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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
651f374c TTN |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003, |
4 | @c 2004, 2005 Free Software Foundation, Inc. | |
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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 | |
9 | @cindex parsing | |
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 |
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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 |
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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. |
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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. |
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32 | @end menu |
33 | ||
34 | @node Syntax Basics | |
35 | @section Syntax Table Concepts | |
36 | ||
37680279 | 37 | @ifnottex |
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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 | |
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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. | |
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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 | |
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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.) | |
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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 |
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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. |
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76 | |
77 | @defun syntax-table-p object | |
f9f59935 | 78 | This function returns @code{t} if @var{object} is a syntax table. |
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79 | @end defun |
80 | ||
81 | @node Syntax Descriptors | |
82 | @section Syntax Descriptors | |
83 | @cindex syntax classes | |
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 | |
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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 |
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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. | |
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101 | |
102 | @cindex syntax descriptor | |
7fd1911a | 103 | A syntax descriptor is a Lisp string that specifies a syntax class, a |
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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 | ||
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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 |
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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, |
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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{-}) |
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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, | |
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133 | newline and formfeed are classified as whitespace in almost all major |
134 | modes. | |
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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. | |
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142 | @end deffn |
143 | ||
144 | @deffn {Syntax class} @w{symbol constituent} | |
f9f59935 | 145 | @dfn{Symbol constituents} (designated by @samp{_}) are the extra |
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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} | |
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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 |
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160 | word constituents all have other uses. Other programming language modes, |
161 | such as C mode, use punctuation syntax for operators. | |
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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 | ||
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175 | The class of open parentheses is designated by @samp{(}, and that of |
176 | close parentheses by @samp{)}. | |
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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 |
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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} | |
f9f59935 | 207 | An @dfn{escape character} (designated by @samp{\}) starts an escape |
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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 |
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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. |
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227 | @end deffn |
228 | ||
229 | @deffn {Syntax class} @w{paired delimiter} | |
f9f59935 | 230 | @dfn{Paired delimiter characters} (designated by @samp{$}) are like |
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231 | string quote characters except that the syntactic properties of the |
232 | characters between the delimiters are not suppressed. Only @TeX{} mode | |
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233 | uses a paired delimiter presently---the @samp{$} that both enters and |
234 | leaves math mode. | |
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235 | @end deffn |
236 | ||
237 | @deffn {Syntax class} @w{expression prefix} | |
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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). | |
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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. |
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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} | |
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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{@@}. |
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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. | |
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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. | |
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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 | ||
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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 | |
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308 | Here is a table of the possible flags for a character @var{c}, |
309 | and what they mean: | |
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310 | |
311 | @itemize @bullet | |
312 | @item | |
7fd1911a | 313 | @samp{1} means @var{c} is the start of a two-character comment-start |
