mapcar 'car (cl-the vector foo))}, a future |
4009494e GM |
2643 | compiler would have enough information to expand the loop in-line. |
2644 | For now, Emacs Lisp will treat the above code as exactly equivalent | |
2645 | to @code{(mapcar 'car foo)}. | |
e1117425 | 2646 | @end defmac |
4009494e | 2647 | |
39a58b5b GM |
2648 | Each @var{decl-spec} in a @code{cl-proclaim}, @code{cl-declaim}, or |
2649 | @code{cl-declare} should be a list beginning with a symbol that says | |
4009494e GM |
2650 | what kind of declaration it is. This package currently understands |
2651 | @code{special}, @code{inline}, @code{notinline}, @code{optimize}, | |
2652 | and @code{warn} declarations. (The @code{warn} declaration is an | |
2653 | extension of standard Common Lisp.) Other Common Lisp declarations, | |
2654 | such as @code{type} and @code{ftype}, are silently ignored. | |
2655 | ||
2656 | @table @code | |
2657 | @item special | |
2658 | Since all variables in Emacs Lisp are ``special'' (in the Common | |
2659 | Lisp sense), @code{special} declarations are only advisory. They | |
2660 | simply tell the optimizing byte compiler that the specified | |
2661 | variables are intentionally being referred to without being | |
2662 | bound in the body of the function. The compiler normally emits | |
2663 | warnings for such references, since they could be typographical | |
2664 | errors for references to local variables. | |
2665 | ||
39a58b5b | 2666 | The declaration @code{(cl-declare (special @var{var1} @var{var2}))} is |
4009494e GM |
2667 | equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the |
2668 | optimizing compiler, or to nothing at all in older compilers (which | |
2669 | do not warn for non-local references). | |
2670 | ||
2671 | In top-level contexts, it is generally better to write | |
39a58b5b | 2672 | @code{(defvar @var{var})} than @code{(cl-declaim (special @var{var}))}, |
4009494e GM |
2673 | since @code{defvar} makes your intentions clearer. But the older |
2674 | byte compilers can not handle @code{defvar}s appearing inside of | |
39a58b5b | 2675 | functions, while @code{(cl-declare (special @var{var}))} takes care |
4009494e GM |
2676 | to work correctly with all compilers. |
2677 | ||
2678 | @item inline | |
2679 | The @code{inline} @var{decl-spec} lists one or more functions | |
2680 | whose bodies should be expanded ``in-line'' into calling functions | |
2681 | whenever the compiler is able to arrange for it. For example, | |
2682 | the Common Lisp function @code{cadr} is declared @code{inline} | |
2683 | by this package so that the form @code{(cadr @var{x})} will | |
2684 | expand directly into @code{(car (cdr @var{x}))} when it is called | |
2685 | in user functions, for a savings of one (relatively expensive) | |
2686 | function call. | |
2687 | ||
2688 | The following declarations are all equivalent. Note that the | |
2689 | @code{defsubst} form is a convenient way to define a function | |
2690 | and declare it inline all at once. | |
2691 | ||
2692 | @example | |
39a58b5b | 2693 | (cl-declaim (inline foo bar)) |
a05cb6e3 GM |
2694 | (cl-eval-when (compile load eval) |
2695 | (cl-proclaim '(inline foo bar))) | |
4009494e GM |
2696 | (defsubst foo (...) ...) ; instead of defun |
2697 | @end example | |
2698 | ||
2699 | @strong{Please note:} this declaration remains in effect after the | |
2700 | containing source file is done. It is correct to use it to | |
2701 | request that a function you have defined should be inlined, | |
2702 | but it is impolite to use it to request inlining of an external | |
2703 | function. | |
2704 | ||
39a58b5b | 2705 | In Common Lisp, it is possible to use @code{(cl-declare (inline @dots{}))} |
4009494e GM |
2706 | before a particular call to a function to cause just that call to |
2707 | be inlined; the current byte compilers provide no way to implement | |
39a58b5b | 2708 | this, so @code{(cl-declare (inline @dots{}))} is currently ignored by |
4009494e GM |
2709 | this package. |
2710 | ||
2711 | @item notinline | |
2712 | The @code{notinline} declaration lists functions which should | |
2713 | not be inlined after all; it cancels a previous @code{inline} | |
2714 | declaration. | |
2715 | ||
2716 | @item optimize | |
2717 | This declaration controls how much optimization is performed by | |
2718 | the compiler. Naturally, it is ignored by the earlier non-optimizing | |
2719 | compilers. | |
2720 | ||
2721 | The word @code{optimize} is followed by any number of lists like | |
2722 | @code{(speed 3)} or @code{(safety 2)}. Common Lisp defines several | |
2723 | optimization ``qualities''; this package ignores all but @code{speed} | |
2724 | and @code{safety}. The value of a quality should be an integer from | |
a05cb6e3 | 2725 | 0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important''. |
4009494e GM |
2726 | The default level for both qualities is 1. |
2727 | ||
2728 | In this package, with the optimizing compiler, the | |
39ff2cf3 | 2729 | @code{speed} quality is tied to the @code{byte-optimize} |
4009494e GM |
2730 | flag, which is set to @code{nil} for @code{(speed 0)} and to |
2731 | @code{t} for higher settings; and the @code{safety} quality is | |
2732 | tied to the @code{byte-compile-delete-errors} flag, which is | |
39ff2cf3 | 2733 | set to @code{nil} for @code{(safety 3)} and to @code{t} for all |
4009494e GM |
2734 | lower settings. (The latter flag controls whether the compiler |
2735 | is allowed to optimize out code whose only side-effect could | |
2736 | be to signal an error, e.g., rewriting @code{(progn foo bar)} to | |
2737 | @code{bar} when it is not known whether @code{foo} will be bound | |
2738 | at run-time.) | |
2739 | ||
2740 | Note that even compiling with @code{(safety 0)}, the Emacs | |
2741 | byte-code system provides sufficient checking to prevent real | |
2742 | harm from being done. For example, barring serious bugs in | |
2743 | Emacs itself, Emacs will not crash with a segmentation fault | |
2744 | just because of an error in a fully-optimized Lisp program. | |
2745 | ||
2746 | The @code{optimize} declaration is normally used in a top-level | |
39a58b5b GM |
2747 | @code{cl-proclaim} or @code{cl-declaim} in a file; Common Lisp allows |
2748 | it to be used with @code{cl-declare} to set the level of optimization | |
4009494e | 2749 | locally for a given form, but this will not work correctly with the |
39a58b5b | 2750 | current version of the optimizing compiler. (The @code{cl-declare} |
4009494e GM |
2751 | will set the new optimization level, but that level will not |
2752 | automatically be unset after the enclosing form is done.) | |
2753 | ||
2754 | @item warn | |
2755 | This declaration controls what sorts of warnings are generated | |
2756 | by the byte compiler. Again, only the optimizing compiler | |
2757 | generates warnings. The word @code{warn} is followed by any | |
a05cb6e3 | 2758 | number of ``warning qualities'', similar in form to optimization |
4009494e GM |
2759 | qualities. The currently supported warning types are |
2760 | @code{redefine}, @code{callargs}, @code{unresolved}, and | |
2761 | @code{free-vars}; in the current system, a value of 0 will | |
2762 | disable these warnings and any higher value will enable them. | |
2763 | See the documentation for the optimizing byte compiler for details. | |
2764 | @end table | |
2765 | ||
1d5b82ef | 2766 | @node Symbols |
4009494e GM |
2767 | @chapter Symbols |
2768 | ||
2769 | @noindent | |
2770 | This package defines several symbol-related features that were | |
2771 | missing from Emacs Lisp. | |
2772 | ||
2773 | @menu | |
39a58b5b GM |
2774 | * Property Lists:: @code{cl-get}, @code{cl-remprop}, @code{cl-getf}, @code{cl-remf}. |
2775 | * Creating Symbols:: @code{cl-gensym}, @code{cl-gentemp}. | |
4009494e GM |
2776 | @end menu |
2777 | ||
1d5b82ef | 2778 | @node Property Lists |
4009494e GM |
2779 | @section Property Lists |
2780 | ||
2781 | @noindent | |
2782 | These functions augment the standard Emacs Lisp functions @code{get} | |
2783 | and @code{put} for operating on properties attached to symbols. | |
2784 | There are also functions for working with property lists as | |
2785 | first-class data structures not attached to particular symbols. | |
2786 | ||
39a58b5b | 2787 | @defun cl-get symbol property &optional default |
4009494e GM |
2788 | This function is like @code{get}, except that if the property is |
2789 | not found, the @var{default} argument provides the return value. | |
2790 | (The Emacs Lisp @code{get} function always uses @code{nil} as | |
39a58b5b | 2791 | the default; this package's @code{cl-get} is equivalent to Common |
4009494e GM |
2792 | Lisp's @code{get}.) |
2793 | ||
39a58b5b | 2794 | The @code{cl-get} function is @code{setf}-able; when used in this |
4009494e GM |
2795 | fashion, the @var{default} argument is allowed but ignored. |
2796 | @end defun | |
2797 | ||
39a58b5b | 2798 | @defun cl-remprop symbol property |
4009494e GM |
2799 | This function removes the entry for @var{property} from the property |
2800 | list of @var{symbol}. It returns a true value if the property was | |
2801 | indeed found and removed, or @code{nil} if there was no such property. | |
2802 | (This function was probably omitted from Emacs originally because, | |
2803 | since @code{get} did not allow a @var{default}, it was very difficult | |
2804 | to distinguish between a missing property and a property whose value | |
2805 | was @code{nil}; thus, setting a property to @code{nil} was close | |
39a58b5b | 2806 | enough to @code{cl-remprop} for most purposes.) |
4009494e GM |
2807 | @end defun |
2808 | ||
39a58b5b | 2809 | @defun cl-getf place property &optional default |
4009494e GM |
2810 | This function scans the list @var{place} as if it were a property |
2811 | list, i.e., a list of alternating property names and values. If | |
2812 | an even-numbered element of @var{place} is found which is @code{eq} | |
2813 | to @var{property}, the following odd-numbered element is returned. | |
2814 | Otherwise, @var{default} is returned (or @code{nil} if no default | |
2815 | is given). | |
2816 | ||
2817 | In particular, | |
2818 | ||
2819 | @example | |
516e1a08 | 2820 | (get sym prop) @equiv{} (cl-getf (symbol-plist sym) prop) |
4009494e GM |
2821 | @end example |
2822 | ||
516e1a08 | 2823 | It is valid to use @code{cl-getf} as a @code{setf} place, in which case |
4009494e GM |
2824 | its @var{place} argument must itself be a valid @code{setf} place. |
2825 | The @var{default} argument, if any, is ignored in this context. | |
2826 | The effect is to change (via @code{setcar}) the value cell in the | |
2827 | list that corresponds to @var{property}, or to cons a new property-value | |
2828 | pair onto the list if the property is not yet present. | |
2829 | ||
2830 | @example | |
516e1a08 | 2831 | (put sym prop val) @equiv{} (setf (cl-getf (symbol-plist sym) prop) val) |
4009494e GM |
2832 | @end example |
2833 | ||
39a58b5b | 2834 | The @code{get} and @code{cl-get} functions are also @code{setf}-able. |
4009494e GM |
2835 | The fact that @code{default} is ignored can sometimes be useful: |
2836 | ||
2837 | @example | |
39a58b5b | 2838 | (cl-incf (cl-get 'foo 'usage-count 0)) |
4009494e GM |
2839 | @end example |
2840 | ||
2841 | Here, symbol @code{foo}'s @code{usage-count} property is incremented | |
2842 | if it exists, or set to 1 (an incremented 0) otherwise. | |
2843 | ||
516e1a08 | 2844 | When not used as a @code{setf} form, @code{cl-getf} is just a regular |
4009494e GM |
2845 | function and its @var{place} argument can actually be any Lisp |
2846 | expression. | |
2847 | @end defun | |
2848 | ||
e1117425 | 2849 | @defmac cl-remf place property |
4009494e GM |
2850 | This macro removes the property-value pair for @var{property} from |
2851 | the property list stored at @var{place}, which is any @code{setf}-able | |
2852 | place expression. It returns true if the property was found. Note | |
2853 | that if @var{property} happens to be first on the list, this will | |
2854 | effectively do a @code{(setf @var{place} (cddr @var{place}))}, | |
2855 | whereas if it occurs later, this simply uses @code{setcdr} to splice | |
2856 | out the property and value cells. | |
e1117425 | 2857 | @end defmac |
4009494e | 2858 | |
1d5b82ef | 2859 | @node Creating Symbols |
4009494e GM |
2860 | @section Creating Symbols |
2861 | ||
2862 | @noindent | |
2863 | These functions create unique symbols, typically for use as | |
2864 | temporary variables. | |
2865 | ||
39a58b5b | 2866 | @defun cl-gensym &optional x |
4009494e GM |
2867 | This function creates a new, uninterned symbol (using @code{make-symbol}) |
2868 | with a unique name. (The name of an uninterned symbol is relevant | |
2869 | only if the symbol is printed.) By default, the name is generated | |
2870 | from an increasing sequence of numbers, @samp{G1000}, @samp{G1001}, | |
2871 | @samp{G1002}, etc. If the optional argument @var{x} is a string, that | |
2872 | string is used as a prefix instead of @samp{G}. Uninterned symbols | |
2873 | are used in macro expansions for temporary variables, to ensure that | |
2874 | their names will not conflict with ``real'' variables in the user's | |
2875 | code. | |
2876 | @end defun | |
2877 | ||
39a58b5b GM |
2878 | @defvar cl--gensym-counter |
2879 | This variable holds the counter used to generate @code{cl-gensym} names. | |
2880 | It is incremented after each use by @code{cl-gensym}. In Common Lisp | |
4009494e GM |
2881 | this is initialized with 0, but this package initializes it with a |
2882 | random (time-dependent) value to avoid trouble when two files that | |
39a58b5b | 2883 | each used @code{cl-gensym} in their compilation are loaded together. |
4009494e GM |
2884 | (Uninterned symbols become interned when the compiler writes them |
2885 | out to a file and the Emacs loader loads them, so their names have to | |
2886 | be treated a bit more carefully than in Common Lisp where uninterned | |
2887 | symbols remain uninterned after loading.) | |
2888 | @end defvar | |
2889 | ||
39a58b5b GM |
2890 | @defun cl-gentemp &optional x |
2891 | This function is like @code{cl-gensym}, except that it produces a new | |
4009494e GM |
2892 | @emph{interned} symbol. If the symbol that is generated already |
2893 | exists, the function keeps incrementing the counter and trying | |
2894 | again until a new symbol is generated. | |
2895 | @end defun | |
2896 | ||
a6880551 GM |
2897 | This package automatically creates all keywords that are called for by |
2898 | @code{&key} argument specifiers, and discourages the use of keywords | |
2899 | as data unrelated to keyword arguments, so the related function | |
2900 | @code{defkeyword} (to create self-quoting keyword symbols) is not | |
2901 | provided. | |
4009494e | 2902 | |
1d5b82ef | 2903 | @node Numbers |
4009494e GM |
2904 | @chapter Numbers |
2905 | ||
2906 | @noindent | |
2907 | This section defines a few simple Common Lisp operations on numbers | |
2908 | which were left out of Emacs Lisp. | |
2909 | ||
2910 | @menu | |
39a58b5b GM |
2911 | * Predicates on Numbers:: @code{cl-plusp}, @code{cl-oddp}, @code{cl-floatp-safe}, etc. |
2912 | * Numerical Functions:: @code{abs}, @code{cl-floor}, etc. | |
2913 | * Random Numbers:: @code{cl-random}, @code{cl-make-random-state}. | |
2914 | * Implementation Parameters:: @code{cl-most-positive-float}. | |
4009494e GM |
2915 | @end menu |
2916 | ||
1d5b82ef | 2917 | @node Predicates on Numbers |
4009494e GM |
2918 | @section Predicates on Numbers |
2919 | ||
2920 | @noindent | |
2921 | These functions return @code{t} if the specified condition is | |
2922 | true of the numerical argument, or @code{nil} otherwise. | |
2923 | ||
39a58b5b | 2924 | @defun cl-plusp number |
4009494e GM |
2925 | This predicate tests whether @var{number} is positive. It is an |
2926 | error if the argument is not a number. | |
2927 | @end defun | |
2928 | ||
39a58b5b | 2929 | @defun cl-minusp number |
4009494e GM |
2930 | This predicate tests whether @var{number} is negative. It is an |
2931 | error if the argument is not a number. | |
2932 | @end defun | |
2933 | ||
39a58b5b | 2934 | @defun cl-oddp integer |
4009494e GM |
2935 | This predicate tests whether @var{integer} is odd. It is an |
2936 | error if the argument is not an integer. | |
2937 | @end defun | |
2938 | ||
39a58b5b | 2939 | @defun cl-evenp integer |
4009494e GM |
2940 | This predicate tests whether @var{integer} is even. It is an |
2941 | error if the argument is not an integer. | |
2942 | @end defun | |
2943 | ||
39a58b5b | 2944 | @defun cl-floatp-safe object |
