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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
73b0cd50 | 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2011 |
d24880de | 4 | @c Free Software Foundation, Inc. |
b8d4c8d0 | 5 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 6 | @setfilename ../../info/syntax |
b8d4c8d0 GM |
7 | @node Syntax Tables, Abbrevs, Searching and Matching, Top |
8 | @chapter Syntax Tables | |
9 | @cindex parsing buffer text | |
10 | @cindex syntax table | |
11 | @cindex text parsing | |
12 | ||
13 | A @dfn{syntax table} specifies the syntactic textual function of each | |
14 | character. This information is used by the @dfn{parsing functions}, the | |
15 | complex movement commands, and others to determine where words, symbols, | |
16 | and other syntactic constructs begin and end. The current syntax table | |
17 | controls the meaning of the word motion functions (@pxref{Word Motion}) | |
18 | and the list motion functions (@pxref{List Motion}), as well as the | |
19 | functions in this chapter. | |
20 | ||
21 | @menu | |
22 | * Basics: Syntax Basics. Basic concepts of syntax tables. | |
23 | * Desc: Syntax Descriptors. How characters are classified. | |
24 | * Syntax Table Functions:: How to create, examine and alter syntax tables. | |
25 | * Syntax Properties:: Overriding syntax with text properties. | |
d24880de | 26 | * Motion and Syntax:: Moving over characters with certain syntaxes. |
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27 | * Parsing Expressions:: Parsing balanced expressions |
28 | using the syntax table. | |
29 | * Standard Syntax Tables:: Syntax tables used by various major modes. | |
30 | * Syntax Table Internals:: How syntax table information is stored. | |
31 | * Categories:: Another way of classifying character syntax. | |
32 | @end menu | |
33 | ||
34 | @node Syntax Basics | |
35 | @section Syntax Table Concepts | |
36 | ||
37 | @ifnottex | |
38 | A @dfn{syntax table} provides Emacs with the information that | |
39 | determines the syntactic use of each character in a buffer. This | |
40 | information is used by the parsing commands, the complex movement | |
41 | commands, and others to determine where words, symbols, and other | |
42 | syntactic constructs begin and end. The current syntax table controls | |
43 | the meaning of the word motion functions (@pxref{Word Motion}) and the | |
44 | list motion functions (@pxref{List Motion}) as well as the functions in | |
45 | this chapter. | |
46 | @end ifnottex | |
47 | ||
48 | A syntax table is a char-table (@pxref{Char-Tables}). The element at | |
49 | index @var{c} describes the character with code @var{c}. The element's | |
50 | value should be a list that encodes the syntax of the character in | |
51 | question. | |
52 | ||
53 | Syntax tables are used only for moving across text, not for the Emacs | |
54 | Lisp reader. Emacs Lisp uses built-in syntactic rules when reading Lisp | |
55 | expressions, and these rules cannot be changed. (Some Lisp systems | |
56 | provide ways to redefine the read syntax, but we decided to leave this | |
57 | feature out of Emacs Lisp for simplicity.) | |
58 | ||
59 | Each buffer has its own major mode, and each major mode has its own | |
60 | idea of the syntactic class of various characters. For example, in Lisp | |
61 | mode, the character @samp{;} begins a comment, but in C mode, it | |
62 | terminates a statement. To support these variations, Emacs makes the | |
63 | choice of syntax table local to each buffer. Typically, each major | |
64 | mode has its own syntax table and installs that table in each buffer | |
65 | that uses that mode. Changing this table alters the syntax in all | |
66 | those buffers as well as in any buffers subsequently put in that mode. | |
67 | Occasionally several similar modes share one syntax table. | |
68 | @xref{Example Major Modes}, for an example of how to set up a syntax | |
69 | table. | |
70 | ||
71 | A syntax table can inherit the data for some characters from the | |
72 | standard syntax table, while specifying other characters itself. The | |
73 | ``inherit'' syntax class means ``inherit this character's syntax from | |
74 | the standard syntax table.'' Just changing the standard syntax for a | |
75 | character affects all syntax tables that inherit from it. | |
76 | ||
77 | @defun syntax-table-p object | |
78 | This function returns @code{t} if @var{object} is a syntax table. | |
79 | @end defun | |
80 | ||
81 | @node Syntax Descriptors | |
82 | @section Syntax Descriptors | |
83 | @cindex syntax class | |
84 | ||
85 | This section describes the syntax classes and flags that denote the | |
86 | syntax of a character, and how they are represented as a @dfn{syntax | |
87 | descriptor}, which is a Lisp string that you pass to | |
88 | @code{modify-syntax-entry} to specify the syntax you want. | |
89 | ||
90 | The syntax table specifies a syntax class for each character. There | |
91 | is no necessary relationship between the class of a character in one | |
92 | syntax table and its class in any other table. | |
93 | ||
94 | Each class is designated by a mnemonic character, which serves as the | |
95 | name of the class when you need to specify a class. Usually the | |
96 | designator character is one that is often assigned that class; however, | |
97 | its meaning as a designator is unvarying and independent of what syntax | |
98 | that character currently has. Thus, @samp{\} as a designator character | |
99 | always gives ``escape character'' syntax, regardless of what syntax | |
100 | @samp{\} currently has. | |
101 | ||
102 | @cindex syntax descriptor | |
103 | A syntax descriptor is a Lisp string that specifies a syntax class, a | |
104 | matching character (used only for the parenthesis classes) and flags. | |
105 | The first character is the designator for a syntax class. The second | |
106 | character is the character to match; if it is unused, put a space there. | |
107 | Then come the characters for any desired flags. If no matching | |
108 | character or flags are needed, one character is sufficient. | |
109 | ||
110 | For example, the syntax descriptor for the character @samp{*} in C | |
ad21a12a | 111 | mode is @code{". 23"} (i.e., punctuation, matching character slot |
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112 | unused, second character of a comment-starter, first character of a |
113 | comment-ender), and the entry for @samp{/} is @samp{@w{. 14}} (i.e., | |
114 | punctuation, matching character slot unused, first character of a | |
115 | comment-starter, second character of a comment-ender). | |
116 | ||
117 | @menu | |
118 | * Syntax Class Table:: Table of syntax classes. | |
119 | * Syntax Flags:: Additional flags each character can have. | |
120 | @end menu | |
121 | ||
122 | @node Syntax Class Table | |
123 | @subsection Table of Syntax Classes | |
124 | ||
125 | Here is a table of syntax classes, the characters that stand for them, | |
126 | their meanings, and examples of their use. | |
127 | ||
128 | @deffn {Syntax class} @w{whitespace character} | |
129 | @dfn{Whitespace characters} (designated by @w{@samp{@ }} or @samp{-}) | |
130 | separate symbols and words from each other. Typically, whitespace | |
