Commit | Line | Data |
---|---|---|
7015aca4 RS |
1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
b3d90e46 GM |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, |
4 | @c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. | |
7015aca4 RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/syntax | |
7 | @node Syntax Tables, Abbrevs, Searching and Matching, Top | |
8 | @chapter Syntax Tables | |
c9b965bd | 9 | @cindex parsing buffer text |
7015aca4 RS |
10 | @cindex syntax table |
11 | @cindex text parsing | |
12 | ||
13 | A @dfn{syntax table} specifies the syntactic textual function of each | |
a9f0a989 | 14 | character. This information is used by the @dfn{parsing functions}, the |
7015aca4 RS |
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}) | |
f9f59935 | 18 | and the list motion functions (@pxref{List Motion}), as well as the |
7015aca4 RS |
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. | |
f9f59935 | 25 | * Syntax Properties:: Overriding syntax with text properties. |
7015aca4 RS |
26 | * Motion and Syntax:: Moving over characters with certain syntaxes. |
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. | |
f9f59935 | 31 | * Categories:: Another way of classifying character syntax. |
7015aca4 RS |
32 | @end menu |
33 | ||
34 | @node Syntax Basics | |
35 | @section Syntax Table Concepts | |
36 | ||
37680279 | 37 | @ifnottex |
7015aca4 RS |
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. | |
37680279 | 46 | @end ifnottex |
7015aca4 | 47 | |
969fe9b5 RS |
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. | |
7015aca4 RS |
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 | |
969fe9b5 RS |
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.) | |
7015aca4 RS |
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 | |
7fd1911a | 65 | that uses that mode. Changing this table alters the syntax in all |
7015aca4 RS |
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 | |
f9f59935 | 74 | the standard syntax table.'' Just changing the standard syntax for a |
8241495d | 75 | character affects all syntax tables that inherit from it. |
7015aca4 RS |
76 | |
77 | @defun syntax-table-p object | |
f9f59935 | 78 | This function returns @code{t} if @var{object} is a syntax table. |
7015aca4 RS |
79 | @end defun |
80 | ||
81 | @node Syntax Descriptors | |
82 | @section Syntax Descriptors | |
c9b965bd | 83 | @cindex syntax class |
7015aca4 RS |
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 | |
969fe9b5 | 88 | @code{modify-syntax-entry} to specify the syntax you want. |
7015aca4 | 89 | |
969fe9b5 RS |
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. | |
7015aca4 | 93 | |
7fd1911a | 94 | Each class is designated by a mnemonic character, which serves as the |
7015aca4 | 95 | name of the class when you need to specify a class. Usually the |
8241495d | 96 | designator character is one that is often assigned that class; however, |
7fd1911a | 97 | its meaning as a designator is unvarying and independent of what syntax |
8241495d RS |
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. | |
7015aca4 RS |
101 | |
102 | @cindex syntax descriptor | |
7fd1911a | 103 | A syntax descriptor is a Lisp string that specifies a syntax class, a |
7015aca4 RS |
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 | ||
f9f59935 RS |
110 | For example, the syntax descriptor for the character @samp{*} in C |
111 | mode is @samp{@w{. 23}} (i.e., punctuation, matching character slot | |
8241495d | 112 | unused, second character of a comment-starter, first character of a |
7015aca4 RS |
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 | ||
7fd1911a | 125 | Here is a table of syntax classes, the characters that stand for them, |
7015aca4 RS |
126 | their meanings, and examples of their use. |
127 | ||
128 | @deffn {Syntax class} @w{whitespace character} | |
f9f59935 | 129 | @dfn{Whitespace characters} (designated by @w{@samp{@ }} or @samp{-}) |
7015aca4 RS |
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, | |
969fe9b5 RS |
133 | newline and formfeed are classified as whitespace in almost all major |
134 | modes. | |
7015aca4 RS |
135 | @end deffn |
136 | ||
137 | @deffn {Syntax class} @w{word constituent} | |
ca50933a RS |
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. | |
7015aca4 RS |
142 | @end deffn |
143 | ||
144 | @deffn {Syntax class} @w{symbol constituent} | |
f9f59935 | 145 | @dfn{Symbol constituents} (designated by @samp{_}) are the extra |
7015aca4 RS |
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} | |
f9f59935 RS |
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. | |
8a2f014e | 158 | Some programming language modes, such as Emacs Lisp mode, have no |
f9f59935 | 159 | characters in this class since the few characters that are not symbol or |
8a2f014e RS |
160 | word constituents all have other uses. Other programming language modes, |
161 | such as C mode, use punctuation syntax for operators. | |
7015aca4 RS |
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 | ||
f9f59935 RS |
175 | The class of open parentheses is designated by @samp{(}, and that of |
176 | close parentheses by @samp{)}. | |
7015aca4 RS |
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} | |
f9f59935 | 185 | @dfn{String quote characters} (designated by @samp{"}) are used in |
7015aca4 RS |
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 | ||
c9b965bd | 206 | @deffn {Syntax class} @w{escape-syntax character} |
f9f59935 | 207 | An @dfn{escape character} (designated by @samp{\}) starts an escape |
7015aca4 RS |
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} | |
f9f59935 | 218 | A @dfn{character quote character} (designated by @samp{/}) quotes the |
7015aca4 RS |
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 | ||
e30ab160 | 226 | This class is used for backslash in @TeX{} mode. |
7015aca4 RS |
227 | @end deffn |
228 | ||
229 | @deffn {Syntax class} @w{paired delimiter} | |
f9f59935 | 230 | @dfn{Paired delimiter characters} (designated by @samp{$}) are like |
7015aca4 RS |
231 | string quote characters except that the syntactic properties of the |
232 | characters between the delimiters are not suppressed. Only @TeX{} mode | |
7fd1911a RS |