4009494e GM |
2945 | This predicate tests whether @var{object} is a floating-point |
2946 | number. On systems that support floating-point, this is equivalent | |
2947 | to @code{floatp}. On other systems, this always returns @code{nil}. | |
2948 | @end defun | |
2949 | ||
1d5b82ef | 2950 | @node Numerical Functions |
4009494e GM |
2951 | @section Numerical Functions |
2952 | ||
2953 | @noindent | |
2954 | These functions perform various arithmetic operations on numbers. | |
2955 | ||
39a58b5b | 2956 | @defun cl-gcd &rest integers |
4009494e GM |
2957 | This function returns the Greatest Common Divisor of the arguments. |
2958 | For one argument, it returns the absolute value of that argument. | |
2959 | For zero arguments, it returns zero. | |
2960 | @end defun | |
2961 | ||
39a58b5b | 2962 | @defun cl-lcm &rest integers |
4009494e GM |
2963 | This function returns the Least Common Multiple of the arguments. |
2964 | For one argument, it returns the absolute value of that argument. | |
2965 | For zero arguments, it returns one. | |
2966 | @end defun | |
2967 | ||
39a58b5b | 2968 | @defun cl-isqrt integer |
4009494e GM |
2969 | This function computes the ``integer square root'' of its integer |
2970 | argument, i.e., the greatest integer less than or equal to the true | |
2971 | square root of the argument. | |
2972 | @end defun | |
2973 | ||
39a58b5b GM |
2974 | @defun cl-floor number &optional divisor |
2975 | With one argument, @code{cl-floor} returns a list of two numbers: | |
4009494e GM |
2976 | The argument rounded down (toward minus infinity) to an integer, |
2977 | and the ``remainder'' which would have to be added back to the | |
2978 | first return value to yield the argument again. If the argument | |
2979 | is an integer @var{x}, the result is always the list @code{(@var{x} 0)}. | |
2980 | If the argument is a floating-point number, the first | |
2981 | result is a Lisp integer and the second is a Lisp float between | |
2982 | 0 (inclusive) and 1 (exclusive). | |
2983 | ||
39a58b5b | 2984 | With two arguments, @code{cl-floor} divides @var{number} by |
4009494e GM |
2985 | @var{divisor}, and returns the floor of the quotient and the |
2986 | corresponding remainder as a list of two numbers. If | |
39a58b5b | 2987 | @code{(cl-floor @var{x} @var{y})} returns @code{(@var{q} @var{r})}, |
4009494e GM |
2988 | then @code{@var{q}*@var{y} + @var{r} = @var{x}}, with @var{r} |
2989 | between 0 (inclusive) and @var{r} (exclusive). Also, note | |
39a58b5b GM |
2990 | that @code{(cl-floor @var{x})} is exactly equivalent to |
2991 | @code{(cl-floor @var{x} 1)}. | |
4009494e GM |
2992 | |
2993 | This function is entirely compatible with Common Lisp's @code{floor} | |
2994 | function, except that it returns the two results in a list since | |
2995 | Emacs Lisp does not support multiple-valued functions. | |
2996 | @end defun | |
2997 | ||
39a58b5b | 2998 | @defun cl-ceiling number &optional divisor |
4009494e GM |
2999 | This function implements the Common Lisp @code{ceiling} function, |
3000 | which is analogous to @code{floor} except that it rounds the | |
3001 | argument or quotient of the arguments up toward plus infinity. | |
3002 | The remainder will be between 0 and minus @var{r}. | |
3003 | @end defun | |
3004 | ||
39a58b5b | 3005 | @defun cl-truncate number &optional divisor |
4009494e GM |
3006 | This function implements the Common Lisp @code{truncate} function, |
3007 | which is analogous to @code{floor} except that it rounds the | |
3008 | argument or quotient of the arguments toward zero. Thus it is | |
39a58b5b GM |
3009 | equivalent to @code{cl-floor} if the argument or quotient is |
3010 | positive, or to @code{cl-ceiling} otherwise. The remainder has | |
4009494e GM |
3011 | the same sign as @var{number}. |
3012 | @end defun | |
3013 | ||
39a58b5b | 3014 | @defun cl-round number &optional divisor |
4009494e GM |
3015 | This function implements the Common Lisp @code{round} function, |
3016 | which is analogous to @code{floor} except that it rounds the | |
3017 | argument or quotient of the arguments to the nearest integer. | |
3018 | In the case of a tie (the argument or quotient is exactly | |
3019 | halfway between two integers), it rounds to the even integer. | |
3020 | @end defun | |
3021 | ||
39a58b5b | 3022 | @defun cl-mod number divisor |
4009494e | 3023 | This function returns the same value as the second return value |
39a58b5b | 3024 | of @code{cl-floor}. |
4009494e GM |
3025 | @end defun |
3026 | ||
39a58b5b | 3027 | @defun cl-rem number divisor |
4009494e | 3028 | This function returns the same value as the second return value |
39a58b5b | 3029 | of @code{cl-truncate}. |
4009494e GM |
3030 | @end defun |
3031 | ||
1d5b82ef | 3032 | @node Random Numbers |
4009494e GM |
3033 | @section Random Numbers |
3034 | ||
3035 | @noindent | |
3036 | This package also provides an implementation of the Common Lisp | |
3037 | random number generator. It uses its own additive-congruential | |
3038 | algorithm, which is much more likely to give statistically clean | |
3039 | random numbers than the simple generators supplied by many | |
3040 | operating systems. | |
3041 | ||
39a58b5b | 3042 | @defun cl-random number &optional state |
4009494e GM |
3043 | This function returns a random nonnegative number less than |
3044 | @var{number}, and of the same type (either integer or floating-point). | |
3045 | The @var{state} argument should be a @code{random-state} object | |
3046 | which holds the state of the random number generator. The | |
3047 | function modifies this state object as a side effect. If | |
3048 | @var{state} is omitted, it defaults to the variable | |
a05cb6e3 | 3049 | @code{cl--random-state}, which contains a pre-initialized |
4009494e GM |
3050 | @code{random-state} object. |
3051 | @end defun | |
3052 | ||
39a58b5b | 3053 | @defvar cl--random-state |
4009494e | 3054 | This variable contains the system ``default'' @code{random-state} |
39a58b5b | 3055 | object, used for calls to @code{cl-random} that do not specify an |
4009494e | 3056 | alternative state object. Since any number of programs in the |
39a58b5b | 3057 | Emacs process may be accessing @code{cl--random-state} in interleaved |
4009494e GM |
3058 | fashion, the sequence generated from this variable will be |
3059 | irreproducible for all intents and purposes. | |
3060 | @end defvar | |
3061 | ||
39a58b5b | 3062 | @defun cl-make-random-state &optional state |
4009494e GM |
3063 | This function creates or copies a @code{random-state} object. |
3064 | If @var{state} is omitted or @code{nil}, it returns a new copy of | |
39a58b5b GM |
3065 | @code{cl--random-state}. This is a copy in the sense that future |
3066 | sequences of calls to @code{(cl-random @var{n})} and | |
3067 | @code{(cl-random @var{n} @var{s})} (where @var{s} is the new | |
4009494e GM |
3068 | random-state object) will return identical sequences of random |
3069 | numbers. | |
3070 | ||
3071 | If @var{state} is a @code{random-state} object, this function | |
3072 | returns a copy of that object. If @var{state} is @code{t}, this | |
3073 | function returns a new @code{random-state} object seeded from the | |
3074 | date and time. As an extension to Common Lisp, @var{state} may also | |
3075 | be an integer in which case the new object is seeded from that | |
3076 | integer; each different integer seed will result in a completely | |
3077 | different sequence of random numbers. | |
3078 | ||
3079 | It is valid to print a @code{random-state} object to a buffer or | |
3080 | file and later read it back with @code{read}. If a program wishes | |
3081 | to use a sequence of pseudo-random numbers which can be reproduced | |
39a58b5b | 3082 | later for debugging, it can call @code{(cl-make-random-state t)} to |
4009494e GM |
3083 | get a new sequence, then print this sequence to a file. When the |
3084 | program is later rerun, it can read the original run's random-state | |
3085 | from the file. | |
3086 | @end defun | |
3087 | ||
39a58b5b | 3088 | @defun cl-random-state-p object |
4009494e GM |
3089 | This predicate returns @code{t} if @var{object} is a |
3090 | @code{random-state} object, or @code{nil} otherwise. | |
3091 | @end defun | |
3092 | ||
1d5b82ef | 3093 | @node Implementation Parameters |
4009494e GM |
3094 | @section Implementation Parameters |
3095 | ||
3096 | @noindent | |
3097 | This package defines several useful constants having to with numbers. | |
3098 | ||
3099 | The following parameters have to do with floating-point numbers. | |
3100 | This package determines their values by exercising the computer's | |
3101 | floating-point arithmetic in various ways. Because this operation | |
3102 | might be slow, the code for initializing them is kept in a separate | |
3103 | function that must be called before the parameters can be used. | |
3104 | ||
3105 | @defun cl-float-limits | |
3106 | This function makes sure that the Common Lisp floating-point parameters | |
39a58b5b | 3107 | like @code{cl-most-positive-float} have been initialized. Until it is |
4009494e GM |
3108 | called, these parameters will be @code{nil}. If this version of Emacs |
3109 | does not support floats, the parameters will remain @code{nil}. If the | |
3110 | parameters have already been initialized, the function returns | |
3111 | immediately. | |
3112 | ||
3113 | The algorithm makes assumptions that will be valid for most modern | |
3114 | machines, but will fail if the machine's arithmetic is extremely | |
3115 | unusual, e.g., decimal. | |
3116 | @end defun | |
3117 | ||
3118 | Since true Common Lisp supports up to four different floating-point | |
3119 | precisions, it has families of constants like | |
3120 | @code{most-positive-single-float}, @code{most-positive-double-float}, | |
3121 | @code{most-positive-long-float}, and so on. Emacs has only one | |
3122 | floating-point precision, so this package omits the precision word | |
3123 | from the constants' names. | |
3124 | ||
39a58b5b | 3125 | @defvar cl-most-positive-float |
4009494e GM |
3126 | This constant equals the largest value a Lisp float can hold. |
3127 | For those systems whose arithmetic supports infinities, this is | |
3128 | the largest @emph{finite} value. For IEEE machines, the value | |
3129 | is approximately @code{1.79e+308}. | |
3130 | @end defvar | |
3131 | ||
39a58b5b | 3132 | @defvar cl-most-negative-float |
4009494e | 3133 | This constant equals the most-negative value a Lisp float can hold. |
39a58b5b | 3134 | (It is assumed to be equal to @code{(- cl-most-positive-float)}.) |
4009494e GM |
3135 | @end defvar |
3136 | ||
39a58b5b | 3137 | @defvar cl-least-positive-float |
4009494e GM |
3138 | This constant equals the smallest Lisp float value greater than zero. |
3139 | For IEEE machines, it is about @code{4.94e-324} if denormals are | |
3140 | supported or @code{2.22e-308} if not. | |
3141 | @end defvar | |
3142 | ||
39a58b5b | 3143 | @defvar cl-least-positive-normalized-float |
4009494e GM |
3144 | This constant equals the smallest @emph{normalized} Lisp float greater |
3145 | than zero, i.e., the smallest value for which IEEE denormalization | |
3146 | will not result in a loss of precision. For IEEE machines, this | |
3147 | value is about @code{2.22e-308}. For machines that do not support | |
3148 | the concept of denormalization and gradual underflow, this constant | |
39a58b5b | 3149 | will always equal @code{cl-least-positive-float}. |
4009494e GM |
3150 | @end defvar |
3151 | ||
39a58b5b GM |
3152 | @defvar cl-least-negative-float |
3153 | This constant is the negative counterpart of @code{cl-least-positive-float}. | |
4009494e GM |
3154 | @end defvar |
3155 | ||
39a58b5b | 3156 | @defvar cl-least-negative-normalized-float |
4009494e | 3157 | This constant is the negative counterpart of |
39a58b5b | 3158 | @code{cl-least-positive-normalized-float}. |
4009494e GM |
3159 | @end defvar |
3160 | ||
39a58b5b | 3161 | @defvar cl-float-epsilon |
4009494e GM |
3162 | This constant is the smallest positive Lisp float that can be added |
3163 | to 1.0 to produce a distinct value. Adding a smaller number to 1.0 | |
3164 | will yield 1.0 again due to roundoff. For IEEE machines, epsilon | |
3165 | is about @code{2.22e-16}. | |
3166 | @end defvar | |
3167 | ||
39a58b5b | 3168 | @defvar cl-float-negative-epsilon |
4009494e GM |
3169 | This is the smallest positive value that can be subtracted from |
3170 | 1.0 to produce a distinct value. For IEEE machines, it is about | |
3171 | @code{1.11e-16}. | |
3172 | @end defvar | |
3173 | ||
1d5b82ef | 3174 | @node Sequences |
4009494e GM |
3175 | @chapter Sequences |
3176 | ||
3177 | @noindent | |
3178 | Common Lisp defines a number of functions that operate on | |
3179 | @dfn{sequences}, which are either lists, strings, or vectors. | |
3180 | Emacs Lisp includes a few of these, notably @code{elt} and | |
3181 | @code{length}; this package defines most of the rest. | |
3182 | ||
3183 | @menu | |
8d6510b9 | 3184 | * Sequence Basics:: Arguments shared by all sequence functions. |
39a58b5b GM |
3185 | * Mapping over Sequences:: @code{cl-mapcar}, @code{cl-mapcan}, @code{cl-map}, @code{cl-every}, etc. |
3186 | * Sequence Functions:: @code{cl-subseq}, @code{cl-remove}, @code{cl-substitute}, etc. | |
3187 | * Searching Sequences:: @code{cl-find}, @code{cl-position}, @code{cl-count}, @code{cl-search}, etc. | |
3188 | * Sorting Sequences:: @code{cl-sort}, @code{cl-stable-sort}, @code{cl-merge}. | |
4009494e GM |
3189 | @end menu |
3190 | ||
1d5b82ef | 3191 | @node Sequence Basics |
4009494e GM |
3192 | @section Sequence Basics |
3193 | ||
3194 | @noindent | |
3195 | Many of the sequence functions take keyword arguments; @pxref{Argument | |
3196 | Lists}. All keyword arguments are optional and, if specified, | |
3197 | may appear in any order. | |
3198 | ||
3199 | The @code{:key} argument should be passed either @code{nil}, or a | |
3200 | function of one argument. This key function is used as a filter | |
3201 | through which the elements of the sequence are seen; for example, | |
39a58b5b | 3202 | @code{(cl-find x y :key 'car)} is similar to @code{(cl-assoc x y)}: |
4009494e GM |
3203 | It searches for an element of the list whose @code{car} equals |
3204 | @code{x}, rather than for an element which equals @code{x} itself. | |
3205 | If @code{:key} is omitted or @code{nil}, the filter is effectively | |
3206 | the identity function. | |
3207 | ||
3208 | The @code{:test} and @code{:test-not} arguments should be either | |
3209 | @code{nil}, or functions of two arguments. The test function is | |
3210 | used to compare two sequence elements, or to compare a search value | |
3211 | with sequence elements. (The two values are passed to the test | |
3212 | function in the same order as the original sequence function | |
3213 | arguments from which they are derived, or, if they both come from | |
3214 | the same sequence, in the same order as they appear in that sequence.) | |
3215 | The @code{:test} argument specifies a function which must return | |
3216 | true (non-@code{nil}) to indicate a match; instead, you may use | |
3217 | @code{:test-not} to give a function which returns @emph{false} to | |
0a3333b5 | 3218 | indicate a match. The default test function is @code{eql}. |
4009494e GM |
3219 | |
3220 | Many functions which take @var{item} and @code{:test} or @code{:test-not} | |
3221 | arguments also come in @code{-if} and @code{-if-not} varieties, | |
3222 | where a @var{predicate} function is passed instead of @var{item}, | |
3223 | and sequence elements match if the predicate returns true on them | |
3224 | (or false in the case of @code{-if-not}). For example: | |
3225 | ||
3226 | @example | |
39a58b5b | 3227 | (cl-remove 0 seq :test '=) @equiv{} (cl-remove-if 'zerop seq) |
4009494e GM |
3228 | @end example |
3229 | ||
3230 | @noindent | |
3231 | to remove all zeros from sequence @code{seq}. | |
3232 | ||
3233 | Some operations can work on a subsequence of the argument sequence; | |
3234 | these function take @code{:start} and @code{:end} arguments which | |
3235 | default to zero and the length of the sequence, respectively. | |
3236 | Only elements between @var{start} (inclusive) and @var{end} | |
3237 | (exclusive) are affected by the operation. The @var{end} argument | |
3238 | may be passed @code{nil} to signify the length of the sequence; | |
3239 | otherwise, both @var{start} and @var{end} must be integers, with | |
3240 | @code{0 <= @var{start} <= @var{end} <= (length @var{seq})}. | |
3241 | If the function takes two sequence arguments, the limits are | |