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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 |
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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 | |
335 | the comment-start sequence of style ``b'', it must also end with the | |
336 | comment-end sequence of style ``b''. | |
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. |
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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 | ||
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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. |
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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 | ||
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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. |
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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}. | |
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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 |
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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 |
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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 " ") |
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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") |
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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 | ||
2468d0c0 DL |
515 | @defmac with-syntax-table @var{table} @var{body}... |
516 | @tindex with-syntax-table | |
517 | This macro executes @var{body} using @var{table} as the current syntax | |
518 | table. It returns the value of the last form in @var{body}, after | |
519 | restoring the old current syntax table. | |
520 | ||
521 | Since each buffer has its own current syntax table, we should make that | |
522 | more precise: @code{with-syntax-table} temporarily alters the current | |
523 | syntax table of whichever buffer is current at the time the macro | |
524 | execution starts. Other buffers are not affected. | |
525 | @end defmac | |
526 | ||
f9f59935 RS |
527 | @node Syntax Properties |
528 | @section Syntax Properties | |
529 | @kindex syntax-table @r{(text property)} | |
530 | ||
51750684 LK |
531 | When the syntax table is not flexible enough to specify the syntax of |
532 | a language, you can use @code{syntax-table} text properties to | |
533 | override the syntax table for specific character occurrences in the | |
534 | buffer. @xref{Text Properties}. You can use Font Lock mode to set | |
535 | @code{syntax-table} text properties. @xref{Setting Syntax | |
536 | Properties}. | |
f9f59935 | 537 | |
969fe9b5 | 538 | The valid values of @code{syntax-table} text property are: |
f9f59935 RS |
539 | |
540 | @table @asis | |
541 | @item @var{syntax-table} | |
542 | If the property value is a syntax table, that table is used instead of | |
543 | the current buffer's syntax table to determine the syntax for this | |
544 | occurrence of the character. | |
545 | ||
546 | @item @code{(@var{syntax-code} . @var{matching-char})} | |
547 | A cons cell of this format specifies the syntax for this | |
d1f08d85 | 548 | occurrence of the character. (@pxref{Syntax Table Internals}) |
f9f59935 RS |
549 | |
550 | @item @code{nil} | |
551 | If the property is @code{nil}, the character's syntax is determined from | |
552 | the current syntax table in the usual way. | |
553 | @end table | |
554 | ||
f9f59935 RS |
555 | @defvar parse-sexp-lookup-properties |
556 | If this is non-@code{nil}, the syntax scanning functions pay attention | |
557 | to syntax text properties. Otherwise they use only the current syntax | |
558 | table. | |
559 | @end defvar | |
560 | ||
7015aca4 RS |
561 | @node Motion and Syntax |
562 | @section Motion and Syntax | |
563 | ||
969fe9b5 RS |
564 | This section describes functions for moving across characters that |
565 | have certain syntax classes. | |
7015aca4 RS |
566 | |
567 | @defun skip-syntax-forward syntaxes &optional limit | |
9c5609e8 | 568 | This function moves point forward across characters having syntax |
b5305167 | 569 | classes mentioned in @var{syntaxes} (a string of syntax class |
9c5609e8 LT |
570 | characters). It stops when it encounters the end of the buffer, or |
571 | position @var{limit} (if specified), or a character it is not supposed | |
572 | to skip. | |
8241495d RS |
573 | |
574 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
575 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
576 | ||
7015aca4 RS |
577 | The return value is the distance traveled, which is a nonnegative |
578 | integer. | |
7015aca4 RS |
579 | @end defun |
580 | ||
581 | @defun skip-syntax-backward syntaxes &optional limit | |
582 | This function moves point backward across characters whose syntax | |
583 | classes are mentioned in @var{syntaxes}. It stops when it encounters | |
8241495d RS |
584 | the beginning of the buffer, or position @var{limit} (if specified), or |
585 | a character it is not supposed to skip. | |
586 | ||
587 | If @var{syntaxes} starts with @samp{^}, then the function skips | |
588 | characters whose syntax is @emph{not} in @var{syntaxes}. | |
1911e6e5 | 589 | |
7015aca4 RS |
590 | The return value indicates the distance traveled. It is an integer that |
591 | is zero or less. | |
7015aca4 RS |
592 | @end defun |
593 | ||
594 | @defun backward-prefix-chars | |
595 | This function moves point backward over any number of characters with | |
596 | expression prefix syntax. This includes both characters in the | |
597 | expression prefix syntax class, and characters with the @samp{p} flag. | |
598 | @end defun | |
599 | ||
600 | @node Parsing Expressions | |
601 | @section Parsing Balanced Expressions | |
602 | ||
603 | Here are several functions for parsing and scanning balanced | |
6cbdd38b RS |
604 | expressions, also known as @dfn{sexps}. Basically, a sexp is either a |
605 | balanced parenthetical grouping, or a symbol name (a sequence of | |
606 | characters whose syntax is either word constituent or symbol | |
607 | constituent). However, characters whose syntax is expression prefix | |
608 | are treated as part of the sexp if they appear next to it. | |
609 | ||
610 | The syntax table controls the interpretation of characters, so these | |
611 | functions can be used for Lisp expressions when in Lisp mode and for C | |
612 | expressions when in C mode. @xref{List Motion}, for convenient | |
7015aca4 RS |
613 | higher-level functions for moving over balanced expressions. |
614 | ||
6cbdd38b RS |
615 | A syntax table only describes how each character changes the state |