233 | uses a paired delimiter presently---the @samp{$} that both enters and |
234 | leaves math mode. | |
7015aca4 RS |
235 | @end deffn |
236 | ||
237 | @deffn {Syntax class} @w{expression prefix} | |
f9f59935 RS |
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). | |
7015aca4 RS |
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 | |
f9f59935 | 250 | by @samp{<} and @samp{>}, respectively. |
7015aca4 RS |
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 | ||
c9b965bd | 256 | @deffn {Syntax class} @w{inherit standard syntax} |
f9f59935 RS |
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 | |
b5305167 | 259 | designator for this syntax class is @samp{@@}. |
7015aca4 RS |
260 | @end deffn |
261 | ||
f9f59935 | 262 | @deffn {Syntax class} @w{generic comment delimiter} |
d1f08d85 SM |
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. | |
f9f59935 RS |
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} | |
d1f08d85 SM |
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. | |
f9f59935 RS |
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 | ||
7015aca4 RS |
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 | |
79ddc9c9 GM |
294 | can specify flags. There are seven possible flags, represented by the |
295 | characters @samp{1}, @samp{2}, @samp{3}, @samp{4}, @samp{b}, @samp{n}, | |
296 | and @samp{p}. | |
297 | ||
298 | All the flags except @samp{n} and @samp{p} are used to describe | |
299 | multi-character comment delimiters. The digit flags indicate that a | |
300 | character can @emph{also} be part of a comment sequence, in addition to | |
301 | the syntactic properties associated with its character class. The flags | |
302 | are independent of the class and each other for the sake of characters | |
303 | such as @samp{*} in C mode, which is a punctuation character, @emph{and} | |
304 | the second character of a start-of-comment sequence (@samp{/*}), | |
305 | @emph{and} the first character of an end-of-comment sequence | |
306 | (@samp{*/}). | |
7015aca4 | 307 | |
f9f59935 RS |
308 | Here is a table of the possible flags for a character @var{c}, |
309 | and what they mean: | |
7015aca4 RS |
310 | |
311 | @itemize @bullet | |
312 | @item | |
7fd1911a | 313 | @samp{1} means @var{c} is the start of a two-character comment-start |
7015aca4 RS |
314 | sequence. |
315 | ||
316 | @item | |
317 | @samp{2} means @var{c} is the second character of such a sequence. | |
318 | ||
319 | @item | |
7fd1911a | 320 | @samp{3} means @var{c} is the start of a two-character comment-end |
7015aca4 RS |
321 | sequence. |
322 | ||
323 | @item | |
324 | @samp{4} means @var{c} is the second character of such a sequence. | |
325 | ||
326 | @item | |
327 | @c Emacs 19 feature | |
328 | @samp{b} means that @var{c} as a comment delimiter belongs to the | |
329 | alternative ``b'' comment style. | |
330 | ||
331 | Emacs supports two comment styles simultaneously in any one syntax | |
332 | table. This is for the sake of C++. Each style of comment syntax has | |
333 | its own comment-start sequence and its own comment-end sequence. Each | |
334 | comment must stick to one style or the other; thus, if it starts with | |
827b7ee7 RS |
335 | the comment-start sequence of style ``b,'' it must also end with the |
336 | comment-end sequence of style ``b.'' | |
7015aca4 RS |
337 | |
338 | The two comment-start sequences must begin with the same character; only | |
339 | the second character may differ. Mark the second character of the | |
7fd1911a | 340 | ``b''-style comment-start sequence with the @samp{b} flag. |
7015aca4 RS |
341 | |
342 | A comment-end sequence (one or two characters) applies to the ``b'' | |
343 | style if its first character has the @samp{b} flag set; otherwise, it | |
344 | applies to the ``a'' style. | |
345 | ||
346 | The appropriate comment syntax settings for C++ are as follows: | |
347 | ||
348 | @table @asis | |
349 | @item @samp{/} | |
350 | @samp{124b} | |
351 | @item @samp{*} | |
352 | @samp{23} | |
353 | @item newline | |
354 | @samp{>b} | |
355 | @end table | |
356 | ||
7fd1911a RS |
357 | This defines four comment-delimiting sequences: |
358 | ||
359 | @table @asis | |
360 | @item @samp{/*} | |
361 | This is a comment-start sequence for ``a'' style because the | |
362 | second character, @samp{*}, does not have the @samp{b} flag. | |
363 | ||
364 | @item @samp{//} | |
365 | This is a comment-start sequence for ``b'' style because the second | |
366 | character, @samp{/}, does have the @samp{b} flag. | |
367 | ||
368 | @item @samp{*/} | |
369 | This is a comment-end sequence for ``a'' style because the first | |
1911e6e5 | 370 | character, @samp{*}, does not have the @samp{b} flag. |
7fd1911a RS |
371 | |
372 | @item newline | |
373 | This is a comment-end sequence for ``b'' style, because the newline | |
374 | character has the @samp{b} flag. | |
375 | @end table | |
7015aca4 | 376 | |
79ddc9c9 GM |
377 | @item |
378 | @samp{n} on a comment delimiter character specifies | |
379 | that this kind of comment can be nested. For a two-character | |
380 | comment delimiter, @samp{n} on either character makes it | |
381 | nestable. | |
382 | ||
7015aca4 RS |
383 | @item |
384 | @c Emacs 19 feature | |
385 | @samp{p} identifies an additional ``prefix character'' for Lisp syntax. | |
386 | These characters are treated as whitespace when they appear between | |
387 | expressions. When they appear within an expression, they are handled | |
b5305167 | 388 | according to their usual syntax classes. |
7015aca4 RS |
389 | |
390 | The function @code{backward-prefix-chars} moves back over these | |
391 | characters, as well as over characters whose primary syntax class is | |
392 | prefix (@samp{'}). @xref{Motion and Syntax}. | |
393 | @end itemize | |
394 | ||
395 | @node Syntax Table Functions | |
396 | @section Syntax Table Functions | |
397 | ||
398 | In this section we describe functions for creating, accessing and | |
399 | altering syntax tables. | |
400 | ||
9c5609e8 LT |
401 | @defun make-syntax-table &optional table |
402 | This function creates a new syntax table, with all values initialized | |
403 | to @code{nil}. If @var{table} is non-@code{nil}, it becomes the | |