3242 | defined by keywords @code{:start1} and @code{:end1} for the first, | |
3243 | and @code{:start2} and @code{:end2} for the second. | |
3244 | ||
3245 | A few functions accept a @code{:from-end} argument, which, if | |
3246 | non-@code{nil}, causes the operation to go from right-to-left | |
3247 | through the sequence instead of left-to-right, and a @code{:count} | |
3248 | argument, which specifies an integer maximum number of elements | |
3249 | to be removed or otherwise processed. | |
3250 | ||
3251 | The sequence functions make no guarantees about the order in | |
3252 | which the @code{:test}, @code{:test-not}, and @code{:key} functions | |
3253 | are called on various elements. Therefore, it is a bad idea to depend | |
3254 | on side effects of these functions. For example, @code{:from-end} | |
3255 | may cause the sequence to be scanned actually in reverse, or it may | |
3256 | be scanned forwards but computing a result ``as if'' it were scanned | |
39a58b5b | 3257 | backwards. (Some functions, like @code{cl-mapcar} and @code{cl-every}, |
4009494e GM |
3258 | @emph{do} specify exactly the order in which the function is called |
3259 | so side effects are perfectly acceptable in those cases.) | |
3260 | ||
3261 | Strings may contain ``text properties'' as well | |
3262 | as character data. Except as noted, it is undefined whether or | |
3263 | not text properties are preserved by sequence functions. For | |
39a58b5b | 3264 | example, @code{(cl-remove ?A @var{str})} may or may not preserve |
4009494e GM |
3265 | the properties of the characters copied from @var{str} into the |
3266 | result. | |
3267 | ||
1d5b82ef | 3268 | @node Mapping over Sequences |
4009494e GM |
3269 | @section Mapping over Sequences |
3270 | ||
3271 | @noindent | |
3272 | These functions ``map'' the function you specify over the elements | |
3273 | of lists or arrays. They are all variations on the theme of the | |
3274 | built-in function @code{mapcar}. | |
3275 | ||
39a58b5b | 3276 | @defun cl-mapcar function seq &rest more-seqs |
4009494e GM |
3277 | This function calls @var{function} on successive parallel sets of |
3278 | elements from its argument sequences. Given a single @var{seq} | |
3279 | argument it is equivalent to @code{mapcar}; given @var{n} sequences, | |
3280 | it calls the function with the first elements of each of the sequences | |
3281 | as the @var{n} arguments to yield the first element of the result | |
3282 | list, then with the second elements, and so on. The mapping stops as | |
3283 | soon as the shortest sequence runs out. The argument sequences may | |
3284 | be any mixture of lists, strings, and vectors; the return sequence | |
3285 | is always a list. | |
3286 | ||
3287 | Common Lisp's @code{mapcar} accepts multiple arguments but works | |
3288 | only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence | |
39a58b5b | 3289 | argument. This package's @code{cl-mapcar} works as a compatible |
4009494e GM |
3290 | superset of both. |
3291 | @end defun | |
3292 | ||
39a58b5b | 3293 | @defun cl-map result-type function seq &rest more-seqs |
4009494e | 3294 | This function maps @var{function} over the argument sequences, |
39a58b5b | 3295 | just like @code{cl-mapcar}, but it returns a sequence of type |
4009494e GM |
3296 | @var{result-type} rather than a list. @var{result-type} must |
3297 | be one of the following symbols: @code{vector}, @code{string}, | |
3298 | @code{list} (in which case the effect is the same as for | |
a05cb6e3 | 3299 | @code{cl-mapcar}), or @code{nil} (in which case the results are |
39a58b5b | 3300 | thrown away and @code{cl-map} returns @code{nil}). |
4009494e GM |
3301 | @end defun |
3302 | ||
39a58b5b | 3303 | @defun cl-maplist function list &rest more-lists |
4009494e GM |
3304 | This function calls @var{function} on each of its argument lists, |
3305 | then on the @code{cdr}s of those lists, and so on, until the | |
3306 | shortest list runs out. The results are returned in the form | |
39a58b5b | 3307 | of a list. Thus, @code{cl-maplist} is like @code{cl-mapcar} except |
4009494e GM |
3308 | that it passes in the list pointers themselves rather than the |
3309 | @code{car}s of the advancing pointers. | |
3310 | @end defun | |
3311 | ||
39a58b5b | 3312 | @c FIXME does not exist? |
b695beda | 3313 | @defun cl-mapc function seq &rest more-seqs |
39a58b5b | 3314 | This function is like @code{cl-mapcar}, except that the values returned |
4009494e | 3315 | by @var{function} are ignored and thrown away rather than being |
b695beda | 3316 | collected into a list. The return value of @code{cl-mapc} is @var{seq}, |
4009494e GM |
3317 | the first sequence. This function is more general than the Emacs |
3318 | primitive @code{mapc}. | |
3319 | @end defun | |
3320 | ||
39a58b5b GM |
3321 | @defun cl-mapl function list &rest more-lists |
3322 | This function is like @code{cl-maplist}, except that it throws away | |
4009494e GM |
3323 | the values returned by @var{function}. |
3324 | @end defun | |
3325 | ||
39a58b5b GM |
3326 | @defun cl-mapcan function seq &rest more-seqs |
3327 | This function is like @code{cl-mapcar}, except that it concatenates | |
4009494e GM |
3328 | the return values (which must be lists) using @code{nconc}, |
3329 | rather than simply collecting them into a list. | |
3330 | @end defun | |
3331 | ||
39a58b5b GM |
3332 | @defun cl-mapcon function list &rest more-lists |
3333 | This function is like @code{cl-maplist}, except that it concatenates | |
4009494e GM |
3334 | the return values using @code{nconc}. |
3335 | @end defun | |
3336 | ||
39a58b5b | 3337 | @defun cl-some predicate seq &rest more-seqs |
4009494e GM |
3338 | This function calls @var{predicate} on each element of @var{seq} |
3339 | in turn; if @var{predicate} returns a non-@code{nil} value, | |
3340 | @code{some} returns that value, otherwise it returns @code{nil}. | |
3341 | Given several sequence arguments, it steps through the sequences | |
3342 | in parallel until the shortest one runs out, just as in | |
39a58b5b | 3343 | @code{cl-mapcar}. You can rely on the left-to-right order in which |
4009494e GM |
3344 | the elements are visited, and on the fact that mapping stops |
3345 | immediately as soon as @var{predicate} returns non-@code{nil}. | |
3346 | @end defun | |
3347 | ||
39a58b5b | 3348 | @defun cl-every predicate seq &rest more-seqs |
4009494e GM |
3349 | This function calls @var{predicate} on each element of the sequence(s) |
3350 | in turn; it returns @code{nil} as soon as @var{predicate} returns | |
3351 | @code{nil} for any element, or @code{t} if the predicate was true | |
3352 | for all elements. | |
3353 | @end defun | |
3354 | ||
39a58b5b | 3355 | @defun cl-notany predicate seq &rest more-seqs |
4009494e GM |
3356 | This function calls @var{predicate} on each element of the sequence(s) |
3357 | in turn; it returns @code{nil} as soon as @var{predicate} returns | |
3358 | a non-@code{nil} value for any element, or @code{t} if the predicate | |
3359 | was @code{nil} for all elements. | |
3360 | @end defun | |
3361 | ||
39a58b5b | 3362 | @defun cl-notevery predicate seq &rest more-seqs |
4009494e GM |
3363 | This function calls @var{predicate} on each element of the sequence(s) |
3364 | in turn; it returns a non-@code{nil} value as soon as @var{predicate} | |
3365 | returns @code{nil} for any element, or @code{t} if the predicate was | |
3366 | true for all elements. | |
3367 | @end defun | |
3368 | ||
39a58b5b | 3369 | @defun cl-reduce function seq @t{&key :from-end :start :end :initial-value :key} |
4009494e GM |
3370 | This function combines the elements of @var{seq} using an associative |
3371 | binary operation. Suppose @var{function} is @code{*} and @var{seq} is | |
3372 | the list @code{(2 3 4 5)}. The first two elements of the list are | |
3373 | combined with @code{(* 2 3) = 6}; this is combined with the next | |
3374 | element, @code{(* 6 4) = 24}, and that is combined with the final | |
3375 | element: @code{(* 24 5) = 120}. Note that the @code{*} function happens | |
3376 | to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as | |
39a58b5b | 3377 | an explicit call to @code{cl-reduce}. |
4009494e GM |
3378 | |
3379 | If @code{:from-end} is true, the reduction is right-associative instead | |
3380 | of left-associative: | |
3381 | ||
3382 | @example | |
39a58b5b GM |
3383 | (cl-reduce '- '(1 2 3 4)) |
3384 | @equiv{} (- (- (- 1 2) 3) 4) @result{} -8 | |
3385 | (cl-reduce '- '(1 2 3 4) :from-end t) | |
3386 | @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2 | |
4009494e GM |
3387 | @end example |
3388 | ||
3389 | If @code{:key} is specified, it is a function of one argument which | |
3390 | is called on each of the sequence elements in turn. | |
3391 | ||
3392 | If @code{:initial-value} is specified, it is effectively added to the | |
3393 | front (or rear in the case of @code{:from-end}) of the sequence. | |
3394 | The @code{:key} function is @emph{not} applied to the initial value. | |
3395 | ||
3396 | If the sequence, including the initial value, has exactly one element | |
3397 | then that element is returned without ever calling @var{function}. | |
3398 | If the sequence is empty (and there is no initial value), then | |
3399 | @var{function} is called with no arguments to obtain the return value. | |
3400 | @end defun | |
3401 | ||
3402 | All of these mapping operations can be expressed conveniently in | |
39a58b5b | 3403 | terms of the @code{cl-loop} macro. In compiled code, @code{cl-loop} will |
4009494e GM |
3404 | be faster since it generates the loop as in-line code with no |
3405 | function calls. | |
3406 | ||
1d5b82ef | 3407 | @node Sequence Functions |
4009494e GM |
3408 | @section Sequence Functions |
3409 | ||
3410 | @noindent | |
3411 | This section describes a number of Common Lisp functions for | |
3412 | operating on sequences. | |
3413 | ||
39a58b5b | 3414 | @defun cl-subseq sequence start &optional end |
4009494e GM |
3415 | This function returns a given subsequence of the argument |
3416 | @var{sequence}, which may be a list, string, or vector. | |
3417 | The indices @var{start} and @var{end} must be in range, and | |
3418 | @var{start} must be no greater than @var{end}. If @var{end} | |
3419 | is omitted, it defaults to the length of the sequence. The | |
3420 | return value is always a copy; it does not share structure | |
3421 | with @var{sequence}. | |
3422 | ||
3423 | As an extension to Common Lisp, @var{start} and/or @var{end} | |
3424 | may be negative, in which case they represent a distance back | |
3425 | from the end of the sequence. This is for compatibility with | |
39a58b5b | 3426 | Emacs's @code{substring} function. Note that @code{cl-subseq} is |
4009494e GM |
3427 | the @emph{only} sequence function that allows negative |
3428 | @var{start} and @var{end}. | |
3429 | ||
39a58b5b | 3430 | You can use @code{setf} on a @code{cl-subseq} form to replace a |
4009494e | 3431 | specified range of elements with elements from another sequence. |
39a58b5b | 3432 | The replacement is done as if by @code{cl-replace}, described below. |
4009494e GM |
3433 | @end defun |
3434 | ||
39a58b5b | 3435 | @defun cl-concatenate result-type &rest seqs |
4009494e GM |
3436 | This function concatenates the argument sequences together to |
3437 | form a result sequence of type @var{result-type}, one of the | |
3438 | symbols @code{vector}, @code{string}, or @code{list}. The | |
3439 | arguments are always copied, even in cases such as | |
39a58b5b | 3440 | @code{(cl-concatenate 'list '(1 2 3))} where the result is |
4009494e GM |
3441 | identical to an argument. |
3442 | @end defun | |
3443 | ||
39a58b5b | 3444 | @defun cl-fill seq item @t{&key :start :end} |
4009494e GM |
3445 | This function fills the elements of the sequence (or the specified |
3446 | part of the sequence) with the value @var{item}. | |
3447 | @end defun | |
3448 | ||
39a58b5b | 3449 | @defun cl-replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2} |
4009494e GM |
3450 | This function copies part of @var{seq2} into part of @var{seq1}. |
3451 | The sequence @var{seq1} is not stretched or resized; the amount | |
3452 | of data copied is simply the shorter of the source and destination | |
3453 | (sub)sequences. The function returns @var{seq1}. | |
3454 | ||
3455 | If @var{seq1} and @var{seq2} are @code{eq}, then the replacement | |
3456 | will work correctly even if the regions indicated by the start | |
3457 | and end arguments overlap. However, if @var{seq1} and @var{seq2} | |
3458 | are lists which share storage but are not @code{eq}, and the | |
3459 | start and end arguments specify overlapping regions, the effect | |
3460 | is undefined. | |
3461 | @end defun | |
3462 | ||
39a58b5b | 3463 | @defun cl-remove item seq @t{&key :test :test-not :key :count :start :end :from-end} |
4009494e GM |
3464 | This returns a copy of @var{seq} with all elements matching |
3465 | @var{item} removed. The result may share storage with or be | |
3466 | @code{eq} to @var{seq} in some circumstances, but the original | |
3467 | @var{seq} will not be modified. The @code{:test}, @code{:test-not}, | |
3468 | and @code{:key} arguments define the matching test that is used; | |
3469 | by default, elements @code{eql} to @var{item} are removed. The | |
3470 | @code{:count} argument specifies the maximum number of matching | |
3471 | elements that can be removed (only the leftmost @var{count} matches | |
3472 | are removed). The @code{:start} and @code{:end} arguments specify | |
3473 | a region in @var{seq} in which elements will be removed; elements | |
3474 | outside that region are not matched or removed. The @code{:from-end} | |
3475 | argument, if true, says that elements should be deleted from the | |
3476 | end of the sequence rather than the beginning (this matters only | |
3477 | if @var{count} was also specified). | |
3478 | @end defun | |
3479 | ||
39a58b5b | 3480 | @defun cl-delete item seq @t{&key :test :test-not :key :count :start :end :from-end} |
4009494e GM |
3481 | This deletes all elements of @var{seq} which match @var{item}. |
3482 | It is a destructive operation. Since Emacs Lisp does not support | |
39a58b5b GM |
3483 | stretchable strings or vectors, this is the same as @code{cl-remove} |
3484 | for those sequence types. On lists, @code{cl-remove} will copy the | |
4009494e | 3485 | list if necessary to preserve the original list, whereas |
39a58b5b | 3486 | @code{cl-delete} will splice out parts of the argument list. |
4009494e GM |
3487 | Compare @code{append} and @code{nconc}, which are analogous |
3488 | non-destructive and destructive list operations in Emacs Lisp. | |
3489 | @end defun | |
3490 | ||
39a58b5b GM |
3491 | @findex cl-remove-if |
3492 | @findex cl-remove-if-not | |
3493 | @findex cl-delete-if | |
3494 | @findex cl-delete-if-not | |
3495 | The predicate-oriented functions @code{cl-remove-if}, @code{cl-remove-if-not}, | |
3496 | @code{cl-delete-if}, and @code{cl-delete-if-not} are defined similarly. | |
4009494e | 3497 | |
39a58b5b | 3498 | @defun cl-remove-duplicates seq @t{&key :test :test-not :key :start :end :from-end} |
4009494e GM |
3499 | This function returns a copy of @var{seq} with duplicate elements |
3500 | removed. Specifically, if two elements from the sequence match | |
3501 | according to the @code{:test}, @code{:test-not}, and @code{:key} | |
3502 | arguments, only the rightmost one is retained. If @code{:from-end} | |
3503 | is true, the leftmost one is retained instead. If @code{:start} or | |
3504 | @code{:end} is specified, only elements within that subsequence are | |
3505 | examined or removed. | |
3506 | @end defun | |
3507 | ||
39a58b5b | 3508 | @defun cl-delete-duplicates seq @t{&key :test :test-not :key :start :end :from-end} |
4009494e | 3509 | This function deletes duplicate elements from @var{seq}. It is |
39a58b5b | 3510 | a destructive version of @code{cl-remove-duplicates}. |
4009494e GM |
3511 | @end defun |
3512 | ||
39a58b5b | 3513 | @defun cl-substitute new old seq @t{&key :test :test-not :key :count :start :end :from-end} |
4009494e GM |
3514 | This function returns a copy of @var{seq}, with all elements |
3515 | matching @var{old} replaced with @var{new}. The @code{:count}, | |
3516 | @code{:start}, @code{:end}, and @code{:from-end} arguments may be | |
3517 | used to limit the number of substitutions made. | |
3518 | @end defun | |
3519 | ||
39a58b5b GM |
3520 | @defun cl-nsubstitute new old seq @t{&key :test :test-not :key :count :start :end :from-end} |
3521 | This is a destructive version of @code{cl-substitute}; it performs | |
4009494e GM |