131 | characters have no other syntactic significance, and multiple whitespace | |
132 | characters are syntactically equivalent to a single one. Space, tab, | |
133 | newline and formfeed are classified as whitespace in almost all major | |
134 | modes. | |
135 | @end deffn | |
136 | ||
137 | @deffn {Syntax class} @w{word constituent} | |
138 | @dfn{Word constituents} (designated by @samp{w}) are parts of words in | |
139 | human languages, and are typically used in variable and command names | |
140 | in programs. All upper- and lower-case letters, and the digits, are | |
141 | typically word constituents. | |
142 | @end deffn | |
143 | ||
144 | @deffn {Syntax class} @w{symbol constituent} | |
145 | @dfn{Symbol constituents} (designated by @samp{_}) are the extra | |
146 | characters that are used in variable and command names along with word | |
147 | constituents. For example, the symbol constituents class is used in | |
148 | Lisp mode to indicate that certain characters may be part of symbol | |
149 | names even though they are not part of English words. These characters | |
150 | are @samp{$&*+-_<>}. In standard C, the only non-word-constituent | |
151 | character that is valid in symbols is underscore (@samp{_}). | |
152 | @end deffn | |
153 | ||
154 | @deffn {Syntax class} @w{punctuation character} | |
155 | @dfn{Punctuation characters} (designated by @samp{.}) are those | |
156 | characters that are used as punctuation in English, or are used in some | |
157 | way in a programming language to separate symbols from one another. | |
158 | Some programming language modes, such as Emacs Lisp mode, have no | |
159 | characters in this class since the few characters that are not symbol or | |
160 | word constituents all have other uses. Other programming language modes, | |
161 | such as C mode, use punctuation syntax for operators. | |
162 | @end deffn | |
163 | ||
164 | @deffn {Syntax class} @w{open parenthesis character} | |
165 | @deffnx {Syntax class} @w{close parenthesis character} | |
166 | @cindex parenthesis syntax | |
167 | Open and close @dfn{parenthesis characters} are characters used in | |
168 | dissimilar pairs to surround sentences or expressions. Such a grouping | |
169 | is begun with an open parenthesis character and terminated with a close. | |
170 | Each open parenthesis character matches a particular close parenthesis | |
171 | character, and vice versa. Normally, Emacs indicates momentarily the | |
172 | matching open parenthesis when you insert a close parenthesis. | |
173 | @xref{Blinking}. | |
174 | ||
175 | The class of open parentheses is designated by @samp{(}, and that of | |
176 | close parentheses by @samp{)}. | |
177 | ||
178 | In English text, and in C code, the parenthesis pairs are @samp{()}, | |
179 | @samp{[]}, and @samp{@{@}}. In Emacs Lisp, the delimiters for lists and | |
180 | vectors (@samp{()} and @samp{[]}) are classified as parenthesis | |
181 | characters. | |
182 | @end deffn | |
183 | ||
184 | @deffn {Syntax class} @w{string quote} | |
185 | @dfn{String quote characters} (designated by @samp{"}) are used in | |
186 | many languages, including Lisp and C, to delimit string constants. The | |
187 | same string quote character appears at the beginning and the end of a | |
188 | string. Such quoted strings do not nest. | |
189 | ||
190 | The parsing facilities of Emacs consider a string as a single token. | |
191 | The usual syntactic meanings of the characters in the string are | |
192 | suppressed. | |
193 | ||
194 | The Lisp modes have two string quote characters: double-quote (@samp{"}) | |
195 | and vertical bar (@samp{|}). @samp{|} is not used in Emacs Lisp, but it | |
196 | is used in Common Lisp. C also has two string quote characters: | |
197 | double-quote for strings, and single-quote (@samp{'}) for character | |
198 | constants. | |
199 | ||
200 | English text has no string quote characters because English is not a | |
201 | programming language. Although quotation marks are used in English, | |
202 | we do not want them to turn off the usual syntactic properties of | |
203 | other characters in the quotation. | |
204 | @end deffn | |
205 | ||
206 | @deffn {Syntax class} @w{escape-syntax character} | |
207 | An @dfn{escape character} (designated by @samp{\}) starts an escape | |
208 | sequence such as is used in C string and character constants. The | |
209 | character @samp{\} belongs to this class in both C and Lisp. (In C, it | |
210 | is used thus only inside strings, but it turns out to cause no trouble | |
211 | to treat it this way throughout C code.) | |
212 | ||
213 | Characters in this class count as part of words if | |
214 | @code{words-include-escapes} is non-@code{nil}. @xref{Word Motion}. | |
215 | @end deffn | |
216 | ||
217 | @deffn {Syntax class} @w{character quote} | |
218 | A @dfn{character quote character} (designated by @samp{/}) quotes the | |
219 | following character so that it loses its normal syntactic meaning. This | |
220 | differs from an escape character in that only the character immediately | |
221 | following is ever affected. | |
222 | ||
223 | Characters in this class count as part of words if | |
224 | @code{words-include-escapes} is non-@code{nil}. @xref{Word Motion}. | |
225 | ||
226 | This class is used for backslash in @TeX{} mode. | |
227 | @end deffn | |
228 | ||
229 | @deffn {Syntax class} @w{paired delimiter} | |
230 | @dfn{Paired delimiter characters} (designated by @samp{$}) are like | |
231 | string quote characters except that the syntactic properties of the | |
232 | characters between the delimiters are not suppressed. Only @TeX{} mode | |
233 | uses a paired delimiter presently---the @samp{$} that both enters and | |
234 | leaves math mode. | |
235 | @end deffn | |
236 | ||
237 | @deffn {Syntax class} @w{expression prefix} | |
238 | An @dfn{expression prefix operator} (designated by @samp{'}) is used for | |
239 | syntactic operators that are considered as part of an expression if they | |
240 | appear next to one. In Lisp modes, these characters include the | |
241 | apostrophe, @samp{'} (used for quoting), the comma, @samp{,} (used in | |
242 | macros), and @samp{#} (used in the read syntax for certain data types). | |
243 | @end deffn | |
244 | ||
245 | @deffn {Syntax class} @w{comment starter} | |
246 | @deffnx {Syntax class} @w{comment ender} | |
247 | @cindex comment syntax | |
248 | The @dfn{comment starter} and @dfn{comment ender} characters are used in | |
249 | various languages to delimit comments. These classes are designated | |
250 | by @samp{<} and @samp{>}, respectively. | |
251 | ||
252 | English text has no comment characters. In Lisp, the semicolon | |
253 | (@samp{;}) starts a comment and a newline or formfeed ends one. | |
254 | @end deffn | |
255 | ||
256 | @deffn {Syntax class} @w{inherit standard syntax} | |
257 | This syntax class does not specify a particular syntax. It says to look | |
258 | in the standard syntax table to find the syntax of this character. The | |
259 | designator for this syntax class is @samp{@@}. | |
260 | @end deffn | |
261 | ||
262 | @deffn {Syntax class} @w{generic comment delimiter} | |
263 | A @dfn{generic comment delimiter} (designated by @samp{!}) starts | |