404 | parent of the new syntax table, otherwise the standard syntax table is | |
405 | the parent. Like all char-tables, a syntax table inherits from its | |
406 | parent. Thus the original syntax of all characters in the returned | |
407 | syntax table is determined by the parent. @xref{Char-Tables}. | |
7015aca4 RS |
408 | |
409 | Most major mode syntax tables are created in this way. | |
410 | @end defun | |
411 | ||
412 | @defun copy-syntax-table &optional table | |
413 | This function constructs a copy of @var{table} and returns it. If | |
414 | @var{table} is not supplied (or is @code{nil}), it returns a copy of the | |
9c5609e8 | 415 | standard syntax table. Otherwise, an error is signaled if @var{table} is |
7015aca4 RS |
416 | not a syntax table. |
417 | @end defun | |
418 | ||
419 | @deffn Command modify-syntax-entry char syntax-descriptor &optional table | |
420 | This function sets the syntax entry for @var{char} according to | |
421 | @var{syntax-descriptor}. The syntax is changed only for @var{table}, | |
422 | which defaults to the current buffer's syntax table, and not in any | |
423 | other syntax table. The argument @var{syntax-descriptor} specifies the | |
424 | desired syntax; this is a string beginning with a class designator | |
425 | character, and optionally containing a matching character and flags as | |
426 | well. @xref{Syntax Descriptors}. | |
427 | ||
428 | This function always returns @code{nil}. The old syntax information in | |
429 | the table for this character is discarded. | |
430 | ||
431 | An error is signaled if the first character of the syntax descriptor is not | |
9c5609e8 | 432 | one of the seventeen syntax class designator characters. An error is also |
7015aca4 RS |
433 | signaled if @var{char} is not a character. |
434 | ||
435 | @example | |
436 | @group | |
437 | @exdent @r{Examples:} | |
438 | ||
439 | ;; @r{Put the space character in class whitespace.} | |
2b01bb55 | 440 | (modify-syntax-entry ?\s " ") |
7015aca4 RS |
441 | @result{} nil |
442 | @end group | |
443 | ||
444 | @group | |
445 | ;; @r{Make @samp{$} an open parenthesis character,} | |
446 | ;; @r{with @samp{^} as its matching close.} | |
447 | (modify-syntax-entry ?$ "(^") | |
448 | @result{} nil | |
449 | @end group | |
450 | ||
451 | @group | |
452 | ;; @r{Make @samp{^} a close parenthesis character,} | |
453 | ;; @r{with @samp{$} as its matching open.} | |
454 | (modify-syntax-entry ?^ ")$") | |
455 | @result{} nil | |
456 | @end group | |
457 | ||
458 | @group | |
459 | ;; @r{Make @samp{/} a punctuation character,} | |
460 | ;; @r{the first character of a start-comment sequence,} | |
461 | ;; @r{and the second character of an end-comment sequence.} | |
462 | ;; @r{This is used in C mode.} | |
7fd1911a | 463 | (modify-syntax-entry ?/ ". 14") |
7015aca4 RS |
464 | @result{} nil |
465 | @end group | |
466 | @end example | |
467 | @end deffn | |
468 | ||
469 | @defun char-syntax character | |
470 | This function returns the syntax class of @var{character}, represented | |
f9f59935 | 471 | by its mnemonic designator character. This returns @emph{only} the |
7015aca4 RS |
472 | class, not any matching parenthesis or flags. |
473 | ||
474 | An error is signaled if @var{char} is not a character. | |
475 | ||
476 | The following examples apply to C mode. The first example shows that | |
477 | the syntax class of space is whitespace (represented by a space). The | |
478 | second example shows that the syntax of @samp{/} is punctuation. This | |
7fd1911a RS |
479 | does not show the fact that it is also part of comment-start and -end |
480 | sequences. The third example shows that open parenthesis is in the class | |
7015aca4 RS |
481 | of open parentheses. This does not show the fact that it has a matching |
482 | character, @samp{)}. | |
483 | ||
484 | @example | |
485 | @group | |
2b01bb55 | 486 | (string (char-syntax ?\s)) |
7015aca4 RS |
487 | @result{} " " |
488 | @end group | |
489 | ||
490 | @group | |
969fe9b5 | 491 | (string (char-syntax ?/)) |
7015aca4 RS |
492 | @result{} "." |
493 | @end group | |
494 | ||
495 | @group | |
969fe9b5 | 496 | (string (char-syntax ?\()) |
7015aca4 RS |
497 | @result{} "(" |
498 | @end group | |
499 | @end example | |
969fe9b5 RS |
500 | |
501 | We use @code{string} to make it easier to see the character returned by | |
502 | @code{char-syntax}. | |
7015aca4 RS |
503 | @end defun |
504 | ||
505 | @defun set-syntax-table table | |
506 | This function makes @var{table} the syntax table for the current buffer. | |
507 | It returns @var{table}. | |
508 | @end defun | |
509 | ||
510 | @defun syntax-table | |
511 | This function returns the current syntax table, which is the table for | |
512 | the current buffer. | |
513 | @end defun | |
514 | ||
099829c3 | 515 | @defmac with-syntax-table @var{table} @var{body}@dots{} |
2468d0c0 DL |
516 | This macro executes @var{body} using @var{table} as the current syntax |
517 | table. It returns the value of the last form in @var{body}, after | |
518 | restoring the old current syntax table. | |
519 | ||
520 | Since each buffer has its own current syntax table, we should make that | |
521 | more precise: @code{with-syntax-table} temporarily alters the current | |
522 | syntax table of whichever buffer is current at the time the macro | |
523 | execution starts. Other buffers are not affected. | |
524 | @end defmac | |
525 | ||
f9f59935 RS |
526 | @node Syntax Properties |
527 | @section Syntax Properties | |
528 | @kindex syntax-table @r{(text property)} | |
529 | ||
51750684 LK |
530 | When the syntax table is not flexible enough to specify the syntax of |
531 | a language, you can use @code{syntax-table} text properties to | |
532 | override the syntax table for specific character occurrences in the | |
533 | buffer. @xref{Text Properties}. You can use Font Lock mode to set | |
534 | @code{syntax-table} text properties. @xref{Setting Syntax | |
535 | Properties}. | |
f9f59935 | 536 | |
969fe9b5 | 537 | The valid values of @code{syntax-table} text property are: |
f9f59935 RS |
538 | |
539 | @table @asis | |
540 | @item @var{syntax-table} | |
541 | If the property value is a syntax table, that table is used instead of | |