3522 | the substitution using @code{setcar} or @code{aset} rather than |
3523 | by returning a changed copy of the sequence. | |
3524 | @end defun | |
3525 | ||
39a58b5b GM |
3526 | @findex cl-substitute-if |
3527 | @findex cl-substitute-if-not | |
3528 | @findex cl-nsubstitute-if | |
3529 | @findex cl-nsubstitute-if-not | |
a05cb6e3 GM |
3530 | The functions @code{cl-substitute-if}, @code{cl-substitute-if-not}, |
3531 | @code{cl-nsubstitute-if}, and @code{cl-nsubstitute-if-not} are defined | |
3532 | similarly. For these, a @var{predicate} is given in place of the | |
3533 | @var{old} argument. | |
4009494e | 3534 | |
1d5b82ef | 3535 | @node Searching Sequences |
4009494e GM |
3536 | @section Searching Sequences |
3537 | ||
3538 | @noindent | |
3539 | These functions search for elements or subsequences in a sequence. | |
39a58b5b | 3540 | (See also @code{cl-member} and @code{cl-assoc}; @pxref{Lists}.) |
4009494e | 3541 | |
39a58b5b | 3542 | @defun cl-find item seq @t{&key :test :test-not :key :start :end :from-end} |
4009494e GM |
3543 | This function searches @var{seq} for an element matching @var{item}. |
3544 | If it finds a match, it returns the matching element. Otherwise, | |
3545 | it returns @code{nil}. It returns the leftmost match, unless | |
3546 | @code{:from-end} is true, in which case it returns the rightmost | |
3547 | match. The @code{:start} and @code{:end} arguments may be used to | |
3548 | limit the range of elements that are searched. | |
3549 | @end defun | |
3550 | ||
39a58b5b GM |
3551 | @defun cl-position item seq @t{&key :test :test-not :key :start :end :from-end} |
3552 | This function is like @code{cl-find}, except that it returns the | |
4009494e GM |
3553 | integer position in the sequence of the matching item rather than |
3554 | the item itself. The position is relative to the start of the | |
3555 | sequence as a whole, even if @code{:start} is non-zero. The function | |
3556 | returns @code{nil} if no matching element was found. | |
3557 | @end defun | |
3558 | ||
39a58b5b | 3559 | @defun cl-count item seq @t{&key :test :test-not :key :start :end} |
4009494e GM |
3560 | This function returns the number of elements of @var{seq} which |
3561 | match @var{item}. The result is always a nonnegative integer. | |
3562 | @end defun | |
3563 | ||
39a58b5b GM |
3564 | @findex cl-find-if |
3565 | @findex cl-find-if-not | |
3566 | @findex cl-position-if | |
3567 | @findex cl-position-if-not | |
3568 | @findex cl-count-if | |
3569 | @findex cl-count-if-not | |
3570 | The @code{cl-find-if}, @code{cl-find-if-not}, @code{cl-position-if}, | |
3571 | @code{cl-position-if-not}, @code{cl-count-if}, and @code{cl-count-if-not} | |
4009494e GM |
3572 | functions are defined similarly. |
3573 | ||
39a58b5b | 3574 | @defun cl-mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1 :start2 :end2 :from-end} |
4009494e GM |
3575 | This function compares the specified parts of @var{seq1} and |
3576 | @var{seq2}. If they are the same length and the corresponding | |
3577 | elements match (according to @code{:test}, @code{:test-not}, | |
3578 | and @code{:key}), the function returns @code{nil}. If there is | |
3579 | a mismatch, the function returns the index (relative to @var{seq1}) | |
3580 | of the first mismatching element. This will be the leftmost pair of | |
3581 | elements which do not match, or the position at which the shorter of | |
3582 | the two otherwise-matching sequences runs out. | |
3583 | ||
3584 | If @code{:from-end} is true, then the elements are compared from right | |
3585 | to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}. | |
3586 | If the sequences differ, then one plus the index of the rightmost | |
3587 | difference (relative to @var{seq1}) is returned. | |
3588 | ||
39a58b5b | 3589 | An interesting example is @code{(cl-mismatch str1 str2 :key 'upcase)}, |
4009494e GM |
3590 | which compares two strings case-insensitively. |
3591 | @end defun | |
3592 | ||
39a58b5b | 3593 | @defun cl-search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2} |
4009494e GM |
3594 | This function searches @var{seq2} for a subsequence that matches |
3595 | @var{seq1} (or part of it specified by @code{:start1} and | |
3596 | @code{:end1}.) Only matches which fall entirely within the region | |
3597 | defined by @code{:start2} and @code{:end2} will be considered. | |
3598 | The return value is the index of the leftmost element of the | |
3599 | leftmost match, relative to the start of @var{seq2}, or @code{nil} | |
3600 | if no matches were found. If @code{:from-end} is true, the | |
3601 | function finds the @emph{rightmost} matching subsequence. | |
3602 | @end defun | |
3603 | ||
1d5b82ef | 3604 | @node Sorting Sequences |
4009494e GM |
3605 | @section Sorting Sequences |
3606 | ||
39a58b5b | 3607 | @defun clsort seq predicate @t{&key :key} |
4009494e GM |
3608 | This function sorts @var{seq} into increasing order as determined |
3609 | by using @var{predicate} to compare pairs of elements. @var{predicate} | |
3610 | should return true (non-@code{nil}) if and only if its first argument | |
3611 | is less than (not equal to) its second argument. For example, | |
3612 | @code{<} and @code{string-lessp} are suitable predicate functions | |
3613 | for sorting numbers and strings, respectively; @code{>} would sort | |
3614 | numbers into decreasing rather than increasing order. | |
3615 | ||
44e97401 | 3616 | This function differs from Emacs's built-in @code{sort} in that it |
4009494e GM |
3617 | can operate on any type of sequence, not just lists. Also, it |
3618 | accepts a @code{:key} argument which is used to preprocess data | |
3619 | fed to the @var{predicate} function. For example, | |
3620 | ||
3621 | @example | |
39a58b5b | 3622 | (setq data (cl-sort data 'string-lessp :key 'downcase)) |
4009494e GM |
3623 | @end example |
3624 | ||
3625 | @noindent | |
3626 | sorts @var{data}, a sequence of strings, into increasing alphabetical | |
3627 | order without regard to case. A @code{:key} function of @code{car} | |
3628 | would be useful for sorting association lists. It should only be a | |
3629 | simple accessor though, it's used heavily in the current | |
3630 | implementation. | |
3631 | ||
39a58b5b | 3632 | The @code{cl-sort} function is destructive; it sorts lists by actually |
4009494e GM |
3633 | rearranging the @code{cdr} pointers in suitable fashion. |
3634 | @end defun | |
3635 | ||
39a58b5b | 3636 | @defun cl-stable-sort seq predicate @t{&key :key} |
4009494e GM |
3637 | This function sorts @var{seq} @dfn{stably}, meaning two elements |
3638 | which are equal in terms of @var{predicate} are guaranteed not to | |
3639 | be rearranged out of their original order by the sort. | |
3640 | ||
39a58b5b | 3641 | In practice, @code{cl-sort} and @code{cl-stable-sort} are equivalent |
4009494e GM |
3642 | in Emacs Lisp because the underlying @code{sort} function is |
3643 | stable by default. However, this package reserves the right to | |
39a58b5b | 3644 | use non-stable methods for @code{cl-sort} in the future. |
4009494e GM |
3645 | @end defun |
3646 | ||
39a58b5b | 3647 | @defun cl-merge type seq1 seq2 predicate @t{&key :key} |
4009494e GM |
3648 | This function merges two sequences @var{seq1} and @var{seq2} by |
3649 | interleaving their elements. The result sequence, of type @var{type} | |
39a58b5b | 3650 | (in the sense of @code{cl-concatenate}), has length equal to the sum |
4009494e GM |
3651 | of the lengths of the two input sequences. The sequences may be |
3652 | modified destructively. Order of elements within @var{seq1} and | |
3653 | @var{seq2} is preserved in the interleaving; elements of the two | |
3654 | sequences are compared by @var{predicate} (in the sense of | |
3655 | @code{sort}) and the lesser element goes first in the result. | |
3656 | When elements are equal, those from @var{seq1} precede those from | |
3657 | @var{seq2} in the result. Thus, if @var{seq1} and @var{seq2} are | |
3658 | both sorted according to @var{predicate}, then the result will be | |
3659 | a merged sequence which is (stably) sorted according to | |
3660 | @var{predicate}. | |
3661 | @end defun | |
3662 | ||
1d5b82ef | 3663 | @node Lists |
4009494e GM |
3664 | @chapter Lists |
3665 | ||
3666 | @noindent | |
3667 | The functions described here operate on lists. | |
3668 | ||
3669 | @menu | |
39a58b5b GM |
3670 | * List Functions:: @code{cl-caddr}, @code{cl-first}, @code{cl-list*}, etc. |
3671 | * Substitution of Expressions:: @code{cl-subst}, @code{cl-sublis}, etc. | |
3672 | * Lists as Sets:: @code{cl-member}, @code{cl-adjoin}, @code{cl-union}, etc. | |
3673 | * Association Lists:: @code{cl-assoc}, @code{cl-rassoc}, @code{cl-acons}, @code{cl-pairlis}. | |
4009494e GM |
3674 | @end menu |
3675 | ||
1d5b82ef | 3676 | @node List Functions |
4009494e GM |
3677 | @section List Functions |
3678 | ||
3679 | @noindent | |
3680 | This section describes a number of simple operations on lists, | |
3681 | i.e., chains of cons cells. | |
3682 | ||
39a58b5b | 3683 | @defun cl-caddr x |
4009494e GM |
3684 | This function is equivalent to @code{(car (cdr (cdr @var{x})))}. |
3685 | Likewise, this package defines all 28 @code{c@var{xxx}r} functions | |
3686 | where @var{xxx} is up to four @samp{a}s and/or @samp{d}s. | |
3687 | All of these functions are @code{setf}-able, and calls to them | |
3688 | are expanded inline by the byte-compiler for maximum efficiency. | |
3689 | @end defun | |
3690 | ||
39a58b5b | 3691 | @defun cl-first x |
4009494e | 3692 | This function is a synonym for @code{(car @var{x})}. Likewise, |
39a58b5b GM |
3693 | the functions @code{cl-second}, @code{cl-third}, @dots{}, through |
3694 | @code{cl-tenth} return the given element of the list @var{x}. | |
4009494e GM |
3695 | @end defun |
3696 | ||
39a58b5b | 3697 | @defun cl-rest x |
4009494e GM |
3698 | This function is a synonym for @code{(cdr @var{x})}. |
3699 | @end defun | |
3700 | ||
39a58b5b | 3701 | @defun cl-endp x |
4009494e GM |
3702 | Common Lisp defines this function to act like @code{null}, but |
3703 | signaling an error if @code{x} is neither a @code{nil} nor a | |
39a58b5b | 3704 | cons cell. This package simply defines @code{cl-endp} as a synonym |
4009494e GM |
3705 | for @code{null}. |
3706 | @end defun | |
3707 | ||
39a58b5b | 3708 | @defun cl-list-length x |
4009494e GM |
3709 | This function returns the length of list @var{x}, exactly like |
3710 | @code{(length @var{x})}, except that if @var{x} is a circular | |
3711 | list (where the cdr-chain forms a loop rather than terminating | |
3712 | with @code{nil}), this function returns @code{nil}. (The regular | |
3713 | @code{length} function would get stuck if given a circular list.) | |
3714 | @end defun | |
3715 | ||
39a58b5b | 3716 | @defun cl-list* arg &rest others |
4009494e GM |
3717 | This function constructs a list of its arguments. The final |
3718 | argument becomes the @code{cdr} of the last cell constructed. | |
39a58b5b | 3719 | Thus, @code{(cl-list* @var{a} @var{b} @var{c})} is equivalent to |
4009494e | 3720 | @code{(cons @var{a} (cons @var{b} @var{c}))}, and |
39a58b5b | 3721 | @code{(cl-list* @var{a} @var{b} nil)} is equivalent to |
4009494e | 3722 | @code{(list @var{a} @var{b})}. |
4009494e GM |
3723 | @end defun |
3724 | ||
39a58b5b | 3725 | @defun cl-ldiff list sublist |
4009494e GM |
3726 | If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to |
3727 | one of the cons cells of @var{list}, then this function returns | |
3728 | a copy of the part of @var{list} up to but not including | |
39a58b5b | 3729 | @var{sublist}. For example, @code{(cl-ldiff x (cddr x))} returns |
4009494e GM |
3730 | the first two elements of the list @code{x}. The result is a |
3731 | copy; the original @var{list} is not modified. If @var{sublist} | |
3732 | is not a sublist of @var{list}, a copy of the entire @var{list} | |
3733 | is returned. | |
3734 | @end defun | |
3735 | ||
39a58b5b | 3736 | @defun cl-copy-list list |
4009494e GM |
3737 | This function returns a copy of the list @var{list}. It copies |
3738 | dotted lists like @code{(1 2 . 3)} correctly. | |
3739 | @end defun | |
3740 | ||
3741 | @defun copy-tree x &optional vecp | |
3742 | This function returns a copy of the tree of cons cells @var{x}. | |
39a58b5b GM |
3743 | @c FIXME? cl-copy-list is not an alias of copy-sequence. |
3744 | Unlike @code{copy-sequence} (and its alias @code{cl-copy-list}), | |
4009494e GM |
3745 | which copies only along the @code{cdr} direction, this function |
3746 | copies (recursively) along both the @code{car} and the @code{cdr} | |
3747 | directions. If @var{x} is not a cons cell, the function simply | |
3748 | returns @var{x} unchanged. If the optional @var{vecp} argument | |
3749 | is true, this function copies vectors (recursively) as well as | |
3750 | cons cells. | |
3751 | @end defun | |
3752 | ||
39a58b5b | 3753 | @defun cl-tree-equal x y @t{&key :test :test-not :key} |
4009494e GM |
3754 | This function compares two trees of cons cells. If @var{x} and |
3755 | @var{y} are both cons cells, their @code{car}s and @code{cdr}s are | |
3756 | compared recursively. If neither @var{x} nor @var{y} is a cons | |
3757 | cell, they are compared by @code{eql}, or according to the | |
3758 | specified test. The @code{:key} function, if specified, is | |
3759 | applied to the elements of both trees. @xref{Sequences}. | |
3760 | @end defun | |
3761 | ||
1d5b82ef | 3762 | @node Substitution of Expressions |
4009494e GM |
3763 | @section Substitution of Expressions |
3764 | ||
3765 | @noindent | |
3766 | These functions substitute elements throughout a tree of cons | |
39a58b5b | 3767 | cells. (@xref{Sequence Functions}, for the @code{cl-substitute} |
4009494e GM |
3768 | function, which works on just the top-level elements of a list.) |
3769 | ||
39a58b5b | 3770 | @defun cl-subst new old tree @t{&key :test :test-not :key} |
4009494e GM |
3771 | This function substitutes occurrences of @var{old} with @var{new} |
3772 | in @var{tree}, a tree of cons cells. It returns a substituted | |
3773 | tree, which will be a copy except that it may share storage with | |
3774 | the argument @var{tree} in parts where no substitutions occurred. | |
3775 | The original @var{tree} is not modified. This function recurses | |
3776 | on, and compares against @var{old}, both @code{car}s and @code{cdr}s | |
3777 | of the component cons cells. If @var{old} is itself a cons cell, | |
3778 | then matching cells in the tree are substituted as usual without | |
3779 | recursively substituting in that cell. Comparisons with @var{old} | |
3780 | are done according to the specified test (@code{eql} by default). | |
3781 | The @code{:key} function is applied to the elements of the tree | |
3782 | but not to @var{old}. | |
3783 | @end defun | |
3784 | ||
39a58b5b GM |
3785 | @defun cl-nsubst new old tree @t{&key :test :test-not :key} |
3786 | This function is like @code{cl-subst}, except that it works by | |
4009494e GM |
3787 | destructive modification (by @code{setcar} or @code{setcdr}) |
3788 | rather than copying. | |
3789 | @end defun | |
3790 | ||
39a58b5b GM |
3791 | @findex cl-subst-if |
3792 | @findex cl-subst-if-not | |
3793 | @findex cl-nsubst-if | |
3794 | @findex cl-nsubst-if-not | |
3795 | The @code{cl-subst-if}, @code{cl-subst-if-not}, @code{cl-nsubst-if}, and | |
3796 | @code{cl-nsubst-if-not} functions are defined similarly. | |
4009494e | 3797 | |
39a58b5b GM |
3798 | @defun cl-sublis alist tree @t{&key :test :test-not :key} |
3799 | This function is like @code{cl-subst}, except that it takes an | |
4009494e GM |
3800 | association list @var{alist} of @var{old}-@var{new} pairs. |
3801 | Each element of the tree (after applying the @code{:key} | |
3802 | function, if any), is compared with the @code{car}s of | |
3803 | @var{alist}; if it matches, it is replaced by the corresponding | |
3804 | @code{cdr}. | |
3805 | @end defun | |
3806 | ||
39a58b5b GM |
3807 | @defun cl-nsublis alist tree @t{&key :test :test-not :key} |
3808 | This is a destructive version of @code{cl-sublis}. | |
4009494e GM |
3809 | @end defun |
3810 | ||
1d5b82ef | 3811 | @node Lists as Sets |
4009494e GM |
3812 | @section Lists as Sets |
3813 | ||
3814 | @noindent | |
3815 | These functions perform operations on lists which represent sets | |
3816 | of elements. | |
3817 | ||
39a58b5b | 3818 | @defun cl-member item list @t{&key :test :test-not :key} |
4009494e GM |
3819 | This function searches @var{list} for an element matching @var{item}. |
3820 | If a match is found, it returns the cons cell whose @code{car} was | |