264 | or ends a special kind of comment. @emph{Any} generic comment delimiter | |
265 | matches @emph{any} generic comment delimiter, but they cannot match | |
266 | a comment starter or comment ender; generic comment delimiters can only | |
267 | match each other. | |
268 | ||
269 | This syntax class is primarily meant for use with the | |
270 | @code{syntax-table} text property (@pxref{Syntax Properties}). You can | |
271 | mark any range of characters as forming a comment, by giving the first | |
272 | and last characters of the range @code{syntax-table} properties | |
273 | identifying them as generic comment delimiters. | |
274 | @end deffn | |
275 | ||
276 | @deffn {Syntax class} @w{generic string delimiter} | |
277 | A @dfn{generic string delimiter} (designated by @samp{|}) starts or ends | |
278 | a string. This class differs from the string quote class in that @emph{any} | |
279 | generic string delimiter can match any other generic string delimiter; but | |
280 | they do not match ordinary string quote characters. | |
281 | ||
282 | This syntax class is primarily meant for use with the | |
283 | @code{syntax-table} text property (@pxref{Syntax Properties}). You can | |
284 | mark any range of characters as forming a string constant, by giving the | |
285 | first and last characters of the range @code{syntax-table} properties | |
286 | identifying them as generic string delimiters. | |
287 | @end deffn | |
288 | ||
289 | @node Syntax Flags | |
290 | @subsection Syntax Flags | |
291 | @cindex syntax flags | |
292 | ||
293 | In addition to the classes, entries for characters in a syntax table | |
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294 | can specify flags. There are eight possible flags, represented by the |
295 | characters @samp{1}, @samp{2}, @samp{3}, @samp{4}, @samp{b}, @samp{c}, | |
296 | @samp{n}, and @samp{p}. | |
297 | ||
298 | All the flags except @samp{p} are used to describe comment | |
299 | delimiters. The digit flags are used for comment delimiters made up | |
300 | of 2 characters. They indicate that a character can @emph{also} be | |
301 | part of a comment sequence, in addition to the syntactic properties | |
302 | associated with its character class. The flags are independent of the | |
303 | class and each other for the sake of characters such as @samp{*} in | |
304 | C mode, which is a punctuation character, @emph{and} the second | |
305 | character of a start-of-comment sequence (@samp{/*}), @emph{and} the | |
306 | first character of an end-of-comment sequence (@samp{*/}). The flags | |
307 | @samp{b}, @samp{c}, and @samp{n} are used to qualify the corresponding | |
308 | comment delimiter. | |
b8d4c8d0 GM |
309 | |
310 | Here is a table of the possible flags for a character @var{c}, | |
311 | and what they mean: | |
312 | ||
313 | @itemize @bullet | |
314 | @item | |
315 | @samp{1} means @var{c} is the start of a two-character comment-start | |
316 | sequence. | |
317 | ||
318 | @item | |
319 | @samp{2} means @var{c} is the second character of such a sequence. | |
320 | ||
321 | @item | |
322 | @samp{3} means @var{c} is the start of a two-character comment-end | |
323 | sequence. | |
324 | ||
325 | @item | |
326 | @samp{4} means @var{c} is the second character of such a sequence. | |
327 | ||
328 | @item | |
b8d4c8d0 | 329 | @samp{b} means that @var{c} as a comment delimiter belongs to the |
7cf78aac SM |
330 | alternative ``b'' comment style. For a two-character comment starter, |
331 | this flag is only significant on the second char, and for a 2-character | |
332 | comment ender it is only significant on the first char. | |
b8d4c8d0 | 333 | |
7cf78aac SM |
334 | @item |
335 | @samp{c} means that @var{c} as a comment delimiter belongs to the | |
336 | alternative ``c'' comment style. For a two-character comment | |
337 | delimiter, @samp{c} on either character makes it of style ``c''. | |
b8d4c8d0 | 338 | |
7cf78aac SM |
339 | @item |
340 | @samp{n} on a comment delimiter character specifies | |
341 | that this kind of comment can be nested. For a two-character | |
342 | comment delimiter, @samp{n} on either character makes it | |
343 | nestable. | |
b8d4c8d0 | 344 | |
7cf78aac SM |
345 | Emacs supports several comment styles simultaneously in any one syntax |
346 | table. A comment style is a set of flags @samp{b}, @samp{c}, and | |
347 | @samp{n}, so there can be up to 8 different comment styles. | |
348 | Each comment delimiter has a style and only matches comment delimiters | |
349 | of the same style. Thus if a comment starts with the comment-start | |
350 | sequence of style ``bn'', it will extend until the next matching | |
351 | comment-end sequence of style ``bn''. | |
b8d4c8d0 | 352 | |
7cf78aac | 353 | The appropriate comment syntax settings for C++ can be as follows: |
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354 | |
355 | @table @asis | |
356 | @item @samp{/} | |
7cf78aac | 357 | @samp{124} |
b8d4c8d0 | 358 | @item @samp{*} |
7cf78aac | 359 | @samp{23b} |
b8d4c8d0 | 360 | @item newline |
7cf78aac | 361 | @samp{>} |
b8d4c8d0 GM |
362 | @end table |
363 | ||
364 | This defines four comment-delimiting sequences: | |
365 | ||
366 | @table @asis | |
367 | @item @samp{/*} | |
7cf78aac SM |
368 | This is a comment-start sequence for ``b'' style because the |
369 | second character, @samp{*}, has the @samp{b} flag. | |
b8d4c8d0 GM |
370 | |
371 | @item @samp{//} | |
7cf78aac SM |
372 | This is a comment-start sequence for ``a'' style because the second |
373 | character, @samp{/}, does not have the @samp{b} flag. | |
b8d4c8d0 GM |
374 | |
375 | @item @samp{*/} | |
7cf78aac | 376 | This is a comment-end sequence for ``b'' style because the first |
35a30759 | 377 | character, @samp{*}, has the @samp{b} flag. |
b8d4c8d0 GM |
378 | |
379 | @item newline | |
7cf78aac SM |
380 | This is a comment-end sequence for ``a'' style, because the newline |
381 | character does not have the @samp{b} flag. | |
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382 | @end table |
383 | ||
b8d4c8d0 GM |
384 | @item |
385 | @c Emacs 19 feature | |
386 | @samp{p} identifies an additional ``prefix character'' for Lisp syntax. | |
387 | These characters are treated as whitespace when they appear between | |
388 | expressions. When they appear within an expression, they are handled | |
389 | according to their usual syntax classes. | |
390 | ||
391 | The function @code{backward-prefix-chars} moves back over these | |
392 | characters, as well as over characters whose primary syntax class is | |
393 | prefix (@samp{'}). @xref{Motion and Syntax}. | |
394 | @end itemize | |
395 | ||
396 | @node Syntax Table Functions | |
397 | @section Syntax Table Functions | |
398 | ||
399 | In this section we describe functions for creating, accessing and | |
400 | altering syntax tables. | |
401 | ||
402 | @defun make-syntax-table &optional table | |
403 | This function creates a new syntax table, with all values initialized | |
404 | to @code{nil}. If @var{table} is non-@code{nil}, it becomes the | |
405 | parent of the new syntax table, otherwise the standard syntax table is | |
406 | the parent. Like all char-tables, a syntax table inherits from its | |