542 | the current buffer's syntax table to determine the syntax for this | |
543 | occurrence of the character. | |
544 | ||
545 | @item @code{(@var{syntax-code} . @var{matching-char})} | |
546 | A cons cell of this format specifies the syntax for this | |
d1f08d85 | 547 | occurrence of the character. (@pxref{Syntax Table Internals}) |
f9f59935 RS |
548 | |
549 | @item @code{nil} | |
550 | If the property is @code{nil}, the character's syntax is determined from | |
551 | the current syntax table in the usual way. | |
552 | @end table | |
553 | ||
f9f59935 RS |
554 | @defvar parse-sexp-lookup-properties |
555 | If this is non-@code{nil}, the syntax scanning functions pay attention | |
556 | to syntax text properties. Otherwise they use only the current syntax | |
557 | table. | |
558 | @end defvar | |
559 | ||
7015aca4 RS |
560 | @node Motion and Syntax |
561 | @section Motion and Syntax | |
562 | ||
969fe9b5 RS |
563 | This section describes functions for moving across characters that |
564 | have certain syntax classes. | |
7015aca4 RS |
565 | |
566 | @defun skip-syntax-forward syntaxes &optional limit | |
9c5609e8 | 567 | This function moves point forward across characters having syntax |
b5305167 | 568 | classes mentioned in @var{syntaxes} (a string of syntax class |
9c5609e8 LT |
569 | characters). It stops when it encounters the end of the buffer, or |
570 | position @var{limit} (if specified), or a character it is not supposed | |
571 | to skip. | |
8241495d RS |
572 | |
573 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
574 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
575 | ||
7015aca4 RS |
576 | The return value is the distance traveled, which is a nonnegative |
577 | integer. | |
7015aca4 RS |
578 | @end defun |
579 | ||
580 | @defun skip-syntax-backward syntaxes &optional limit | |
581 | This function moves point backward across characters whose syntax | |
582 | classes are mentioned in @var{syntaxes}. It stops when it encounters | |
8241495d RS |
583 | the beginning of the buffer, or position @var{limit} (if specified), or |
584 | a character it is not supposed to skip. | |
585 | ||
586 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
587 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
1911e6e5 | 588 | |
7015aca4 RS |
589 | The return value indicates the distance traveled. It is an integer that |
590 | is zero or less. | |
7015aca4 RS |
591 | @end defun |
592 | ||
593 | @defun backward-prefix-chars | |
594 | This function moves point backward over any number of characters with | |
595 | expression prefix syntax. This includes both characters in the | |
596 | expression prefix syntax class, and characters with the @samp{p} flag. | |
597 | @end defun | |
598 | ||
599 | @node Parsing Expressions | |
fe963f84 | 600 | @section Parsing Expressions |
7015aca4 | 601 | |
fe963f84 | 602 | This section describes functions for parsing and scanning balanced |
6cbdd38b | 603 | expressions, also known as @dfn{sexps}. Basically, a sexp is either a |
fe963f84 RS |
604 | balanced parenthetical grouping, a string, or a symbol name (a |
605 | sequence of characters whose syntax is either word constituent or | |
606 | symbol constituent). However, characters whose syntax is expression | |
607 | prefix are treated as part of the sexp if they appear next to it. | |
6cbdd38b RS |
608 | |
609 | The syntax table controls the interpretation of characters, so these | |
610 | functions can be used for Lisp expressions when in Lisp mode and for C | |
611 | expressions when in C mode. @xref{List Motion}, for convenient | |
7015aca4 RS |
612 | higher-level functions for moving over balanced expressions. |
613 | ||
fe963f84 RS |
614 | A character's syntax controls how it changes the state of the |
615 | parser, rather than describing the state itself. For example, a | |
616 | string delimiter character toggles the parser state between | |
617 | ``in-string'' and ``in-code,'' but the syntax of characters does not | |
618 | directly say whether they are inside a string. For example (note that | |
619 | 15 is the syntax code for generic string delimiters), | |
45493fb7 SM |
620 | |
621 | @example | |
622 | (put-text-property 1 9 'syntax-table '(15 . nil)) | |
623 | @end example | |
624 | ||
6cbdd38b | 625 | @noindent |
45493fb7 | 626 | does not tell Emacs that the first eight chars of the current buffer |
6cbdd38b RS |
627 | are a string, but rather that they are all string delimiters. As a |
628 | result, Emacs treats them as four consecutive empty string constants. | |
629 | ||
fe963f84 RS |
630 | @menu |
631 | * Motion via Parsing:: Motion functions that work by parsing. | |
632 | * Position Parse:: Determining the syntactic state of a position. | |
633 | * Parser State:: How Emacs represents a syntactic state. | |
634 | * Low-Level Parsing:: Parsing across a specified region. | |
635 | * Control Parsing:: Parameters that affect parsing. | |
636 | @end menu | |
45493fb7 | 637 | |
fe963f84 RS |
638 | @node Motion via Parsing |
639 | @subsection Motion Commands Based on Parsing | |
7015aca4 | 640 | |
fe963f84 RS |
641 | This section describes simple point-motion functions that operate |
642 | based on parsing expressions. | |
7015aca4 | 643 | |
fe963f84 RS |
644 | @defun scan-lists from count depth |
645 | This function scans forward @var{count} balanced parenthetical groupings | |
646 | from position @var{from}. It returns the position where the scan stops. | |
647 | If @var{count} is negative, the scan moves backwards. | |
7015aca4 | 648 | |
fe963f84 RS |
649 | If @var{depth} is nonzero, parenthesis depth counting begins from that |
650 | value. The only candidates for stopping are places where the depth in | |
651 | parentheses becomes zero; @code{scan-lists} counts @var{count} such | |
652 | places and then stops. Thus, a positive value for @var{depth} means go | |
653 | out @var{depth} levels of parenthesis. | |
654 | ||
655 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
656 | non-@code{nil}. | |
657 | ||
658 | If the scan reaches the beginning or end of the buffer (or its | |
659 | accessible portion), and the depth is not zero, an error is signaled. | |
660 | If the depth is zero but the count is not used up, @code{nil} is | |