3821 | the matching element. Otherwise, it returns @code{nil}. Elements | |
3822 | are compared by @code{eql} by default; you can use the @code{:test}, | |
3823 | @code{:test-not}, and @code{:key} arguments to modify this behavior. | |
3824 | @xref{Sequences}. | |
3825 | ||
39a58b5b GM |
3826 | The standard Emacs lisp function @code{member} uses @code{equal} for |
3827 | comparisons; it is equivalent to @code{(cl-member @var{item} @var{list} | |
3828 | :test 'equal)}. | |
4009494e GM |
3829 | @end defun |
3830 | ||
39a58b5b GM |
3831 | @findex cl-member-if |
3832 | @findex cl-member-if-not | |
3833 | The @code{cl-member-if} and @code{cl-member-if-not} functions | |
4009494e GM |
3834 | analogously search for elements which satisfy a given predicate. |
3835 | ||
39a58b5b | 3836 | @defun cl-tailp sublist list |
4009494e GM |
3837 | This function returns @code{t} if @var{sublist} is a sublist of |
3838 | @var{list}, i.e., if @var{sublist} is @code{eql} to @var{list} or to | |
3839 | any of its @code{cdr}s. | |
3840 | @end defun | |
3841 | ||
39a58b5b | 3842 | @defun cl-adjoin item list @t{&key :test :test-not :key} |
4009494e GM |
3843 | This function conses @var{item} onto the front of @var{list}, |
3844 | like @code{(cons @var{item} @var{list})}, but only if @var{item} | |
39a58b5b | 3845 | is not already present on the list (as determined by @code{cl-member}). |
4009494e GM |
3846 | If a @code{:key} argument is specified, it is applied to |
3847 | @var{item} as well as to the elements of @var{list} during | |
3848 | the search, on the reasoning that @var{item} is ``about'' to | |
3849 | become part of the list. | |
3850 | @end defun | |
3851 | ||
39a58b5b | 3852 | @defun cl-union list1 list2 @t{&key :test :test-not :key} |
4009494e GM |
3853 | This function combines two lists which represent sets of items, |
3854 | returning a list that represents the union of those two sets. | |
3855 | The result list will contain all items which appear in @var{list1} | |
3856 | or @var{list2}, and no others. If an item appears in both | |
3857 | @var{list1} and @var{list2} it will be copied only once. If | |
3858 | an item is duplicated in @var{list1} or @var{list2}, it is | |
3859 | undefined whether or not that duplication will survive in the | |
3860 | result list. The order of elements in the result list is also | |
3861 | undefined. | |
3862 | @end defun | |
3863 | ||
39a58b5b GM |
3864 | @defun cl-nunion list1 list2 @t{&key :test :test-not :key} |
3865 | This is a destructive version of @code{cl-union}; rather than copying, | |
4009494e GM |
3866 | it tries to reuse the storage of the argument lists if possible. |
3867 | @end defun | |
3868 | ||
39a58b5b | 3869 | @defun cl-intersection list1 list2 @t{&key :test :test-not :key} |
4009494e GM |
3870 | This function computes the intersection of the sets represented |
3871 | by @var{list1} and @var{list2}. It returns the list of items | |
3872 | which appear in both @var{list1} and @var{list2}. | |
3873 | @end defun | |
3874 | ||
39a58b5b GM |
3875 | @defun cl-nintersection list1 list2 @t{&key :test :test-not :key} |
3876 | This is a destructive version of @code{cl-intersection}. It | |
4009494e GM |
3877 | tries to reuse storage of @var{list1} rather than copying. |
3878 | It does @emph{not} reuse the storage of @var{list2}. | |
3879 | @end defun | |
3880 | ||
39a58b5b | 3881 | @defun cl-set-difference list1 list2 @t{&key :test :test-not :key} |
4009494e GM |
3882 | This function computes the ``set difference'' of @var{list1} |
3883 | and @var{list2}, i.e., the set of elements that appear in | |
3884 | @var{list1} but @emph{not} in @var{list2}. | |
3885 | @end defun | |
3886 | ||
39a58b5b GM |
3887 | @defun cl-nset-difference list1 list2 @t{&key :test :test-not :key} |
3888 | This is a destructive @code{cl-set-difference}, which will try | |
4009494e GM |
3889 | to reuse @var{list1} if possible. |
3890 | @end defun | |
3891 | ||
39a58b5b | 3892 | @defun cl-set-exclusive-or list1 list2 @t{&key :test :test-not :key} |
4009494e GM |
3893 | This function computes the ``set exclusive or'' of @var{list1} |
3894 | and @var{list2}, i.e., the set of elements that appear in | |
3895 | exactly one of @var{list1} and @var{list2}. | |
3896 | @end defun | |
3897 | ||
39a58b5b GM |
3898 | @defun cl-nset-exclusive-or list1 list2 @t{&key :test :test-not :key} |
3899 | This is a destructive @code{cl-set-exclusive-or}, which will try | |
4009494e GM |
3900 | to reuse @var{list1} and @var{list2} if possible. |
3901 | @end defun | |
3902 | ||
39a58b5b | 3903 | @defun cl-subsetp list1 list2 @t{&key :test :test-not :key} |
4009494e GM |
3904 | This function checks whether @var{list1} represents a subset |
3905 | of @var{list2}, i.e., whether every element of @var{list1} | |
3906 | also appears in @var{list2}. | |
3907 | @end defun | |
3908 | ||
1d5b82ef | 3909 | @node Association Lists |
4009494e GM |
3910 | @section Association Lists |
3911 | ||
3912 | @noindent | |
3913 | An @dfn{association list} is a list representing a mapping from | |
3914 | one set of values to another; any list whose elements are cons | |
3915 | cells is an association list. | |
3916 | ||
39a58b5b | 3917 | @defun cl-assoc item a-list @t{&key :test :test-not :key} |
4009494e GM |
3918 | This function searches the association list @var{a-list} for an |
3919 | element whose @code{car} matches (in the sense of @code{:test}, | |
3920 | @code{:test-not}, and @code{:key}, or by comparison with @code{eql}) | |
3921 | a given @var{item}. It returns the matching element, if any, | |
3922 | otherwise @code{nil}. It ignores elements of @var{a-list} which | |
3923 | are not cons cells. (This corresponds to the behavior of | |
3924 | @code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's | |
3925 | @code{assoc} ignores @code{nil}s but considers any other non-cons | |
3926 | elements of @var{a-list} to be an error.) | |
3927 | @end defun | |
3928 | ||
39a58b5b | 3929 | @defun cl-rassoc item a-list @t{&key :test :test-not :key} |
4009494e GM |
3930 | This function searches for an element whose @code{cdr} matches |
3931 | @var{item}. If @var{a-list} represents a mapping, this applies | |
3932 | the inverse of the mapping to @var{item}. | |
3933 | @end defun | |
3934 | ||
39a58b5b GM |
3935 | @findex cl-assoc-if |
3936 | @findex cl-assoc-if-not | |
3937 | @findex cl-rassoc-if | |
3938 | @findex cl-rassoc-if-not | |
3939 | The @code{cl-assoc-if}, @code{cl-assoc-if-not}, @code{cl-rassoc-if}, | |
3940 | and @code{cl-rassoc-if-not} functions are defined similarly. | |
4009494e GM |
3941 | |
3942 | Two simple functions for constructing association lists are: | |
3943 | ||
39a58b5b | 3944 | @defun cl-acons key value alist |
4009494e GM |
3945 | This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}. |
3946 | @end defun | |
3947 | ||
39a58b5b GM |
3948 | @defun cl-pairlis keys values &optional alist |
3949 | This is equivalent to @code{(nconc (cl-mapcar 'cons @var{keys} @var{values}) | |
4009494e GM |
3950 | @var{alist})}. |
3951 | @end defun | |
3952 | ||
1d5b82ef | 3953 | @node Structures |
4009494e GM |
3954 | @chapter Structures |
3955 | ||
3956 | @noindent | |
3957 | The Common Lisp @dfn{structure} mechanism provides a general way | |
3958 | to define data types similar to C's @code{struct} types. A | |
3959 | structure is a Lisp object containing some number of @dfn{slots}, | |
3960 | each of which can hold any Lisp data object. Functions are | |
3961 | provided for accessing and setting the slots, creating or copying | |
3962 | structure objects, and recognizing objects of a particular structure | |
3963 | type. | |
3964 | ||
3965 | In true Common Lisp, each structure type is a new type distinct | |
3966 | from all existing Lisp types. Since the underlying Emacs Lisp | |
3967 | system provides no way to create new distinct types, this package | |
3968 | implements structures as vectors (or lists upon request) with a | |
3969 | special ``tag'' symbol to identify them. | |
3970 | ||
e1117425 | 3971 | @defmac cl-defstruct name slots@dots{} |
39a58b5b | 3972 | The @code{cl-defstruct} form defines a new structure type called |
4009494e GM |
3973 | @var{name}, with the specified @var{slots}. (The @var{slots} |
3974 | may begin with a string which documents the structure type.) | |
3975 | In the simplest case, @var{name} and each of the @var{slots} | |
3976 | are symbols. For example, | |
3977 | ||
3978 | @example | |
39a58b5b | 3979 | (cl-defstruct person name age sex) |
4009494e GM |
3980 | @end example |
3981 | ||
3982 | @noindent | |
3983 | defines a struct type called @code{person} which contains three | |
3984 | slots. Given a @code{person} object @var{p}, you can access those | |
3985 | slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})}, | |
3986 | and @code{(person-sex @var{p})}. You can also change these slots by | |
3987 | using @code{setf} on any of these place forms: | |
3988 | ||
3989 | @example | |
39a58b5b | 3990 | (cl-incf (person-age birthday-boy)) |
4009494e GM |
3991 | @end example |
3992 | ||
3993 | You can create a new @code{person} by calling @code{make-person}, | |
3994 | which takes keyword arguments @code{:name}, @code{:age}, and | |
3995 | @code{:sex} to specify the initial values of these slots in the | |
3996 | new object. (Omitting any of these arguments leaves the corresponding | |
a05cb6e3 | 3997 | slot ``undefined'', according to the Common Lisp standard; in Emacs |
4009494e GM |
3998 | Lisp, such uninitialized slots are filled with @code{nil}.) |
3999 | ||
4000 | Given a @code{person}, @code{(copy-person @var{p})} makes a new | |
4001 | object of the same type whose slots are @code{eq} to those of @var{p}. | |
4002 | ||
4003 | Given any Lisp object @var{x}, @code{(person-p @var{x})} returns | |
4004 | true if @var{x} looks like a @code{person}, false otherwise. (Again, | |
4005 | in Common Lisp this predicate would be exact; in Emacs Lisp the | |
4006 | best it can do is verify that @var{x} is a vector of the correct | |
4007 | length which starts with the correct tag symbol.) | |
4008 | ||
4009 | Accessors like @code{person-name} normally check their arguments | |
4010 | (effectively using @code{person-p}) and signal an error if the | |
4011 | argument is the wrong type. This check is affected by | |
4012 | @code{(optimize (safety @dots{}))} declarations. Safety level 1, | |
4013 | the default, uses a somewhat optimized check that will detect all | |
4014 | incorrect arguments, but may use an uninformative error message | |
4015 | (e.g., ``expected a vector'' instead of ``expected a @code{person}''). | |
4016 | Safety level 0 omits all checks except as provided by the underlying | |
4017 | @code{aref} call; safety levels 2 and 3 do rigorous checking that will | |
4018 | always print a descriptive error message for incorrect inputs. | |
4019 | @xref{Declarations}. | |
4020 | ||
4021 | @example | |
4022 | (setq dave (make-person :name "Dave" :sex 'male)) | |
4023 | @result{} [cl-struct-person "Dave" nil male] | |
4024 | (setq other (copy-person dave)) | |
4025 | @result{} [cl-struct-person "Dave" nil male] | |
4026 | (eq dave other) | |
4027 | @result{} nil | |
4028 | (eq (person-name dave) (person-name other)) | |
4029 | @result{} t | |
4030 | (person-p dave) | |
4031 | @result{} t | |
4032 | (person-p [1 2 3 4]) | |
4033 | @result{} nil | |
4034 | (person-p "Bogus") | |
4035 | @result{} nil | |
4036 | (person-p '[cl-struct-person counterfeit person object]) | |
4037 | @result{} t | |
4038 | @end example | |
4039 | ||
4040 | In general, @var{name} is either a name symbol or a list of a name | |
4041 | symbol followed by any number of @dfn{struct options}; each @var{slot} | |
4042 | is either a slot symbol or a list of the form @samp{(@var{slot-name} | |
4043 | @var{default-value} @var{slot-options}@dots{})}. The @var{default-value} | |
4044 | is a Lisp form which is evaluated any time an instance of the | |
4045 | structure type is created without specifying that slot's value. | |
4046 | ||
4047 | Common Lisp defines several slot options, but the only one | |
4048 | implemented in this package is @code{:read-only}. A non-@code{nil} | |
4049 | value for this option means the slot should not be @code{setf}-able; | |
4050 | the slot's value is determined when the object is created and does | |
4051 | not change afterward. | |
4052 | ||
4053 | @example | |
39a58b5b GM |
4054 | (cl-defstruct person |
4055 | (name nil :read-only t) | |
4056 | age | |
4057 | (sex 'unknown)) | |
4009494e GM |
4058 | @end example |
4059 | ||
4060 | Any slot options other than @code{:read-only} are ignored. | |
4061 | ||
4062 | For obscure historical reasons, structure options take a different | |
4063 | form than slot options. A structure option is either a keyword | |
4064 | symbol, or a list beginning with a keyword symbol possibly followed | |
4065 | by arguments. (By contrast, slot options are key-value pairs not | |
4066 | enclosed in lists.) | |
4067 | ||
4068 | @example | |
39a58b5b GM |
4069 | (cl-defstruct (person (:constructor create-person) |
4070 | (:type list) | |
4071 | :named) | |
4072 | name age sex) | |
4009494e GM |
4073 | @end example |
4074 | ||
4075 | The following structure options are recognized. | |
4076 | ||
4077 | @table @code | |
4009494e GM |
4078 | @item :conc-name |
4079 | The argument is a symbol whose print name is used as the prefix for | |
4080 | the names of slot accessor functions. The default is the name of | |
4081 | the struct type followed by a hyphen. The option @code{(:conc-name p-)} | |
4082 | would change this prefix to @code{p-}. Specifying @code{nil} as an | |
4083 | argument means no prefix, so that the slot names themselves are used | |
4084 | to name the accessor functions. | |
4085 | ||
4086 | @item :constructor | |
4087 | In the simple case, this option takes one argument which is an | |
4088 | alternate name to use for the constructor function. The default | |
4089 | is @code{make-@var{name}}, e.g., @code{make-person}. The above | |
4090 | example changes this to @code{create-person}. Specifying @code{nil} | |
4091 | as an argument means that no standard constructor should be | |
4092 | generated at all. | |
4093 | ||
4094 | In the full form of this option, the constructor name is followed | |
4095 | by an arbitrary argument list. @xref{Program Structure}, for a | |
4096 | description of the format of Common Lisp argument lists. All | |
4097 | options, such as @code{&rest} and @code{&key}, are supported. | |
4098 | The argument names should match the slot names; each slot is | |
4099 | initialized from the corresponding argument. Slots whose names | |
4100 | do not appear in the argument list are initialized based on the | |
4101 | @var{default-value} in their slot descriptor. Also, @code{&optional} | |
4102 | and @code{&key} arguments which don't specify defaults take their | |
4103 | defaults from the slot descriptor. It is valid to include arguments | |
4104 | which don't correspond to slot names; these are useful if they are | |
4105 | referred to in the defaults for optional, keyword, or @code{&aux} | |
4106 | arguments which @emph{do} correspond to slots. | |
4107 | ||
4108 | You can specify any number of full-format @code{:constructor} | |
4109 | options on a structure. The default constructor is still generated | |
4110 | as well unless you disable it with a simple-format @code{:constructor} | |
4111 | option. | |
4112 | ||
4113 | @example | |
39a58b5b GM |
4114 | (cl-defstruct |
4115 | (person | |
4116 | (:constructor nil) ; no default constructor | |
a05cb6e3 GM |
4117 | (:constructor new-person |
4118 | (name sex &optional (age 0))) | |
39a58b5b GM |
4119 | (:constructor new-hound (&key (name "Rover") |
4120 | (dog-years 0) | |
4121 | &aux (age (* 7 dog-years)) | |
4122 | (sex 'canine)))) | |
4123 | name age sex) | |
4009494e GM |
4124 | @end example |
4125 | ||
4126 | The first constructor here takes its arguments positionally rather | |
4127 | than by keyword. (In official Common Lisp terminology, constructors | |
4128 | that work By Order of Arguments instead of by keyword are called | |
a05cb6e3 | 4129 | ``BOA constructors''. No, I'm not making this up.) For example, |
4009494e GM |
4130 | @code{(new-person "Jane" 'female)} generates a person whose slots |
4131 | are @code{"Jane"}, 0, and @code{female}, respectively. | |
4132 | ||
4133 | The second constructor takes two keyword arguments, @code{:name}, | |
4134 | which initializes the @code{name} slot and defaults to @code{"Rover"}, | |
4135 | and @code{:dog-years}, which does not itself correspond to a slot | |