407 | parent. Thus the original syntax of all characters in the returned | |
408 | syntax table is determined by the parent. @xref{Char-Tables}. | |
409 | ||
410 | Most major mode syntax tables are created in this way. | |
411 | @end defun | |
412 | ||
413 | @defun copy-syntax-table &optional table | |
414 | This function constructs a copy of @var{table} and returns it. If | |
415 | @var{table} is not supplied (or is @code{nil}), it returns a copy of the | |
416 | standard syntax table. Otherwise, an error is signaled if @var{table} is | |
417 | not a syntax table. | |
418 | @end defun | |
419 | ||
420 | @deffn Command modify-syntax-entry char syntax-descriptor &optional table | |
421 | This function sets the syntax entry for @var{char} according to | |
f147ff75 CY |
422 | @var{syntax-descriptor}. @var{char} can be a character, or a cons |
423 | cell of the form @code{(@var{min} . @var{max})}; in the latter case, | |
424 | the function sets the syntax entries for all characters in the range | |
425 | between @var{min} and @var{max}, inclusive. | |
426 | ||
427 | The syntax is changed only for @var{table}, which defaults to the | |
428 | current buffer's syntax table, and not in any other syntax table. The | |
429 | argument @var{syntax-descriptor} specifies the desired syntax; this is | |
430 | a string beginning with a class designator character, and optionally | |
431 | containing a matching character and flags as well. @xref{Syntax | |
432 | Descriptors}. | |
b8d4c8d0 GM |
433 | |
434 | This function always returns @code{nil}. The old syntax information in | |
435 | the table for this character is discarded. | |
436 | ||
437 | An error is signaled if the first character of the syntax descriptor is not | |
438 | one of the seventeen syntax class designator characters. An error is also | |
439 | signaled if @var{char} is not a character. | |
440 | ||
441 | @example | |
442 | @group | |
443 | @exdent @r{Examples:} | |
444 | ||
445 | ;; @r{Put the space character in class whitespace.} | |
446 | (modify-syntax-entry ?\s " ") | |
447 | @result{} nil | |
448 | @end group | |
449 | ||
450 | @group | |
451 | ;; @r{Make @samp{$} an open parenthesis character,} | |
452 | ;; @r{with @samp{^} as its matching close.} | |
453 | (modify-syntax-entry ?$ "(^") | |
454 | @result{} nil | |
455 | @end group | |
456 | ||
457 | @group | |
458 | ;; @r{Make @samp{^} a close parenthesis character,} | |
459 | ;; @r{with @samp{$} as its matching open.} | |
460 | (modify-syntax-entry ?^ ")$") | |
461 | @result{} nil | |
462 | @end group | |
463 | ||
464 | @group | |
465 | ;; @r{Make @samp{/} a punctuation character,} | |
466 | ;; @r{the first character of a start-comment sequence,} | |
467 | ;; @r{and the second character of an end-comment sequence.} | |
468 | ;; @r{This is used in C mode.} | |
469 | (modify-syntax-entry ?/ ". 14") | |
470 | @result{} nil | |
471 | @end group | |
472 | @end example | |
473 | @end deffn | |
474 | ||
475 | @defun char-syntax character | |
476 | This function returns the syntax class of @var{character}, represented | |
477 | by its mnemonic designator character. This returns @emph{only} the | |
478 | class, not any matching parenthesis or flags. | |
479 | ||
480 | An error is signaled if @var{char} is not a character. | |
481 | ||
482 | The following examples apply to C mode. The first example shows that | |
483 | the syntax class of space is whitespace (represented by a space). The | |
484 | second example shows that the syntax of @samp{/} is punctuation. This | |
485 | does not show the fact that it is also part of comment-start and -end | |
486 | sequences. The third example shows that open parenthesis is in the class | |
487 | of open parentheses. This does not show the fact that it has a matching | |
488 | character, @samp{)}. | |
489 | ||
490 | @example | |
491 | @group | |
492 | (string (char-syntax ?\s)) | |
493 | @result{} " " | |
494 | @end group | |
495 | ||
496 | @group | |
497 | (string (char-syntax ?/)) | |
498 | @result{} "." | |
499 | @end group | |
500 | ||
501 | @group | |
502 | (string (char-syntax ?\()) | |
503 | @result{} "(" | |
504 | @end group | |
505 | @end example | |
506 | ||
507 | We use @code{string} to make it easier to see the character returned by | |
508 | @code{char-syntax}. | |
509 | @end defun | |
510 | ||
511 | @defun set-syntax-table table | |
512 | This function makes @var{table} the syntax table for the current buffer. | |
513 | It returns @var{table}. | |
514 | @end defun | |
515 | ||
516 | @defun syntax-table | |
517 | This function returns the current syntax table, which is the table for | |
518 | the current buffer. | |
519 | @end defun | |
520 | ||
521 | @defmac with-syntax-table @var{table} @var{body}@dots{} | |
522 | This macro executes @var{body} using @var{table} as the current syntax | |
523 | table. It returns the value of the last form in @var{body}, after | |
524 | restoring the old current syntax table. | |
525 | ||
526 | Since each buffer has its own current syntax table, we should make that | |
527 | more precise: @code{with-syntax-table} temporarily alters the current | |
528 | syntax table of whichever buffer is current at the time the macro | |
529 | execution starts. Other buffers are not affected. | |
530 | @end defmac | |
531 | ||
532 | @node Syntax Properties | |
533 | @section Syntax Properties | |
534 | @kindex syntax-table @r{(text property)} | |
535 | ||
536 | When the syntax table is not flexible enough to specify the syntax of | |
537 | a language, you can use @code{syntax-table} text properties to | |
538 | override the syntax table for specific character occurrences in the | |
539 | buffer. @xref{Text Properties}. You can use Font Lock mode to set | |
540 | @code{syntax-table} text properties. @xref{Setting Syntax | |
541 | Properties}. | |
542 | ||
543 | The valid values of @code{syntax-table} text property are: | |
544 | ||
545 | @table @asis | |
546 | @item @var{syntax-table} | |
547 | If the property value is a syntax table, that table is used instead of | |
548 | the current buffer's syntax table to determine the syntax for this | |
549 | occurrence of the character. | |
550 | ||
551 | @item @code{(@var{syntax-code} . @var{matching-char})} | |
552 | A cons cell of this format specifies the syntax for this | |
553 | occurrence of the character. (@pxref{Syntax Table Internals}) | |
554 | ||
555 | @item @code{nil} | |
556 | If the property is @code{nil}, the character's syntax is determined from | |
557 | the current syntax table in the usual way. | |
558 | @end table | |
559 | ||
560 | @defvar parse-sexp-lookup-properties | |
561 | If this is non-@code{nil}, the syntax scanning functions pay attention | |
562 | to syntax text properties. Otherwise they use only the current syntax | |
563 | table. | |
564 | @end defvar | |
565 | ||
566 | @node Motion and Syntax | |
567 | @section Motion and Syntax | |
568 | ||
569 | This section describes functions for moving across characters that | |
570 | have certain syntax classes. | |
571 | ||
572 | @defun skip-syntax-forward syntaxes &optional limit | |
573 | This function moves point forward across characters having syntax | |
574 | classes mentioned in @var{syntaxes} (a string of syntax class | |