661 | returned. | |
662 | @end defun | |
663 | ||
664 | @defun scan-sexps from count | |
665 | This function scans forward @var{count} sexps from position @var{from}. | |
666 | It returns the position where the scan stops. If @var{count} is | |
667 | negative, the scan moves backwards. | |
668 | ||
669 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
670 | non-@code{nil}. | |
671 | ||
672 | If the scan reaches the beginning or end of (the accessible part of) the | |
673 | buffer while in the middle of a parenthetical grouping, an error is | |
674 | signaled. If it reaches the beginning or end between groupings but | |
675 | before count is used up, @code{nil} is returned. | |
676 | @end defun | |
677 | ||
678 | @defun forward-comment count | |
679 | This function moves point forward across @var{count} complete comments | |
680 | (that is, including the starting delimiter and the terminating | |
681 | delimiter if any), plus any whitespace encountered on the way. It | |
682 | moves backward if @var{count} is negative. If it encounters anything | |
683 | other than a comment or whitespace, it stops, leaving point at the | |
684 | place where it stopped. This includes (for instance) finding the end | |
685 | of a comment when moving forward and expecting the beginning of one. | |
686 | The function also stops immediately after moving over the specified | |
687 | number of complete comments. If @var{count} comments are found as | |
688 | expected, with nothing except whitespace between them, it returns | |
689 | @code{t}; otherwise it returns @code{nil}. | |
690 | ||
691 | This function cannot tell whether the ``comments'' it traverses are | |
692 | embedded within a string. If they look like comments, it treats them | |
693 | as comments. | |
694 | @end defun | |
695 | ||
696 | To move forward over all comments and whitespace following point, use | |
697 | @code{(forward-comment (buffer-size))}. @code{(buffer-size)} is a good | |
698 | argument to use, because the number of comments in the buffer cannot | |
699 | exceed that many. | |
700 | ||
701 | @node Position Parse | |
702 | @subsection Finding the Parse State for a Position | |
703 | ||
704 | For syntactic analysis, such as in indentation, often the useful | |
705 | thing is to compute the syntactic state corresponding to a given buffer | |
706 | position. This function does that conveniently. | |
707 | ||
708 | @defun syntax-ppss &optional pos | |
709 | This function returns the parser state (see next section) that the | |
710 | parser would reach at position @var{pos} starting from the beginning | |
711 | of the buffer. This is equivalent to @code{(parse-partial-sexp | |
712 | (point-min) @var{pos})}, except that @code{syntax-ppss} uses a cache | |
713 | to speed up the computation. Due to this optimization, the 2nd value | |
714 | (previous complete subexpression) and 6th value (minimum parenthesis | |
715 | depth) of the returned parser state are not meaningful. | |
716 | @end defun | |
717 | ||
718 | @code{syntax-ppss} automatically hooks itself to | |
719 | @code{before-change-functions} to keep its cache consistent. But | |
720 | updating can fail if @code{syntax-ppss} is called while | |
721 | @code{before-change-functions} is temporarily let-bound, or if the | |
722 | buffer is modified without obeying the hook, such as when using | |
723 | @code{inhibit-modification-hooks}. For this reason, it is sometimes | |
724 | necessary to flush the cache manually. | |
725 | ||
726 | @defun syntax-ppss-flush-cache beg | |
727 | This function flushes the cache used by @code{syntax-ppss}, starting at | |
728 | position @var{beg}. | |
729 | @end defun | |
730 | ||
731 | Major modes can make @code{syntax-ppss} run faster by specifying | |
732 | where it needs to start parsing. | |
7015aca4 | 733 | |
fe963f84 RS |
734 | @defvar syntax-begin-function |
735 | If this is non-@code{nil}, it should be a function that moves to an | |
736 | earlier buffer position where the parser state is equivalent to | |
737 | @code{nil}---in other words, a position outside of any comment, | |
738 | string, or parenthesis. @code{syntax-ppss} uses it to further | |
739 | optimize its computations, when the cache gives no help. | |
740 | @end defvar | |
741 | ||
742 | @node Parser State | |
743 | @subsection Parser State | |
744 | @cindex parser state | |
7015aca4 | 745 | |
fe963f84 RS |
746 | A @dfn{parser state} is a list of ten elements describing the final |
747 | state of parsing text syntactically as part of an expression. The | |
748 | parsing functions in the following sections return a parser state as | |
749 | the value, and in some cases accept one as an argument also, so that | |
750 | you can resume parsing after it stops. Here are the meanings of the | |
751 | elements of the parser state: | |
7015aca4 RS |
752 | |
753 | @enumerate 0 | |
177c0ea7 | 754 | @item |
8ac3a455 RS |
755 | The depth in parentheses, counting from 0. @strong{Warning:} this can |
756 | be negative if there are more close parens than open parens between | |
757 | the start of the defun and point. | |
7015aca4 | 758 | |
177c0ea7 | 759 | @item |
7015aca4 | 760 | @cindex innermost containing parentheses |
7fd1911a RS |
761 | The character position of the start of the innermost parenthetical |
762 | grouping containing the stopping point; @code{nil} if none. | |
7015aca4 | 763 | |
177c0ea7 | 764 | @item |
7015aca4 RS |
765 | @cindex previous complete subexpression |
766 | The character position of the start of the last complete subexpression | |
767 | terminated; @code{nil} if none. | |
768 | ||
177c0ea7 | 769 | @item |
7015aca4 RS |
770 | @cindex inside string |
771 | Non-@code{nil} if inside a string. More precisely, this is the | |
f9f59935 RS |
772 | character that will terminate the string, or @code{t} if a generic |
773 | string delimiter character should terminate it. | |
7015aca4 | 774 | |
177c0ea7 | 775 | @item |
7015aca4 | 776 | @cindex inside comment |
79ddc9c9 GM |
777 | @code{t} if inside a comment (of either style), |
778 | or the comment nesting level if inside a kind of comment | |
779 | that can be nested. | |
7015aca4 | 780 | |
177c0ea7 | 781 | @item |
7015aca4 RS |
782 | @cindex quote character |