4136 | but which is used to initialize the @code{age} slot. The @code{sex} | |
4137 | slot is forced to the symbol @code{canine} with no syntax for | |
4138 | overriding it. | |
4139 | ||
4140 | @item :copier | |
4141 | The argument is an alternate name for the copier function for | |
4142 | this type. The default is @code{copy-@var{name}}. @code{nil} | |
4143 | means not to generate a copier function. (In this implementation, | |
4144 | all copier functions are simply synonyms for @code{copy-sequence}.) | |
4145 | ||
4146 | @item :predicate | |
4147 | The argument is an alternate name for the predicate which recognizes | |
4148 | objects of this type. The default is @code{@var{name}-p}. @code{nil} | |
4149 | means not to generate a predicate function. (If the @code{:type} | |
4150 | option is used without the @code{:named} option, no predicate is | |
4151 | ever generated.) | |
4152 | ||
4153 | In true Common Lisp, @code{typep} is always able to recognize a | |
4154 | structure object even if @code{:predicate} was used. In this | |
a05cb6e3 | 4155 | package, @code{cl-typep} simply looks for a function called |
4009494e GM |
4156 | @code{@var{typename}-p}, so it will work for structure types |
4157 | only if they used the default predicate name. | |
4158 | ||
4159 | @item :include | |
4160 | This option implements a very limited form of C++-style inheritance. | |
4161 | The argument is the name of another structure type previously | |
39a58b5b | 4162 | created with @code{cl-defstruct}. The effect is to cause the new |
4009494e GM |
4163 | structure type to inherit all of the included structure's slots |
4164 | (plus, of course, any new slots described by this struct's slot | |
4165 | descriptors). The new structure is considered a ``specialization'' | |
4166 | of the included one. In fact, the predicate and slot accessors | |
4167 | for the included type will also accept objects of the new type. | |
4168 | ||
4169 | If there are extra arguments to the @code{:include} option after | |
4170 | the included-structure name, these options are treated as replacement | |
4171 | slot descriptors for slots in the included structure, possibly with | |
4172 | modified default values. Borrowing an example from Steele: | |
4173 | ||
4174 | @example | |
39a58b5b GM |
4175 | (cl-defstruct person name (age 0) sex) |
4176 | @result{} person | |
4177 | (cl-defstruct (astronaut (:include person (age 45))) | |
4178 | helmet-size | |
4179 | (favorite-beverage 'tang)) | |
4180 | @result{} astronaut | |
4009494e GM |
4181 | |
4182 | (setq joe (make-person :name "Joe")) | |
4183 | @result{} [cl-struct-person "Joe" 0 nil] | |
4184 | (setq buzz (make-astronaut :name "Buzz")) | |
4185 | @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang] | |
4186 | ||
4187 | (list (person-p joe) (person-p buzz)) | |
4188 | @result{} (t t) | |
4189 | (list (astronaut-p joe) (astronaut-p buzz)) | |
4190 | @result{} (nil t) | |
4191 | ||
4192 | (person-name buzz) | |
4193 | @result{} "Buzz" | |
4194 | (astronaut-name joe) | |
4195 | @result{} error: "astronaut-name accessing a non-astronaut" | |
4196 | @end example | |
4197 | ||
4198 | Thus, if @code{astronaut} is a specialization of @code{person}, | |
4199 | then every @code{astronaut} is also a @code{person} (but not the | |
4200 | other way around). Every @code{astronaut} includes all the slots | |
4201 | of a @code{person}, plus extra slots that are specific to | |
4202 | astronauts. Operations that work on people (like @code{person-name}) | |
4203 | work on astronauts just like other people. | |
4204 | ||
4205 | @item :print-function | |
4206 | In full Common Lisp, this option allows you to specify a function | |
4207 | which is called to print an instance of the structure type. The | |
4208 | Emacs Lisp system offers no hooks into the Lisp printer which would | |
4209 | allow for such a feature, so this package simply ignores | |
4210 | @code{:print-function}. | |
4211 | ||
4212 | @item :type | |
4213 | The argument should be one of the symbols @code{vector} or @code{list}. | |
4214 | This tells which underlying Lisp data type should be used to implement | |
4215 | the new structure type. Vectors are used by default, but | |
4216 | @code{(:type list)} will cause structure objects to be stored as | |
4217 | lists instead. | |
4218 | ||
4219 | The vector representation for structure objects has the advantage | |
4220 | that all structure slots can be accessed quickly, although creating | |
4221 | vectors is a bit slower in Emacs Lisp. Lists are easier to create, | |
4222 | but take a relatively long time accessing the later slots. | |
4223 | ||
4224 | @item :named | |
4225 | This option, which takes no arguments, causes a characteristic ``tag'' | |
4226 | symbol to be stored at the front of the structure object. Using | |
4227 | @code{:type} without also using @code{:named} will result in a | |
4228 | structure type stored as plain vectors or lists with no identifying | |
4229 | features. | |
4230 | ||
4231 | The default, if you don't specify @code{:type} explicitly, is to | |
4232 | use named vectors. Therefore, @code{:named} is only useful in | |
4233 | conjunction with @code{:type}. | |
4234 | ||
4235 | @example | |
39a58b5b GM |
4236 | (cl-defstruct (person1) name age sex) |
4237 | (cl-defstruct (person2 (:type list) :named) name age sex) | |
4238 | (cl-defstruct (person3 (:type list)) name age sex) | |
4009494e GM |
4239 | |
4240 | (setq p1 (make-person1)) | |
4241 | @result{} [cl-struct-person1 nil nil nil] | |
4242 | (setq p2 (make-person2)) | |
4243 | @result{} (person2 nil nil nil) | |
4244 | (setq p3 (make-person3)) | |
4245 | @result{} (nil nil nil) | |
4246 | ||
4247 | (person1-p p1) | |
4248 | @result{} t | |
4249 | (person2-p p2) | |
4250 | @result{} t | |
4251 | (person3-p p3) | |
4252 | @result{} error: function person3-p undefined | |
4253 | @end example | |
4254 | ||
39a58b5b | 4255 | Since unnamed structures don't have tags, @code{cl-defstruct} is not |
4009494e GM |
4256 | able to make a useful predicate for recognizing them. Also, |
4257 | accessors like @code{person3-name} will be generated but they | |
4258 | will not be able to do any type checking. The @code{person3-name} | |
4259 | function, for example, will simply be a synonym for @code{car} in | |
4260 | this case. By contrast, @code{person2-name} is able to verify | |
4261 | that its argument is indeed a @code{person2} object before | |
4262 | proceeding. | |
4263 | ||
4264 | @item :initial-offset | |
4265 | The argument must be a nonnegative integer. It specifies a | |
4266 | number of slots to be left ``empty'' at the front of the | |
4267 | structure. If the structure is named, the tag appears at the | |
4268 | specified position in the list or vector; otherwise, the first | |
4269 | slot appears at that position. Earlier positions are filled | |
4270 | with @code{nil} by the constructors and ignored otherwise. If | |
4271 | the type @code{:include}s another type, then @code{:initial-offset} | |
4272 | specifies a number of slots to be skipped between the last slot | |
4273 | of the included type and the first new slot. | |
4274 | @end table | |
e1117425 | 4275 | @end defmac |
4009494e | 4276 | |
39a58b5b | 4277 | Except as noted, the @code{cl-defstruct} facility of this package is |
4009494e GM |
4278 | entirely compatible with that of Common Lisp. |
4279 | ||
1d5b82ef | 4280 | @node Assertions |
4009494e GM |
4281 | @chapter Assertions and Errors |
4282 | ||
4283 | @noindent | |
4284 | This section describes two macros that test @dfn{assertions}, i.e., | |
4285 | conditions which must be true if the program is operating correctly. | |
4286 | Assertions never add to the behavior of a Lisp program; they simply | |
4287 | make ``sanity checks'' to make sure everything is as it should be. | |
4288 | ||
4289 | If the optimization property @code{speed} has been set to 3, and | |
4290 | @code{safety} is less than 3, then the byte-compiler will optimize | |
4291 | away the following assertions. Because assertions might be optimized | |
4292 | away, it is a bad idea for them to include side-effects. | |
4293 | ||
e1117425 | 4294 | @defmac cl-assert test-form [show-args string args@dots{}] |
4009494e GM |
4295 | This form verifies that @var{test-form} is true (i.e., evaluates to |
4296 | a non-@code{nil} value). If so, it returns @code{nil}. If the test | |
39a58b5b | 4297 | is not satisfied, @code{cl-assert} signals an error. |
4009494e GM |
4298 | |
4299 | A default error message will be supplied which includes @var{test-form}. | |
4300 | You can specify a different error message by including a @var{string} | |
4301 | argument plus optional extra arguments. Those arguments are simply | |
4302 | passed to @code{error} to signal the error. | |
4303 | ||
4304 | If the optional second argument @var{show-args} is @code{t} instead | |
4305 | of @code{nil}, then the error message (with or without @var{string}) | |
4306 | will also include all non-constant arguments of the top-level | |
4307 | @var{form}. For example: | |
4308 | ||
4309 | @example | |
39a58b5b | 4310 | (cl-assert (> x 10) t "x is too small: %d") |
4009494e GM |
4311 | @end example |
4312 | ||
4313 | This usage of @var{show-args} is an extension to Common Lisp. In | |
4314 | true Common Lisp, the second argument gives a list of @var{places} | |
4315 | which can be @code{setf}'d by the user before continuing from the | |
4316 | error. Since Emacs Lisp does not support continuable errors, it | |
4317 | makes no sense to specify @var{places}. | |
e1117425 | 4318 | @end defmac |
4009494e | 4319 | |
e1117425 | 4320 | @defmac cl-check-type form type [string] |
4009494e | 4321 | This form verifies that @var{form} evaluates to a value of type |
39a58b5b | 4322 | @var{type}. If so, it returns @code{nil}. If not, @code{cl-check-type} |
4009494e GM |
4323 | signals a @code{wrong-type-argument} error. The default error message |
4324 | lists the erroneous value along with @var{type} and @var{form} | |
4325 | themselves. If @var{string} is specified, it is included in the | |
4326 | error message in place of @var{type}. For example: | |
4327 | ||
4328 | @example | |
39a58b5b | 4329 | (cl-check-type x (integer 1 *) "a positive integer") |
4009494e GM |
4330 | @end example |
4331 | ||
4332 | @xref{Type Predicates}, for a description of the type specifiers | |
4333 | that may be used for @var{type}. | |
4334 | ||
4335 | Note that in Common Lisp, the first argument to @code{check-type} | |
4336 | must be a @var{place} suitable for use by @code{setf}, because | |
4337 | @code{check-type} signals a continuable error that allows the | |
4338 | user to modify @var{place}. | |
e1117425 | 4339 | @end defmac |
4009494e | 4340 | |
1d5b82ef | 4341 | @node Efficiency Concerns |
4009494e GM |
4342 | @appendix Efficiency Concerns |
4343 | ||
4344 | @appendixsec Macros | |
4345 | ||
4346 | @noindent | |
39a58b5b | 4347 | Many of the advanced features of this package, such as @code{cl-defun}, |
5887564d | 4348 | @code{cl-loop}, etc., are implemented as Lisp macros. In |
4009494e GM |
4349 | byte-compiled code, these complex notations will be expanded into |
4350 | equivalent Lisp code which is simple and efficient. For example, | |
5887564d | 4351 | the form |
4009494e GM |
4352 | |
4353 | @example | |
39a58b5b | 4354 | (cl-incf i n) |
4009494e GM |
4355 | @end example |
4356 | ||
4357 | @noindent | |
5887564d | 4358 | is expanded at compile-time to the Lisp form |
4009494e GM |
4359 | |
4360 | @example | |
4361 | (setq i (+ i n)) | |
4009494e GM |
4362 | @end example |
4363 | ||
4364 | @noindent | |
5887564d | 4365 | which is the most efficient ways of doing this operation |
4009494e | 4366 | in Lisp. Thus, there is no performance penalty for using the more |
5887564d | 4367 | readable @code{cl-incf} form in your compiled code. |
4009494e GM |
4368 | |
4369 | @emph{Interpreted} code, on the other hand, must expand these macros | |
4370 | every time they are executed. For this reason it is strongly | |
4371 | recommended that code making heavy use of macros be compiled. | |
e1117425 GM |
4372 | A loop using @code{cl-incf} a hundred times will execute considerably |
4373 | faster if compiled, and will also garbage-collect less because the | |
4374 | macro expansion will not have to be generated, used, and thrown away a | |
4375 | hundred times. | |
4009494e GM |
4376 | |
4377 | You can find out how a macro expands by using the | |
4378 | @code{cl-prettyexpand} function. | |
4379 | ||
4380 | @defun cl-prettyexpand form &optional full | |
4381 | This function takes a single Lisp form as an argument and inserts | |
4382 | a nicely formatted copy of it in the current buffer (which must be | |
4383 | in Lisp mode so that indentation works properly). It also expands | |
4384 | all Lisp macros which appear in the form. The easiest way to use | |
a05cb6e3 | 4385 | this function is to go to the @file{*scratch*} buffer and type, say, |
4009494e GM |
4386 | |
4387 | @example | |
5887564d | 4388 | (cl-prettyexpand '(cl-loop for x below 10 collect x)) |
4009494e GM |
4389 | @end example |
4390 | ||
4391 | @noindent | |
4392 | and type @kbd{C-x C-e} immediately after the closing parenthesis; | |
4393 | the expansion | |
4394 | ||
4395 | @example | |
39a58b5b GM |
4396 | (cl-block nil |
4397 | (let* ((x 0) | |
4398 | (G1004 nil)) | |
4399 | (while (< x 10) | |
4400 | (setq G1004 (cons x G1004)) | |
4401 | (setq x (+ x 1))) | |
4402 | (nreverse G1004))) | |
4009494e GM |
4403 | @end example |
4404 | ||
4405 | @noindent | |
39a58b5b | 4406 | will be inserted into the buffer. (The @code{cl-block} macro is |
4009494e GM |
4407 | expanded differently in the interpreter and compiler, so |
4408 | @code{cl-prettyexpand} just leaves it alone. The temporary | |
39a58b5b | 4409 | variable @code{G1004} was created by @code{cl-gensym}.) |
4009494e GM |
4410 | |
4411 | If the optional argument @var{full} is true, then @emph{all} | |
39a58b5b | 4412 | macros are expanded, including @code{cl-block}, @code{cl-eval-when}, |
4009494e GM |
4413 | and compiler macros. Expansion is done as if @var{form} were |
4414 | a top-level form in a file being compiled. For example, | |
4415 | ||
4416 | @example | |
39a58b5b GM |
4417 | (cl-prettyexpand '(cl-pushnew 'x list)) |
4418 | @print{} (setq list (cl-adjoin 'x list)) | |
4419 | (cl-prettyexpand '(cl-pushnew 'x list) t) | |
4009494e | 4420 | @print{} (setq list (if (memq 'x list) list (cons 'x list))) |
39a58b5b | 4421 | (cl-prettyexpand '(caddr (cl-member 'a list)) t) |
4009494e GM |
4422 | @print{} (car (cdr (cdr (memq 'a list)))) |
4423 | @end example | |
4424 | ||
39a58b5b | 4425 | Note that @code{cl-adjoin}, @code{cl-caddr}, and @code{cl-member} all |
4009494e GM |
4426 | have built-in compiler macros to optimize them in common cases. |
4427 | @end defun | |
4428 | ||
4429 | @ifinfo | |
4430 | @example | |
4431 | ||
4432 | @end example | |
4433 | @end ifinfo | |
4434 | @appendixsec Error Checking | |
4435 | ||
4436 | @noindent | |
4437 | Common Lisp compliance has in general not been sacrificed for the | |
4438 | sake of efficiency. A few exceptions have been made for cases | |
4439 | where substantial gains were possible at the expense of marginal | |
4440 | incompatibility. | |
4441 | ||
4442 | The Common Lisp standard (as embodied in Steele's book) uses the | |
4443 | phrase ``it is an error if'' to indicate a situation which is not | |
4444 | supposed to arise in complying programs; implementations are strongly | |
4445 | encouraged but not required to signal an error in these situations. | |
4446 | This package sometimes omits such error checking in the interest of | |
39a58b5b | 4447 | compactness and efficiency. For example, @code{cl-do} variable |
4009494e GM |
4448 | specifiers are supposed to be lists of one, two, or three forms; |
4449 | extra forms are ignored by this package rather than signaling a | |
39a58b5b | 4450 | syntax error. The @code{cl-endp} function is simply a synonym for |
4009494e GM |
4451 | @code{null} in this package. Functions taking keyword arguments |
4452 | will accept an odd number of arguments, treating the trailing | |
4453 | keyword as if it were followed by the value @code{nil}. | |
4454 | ||
39a58b5b | 4455 | Argument lists (as processed by @code{cl-defun} and friends) |
4009494e GM |
4456 | @emph{are} checked rigorously except for the minor point just |
4457 | mentioned; in particular, keyword arguments are checked for | |
4458 | validity, and @code{&allow-other-keys} and @code{:allow-other-keys} | |
4459 | are fully implemented. Keyword validity checking is slightly | |