575 | characters). It stops when it encounters the end of the buffer, or | |
576 | position @var{limit} (if specified), or a character it is not supposed | |
577 | to skip. | |
578 | ||
579 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
580 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
581 | ||
582 | The return value is the distance traveled, which is a nonnegative | |
583 | integer. | |
584 | @end defun | |
585 | ||
586 | @defun skip-syntax-backward syntaxes &optional limit | |
587 | This function moves point backward across characters whose syntax | |
588 | classes are mentioned in @var{syntaxes}. It stops when it encounters | |
589 | the beginning of the buffer, or position @var{limit} (if specified), or | |
590 | a character it is not supposed to skip. | |
591 | ||
592 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
593 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
594 | ||
595 | The return value indicates the distance traveled. It is an integer that | |
596 | is zero or less. | |
597 | @end defun | |
598 | ||
599 | @defun backward-prefix-chars | |
600 | This function moves point backward over any number of characters with | |
601 | expression prefix syntax. This includes both characters in the | |
602 | expression prefix syntax class, and characters with the @samp{p} flag. | |
603 | @end defun | |
604 | ||
605 | @node Parsing Expressions | |
606 | @section Parsing Expressions | |
607 | ||
608 | This section describes functions for parsing and scanning balanced | |
609 | expressions, also known as @dfn{sexps}. Basically, a sexp is either a | |
610 | balanced parenthetical grouping, a string, or a symbol name (a | |
611 | sequence of characters whose syntax is either word constituent or | |
612 | symbol constituent). However, characters whose syntax is expression | |
613 | prefix are treated as part of the sexp if they appear next to it. | |
614 | ||
615 | The syntax table controls the interpretation of characters, so these | |
616 | functions can be used for Lisp expressions when in Lisp mode and for C | |
617 | expressions when in C mode. @xref{List Motion}, for convenient | |
618 | higher-level functions for moving over balanced expressions. | |
619 | ||
620 | A character's syntax controls how it changes the state of the | |
621 | parser, rather than describing the state itself. For example, a | |
622 | string delimiter character toggles the parser state between | |
623 | ``in-string'' and ``in-code,'' but the syntax of characters does not | |
624 | directly say whether they are inside a string. For example (note that | |
625 | 15 is the syntax code for generic string delimiters), | |
626 | ||
627 | @example | |
628 | (put-text-property 1 9 'syntax-table '(15 . nil)) | |
629 | @end example | |
630 | ||
631 | @noindent | |
632 | does not tell Emacs that the first eight chars of the current buffer | |
633 | are a string, but rather that they are all string delimiters. As a | |
634 | result, Emacs treats them as four consecutive empty string constants. | |
635 | ||
636 | @menu | |
637 | * Motion via Parsing:: Motion functions that work by parsing. | |
638 | * Position Parse:: Determining the syntactic state of a position. | |
639 | * Parser State:: How Emacs represents a syntactic state. | |
640 | * Low-Level Parsing:: Parsing across a specified region. | |
641 | * Control Parsing:: Parameters that affect parsing. | |
642 | @end menu | |
643 | ||
644 | @node Motion via Parsing | |
645 | @subsection Motion Commands Based on Parsing | |
646 | ||
647 | This section describes simple point-motion functions that operate | |
648 | based on parsing expressions. | |
649 | ||
650 | @defun scan-lists from count depth | |
651 | This function scans forward @var{count} balanced parenthetical groupings | |
652 | from position @var{from}. It returns the position where the scan stops. | |
653 | If @var{count} is negative, the scan moves backwards. | |
654 | ||
655 | If @var{depth} is nonzero, parenthesis depth counting begins from that | |
656 | value. The only candidates for stopping are places where the depth in | |
657 | parentheses becomes zero; @code{scan-lists} counts @var{count} such | |
658 | places and then stops. Thus, a positive value for @var{depth} means go | |
659 | out @var{depth} levels of parenthesis. | |
660 | ||
661 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
662 | non-@code{nil}. | |
663 | ||
664 | If the scan reaches the beginning or end of the buffer (or its | |
665 | accessible portion), and the depth is not zero, an error is signaled. | |
666 | If the depth is zero but the count is not used up, @code{nil} is | |
667 | returned. | |
668 | @end defun | |
669 | ||
670 | @defun scan-sexps from count | |
671 | This function scans forward @var{count} sexps from position @var{from}. | |
672 | It returns the position where the scan stops. If @var{count} is | |
673 | negative, the scan moves backwards. | |
674 | ||
675 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
676 | non-@code{nil}. | |
677 | ||
678 | If the scan reaches the beginning or end of (the accessible part of) the | |
679 | buffer while in the middle of a parenthetical grouping, an error is | |
680 | signaled. If it reaches the beginning or end between groupings but | |
681 | before count is used up, @code{nil} is returned. | |
682 | @end defun | |
683 | ||
684 | @defun forward-comment count | |
685 | This function moves point forward across @var{count} complete comments | |
686 | (that is, including the starting delimiter and the terminating | |
687 | delimiter if any), plus any whitespace encountered on the way. It | |
688 | moves backward if @var{count} is negative. If it encounters anything | |
689 | other than a comment or whitespace, it stops, leaving point at the | |
690 | place where it stopped. This includes (for instance) finding the end | |
691 | of a comment when moving forward and expecting the beginning of one. | |
692 | The function also stops immediately after moving over the specified | |
693 | number of complete comments. If @var{count} comments are found as | |
694 | expected, with nothing except whitespace between them, it returns | |
695 | @code{t}; otherwise it returns @code{nil}. | |
696 | ||
697 | This function cannot tell whether the ``comments'' it traverses are | |
698 | embedded within a string. If they look like comments, it treats them | |
699 | as comments. | |
700 | @end defun | |
701 | ||
702 | To move forward over all comments and whitespace following point, use | |
703 | @code{(forward-comment (buffer-size))}. @code{(buffer-size)} is a good | |
704 | argument to use, because the number of comments in the buffer cannot | |
705 | exceed that many. | |
706 | ||
707 | @node Position Parse | |
708 | @subsection Finding the Parse State for a Position | |
709 | ||
710 | For syntactic analysis, such as in indentation, often the useful | |
711 | thing is to compute the syntactic state corresponding to a given buffer | |
712 | position. This function does that conveniently. | |
713 | ||
714 | @defun syntax-ppss &optional pos | |
715 | This function returns the parser state (see next section) that the | |
716 | parser would reach at position @var{pos} starting from the beginning | |
717 | of the buffer. This is equivalent to @code{(parse-partial-sexp | |