783 | @code{t} if point is just after a quote character. | |
784 | ||
177c0ea7 | 785 | @item |
7015aca4 RS |
786 | The minimum parenthesis depth encountered during this scan. |
787 | ||
788 | @item | |
9c5609e8 LT |
789 | What kind of comment is active: @code{nil} for a comment of style |
790 | ``a'' or when not inside a comment, @code{t} for a comment of style | |
827b7ee7 | 791 | ``b,'' and @code{syntax-table} for a comment that should be ended by a |
9c5609e8 | 792 | generic comment delimiter character. |
f9f59935 RS |
793 | |
794 | @item | |
795 | The string or comment start position. While inside a comment, this is | |
796 | the position where the comment began; while inside a string, this is the | |
797 | position where the string began. When outside of strings and comments, | |
798 | this element is @code{nil}. | |
7015aca4 | 799 | |
8a2f014e RS |
800 | @item |
801 | Internal data for continuing the parsing. The meaning of this | |
802 | data is subject to change; it is used if you pass this list | |
803 | as the @var{state} argument to another call. | |
8a2f014e | 804 | @end enumerate |
7015aca4 | 805 | |
fe963f84 RS |
806 | Elements 1, 2, and 6 are ignored in a state which you pass as an |
807 | argument to continue parsing, and elements 8 and 9 are used only in | |
808 | trivial cases. Those elements serve primarily to convey information | |
809 | to the Lisp program which does the parsing. | |
9c5609e8 | 810 | |
fe963f84 RS |
811 | One additional piece of useful information is available from a |
812 | parser state using this function: | |
7015aca4 | 813 | |
fe963f84 RS |
814 | @defun syntax-ppss-toplevel-pos state |
815 | This function extracts, from parser state @var{state}, the last | |
816 | position scanned in the parse which was at top level in grammatical | |
817 | structure. ``At top level'' means outside of any parentheses, | |
818 | comments, or strings. | |
b5305167 | 819 | |
fe963f84 RS |
820 | The value is @code{nil} if @var{state} represents a parse which has |
821 | arrived at a top level position. | |
f99ed2f8 SM |
822 | @end defun |
823 | ||
fe963f84 RS |
824 | We have provided this access function rather than document how the |
825 | data is represented in the state, because we plan to change the | |
826 | representation in the future. | |
7015aca4 | 827 | |
fe963f84 RS |
828 | @node Low-Level Parsing |
829 | @subsection Low-Level Parsing | |
7015aca4 | 830 | |
fe963f84 RS |
831 | The most basic way to use the expression parser is to tell it |
832 | to start at a given position with a certain state, and parse up to | |
833 | a specified end position. | |
7015aca4 | 834 | |
fe963f84 RS |
835 | @defun parse-partial-sexp start limit &optional target-depth stop-before state stop-comment |
836 | This function parses a sexp in the current buffer starting at | |
837 | @var{start}, not scanning past @var{limit}. It stops at position | |
838 | @var{limit} or when certain criteria described below are met, and sets | |
839 | point to the location where parsing stops. It returns a parser state | |
840 | describing the status of the parse at the point where it stops. | |
7015aca4 | 841 | |
fe963f84 RS |
842 | @cindex parenthesis depth |
843 | If the third argument @var{target-depth} is non-@code{nil}, parsing | |
844 | stops if the depth in parentheses becomes equal to @var{target-depth}. | |
845 | The depth starts at 0, or at whatever is given in @var{state}. | |
7015aca4 | 846 | |
fe963f84 RS |
847 | If the fourth argument @var{stop-before} is non-@code{nil}, parsing |
848 | stops when it comes to any character that starts a sexp. If | |
849 | @var{stop-comment} is non-@code{nil}, parsing stops when it comes to the | |
850 | start of a comment. If @var{stop-comment} is the symbol | |
851 | @code{syntax-table}, parsing stops after the start of a comment or a | |
852 | string, or the end of a comment or a string, whichever comes first. | |
7015aca4 | 853 | |
fe963f84 RS |
854 | If @var{state} is @code{nil}, @var{start} is assumed to be at the top |
855 | level of parenthesis structure, such as the beginning of a function | |
856 | definition. Alternatively, you might wish to resume parsing in the | |
857 | middle of the structure. To do this, you must provide a @var{state} | |
858 | argument that describes the initial status of parsing. The value | |
859 | returned by a previous call to @code{parse-partial-sexp} will do | |
860 | nicely. | |
7015aca4 RS |
861 | @end defun |
862 | ||
fe963f84 RS |
863 | @node Control Parsing |
864 | @subsection Parameters to Control Parsing | |
865 | ||
3357a32f | 866 | @defvar multibyte-syntax-as-symbol |
3357a32f | 867 | If this variable is non-@code{nil}, @code{scan-sexps} treats all |
ad800164 | 868 | non-@acronym{ASCII} characters as symbol constituents regardless |
3357a32f RS |
869 | of what the syntax table says about them. (However, text properties |
870 | can still override the syntax.) | |
871 | @end defvar | |
872 | ||
9c5609e8 | 873 | @defopt parse-sexp-ignore-comments |
7015aca4 RS |
874 | @cindex skipping comments |
875 | If the value is non-@code{nil}, then comments are treated as | |
161e8856 RS |
876 | whitespace by the functions in this section and by @code{forward-sexp}, |
877 | @code{scan-lists} and @code{scan-sexps}. | |
9c5609e8 | 878 | @end defopt |
7015aca4 | 879 | |
cf4ccadb | 880 | @vindex parse-sexp-lookup-properties |
4b53b8d7 | 881 | The behavior of @code{parse-partial-sexp} is also affected by |
075ec3c4 | 882 | @code{parse-sexp-lookup-properties} (@pxref{Syntax Properties}). |
cf4ccadb | 883 | |
7015aca4 RS |
884 | You can use @code{forward-comment} to move forward or backward over |
885 | one comment or several comments. | |
886 | ||
7015aca4 RS |
887 | @node Standard Syntax Tables |
888 | @section Some Standard Syntax Tables | |
889 | ||
bfe721d1 KH |
890 | Most of the major modes in Emacs have their own syntax tables. Here |
891 | are several of them: | |
7015aca4 RS |
892 | |
893 | @defun standard-syntax-table | |
894 | This function returns the standard syntax table, which is the syntax | |
895 | table used in Fundamental mode. | |
896 | @end defun | |
897 | ||
898 | @defvar text-mode-syntax-table | |