4460 | time consuming (though not too bad in byte-compiled code); | |
4461 | you can use @code{&allow-other-keys} to omit this check. Functions | |
39a58b5b | 4462 | defined in this package such as @code{cl-find} and @code{cl-member} |
4009494e GM |
4463 | do check their keyword arguments for validity. |
4464 | ||
4465 | @ifinfo | |
4466 | @example | |
4467 | ||
4468 | @end example | |
4469 | @end ifinfo | |
4470 | @appendixsec Optimizing Compiler | |
4471 | ||
4472 | @noindent | |
4473 | Use of the optimizing Emacs compiler is highly recommended; many of the Common | |
4474 | Lisp macros emit | |
4475 | code which can be improved by optimization. In particular, | |
39a58b5b GM |
4476 | @code{cl-block}s (whether explicit or implicit in constructs like |
4477 | @code{cl-defun} and @code{cl-loop}) carry a fair run-time penalty; the | |
4478 | optimizing compiler removes @code{cl-block}s which are not actually | |
4479 | referenced by @code{cl-return} or @code{cl-return-from} inside the block. | |
4009494e | 4480 | |
1d5b82ef | 4481 | @node Common Lisp Compatibility |
4009494e GM |
4482 | @appendix Common Lisp Compatibility |
4483 | ||
4484 | @noindent | |
4485 | Following is a list of all known incompatibilities between this | |
4486 | package and Common Lisp as documented in Steele (2nd edition). | |
4487 | ||
39a58b5b | 4488 | The word @code{cl-defun} is required instead of @code{defun} in order |
4009494e | 4489 | to use extended Common Lisp argument lists in a function. Likewise, |
39a58b5b | 4490 | @code{cl-defmacro} and @code{cl-function} are versions of those forms |
4009494e GM |
4491 | which understand full-featured argument lists. The @code{&whole} |
4492 | keyword does not work in @code{defmacro} argument lists (except | |
4493 | inside recursive argument lists). | |
4494 | ||
0a3333b5 | 4495 | The @code{equal} predicate does not distinguish |
39a58b5b | 4496 | between IEEE floating-point plus and minus zero. The @code{cl-equalp} |
4009494e GM |
4497 | predicate has several differences with Common Lisp; @pxref{Predicates}. |
4498 | ||
d3094168 | 4499 | @c FIXME no longer provided by cl. |
4009494e GM |
4500 | The @code{setf} mechanism is entirely compatible, except that |
4501 | setf-methods return a list of five values rather than five | |
4502 | values directly. Also, the new ``@code{setf} function'' concept | |
4503 | (typified by @code{(defun (setf foo) @dots{})}) is not implemented. | |
4504 | ||
39a58b5b | 4505 | The @code{cl-do-all-symbols} form is the same as @code{cl-do-symbols} |
4009494e GM |
4506 | with no @var{obarray} argument. In Common Lisp, this form would |
4507 | iterate over all symbols in all packages. Since Emacs obarrays | |
4508 | are not a first-class package mechanism, there is no way for | |
39a58b5b | 4509 | @code{cl-do-all-symbols} to locate any but the default obarray. |
4009494e | 4510 | |
39a58b5b | 4511 | The @code{cl-loop} macro is complete except that @code{loop-finish} |
4009494e GM |
4512 | and type specifiers are unimplemented. |
4513 | ||
4514 | The multiple-value return facility treats lists as multiple | |
4515 | values, since Emacs Lisp cannot support multiple return values | |
4516 | directly. The macros will be compatible with Common Lisp if | |
f94b04fc | 4517 | @code{cl-values} or @code{cl-values-list} is always used to return to |
39a58b5b | 4518 | a @code{cl-multiple-value-bind} or other multiple-value receiver; |
f94b04fc | 4519 | if @code{cl-values} is used without @code{cl-multiple-value-@dots{}} |
4009494e GM |
4520 | or vice-versa the effect will be different from Common Lisp. |
4521 | ||
4522 | Many Common Lisp declarations are ignored, and others match | |
4523 | the Common Lisp standard in concept but not in detail. For | |
4524 | example, local @code{special} declarations, which are purely | |
4525 | advisory in Emacs Lisp, do not rigorously obey the scoping rules | |
4526 | set down in Steele's book. | |
4527 | ||
39a58b5b | 4528 | The variable @code{cl--gensym-counter} starts out with a pseudo-random |
4009494e GM |
4529 | value rather than with zero. This is to cope with the fact that |
4530 | generated symbols become interned when they are written to and | |
4531 | loaded back from a file. | |
4532 | ||
39a58b5b | 4533 | The @code{cl-defstruct} facility is compatible, except that structures |
4009494e GM |
4534 | are of type @code{:type vector :named} by default rather than some |
4535 | special, distinct type. Also, the @code{:type} slot option is ignored. | |
4536 | ||
39a58b5b | 4537 | The second argument of @code{cl-check-type} is treated differently. |
4009494e | 4538 | |
1d5b82ef | 4539 | @node Porting Common Lisp |
4009494e GM |
4540 | @appendix Porting Common Lisp |
4541 | ||
4542 | @noindent | |
4543 | This package is meant to be used as an extension to Emacs Lisp, | |
4544 | not as an Emacs implementation of true Common Lisp. Some of the | |
4545 | remaining differences between Emacs Lisp and Common Lisp make it | |
4546 | difficult to port large Common Lisp applications to Emacs. For | |
4547 | one, some of the features in this package are not fully compliant | |
4548 | with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there | |
4549 | are also quite a few features that this package does not provide | |
4550 | at all. Here are some major omissions that you will want to watch out | |
4551 | for when bringing Common Lisp code into Emacs. | |
4552 | ||
4553 | @itemize @bullet | |
4554 | @item | |
4555 | Case-insensitivity. Symbols in Common Lisp are case-insensitive | |
4556 | by default. Some programs refer to a function or variable as | |
4557 | @code{foo} in one place and @code{Foo} or @code{FOO} in another. | |
4558 | Emacs Lisp will treat these as three distinct symbols. | |
4559 | ||
4560 | Some Common Lisp code is written entirely in upper case. While Emacs | |
4561 | is happy to let the program's own functions and variables use | |
4562 | this convention, calls to Lisp builtins like @code{if} and | |
4563 | @code{defun} will have to be changed to lower case. | |
4564 | ||
4565 | @item | |
4566 | Lexical scoping. In Common Lisp, function arguments and @code{let} | |
3c0c6155 GM |
4567 | bindings apply only to references physically within their bodies (or |
4568 | within macro expansions in their bodies). Traditionally, Emacs Lisp | |
4569 | uses @dfn{dynamic scoping} wherein a binding to a variable is visible | |
9c52d61d GM |
4570 | even inside functions called from the body. |
4571 | @xref{Dynamic Binding,,,elisp,GNU Emacs Lisp Reference Manual}. | |
4572 | Lexical binding is available since Emacs 24.1, so be sure to set | |
4573 | @code{lexical-binding} to @code{t} if you need to emulate this aspect | |
4574 | of Common Lisp. @xref{Lexical Binding,,,elisp,GNU Emacs Lisp Reference Manual}. | |
4009494e | 4575 | |
3c0c6155 GM |
4576 | Here is an example of a Common Lisp code fragment that would fail in |
4577 | Emacs Lisp if @code{lexical-binding} were set to @code{nil}: | |
4009494e GM |
4578 | |
4579 | @example | |
4580 | (defun map-odd-elements (func list) | |
4581 | (loop for x in list | |
4582 | for flag = t then (not flag) | |
4583 | collect (if flag x (funcall func x)))) | |
4584 | ||
4585 | (defun add-odd-elements (list x) | |
db7a4b66 | 4586 | (map-odd-elements (lambda (a) (+ a x)) list)) |
4009494e GM |
4587 | @end example |
4588 | ||
4589 | @noindent | |
3c0c6155 GM |
4590 | With lexical binding, the two functions' usages of @code{x} are |
4591 | completely independent. With dynamic binding, the binding to @code{x} | |
4592 | made by @code{add-odd-elements} will have been hidden by the binding | |
4593 | in @code{map-odd-elements} by the time the @code{(+ a x)} function is | |
4594 | called. | |
4009494e | 4595 | |
3c0c6155 GM |
4596 | Internally, this package uses lexical binding so that such problems do |
4597 | not occur. @xref{Lexical Bindings}, for a description of the obsolete | |
4598 | @code{lexical-let} form that emulates a Common Lisp-style lexical | |
4599 | binding when dynamic binding is in use. | |
4009494e GM |
4600 | |
4601 | @item | |
4602 | Reader macros. Common Lisp includes a second type of macro that | |
4603 | works at the level of individual characters. For example, Common | |
4604 | Lisp implements the quote notation by a reader macro called @code{'}, | |
4605 | whereas Emacs Lisp's parser just treats quote as a special case. | |
4606 | Some Lisp packages use reader macros to create special syntaxes | |
4607 | for themselves, which the Emacs parser is incapable of reading. | |
4608 | ||
4009494e GM |
4609 | @item |
4610 | Other syntactic features. Common Lisp provides a number of | |
4611 | notations beginning with @code{#} that the Emacs Lisp parser | |
4612 | won't understand. For example, @samp{#| ... |#} is an | |
4613 | alternate comment notation, and @samp{#+lucid (foo)} tells | |
4614 | the parser to ignore the @code{(foo)} except in Lucid Common | |
4615 | Lisp. | |
4616 | ||
4617 | @item | |
4618 | Packages. In Common Lisp, symbols are divided into @dfn{packages}. | |
4619 | Symbols that are Lisp built-ins are typically stored in one package; | |
4620 | symbols that are vendor extensions are put in another, and each | |
4621 | application program would have a package for its own symbols. | |
4622 | Certain symbols are ``exported'' by a package and others are | |
4623 | internal; certain packages ``use'' or import the exported symbols | |
4624 | of other packages. To access symbols that would not normally be | |
4625 | visible due to this importing and exporting, Common Lisp provides | |
4626 | a syntax like @code{package:symbol} or @code{package::symbol}. | |
4627 | ||
4628 | Emacs Lisp has a single namespace for all interned symbols, and | |
4629 | then uses a naming convention of putting a prefix like @code{cl-} | |
4630 | in front of the name. Some Emacs packages adopt the Common Lisp-like | |
4631 | convention of using @code{cl:} or @code{cl::} as the prefix. | |
4632 | However, the Emacs parser does not understand colons and just | |
4633 | treats them as part of the symbol name. Thus, while @code{mapcar} | |
4634 | and @code{lisp:mapcar} may refer to the same symbol in Common | |
4635 | Lisp, they are totally distinct in Emacs Lisp. Common Lisp | |
4636 | programs which refer to a symbol by the full name sometimes | |
4637 | and the short name other times will not port cleanly to Emacs. | |
4638 | ||
a05cb6e3 | 4639 | Emacs Lisp does have a concept of ``obarrays'', which are |
4009494e GM |
4640 | package-like collections of symbols, but this feature is not |
4641 | strong enough to be used as a true package mechanism. | |
4642 | ||
4643 | @item | |
4644 | The @code{format} function is quite different between Common | |
4645 | Lisp and Emacs Lisp. It takes an additional ``destination'' | |
4646 | argument before the format string. A destination of @code{nil} | |
4647 | means to format to a string as in Emacs Lisp; a destination | |
4648 | of @code{t} means to write to the terminal (similar to | |
4649 | @code{message} in Emacs). Also, format control strings are | |
4650 | utterly different; @code{~} is used instead of @code{%} to | |
4651 | introduce format codes, and the set of available codes is | |
4652 | much richer. There are no notations like @code{\n} for | |
4653 | string literals; instead, @code{format} is used with the | |
4654 | ``newline'' format code, @code{~%}. More advanced formatting | |
4655 | codes provide such features as paragraph filling, case | |
4656 | conversion, and even loops and conditionals. | |
4657 | ||
4658 | While it would have been possible to implement most of Common | |
a05cb6e3 | 4659 | Lisp @code{format} in this package (under the name @code{cl-format}, |
4009494e GM |
4660 | of course), it was not deemed worthwhile. It would have required |
4661 | a huge amount of code to implement even a decent subset of | |
a05cb6e3 | 4662 | @code{cl-format}, yet the functionality it would provide over |
4009494e GM |
4663 | Emacs Lisp's @code{format} would rarely be useful. |
4664 | ||
4665 | @item | |
4666 | Vector constants use square brackets in Emacs Lisp, but | |
4667 | @code{#(a b c)} notation in Common Lisp. To further complicate | |
4668 | matters, Emacs has its own @code{#(} notation for | |
4669 | something entirely different---strings with properties. | |
4670 | ||
4671 | @item | |
0a3333b5 RS |
4672 | Characters are distinct from integers in Common Lisp. The notation |
4673 | for character constants is also different: @code{#\A} in Common Lisp | |
4674 | where Emacs Lisp uses @code{?A}. Also, @code{string=} and | |
4675 | @code{string-equal} are synonyms in Emacs Lisp, whereas the latter is | |
4676 | case-insensitive in Common Lisp. | |
4009494e GM |
4677 | |
4678 | @item | |
4679 | Data types. Some Common Lisp data types do not exist in Emacs | |
4680 | Lisp. Rational numbers and complex numbers are not present, | |
4681 | nor are large integers (all integers are ``fixnums''). All | |
4682 | arrays are one-dimensional. There are no readtables or pathnames; | |
4683 | streams are a set of existing data types rather than a new data | |
4684 | type of their own. Hash tables, random-states, structures, and | |
4685 | packages (obarrays) are built from Lisp vectors or lists rather | |
4686 | than being distinct types. | |
4687 | ||
4688 | @item | |
4689 | The Common Lisp Object System (CLOS) is not implemented, | |
4690 | nor is the Common Lisp Condition System. However, the EIEIO package | |
159e3ad5 | 4691 | (@pxref{Top, , Introduction, eieio, EIEIO}) does implement some |
4009494e GM |
4692 | CLOS functionality. |
4693 | ||
4694 | @item | |
4695 | Common Lisp features that are completely redundant with Emacs | |
4696 | Lisp features of a different name generally have not been | |
4697 | implemented. For example, Common Lisp writes @code{defconstant} | |
4698 | where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list} | |
4699 | takes its arguments in different ways in the two Lisps but does | |
4700 | exactly the same thing, so this package has not bothered to | |
4701 | implement a Common Lisp-style @code{make-list}. | |
4702 | ||
4703 | @item | |
4704 | A few more notable Common Lisp features not included in this | |
4705 | package: @code{compiler-let}, @code{tagbody}, @code{prog}, | |
4706 | @code{ldb/dpb}, @code{parse-integer}, @code{cerror}. | |
4707 | ||
4708 | @item | |
4709 | Recursion. While recursion works in Emacs Lisp just like it | |
4710 | does in Common Lisp, various details of the Emacs Lisp system | |
4711 | and compiler make recursion much less efficient than it is in | |
4712 | most Lisps. Some schools of thought prefer to use recursion | |
4713 | in Lisp over other techniques; they would sum a list of | |
4714 | numbers using something like | |
4715 | ||
4716 | @example | |
4717 | (defun sum-list (list) | |
4718 | (if list | |
4719 | (+ (car list) (sum-list (cdr list))) | |
4720 | 0)) | |
4721 | @end example | |
4722 | ||
4723 | @noindent | |
4724 | where a more iteratively-minded programmer might write one of | |
4725 | these forms: | |
4726 | ||
4727 | @example | |
39a58b5b | 4728 | (let ((total 0)) (dolist (x my-list) (cl-incf total x)) total) |
5887564d | 4729 | (cl-loop for x in my-list sum x) |
4009494e GM |
4730 | @end example |
4731 | ||
4732 | While this would be mainly a stylistic choice in most Common Lisps, | |
4733 | in Emacs Lisp you should be aware that the iterative forms are | |
4734 | much faster than recursion. Also, Lisp programmers will want to | |
4735 | note that the current Emacs Lisp compiler does not optimize tail | |
4736 | recursion. | |
4737 | @end itemize | |
4738 | ||
3c0c6155 GM |
4739 | @node Obsolete Features |
4740 | @appendix Obsolete Features | |
4741 | ||
4742 | This section describes some features of the package that are obsolete | |
f94b04fc GM |
4743 | and should not be used in new code. They are either only provided by |
4744 | the old @file{cl.el} entry point, not by the newer @file{cl-lib.el}; | |
4745 | or where versions with a @samp{cl-} prefix do exist they do not behave | |
4746 | in exactly the same way. | |
3c0c6155 GM |
4747 | |
4748 | @menu | |
f94b04fc GM |
4749 | * Lexical Bindings:: An approximation of lexical binding. |
4750 | * Obsolete Lexical Macros:: Obsolete macros using lexical-let. | |
4751 | * Obsolete Setf Customization:: Obsolete ways to customize setf. | |
3c0c6155 GM |
4752 | @end menu |
4753 | ||
4754 | @node Lexical Bindings | |
4755 | @appendixsec Lexical Bindings | |
4756 | ||
4757 | The following macros are extensions to Common Lisp, where all bindings | |