718 | (point-min) @var{pos})}, except that @code{syntax-ppss} uses a cache | |
719 | to speed up the computation. Due to this optimization, the 2nd value | |
720 | (previous complete subexpression) and 6th value (minimum parenthesis | |
721 | depth) of the returned parser state are not meaningful. | |
722 | @end defun | |
723 | ||
724 | @code{syntax-ppss} automatically hooks itself to | |
725 | @code{before-change-functions} to keep its cache consistent. But | |
726 | updating can fail if @code{syntax-ppss} is called while | |
727 | @code{before-change-functions} is temporarily let-bound, or if the | |
728 | buffer is modified without obeying the hook, such as when using | |
729 | @code{inhibit-modification-hooks}. For this reason, it is sometimes | |
730 | necessary to flush the cache manually. | |
731 | ||
106e6894 CY |
732 | @defun syntax-ppss-flush-cache beg &rest ignored-args |
733 | This function flushes the cache used by @code{syntax-ppss}, starting | |
734 | at position @var{beg}. The remaining arguments, @var{ignored-args}, | |
735 | are ignored; this function accepts them so that it can be directly | |
736 | used on hooks such as @code{before-change-functions} (@pxref{Change | |
737 | Hooks}). | |
b8d4c8d0 GM |
738 | @end defun |
739 | ||
740 | Major modes can make @code{syntax-ppss} run faster by specifying | |
741 | where it needs to start parsing. | |
742 | ||
743 | @defvar syntax-begin-function | |
744 | If this is non-@code{nil}, it should be a function that moves to an | |
745 | earlier buffer position where the parser state is equivalent to | |
746 | @code{nil}---in other words, a position outside of any comment, | |
747 | string, or parenthesis. @code{syntax-ppss} uses it to further | |
748 | optimize its computations, when the cache gives no help. | |
749 | @end defvar | |
750 | ||
751 | @node Parser State | |
752 | @subsection Parser State | |
753 | @cindex parser state | |
754 | ||
755 | A @dfn{parser state} is a list of ten elements describing the final | |
756 | state of parsing text syntactically as part of an expression. The | |
757 | parsing functions in the following sections return a parser state as | |
758 | the value, and in some cases accept one as an argument also, so that | |
759 | you can resume parsing after it stops. Here are the meanings of the | |
760 | elements of the parser state: | |
761 | ||
762 | @enumerate 0 | |
763 | @item | |
764 | The depth in parentheses, counting from 0. @strong{Warning:} this can | |
765 | be negative if there are more close parens than open parens between | |
766 | the start of the defun and point. | |
767 | ||
768 | @item | |
769 | @cindex innermost containing parentheses | |
770 | The character position of the start of the innermost parenthetical | |
771 | grouping containing the stopping point; @code{nil} if none. | |
772 | ||
773 | @item | |
774 | @cindex previous complete subexpression | |
775 | The character position of the start of the last complete subexpression | |
776 | terminated; @code{nil} if none. | |
777 | ||
778 | @item | |
779 | @cindex inside string | |
780 | Non-@code{nil} if inside a string. More precisely, this is the | |
781 | character that will terminate the string, or @code{t} if a generic | |
782 | string delimiter character should terminate it. | |
783 | ||
784 | @item | |
785 | @cindex inside comment | |
786 | @code{t} if inside a comment (of either style), | |
787 | or the comment nesting level if inside a kind of comment | |
788 | that can be nested. | |
789 | ||
790 | @item | |
791 | @cindex quote character | |
792 | @code{t} if point is just after a quote character. | |
793 | ||
794 | @item | |
795 | The minimum parenthesis depth encountered during this scan. | |
796 | ||
797 | @item | |
798 | What kind of comment is active: @code{nil} for a comment of style | |
799 | ``a'' or when not inside a comment, @code{t} for a comment of style | |
800 | ``b,'' and @code{syntax-table} for a comment that should be ended by a | |
801 | generic comment delimiter character. | |
802 | ||
803 | @item | |
804 | The string or comment start position. While inside a comment, this is | |
805 | the position where the comment began; while inside a string, this is the | |
806 | position where the string began. When outside of strings and comments, | |
807 | this element is @code{nil}. | |
808 | ||
809 | @item | |
810 | Internal data for continuing the parsing. The meaning of this | |
811 | data is subject to change; it is used if you pass this list | |
812 | as the @var{state} argument to another call. | |
813 | @end enumerate | |
814 | ||
815 | Elements 1, 2, and 6 are ignored in a state which you pass as an | |
816 | argument to continue parsing, and elements 8 and 9 are used only in | |
817 | trivial cases. Those elements serve primarily to convey information | |
818 | to the Lisp program which does the parsing. | |
819 | ||
820 | One additional piece of useful information is available from a | |
821 | parser state using this function: | |
822 | ||
823 | @defun syntax-ppss-toplevel-pos state | |
824 | This function extracts, from parser state @var{state}, the last | |
825 | position scanned in the parse which was at top level in grammatical | |
826 | structure. ``At top level'' means outside of any parentheses, | |
827 | comments, or strings. | |
828 | ||
829 | The value is @code{nil} if @var{state} represents a parse which has | |
830 | arrived at a top level position. | |
831 | @end defun | |
832 | ||
833 | We have provided this access function rather than document how the | |
834 | data is represented in the state, because we plan to change the | |
835 | representation in the future. | |
836 | ||
837 | @node Low-Level Parsing | |
838 | @subsection Low-Level Parsing | |
839 | ||
840 | The most basic way to use the expression parser is to tell it | |
841 | to start at a given position with a certain state, and parse up to | |
842 | a specified end position. | |
843 | ||
844 | @defun parse-partial-sexp start limit &optional target-depth stop-before state stop-comment | |
845 | This function parses a sexp in the current buffer starting at | |
846 | @var{start}, not scanning past @var{limit}. It stops at position | |
847 | @var{limit} or when certain criteria described below are met, and sets | |
848 | point to the location where parsing stops. It returns a parser state | |
849 | describing the status of the parse at the point where it stops. | |
850 | ||
851 | @cindex parenthesis depth | |
852 | If the third argument @var{target-depth} is non-@code{nil}, parsing | |
853 | stops if the depth in parentheses becomes equal to @var{target-depth}. | |
854 | The depth starts at 0, or at whatever is given in @var{state}. | |
855 | ||
856 | If the fourth argument @var{stop-before} is non-@code{nil}, parsing | |
857 | stops when it comes to any character that starts a sexp. If | |
858 | @var{stop-comment} is non-@code{nil}, parsing stops when it comes to the | |
859 | start of a comment. If @var{stop-comment} is the symbol | |
860 | @code{syntax-table}, parsing stops after the start of a comment or a | |
861 | string, or the end of a comment or a string, whichever comes first. | |
862 | ||
863 | If @var{state} is @code{nil}, @var{start} is assumed to be at the top | |