899 | The value of this variable is the syntax table used in Text mode. | |
900 | @end defvar | |
901 | ||
902 | @defvar c-mode-syntax-table | |
903 | The value of this variable is the syntax table for C-mode buffers. | |
904 | @end defvar | |
905 | ||
906 | @defvar emacs-lisp-mode-syntax-table | |
907 | The value of this variable is the syntax table used in Emacs Lisp mode | |
908 | by editing commands. (It has no effect on the Lisp @code{read} | |
909 | function.) | |
910 | @end defvar | |
911 | ||
912 | @node Syntax Table Internals | |
913 | @section Syntax Table Internals | |
914 | @cindex syntax table internals | |
915 | ||
f9f59935 | 916 | Lisp programs don't usually work with the elements directly; the |
7015aca4 | 917 | Lisp-level syntax table functions usually work with syntax descriptors |
f9f59935 | 918 | (@pxref{Syntax Descriptors}). Nonetheless, here we document the |
d1f08d85 SM |
919 | internal format. This format is used mostly when manipulating |
920 | syntax properties. | |
f9f59935 RS |
921 | |
922 | Each element of a syntax table is a cons cell of the form | |
923 | @code{(@var{syntax-code} . @var{matching-char})}. The @sc{car}, | |
924 | @var{syntax-code}, is an integer that encodes the syntax class, and any | |
925 | flags. The @sc{cdr}, @var{matching-char}, is non-@code{nil} if | |
926 | a character to match was specified. | |
7015aca4 | 927 | |
f9f59935 RS |
928 | This table gives the value of @var{syntax-code} which corresponds |
929 | to each syntactic type. | |
7015aca4 | 930 | |
fb056bef | 931 | @multitable @columnfractions .05 .3 .3 .31 |
a9f0a989 RS |
932 | @item |
933 | @tab | |
969fe9b5 RS |
934 | @i{Integer} @i{Class} |
935 | @tab | |
936 | @i{Integer} @i{Class} | |
937 | @tab | |
938 | @i{Integer} @i{Class} | |
a9f0a989 RS |
939 | @item |
940 | @tab | |
969fe9b5 RS |
941 | 0 @ @ whitespace |
942 | @tab | |
943 | 5 @ @ close parenthesis | |
944 | @tab | |
945 | 10 @ @ character quote | |
a9f0a989 RS |
946 | @item |
947 | @tab | |
969fe9b5 RS |
948 | 1 @ @ punctuation |
949 | @tab | |
950 | 6 @ @ expression prefix | |
951 | @tab | |
952 | 11 @ @ comment-start | |
a9f0a989 RS |
953 | @item |
954 | @tab | |
969fe9b5 RS |
955 | 2 @ @ word |
956 | @tab | |
957 | 7 @ @ string quote | |
958 | @tab | |
959 | 12 @ @ comment-end | |
a9f0a989 RS |
960 | @item |
961 | @tab | |
969fe9b5 RS |
962 | 3 @ @ symbol |
963 | @tab | |
964 | 8 @ @ paired delimiter | |
965 | @tab | |
966 | 13 @ @ inherit | |
a9f0a989 RS |
967 | @item |
968 | @tab | |
969fe9b5 RS |
969 | 4 @ @ open parenthesis |
970 | @tab | |
971 | 9 @ @ escape | |
972 | @tab | |
85c7ceaa | 973 | 14 @ @ generic comment |
a9f0a989 RS |
974 | @item |
975 | @tab | |
85c7ceaa | 976 | 15 @ generic string |
969fe9b5 | 977 | @end multitable |
7015aca4 | 978 | |
f9f59935 RS |
979 | For example, the usual syntax value for @samp{(} is @code{(4 . 41)}. |
980 | (41 is the character code for @samp{)}.) | |
981 | ||
982 | The flags are encoded in higher order bits, starting 16 bits from the | |
983 | least significant bit. This table gives the power of two which | |
984 | corresponds to each syntax flag. | |
985 | ||
969fe9b5 | 986 | @multitable @columnfractions .05 .3 .3 .3 |
a9f0a989 RS |
987 | @item |
988 | @tab | |
969fe9b5 RS |
989 | @i{Prefix} @i{Flag} |
990 | @tab | |
991 | @i{Prefix} @i{Flag} | |
992 | @tab | |
993 | @i{Prefix} @i{Flag} | |
a9f0a989 RS |
994 | @item |
995 | @tab | |
969fe9b5 RS |
996 | @samp{1} @ @ @code{(lsh 1 16)} |
997 | @tab | |
79ddc9c9 | 998 | @samp{4} @ @ @code{(lsh 1 19)} |
969fe9b5 | 999 | @tab |
79ddc9c9 | 1000 | @samp{b} @ @ @code{(lsh 1 21)} |
a9f0a989 RS |
1001 | @item |
1002 | @tab | |
969fe9b5 RS |
1003 | @samp{2} @ @ @code{(lsh 1 17)} |
1004 | @tab | |
79ddc9c9 | 1005 | @samp{p} @ @ @code{(lsh 1 20)} |
969fe9b5 | 1006 | @tab |
79ddc9c9 GM |
1007 | @samp{n} @ @ @code{(lsh 1 22)} |
1008 | @item | |
1009 | @tab | |
1010 | @samp{3} @ @ @code{(lsh 1 18)} | |
969fe9b5 | 1011 | @end multitable |
f9f59935 | 1012 | |
d1f08d85 | 1013 | @defun string-to-syntax @var{desc} |
cd64b8f1 KB |
1014 | This function returns the internal form corresponding to the syntax |
1015 | descriptor @var{desc}, a cons cell @code{(@var{syntax-code} | |
1016 | . @var{matching-char})}. | |
40153606 | 1017 | @end defun |
d1f08d85 | 1018 | |
8a2f014e RS |
1019 | @defun syntax-after pos |
1020 | This function returns the syntax code of the character in the buffer | |
1021 | after position @var{pos}, taking account of syntax properties as well | |
92426d9c EZ |
1022 | as the syntax table. If @var{pos} is outside the buffer's accessible |
1023 | portion (@pxref{Narrowing, accessible portion}), this function returns | |
1024 | @code{nil}. | |
8a2f014e RS |
1025 | @end defun |
1026 | ||
137a5ef2 | 1027 | @defun syntax-class syntax |
92426d9c EZ |
1028 | This function returns the syntax class of the syntax code |
1029 | @var{syntax}. (It masks off the high 16 bits that hold the flags | |
1030 | encoded in the syntax descriptor.) If @var{syntax} is @code{nil}, it | |
1031 | returns @code{nil}; this is so evaluating the expression | |
1032 | ||
1033 | @example | |
1034 | (syntax-class (syntax-after pos)) | |
1035 | @end example | |
1036 | ||
1037 | @noindent | |
1038 | where @code{pos} is outside the buffer's accessible portion, will | |
1039 | yield @code{nil} without throwing errors or producing wrong syntax | |
1040 | class codes. | |
137a5ef2 SM |
1041 | @end defun |
1042 | ||
f9f59935 RS |
1043 | @node Categories |
1044 | @section Categories | |
1045 | @cindex categories of characters | |
cf8b92db | 1046 | @cindex character categories |
f9f59935 RS |
1047 | |
1048 | @dfn{Categories} provide an alternate way of classifying characters | |
969fe9b5 RS |
1049 | syntactically. You can define several categories as needed, then |
1050 | independently assign each character to one or more categories. Unlike | |
f9f59935 RS |
1051 | syntax classes, categories are not mutually exclusive; it is normal for |
1052 | one character to belong to several categories. | |
1053 | ||
cf8b92db | 1054 | @cindex category table |
f9f59935 RS |
1055 | Each buffer has a @dfn{category table} which records which categories |
1056 | are defined and also which characters belong to each category. Each | |