4758 | are lexical unless declared otherwise. These features are likewise | |
4759 | obsolete since the introduction of true lexical binding in Emacs 24.1. | |
4760 | ||
4761 | @defmac lexical-let (bindings@dots{}) forms@dots{} | |
4762 | This form is exactly like @code{let} except that the bindings it | |
4763 | establishes are purely lexical. | |
4764 | @end defmac | |
4765 | ||
4766 | @c FIXME remove this and refer to elisp manual. | |
4767 | @c Maybe merge some stuff from here to there? | |
4768 | @noindent | |
4769 | Lexical bindings are similar to local variables in a language like C: | |
4770 | Only the code physically within the body of the @code{lexical-let} | |
4771 | (after macro expansion) may refer to the bound variables. | |
4772 | ||
4773 | @example | |
4774 | (setq a 5) | |
4775 | (defun foo (b) (+ a b)) | |
4776 | (let ((a 2)) (foo a)) | |
4777 | @result{} 4 | |
4778 | (lexical-let ((a 2)) (foo a)) | |
4779 | @result{} 7 | |
4780 | @end example | |
4781 | ||
4782 | @noindent | |
4783 | In this example, a regular @code{let} binding of @code{a} actually | |
4784 | makes a temporary change to the global variable @code{a}, so @code{foo} | |
4785 | is able to see the binding of @code{a} to 2. But @code{lexical-let} | |
4786 | actually creates a distinct local variable @code{a} for use within its | |
4787 | body, without any effect on the global variable of the same name. | |
4788 | ||
4789 | The most important use of lexical bindings is to create @dfn{closures}. | |
4790 | A closure is a function object that refers to an outside lexical | |
9c52d61d GM |
4791 | variable (@pxref{Closures,,,elisp,GNU Emacs Lisp Reference Manual}). |
4792 | For example: | |
3c0c6155 GM |
4793 | |
4794 | @example | |
4795 | (defun make-adder (n) | |
4796 | (lexical-let ((n n)) | |
4797 | (function (lambda (m) (+ n m))))) | |
4798 | (setq add17 (make-adder 17)) | |
4799 | (funcall add17 4) | |
4800 | @result{} 21 | |
4801 | @end example | |
4802 | ||
4803 | @noindent | |
4804 | The call @code{(make-adder 17)} returns a function object which adds | |
4805 | 17 to its argument. If @code{let} had been used instead of | |
4806 | @code{lexical-let}, the function object would have referred to the | |
4807 | global @code{n}, which would have been bound to 17 only during the | |
4808 | call to @code{make-adder} itself. | |
4809 | ||
4810 | @example | |
4811 | (defun make-counter () | |
4812 | (lexical-let ((n 0)) | |
4813 | (cl-function (lambda (&optional (m 1)) (cl-incf n m))))) | |
4814 | (setq count-1 (make-counter)) | |
4815 | (funcall count-1 3) | |
4816 | @result{} 3 | |
4817 | (funcall count-1 14) | |
4818 | @result{} 17 | |
4819 | (setq count-2 (make-counter)) | |
4820 | (funcall count-2 5) | |
4821 | @result{} 5 | |
4822 | (funcall count-1 2) | |
4823 | @result{} 19 | |
4824 | (funcall count-2) | |
4825 | @result{} 6 | |
4826 | @end example | |
4827 | ||
4828 | @noindent | |
4829 | Here we see that each call to @code{make-counter} creates a distinct | |
4830 | local variable @code{n}, which serves as a private counter for the | |
4831 | function object that is returned. | |
4832 | ||
4833 | Closed-over lexical variables persist until the last reference to | |
4834 | them goes away, just like all other Lisp objects. For example, | |
4835 | @code{count-2} refers to a function object which refers to an | |
4836 | instance of the variable @code{n}; this is the only reference | |
4837 | to that variable, so after @code{(setq count-2 nil)} the garbage | |
4838 | collector would be able to delete this instance of @code{n}. | |
4839 | Of course, if a @code{lexical-let} does not actually create any | |
4840 | closures, then the lexical variables are free as soon as the | |
4841 | @code{lexical-let} returns. | |
4842 | ||
4843 | Many closures are used only during the extent of the bindings they | |
4844 | refer to; these are known as ``downward funargs'' in Lisp parlance. | |
4845 | When a closure is used in this way, regular Emacs Lisp dynamic | |
4846 | bindings suffice and will be more efficient than @code{lexical-let} | |
4847 | closures: | |
4848 | ||
4849 | @example | |
4850 | (defun add-to-list (x list) | |
4851 | (mapcar (lambda (y) (+ x y))) list) | |
4852 | (add-to-list 7 '(1 2 5)) | |
4853 | @result{} (8 9 12) | |
4854 | @end example | |
4855 | ||
4856 | @noindent | |
4857 | Since this lambda is only used while @code{x} is still bound, | |
4858 | it is not necessary to make a true closure out of it. | |
4859 | ||
4860 | You can use @code{defun} or @code{flet} inside a @code{lexical-let} | |
4861 | to create a named closure. If several closures are created in the | |
4862 | body of a single @code{lexical-let}, they all close over the same | |
4863 | instance of the lexical variable. | |
4864 | ||
4865 | @defmac lexical-let* (bindings@dots{}) forms@dots{} | |
4866 | This form is just like @code{lexical-let}, except that the bindings | |
4867 | are made sequentially in the manner of @code{let*}. | |
4868 | @end defmac | |
4869 | ||
f94b04fc GM |
4870 | @node Obsolete Lexical Macros |
4871 | @appendixsec Macros Defined Using Lexical-Let | |
4872 | ||
4873 | The following macros are defined using @code{lexical-let}. | |
4874 | They are replaced by versions with a @samp{cl-} prefix that use true | |
4875 | lexical binding (and hence rely on @code{lexical-binding} being set to | |
4876 | @code{t} in code using them). | |
4877 | ||
4878 | @defmac flet (bindings@dots{}) forms@dots{} | |
4879 | Replaced by @code{cl-flet} (@pxref{Function Bindings}) | |
4880 | or @code{cl-letf} (@pxref{Modify Macros}). | |
4881 | @end defmac | |
4882 | ||
4883 | @defmac labels (bindings@dots{}) forms@dots{} | |
4884 | Replaced by @code{cl-labels} (@pxref{Function Bindings}). | |
4885 | @end defmac | |
4886 | ||
4887 | @defmac letf (bindings@dots{}) forms@dots{} | |
4ddedf94 GM |
4888 | This macro is almost exactly the same as @code{cl-letf}, which |
4889 | replaces it (@pxref{Modify Macros}). The only difference is in | |
4890 | details that relate to some deprecated usage of @code{symbol-function} | |
4891 | in place forms. | |
f94b04fc GM |
4892 | @end defmac |
4893 | ||
4894 | @node Obsolete Setf Customization | |
4895 | @appendixsec Obsolete Ways to Customize Setf | |
4896 | ||
d571e9c3 GM |
4897 | Common Lisp defines three macros, @code{define-modify-macro}, |
4898 | @code{defsetf}, and @code{define-setf-method}, that allow the | |
4899 | user to extend generalized variables in various ways. | |
4900 | In Emacs, these are obsolete, replaced by various features of | |
4901 | @file{gv.el} in Emacs 24.3. | |
4902 | @c FIXME details. | |
4903 | ||
4904 | @defmac define-modify-macro name arglist function [doc-string] | |
4905 | This macro defines a ``read-modify-write'' macro similar to | |
4906 | @code{cl-incf} and @code{cl-decf}. The macro @var{name} is defined | |
4907 | to take a @var{place} argument followed by additional arguments | |
4908 | described by @var{arglist}. The call | |
4909 | ||
4910 | @example | |
4911 | (@var{name} @var{place} @var{args}...) | |
4912 | @end example | |
4913 | ||
4914 | @noindent | |
4915 | will be expanded to | |
f94b04fc | 4916 | |
d571e9c3 GM |
4917 | @example |
4918 | (cl-callf @var{func} @var{place} @var{args}...) | |
4919 | @end example | |
4920 | ||
4921 | @noindent | |
4922 | which in turn is roughly equivalent to | |
4923 | ||
4924 | @example | |
4925 | (setf @var{place} (@var{func} @var{place} @var{args}...)) | |
4926 | @end example | |
4927 | ||
4928 | For example: | |
4929 | ||
4930 | @example | |
4931 | (define-modify-macro cl-incf (&optional (n 1)) +) | |
4932 | (define-modify-macro cl-concatf (&rest args) concat) | |
4933 | @end example | |
4934 | ||
4935 | Note that @code{&key} is not allowed in @var{arglist}, but | |
4936 | @code{&rest} is sufficient to pass keywords on to the function. | |
4937 | ||
4938 | Most of the modify macros defined by Common Lisp do not exactly | |
4939 | follow the pattern of @code{define-modify-macro}. For example, | |
4940 | @code{push} takes its arguments in the wrong order, and @code{pop} | |
4941 | is completely irregular. You can define these macros ``by hand'' | |
4942 | using @code{get-setf-method}, or consult the source | |
4943 | to see how to use the internal @code{setf} building blocks. | |
f94b04fc GM |
4944 | @end defmac |
4945 | ||
4946 | @defmac defsetf access-fn update-fn | |
d571e9c3 GM |
4947 | This is the simpler of two @code{defsetf} forms. Where |
4948 | @var{access-fn} is the name of a function which accesses a place, | |
4949 | this declares @var{update-fn} to be the corresponding store | |
4950 | function. From now on, | |
4951 | ||
4952 | @example | |
4953 | (setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value}) | |
4954 | @end example | |
4955 | ||
4956 | @noindent | |
4957 | will be expanded to | |
4958 | ||
4959 | @example | |
4960 | (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value}) | |
4961 | @end example | |
4962 | ||
4963 | @noindent | |
4964 | The @var{update-fn} is required to be either a true function, or | |
4965 | a macro which evaluates its arguments in a function-like way. Also, | |
4966 | the @var{update-fn} is expected to return @var{value} as its result. | |
4967 | Otherwise, the above expansion would not obey the rules for the way | |
4968 | @code{setf} is supposed to behave. | |
4969 | ||
4970 | As a special (non-Common-Lisp) extension, a third argument of @code{t} | |
4971 | to @code{defsetf} says that the @code{update-fn}'s return value is | |
4972 | not suitable, so that the above @code{setf} should be expanded to | |
4973 | something more like | |
4974 | ||
4975 | @example | |
4976 | (let ((temp @var{value})) | |
4977 | (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp) | |
4978 | temp) | |
4979 | @end example | |
4980 | ||
4981 | Some examples of the use of @code{defsetf}, drawn from the standard | |
4982 | suite of setf methods, are: | |
4983 | ||
4984 | @example | |
4985 | (defsetf car setcar) | |
4986 | (defsetf symbol-value set) | |
4987 | (defsetf buffer-name rename-buffer t) | |
4988 | @end example | |
f94b04fc GM |
4989 | @end defmac |
4990 | ||
d571e9c3 GM |
4991 | @defmac defsetf access-fn arglist (store-var) forms@dots{} |
4992 | This is the second, more complex, form of @code{defsetf}. It is | |
4993 | rather like @code{defmacro} except for the additional @var{store-var} | |
4994 | argument. The @var{forms} should return a Lisp form which stores | |
4995 | the value of @var{store-var} into the generalized variable formed | |
4996 | by a call to @var{access-fn} with arguments described by @var{arglist}. | |
4997 | The @var{forms} may begin with a string which documents the @code{setf} | |
4998 | method (analogous to the doc string that appears at the front of a | |
4999 | function). | |
5000 | ||
5001 | For example, the simple form of @code{defsetf} is shorthand for | |
5002 | ||
5003 | @example | |
5004 | (defsetf @var{access-fn} (&rest args) (store) | |
5005 | (append '(@var{update-fn}) args (list store))) | |
5006 | @end example | |
5007 | ||
5008 | The Lisp form that is returned can access the arguments from | |
5009 | @var{arglist} and @var{store-var} in an unrestricted fashion; | |
5010 | macros like @code{setf} and @code{cl-incf} which invoke this | |
5011 | setf-method will insert temporary variables as needed to make | |
5012 | sure the apparent order of evaluation is preserved. | |
5013 | ||
5014 | Another example drawn from the standard package: | |
5015 | ||
5016 | @example | |
5017 | (defsetf nth (n x) (store) | |
5018 | (list 'setcar (list 'nthcdr n x) store)) | |
5019 | @end example | |
f94b04fc GM |
5020 | @end defmac |
5021 | ||
d571e9c3 GM |
5022 | @defmac define-setf-method access-fn arglist forms@dots{} |
5023 | This is the most general way to create new place forms. When | |
5024 | a @code{setf} to @var{access-fn} with arguments described by | |
5025 | @var{arglist} is expanded, the @var{forms} are evaluated and | |
5026 | must return a list of five items: | |
5027 | ||
5028 | @enumerate | |
5029 | @item | |
5030 | A list of @dfn{temporary variables}. | |
5031 | ||
5032 | @item | |
5033 | A list of @dfn{value forms} corresponding to the temporary variables | |
5034 | above. The temporary variables will be bound to these value forms | |
5035 | as the first step of any operation on the generalized variable. | |
5036 | ||
5037 | @item | |
5038 | A list of exactly one @dfn{store variable} (generally obtained | |
5039 | from a call to @code{gensym}). | |
5040 | ||
5041 | @item | |
5042 | A Lisp form which stores the contents of the store variable into | |
5043 | the generalized variable, assuming the temporaries have been | |
5044 | bound as described above. | |
5045 | ||
5046 | @item | |
5047 | A Lisp form which accesses the contents of the generalized variable, | |
5048 | assuming the temporaries have been bound. | |
5049 | @end enumerate | |
5050 | ||
5051 | This is exactly like the Common Lisp macro of the same name, | |
5052 | except that the method returns a list of five values rather | |
5053 | than the five values themselves, since Emacs Lisp does not | |
5054 | support Common Lisp's notion of multiple return values. | |
5055 | ||
5056 | Once again, the @var{forms} may begin with a documentation string. | |
5057 | ||
5058 | A setf-method should be maximally conservative with regard to | |
5059 | temporary variables. In the setf-methods generated by | |
5060 | @code{defsetf}, the second return value is simply the list of | |
5061 | arguments in the place form, and the first return value is a | |
5062 | list of a corresponding number of temporary variables generated | |
5063 | by @code{cl-gensym}. Macros like @code{setf} and @code{cl-incf} which | |
5064 | use this setf-method will optimize away most temporaries that | |
5065 | turn out to be unnecessary, so there is little reason for the | |
5066 | setf-method itself to optimize. | |
5067 | @end defmac | |
5068 | ||
5069 | @defun get-setf-method place &optional env | |
5070 | This function returns the setf-method for @var{place}, by | |
5071 | invoking the definition previously recorded by @code{defsetf} | |
5072 | or @code{define-setf-method}. The result is a list of five | |
5073 | values as described above. You can use this function to build | |
5074 | your own @code{cl-incf}-like modify macros. (Actually, it is | |
5075 | @c FIXME? | |
5076 | better to use the internal functions @code{cl-setf-do-modify} | |
5077 | and @code{cl-setf-do-store}, which are a bit easier to use and | |
5078 | which also do a number of optimizations; consult the source | |
5079 | code for the @code{cl-incf} function for a simple example.) | |
5080 | ||
5081 | The argument @var{env} specifies the ``environment'' to be | |
5082 | passed on to @code{macroexpand} if @code{get-setf-method} should | |
5083 | need to expand a macro in @var{place}. It should come from | |
5084 | an @code{&environment} argument to the macro or setf-method | |
5085 | that called @code{get-setf-method}. | |
5086 | ||
6a07d52e GM |
5087 | See also the source code for the setf-method for |
5088 | @c Also @code{apply}, but that is commented out. | |
5089 | @code{substring}, which works by calling @code{get-setf-method} on a | |
5090 | simpler case, then massaging the result. | |
d571e9c3 GM |
5091 | @end defun |
5092 | ||
5093 | Modern Common Lisp defines a second, independent way to specify | |
5094 | the @code{setf} behavior of a function, namely ``@code{setf} | |
5095 | functions'' whose names are lists @code{(setf @var{name})} | |
5096 | rather than symbols. For example, @code{(defun (setf foo) @dots{})} | |
5097 | defines the function that is used when @code{setf} is applied to | |
5098 | @code{foo}. This package does not currently support @code{setf} | |
5099 | functions. In particular, it is a compile-time error to use | |
5100 | @code{setf} on a form which has not already been @code{defsetf}'d | |
5101 | or otherwise declared; in newer Common Lisps, this would not be | |
5102 | an error since the function @code{(setf @var{func})} might be | |
5103 | defined later. | |
5104 | ||
3c0c6155 | 5105 | |
1d5b82ef | 5106 | @node GNU Free Documentation License |
4009494e GM |
5107 | @appendix GNU Free Documentation License |
5108 | @include doclicense.texi | |
5109 | ||
1d5b82ef | 5110 | @node Function Index |
4009494e GM |
5111 | @unnumbered Function Index |
5112 | ||
5113 | @printindex fn | |
5114 | ||
1d5b82ef | 5115 | @node Variable Index |
4009494e GM |
5116 | @unnumbered Variable Index |
5117 | ||
5118 | @printindex vr | |
5119 | ||
4009494e GM |
5120 | @bye |
5121 |