864 | level of parenthesis structure, such as the beginning of a function | |
865 | definition. Alternatively, you might wish to resume parsing in the | |
866 | middle of the structure. To do this, you must provide a @var{state} | |
867 | argument that describes the initial status of parsing. The value | |
868 | returned by a previous call to @code{parse-partial-sexp} will do | |
869 | nicely. | |
870 | @end defun | |
871 | ||
872 | @node Control Parsing | |
873 | @subsection Parameters to Control Parsing | |
874 | ||
875 | @defvar multibyte-syntax-as-symbol | |
876 | If this variable is non-@code{nil}, @code{scan-sexps} treats all | |
877 | non-@acronym{ASCII} characters as symbol constituents regardless | |
878 | of what the syntax table says about them. (However, text properties | |
879 | can still override the syntax.) | |
880 | @end defvar | |
881 | ||
882 | @defopt parse-sexp-ignore-comments | |
883 | @cindex skipping comments | |
884 | If the value is non-@code{nil}, then comments are treated as | |
885 | whitespace by the functions in this section and by @code{forward-sexp}, | |
886 | @code{scan-lists} and @code{scan-sexps}. | |
887 | @end defopt | |
888 | ||
889 | @vindex parse-sexp-lookup-properties | |
890 | The behavior of @code{parse-partial-sexp} is also affected by | |
891 | @code{parse-sexp-lookup-properties} (@pxref{Syntax Properties}). | |
892 | ||
893 | You can use @code{forward-comment} to move forward or backward over | |
894 | one comment or several comments. | |
895 | ||
896 | @node Standard Syntax Tables | |
897 | @section Some Standard Syntax Tables | |
898 | ||
899 | Most of the major modes in Emacs have their own syntax tables. Here | |
900 | are several of them: | |
901 | ||
902 | @defun standard-syntax-table | |
903 | This function returns the standard syntax table, which is the syntax | |
904 | table used in Fundamental mode. | |
905 | @end defun | |
906 | ||
907 | @defvar text-mode-syntax-table | |
908 | The value of this variable is the syntax table used in Text mode. | |
909 | @end defvar | |
910 | ||
911 | @defvar c-mode-syntax-table | |
912 | The value of this variable is the syntax table for C-mode buffers. | |
913 | @end defvar | |
914 | ||
915 | @defvar emacs-lisp-mode-syntax-table | |
916 | The value of this variable is the syntax table used in Emacs Lisp mode | |
917 | by editing commands. (It has no effect on the Lisp @code{read} | |
918 | function.) | |
919 | @end defvar | |
920 | ||
921 | @node Syntax Table Internals | |
922 | @section Syntax Table Internals | |
923 | @cindex syntax table internals | |
924 | ||
925 | Lisp programs don't usually work with the elements directly; the | |
926 | Lisp-level syntax table functions usually work with syntax descriptors | |
927 | (@pxref{Syntax Descriptors}). Nonetheless, here we document the | |
928 | internal format. This format is used mostly when manipulating | |
929 | syntax properties. | |
930 | ||
931 | Each element of a syntax table is a cons cell of the form | |
932 | @code{(@var{syntax-code} . @var{matching-char})}. The @sc{car}, | |
933 | @var{syntax-code}, is an integer that encodes the syntax class, and any | |
934 | flags. The @sc{cdr}, @var{matching-char}, is non-@code{nil} if | |
935 | a character to match was specified. | |
936 | ||
937 | This table gives the value of @var{syntax-code} which corresponds | |
938 | to each syntactic type. | |
939 | ||
940 | @multitable @columnfractions .05 .3 .3 .31 | |
941 | @item | |
942 | @tab | |
943 | @i{Integer} @i{Class} | |
944 | @tab | |
945 | @i{Integer} @i{Class} | |
946 | @tab | |
947 | @i{Integer} @i{Class} | |
948 | @item | |
949 | @tab | |
950 | 0 @ @ whitespace | |
951 | @tab | |
952 | 5 @ @ close parenthesis | |
953 | @tab | |
954 | 10 @ @ character quote | |
955 | @item | |
956 | @tab | |
957 | 1 @ @ punctuation | |
958 | @tab | |
959 | 6 @ @ expression prefix | |
960 | @tab | |
961 | 11 @ @ comment-start | |
962 | @item | |
963 | @tab | |
964 | 2 @ @ word | |
965 | @tab | |
966 | 7 @ @ string quote | |
967 | @tab | |
968 | 12 @ @ comment-end | |
969 | @item | |
970 | @tab | |
971 | 3 @ @ symbol | |
972 | @tab | |
973 | 8 @ @ paired delimiter | |
974 | @tab | |
975 | 13 @ @ inherit | |
976 | @item | |
977 | @tab | |
978 | 4 @ @ open parenthesis | |
979 | @tab | |
980 | 9 @ @ escape | |
981 | @tab | |
982 | 14 @ @ generic comment | |
983 | @item | |
984 | @tab | |
985 | 15 @ generic string | |
986 | @end multitable | |
987 | ||
988 | For example, the usual syntax value for @samp{(} is @code{(4 . 41)}. | |
989 | (41 is the character code for @samp{)}.) | |
990 | ||
991 | The flags are encoded in higher order bits, starting 16 bits from the | |
992 | least significant bit. This table gives the power of two which | |
993 | corresponds to each syntax flag. | |
994 | ||
995 | @multitable @columnfractions .05 .3 .3 .3 | |
996 | @item | |
997 | @tab | |
998 | @i{Prefix} @i{Flag} | |
999 | @tab | |
1000 | @i{Prefix} @i{Flag} | |
1001 | @tab | |
1002 | @i{Prefix} @i{Flag} | |
1003 | @item | |
1004 | @tab | |
1005 | @samp{1} @ @ @code{(lsh 1 16)} | |
1006 | @tab | |
1007 | @samp{4} @ @ @code{(lsh 1 19)} | |
1008 | @tab | |
1009 | @samp{b} @ @ @code{(lsh 1 21)} | |
1010 | @item | |
1011 | @tab | |
1012 | @samp{2} @ @ @code{(lsh 1 17)} | |
1013 | @tab | |
1014 | @samp{p} @ @ @code{(lsh 1 20)} | |
1015 | @tab | |
1016 | @samp{n} @ @ @code{(lsh 1 22)} | |
1017 | @item | |
1018 | @tab | |
1019 | @samp{3} @ @ @code{(lsh 1 18)} | |
1020 | @end multitable | |
1021 | ||
1022 | @defun string-to-syntax @var{desc} | |
1023 | This function returns the internal form corresponding to the syntax | |
1024 | descriptor @var{desc}, a cons cell @code{(@var{syntax-code} | |
1025 | . @var{matching-char})}. | |
1026 | @end defun | |
1027 | ||
1028 | @defun syntax-after pos | |
1029 | This function returns the syntax code of the character in the buffer | |
1030 | after position @var{pos}, taking account of syntax properties as well | |
1031 | as the syntax table. If @var{pos} is outside the buffer's accessible | |
1032 | portion (@pxref{Narrowing, accessible portion}), this function returns | |
1033 | @code{nil}. | |
1034 | @end defun | |
1035 | ||
1036 | @defun syntax-class syntax | |
1037 | This function returns the syntax class of the syntax code | |
1038 | @var{syntax}. (It masks off the high 16 bits that hold the flags | |
1039 | encoded in the syntax descriptor.) If @var{syntax} is @code{nil}, it | |
1040 | returns @code{nil}; this is so evaluating the expression | |
1041 | ||
1042 | @example | |
1043 | (syntax-class (syntax-after pos)) | |
1044 | @end example | |
1045 | ||
1046 | @noindent | |
1047 | where @code{pos} is outside the buffer's accessible portion, will | |
1048 | yield @code{nil} without throwing errors or producing wrong syntax | |
1049 | class codes. | |
1050 | @end defun | |
1051 | ||
1052 | @node Categories | |
1053 | @section Categories | |
1054 | @cindex categories of characters | |
1055 | @cindex character categories | |
1056 | ||
1057 | @dfn{Categories} provide an alternate way of classifying characters | |
1058 | syntactically. You can define several categories as needed, then | |
1059 | independently assign each character to one or more categories. Unlike | |