969fe9b5 RS |
1057 | category table defines its own categories, but normally these are |
1058 | initialized by copying from the standard categories table, so that the | |
1059 | standard categories are available in all modes. | |
1060 | ||
ad800164 | 1061 | Each category has a name, which is an @acronym{ASCII} printing character in |
969fe9b5 RS |
1062 | the range @w{@samp{ }} to @samp{~}. You specify the name of a category |
1063 | when you define it with @code{define-category}. | |
f9f59935 RS |
1064 | |
1065 | The category table is actually a char-table (@pxref{Char-Tables}). | |
1066 | The element of the category table at index @var{c} is a @dfn{category | |
1067 | set}---a bool-vector---that indicates which categories character @var{c} | |
1068 | belongs to. In this category set, if the element at index @var{cat} is | |
1069 | @code{t}, that means category @var{cat} is a member of the set, and that | |
1070 | character @var{c} belongs to category @var{cat}. | |
1071 | ||
9c5609e8 LT |
1072 | For the next three functions, the optional argument @var{table} |
1073 | defaults to the current buffer's category table. | |
1074 | ||
f9f59935 RS |
1075 | @defun define-category char docstring &optional table |
1076 | This function defines a new category, with name @var{char} and | |
8a2f014e | 1077 | documentation @var{docstring}, for the category table @var{table}. |
f9f59935 RS |
1078 | @end defun |
1079 | ||
1080 | @defun category-docstring category &optional table | |
1081 | This function returns the documentation string of category @var{category} | |
1082 | in category table @var{table}. | |
1083 | ||
1084 | @example | |
1085 | (category-docstring ?a) | |
1086 | @result{} "ASCII" | |
1087 | (category-docstring ?l) | |
1088 | @result{} "Latin" | |
1089 | @end example | |
1090 | @end defun | |
1091 | ||
9c5609e8 | 1092 | @defun get-unused-category &optional table |
f9f59935 | 1093 | This function returns a category name (a character) which is not |
969fe9b5 | 1094 | currently defined in @var{table}. If all possible categories are in use |
1911e6e5 | 1095 | in @var{table}, it returns @code{nil}. |
f9f59935 RS |
1096 | @end defun |
1097 | ||
1098 | @defun category-table | |
1099 | This function returns the current buffer's category table. | |
1100 | @end defun | |
1101 | ||
1102 | @defun category-table-p object | |
1103 | This function returns @code{t} if @var{object} is a category table, | |
1104 | otherwise @code{nil}. | |
1105 | @end defun | |
1106 | ||
1107 | @defun standard-category-table | |
1108 | This function returns the standard category table. | |
1109 | @end defun | |
1110 | ||
1111 | @defun copy-category-table &optional table | |
1112 | This function constructs a copy of @var{table} and returns it. If | |
1113 | @var{table} is not supplied (or is @code{nil}), it returns a copy of the | |
9c5609e8 | 1114 | standard category table. Otherwise, an error is signaled if @var{table} |
f9f59935 RS |
1115 | is not a category table. |
1116 | @end defun | |
1117 | ||
1118 | @defun set-category-table table | |
1119 | This function makes @var{table} the category table for the current | |
1120 | buffer. It returns @var{table}. | |
1121 | @end defun | |
1122 | ||
3f26d1e6 | 1123 | @defun make-category-table |
3f26d1e6 GM |
1124 | This creates and returns an empty category table. In an empty category |
1125 | table, no categories have been allocated, and no characters belong to | |
1126 | any categories. | |
2468d0c0 DL |
1127 | @end defun |
1128 | ||
f9f59935 RS |
1129 | @defun make-category-set categories |
1130 | This function returns a new category set---a bool-vector---whose initial | |
1131 | contents are the categories listed in the string @var{categories}. The | |
1132 | elements of @var{categories} should be category names; the new category | |
1133 | set has @code{t} for each of those categories, and @code{nil} for all | |
1134 | other categories. | |
1135 | ||
1136 | @example | |
1137 | (make-category-set "al") | |
1138 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1139 | @end example | |
1140 | @end defun | |
1141 | ||
1142 | @defun char-category-set char | |
9c5609e8 LT |
1143 | This function returns the category set for character @var{char} in the |
1144 | current buffer's category table. This is the bool-vector which | |
1145 | records which categories the character @var{char} belongs to. The | |
1146 | function @code{char-category-set} does not allocate storage, because | |
1147 | it returns the same bool-vector that exists in the category table. | |
f9f59935 RS |
1148 | |
1149 | @example | |
1150 | (char-category-set ?a) | |
1151 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1152 | @end example | |
1153 | @end defun | |
1154 | ||
1155 | @defun category-set-mnemonics category-set | |
1156 | This function converts the category set @var{category-set} into a string | |
2468d0c0 DL |
1157 | containing the characters that designate the categories that are members |
1158 | of the set. | |
f9f59935 RS |
1159 | |
1160 | @example | |
1161 | (category-set-mnemonics (char-category-set ?a)) | |
1162 | @result{} "al" | |
1163 | @end example | |
1164 | @end defun | |
1165 | ||
1166 | @defun modify-category-entry character category &optional table reset | |
1167 | This function modifies the category set of @var{character} in category | |
1168 | table @var{table} (which defaults to the current buffer's category | |
1169 | table). | |
1170 | ||
1171 | Normally, it modifies the category set by adding @var{category} to it. | |
1172 | But if @var{reset} is non-@code{nil}, then it deletes @var{category} | |
1173 | instead. | |
1174 | @end defun | |
a57092e8 | 1175 | |
9c5609e8 | 1176 | @deffn Command describe-categories &optional buffer-or-name |
a57092e8 | 1177 | This function describes the category specifications in the current |
9c5609e8 LT |
1178 | category table. It inserts the descriptions in a buffer, and then |
1179 | displays that buffer. If @var{buffer-or-name} is non-@code{nil}, it | |
1180 | describes the category table of that buffer instead. | |
a57092e8 | 1181 | @end deffn |
ab5796a9 MB |
1182 | |
1183 | @ignore | |
1184 | arch-tag: 4d914e96-0283-445c-9233-75d33662908c | |
1185 | @end ignore |