1060 | syntax classes, categories are not mutually exclusive; it is normal for | |
1061 | one character to belong to several categories. | |
1062 | ||
1063 | @cindex category table | |
1064 | Each buffer has a @dfn{category table} which records which categories | |
1065 | are defined and also which characters belong to each category. Each | |
1066 | category table defines its own categories, but normally these are | |
1067 | initialized by copying from the standard categories table, so that the | |
1068 | standard categories are available in all modes. | |
1069 | ||
1070 | Each category has a name, which is an @acronym{ASCII} printing character in | |
1071 | the range @w{@samp{ }} to @samp{~}. You specify the name of a category | |
1072 | when you define it with @code{define-category}. | |
1073 | ||
1074 | The category table is actually a char-table (@pxref{Char-Tables}). | |
1075 | The element of the category table at index @var{c} is a @dfn{category | |
1076 | set}---a bool-vector---that indicates which categories character @var{c} | |
1077 | belongs to. In this category set, if the element at index @var{cat} is | |
1078 | @code{t}, that means category @var{cat} is a member of the set, and that | |
1079 | character @var{c} belongs to category @var{cat}. | |
1080 | ||
1081 | For the next three functions, the optional argument @var{table} | |
1082 | defaults to the current buffer's category table. | |
1083 | ||
1084 | @defun define-category char docstring &optional table | |
1085 | This function defines a new category, with name @var{char} and | |
1086 | documentation @var{docstring}, for the category table @var{table}. | |
1ea897d5 EZ |
1087 | |
1088 | Here's an example of defining a new category for characters that have | |
1089 | strong right-to-left directionality (@pxref{Bidirectional Display}) | |
1090 | and using it in a special category table: | |
1091 | ||
1092 | @example | |
1093 | (defvar special-category-table-for-bidi | |
1094 | (let ((category-table (make-category-table)) | |
1095 | (uniprop-table (unicode-property-table-internal 'bidi-class))) | |
1096 | (define-category ?R "Characters of bidi-class R, AL, or RLO" | |
1097 | category-table) | |
1098 | (map-char-table | |
1099 | #'(lambda (key val) | |
1100 | (if (memq val '(R AL RLO)) | |
1101 | (modify-category-entry key ?R category-table))) | |
1102 | uniprop-table) | |
1103 | category-table)) | |
1104 | @end example | |
b8d4c8d0 GM |
1105 | @end defun |
1106 | ||
1107 | @defun category-docstring category &optional table | |
1108 | This function returns the documentation string of category @var{category} | |
1109 | in category table @var{table}. | |
1110 | ||
1111 | @example | |
1112 | (category-docstring ?a) | |
1113 | @result{} "ASCII" | |
1114 | (category-docstring ?l) | |
1115 | @result{} "Latin" | |
1116 | @end example | |
1117 | @end defun | |
1118 | ||
1119 | @defun get-unused-category &optional table | |
1120 | This function returns a category name (a character) which is not | |
1121 | currently defined in @var{table}. If all possible categories are in use | |
1122 | in @var{table}, it returns @code{nil}. | |
1123 | @end defun | |
1124 | ||
1125 | @defun category-table | |
1126 | This function returns the current buffer's category table. | |
1127 | @end defun | |
1128 | ||
1129 | @defun category-table-p object | |
1130 | This function returns @code{t} if @var{object} is a category table, | |
1131 | otherwise @code{nil}. | |
1132 | @end defun | |
1133 | ||
1134 | @defun standard-category-table | |
1135 | This function returns the standard category table. | |
1136 | @end defun | |
1137 | ||
1138 | @defun copy-category-table &optional table | |
1139 | This function constructs a copy of @var{table} and returns it. If | |
1140 | @var{table} is not supplied (or is @code{nil}), it returns a copy of the | |
1141 | standard category table. Otherwise, an error is signaled if @var{table} | |
1142 | is not a category table. | |
1143 | @end defun | |
1144 | ||
1145 | @defun set-category-table table | |
1146 | This function makes @var{table} the category table for the current | |
1147 | buffer. It returns @var{table}. | |
1148 | @end defun | |
1149 | ||
1150 | @defun make-category-table | |
1151 | This creates and returns an empty category table. In an empty category | |
1152 | table, no categories have been allocated, and no characters belong to | |
1153 | any categories. | |
1154 | @end defun | |
1155 | ||
1156 | @defun make-category-set categories | |
1157 | This function returns a new category set---a bool-vector---whose initial | |
1158 | contents are the categories listed in the string @var{categories}. The | |
1159 | elements of @var{categories} should be category names; the new category | |
1160 | set has @code{t} for each of those categories, and @code{nil} for all | |
1161 | other categories. | |
1162 | ||
1163 | @example | |
1164 | (make-category-set "al") | |
1165 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1166 | @end example | |
1167 | @end defun | |
1168 | ||
1169 | @defun char-category-set char | |
1170 | This function returns the category set for character @var{char} in the | |
1171 | current buffer's category table. This is the bool-vector which | |
1172 | records which categories the character @var{char} belongs to. The | |
1173 | function @code{char-category-set} does not allocate storage, because | |
1174 | it returns the same bool-vector that exists in the category table. | |
1175 | ||
1176 | @example | |
1177 | (char-category-set ?a) | |
1178 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1179 | @end example | |
1180 | @end defun | |
1181 | ||
1182 | @defun category-set-mnemonics category-set | |
1183 | This function converts the category set @var{category-set} into a string | |
1184 | containing the characters that designate the categories that are members | |
1185 | of the set. | |
1186 | ||
1187 | @example | |
1188 | (category-set-mnemonics (char-category-set ?a)) | |
1189 | @result{} "al" | |
1190 | @end example | |
1191 | @end defun | |
1192 | ||
f147ff75 CY |
1193 | @defun modify-category-entry char category &optional table reset |
1194 | This function modifies the category set of @var{char} in category | |
b8d4c8d0 | 1195 | table @var{table} (which defaults to the current buffer's category |
f147ff75 CY |
1196 | table). @var{char} can be a character, or a cons cell of the form |
1197 | @code{(@var{min} . @var{max})}; in the latter case, the function | |
1198 | modifies the category sets of all characters in the range between | |
1199 | @var{min} and @var{max}, inclusive. | |
b8d4c8d0 | 1200 | |
f147ff75 | 1201 | Normally, it modifies a category set by adding @var{category} to it. |
b8d4c8d0 GM |
1202 | But if @var{reset} is non-@code{nil}, then it deletes @var{category} |
1203 | instead. | |
1204 | @end defun | |
1205 | ||
1206 | @deffn Command describe-categories &optional buffer-or-name | |
1207 | This function describes the category specifications in the current | |
1208 | category table. It inserts the descriptions in a buffer, and then | |
1209 | displays that buffer. If @var{buffer-or-name} is non-@code{nil}, it | |
1210 | describes the category table of that buffer instead. | |
1211 | @end deffn |