616 | of the parser, rather than describing the state itself. For example, | |
617 | a string delimiter character toggles the parser state between | |
618 | ``in-string'' and ``in-code'' but the characters inside the string do | |
619 | not have any particular syntax to identify them as such. For example | |
620 | (note that 15 is the syntax code for generic string delimiters), | |
45493fb7 SM |
621 | |
622 | @example | |
623 | (put-text-property 1 9 'syntax-table '(15 . nil)) | |
624 | @end example | |
625 | ||
6cbdd38b | 626 | @noindent |
45493fb7 | 627 | does not tell Emacs that the first eight chars of the current buffer |
6cbdd38b RS |
628 | are a string, but rather that they are all string delimiters. As a |
629 | result, Emacs treats them as four consecutive empty string constants. | |
630 | ||
631 | Every time you use the parser, you specify it a starting state as | |
632 | well as a starting position. If you omit the starting state, the | |
633 | default is ``top level in parenthesis structure,'' as it would be at | |
634 | the beginning of a function definition. (This is the case for | |
635 | @code{forward-sexp}, which blindly assumes that the starting point is | |
636 | in such a state.) | |
45493fb7 | 637 | |
7015aca4 RS |
638 | @defun parse-partial-sexp start limit &optional target-depth stop-before state stop-comment |
639 | This function parses a sexp in the current buffer starting at | |
7fd1911a RS |
640 | @var{start}, not scanning past @var{limit}. It stops at position |
641 | @var{limit} or when certain criteria described below are met, and sets | |
642 | point to the location where parsing stops. It returns a value | |
643 | describing the status of the parse at the point where it stops. | |
7015aca4 RS |
644 | |
645 | If @var{state} is @code{nil}, @var{start} is assumed to be at the top | |
646 | level of parenthesis structure, such as the beginning of a function | |
647 | definition. Alternatively, you might wish to resume parsing in the | |
648 | middle of the structure. To do this, you must provide a @var{state} | |
649 | argument that describes the initial status of parsing. | |
650 | ||
651 | @cindex parenthesis depth | |
652 | If the third argument @var{target-depth} is non-@code{nil}, parsing | |
653 | stops if the depth in parentheses becomes equal to @var{target-depth}. | |
654 | The depth starts at 0, or at whatever is given in @var{state}. | |
655 | ||
656 | If the fourth argument @var{stop-before} is non-@code{nil}, parsing | |
657 | stops when it comes to any character that starts a sexp. If | |
658 | @var{stop-comment} is non-@code{nil}, parsing stops when it comes to the | |
f9f59935 RS |
659 | start of a comment. If @var{stop-comment} is the symbol |
660 | @code{syntax-table}, parsing stops after the start of a comment or a | |
1911e6e5 | 661 | string, or the end of a comment or a string, whichever comes first. |
7015aca4 RS |
662 | |
663 | @cindex parse state | |
8a2f014e | 664 | The fifth argument @var{state} is a ten-element list of the same form |
969fe9b5 | 665 | as the value of this function, described below. (It is OK to omit the |
8a2f014e RS |
666 | last two elements of this list.) The return value of one call may be |
667 | used to initialize the state of the parse on another call to | |
f9f59935 | 668 | @code{parse-partial-sexp}. |
7015aca4 | 669 | |
8a2f014e | 670 | The result is a list of ten elements describing the final state of |
7015aca4 RS |
671 | the parse: |
672 | ||
673 | @enumerate 0 | |
177c0ea7 | 674 | @item |
7015aca4 RS |
675 | The depth in parentheses, counting from 0. |
676 | ||
177c0ea7 | 677 | @item |
7015aca4 | 678 | @cindex innermost containing parentheses |
7fd1911a RS |
679 | The character position of the start of the innermost parenthetical |
680 | grouping containing the stopping point; @code{nil} if none. | |
7015aca4 | 681 | |
177c0ea7 | 682 | @item |
7015aca4 RS |
683 | @cindex previous complete subexpression |
684 | The character position of the start of the last complete subexpression | |
685 | terminated; @code{nil} if none. | |
686 | ||
177c0ea7 | 687 | @item |
7015aca4 RS |
688 | @cindex inside string |
689 | Non-@code{nil} if inside a string. More precisely, this is the | |
f9f59935 RS |
690 | character that will terminate the string, or @code{t} if a generic |
691 | string delimiter character should terminate it. | |
7015aca4 | 692 | |
177c0ea7 | 693 | @item |
7015aca4 | 694 | @cindex inside comment |
79ddc9c9 GM |
695 | @code{t} if inside a comment (of either style), |
696 | or the comment nesting level if inside a kind of comment | |
697 | that can be nested. | |
7015aca4 | 698 | |
177c0ea7 | 699 | @item |
7015aca4 RS |
700 | @cindex quote character |
701 | @code{t} if point is just after a quote character. | |
702 | ||
177c0ea7 | 703 | @item |
7015aca4 RS |
704 | The minimum parenthesis depth encountered during this scan. |
705 | ||
706 | @item | |
9c5609e8 LT |
707 | What kind of comment is active: @code{nil} for a comment of style |
708 | ``a'' or when not inside a comment, @code{t} for a comment of style | |
709 | ``b'', and @code{syntax-table} for a comment that should be ended by a | |
710 | generic comment delimiter character. | |
f9f59935 RS |
711 | |
712 | @item | |
713 | The string or comment start position. While inside a comment, this is | |
714 | the position where the comment began; while inside a string, this is the | |
715 | position where the string began. When outside of strings and comments, | |
716 | this element is @code{nil}. | |
7015aca4 | 717 | |
8a2f014e RS |
718 | @item |
719 | Internal data for continuing the parsing. The meaning of this | |
720 | data is subject to change; it is used if you pass this list | |
721 | as the @var{state} argument to another call. | |
722 | ||
723 | @end enumerate | |
7015aca4 | 724 | |
8a2f014e RS |
725 | Elements 0, 3, 4, 5, 7 and 9 are significant in the argument |
726 | @var{state}. | |
9c5609e8 | 727 | |
7015aca4 RS |
728 | @cindex indenting with parentheses |
729 | This function is most often used to compute indentation for languages | |
730 | that have nested parentheses. | |
731 | @end defun | |
732 | ||
b5305167 SM |
733 | @defun syntax-ppss &optional pos |
734 | This function returns the state that the parser would have at position | |
735 | @var{pos}, if it were started with a default start state at the | |
736 | beginning of the buffer. Thus, it is equivalent to | |
4b53b8d7 | 737 | @code{(parse-partial-sexp (point-min) @var{pos})}, except that |
b5305167 SM |
738 | @code{syntax-ppss} uses a cache to speed up the computation. Also, |
739 | the 2nd value (previous complete subexpression) and 6th value (minimum | |
740 | parenthesis depth) of the returned state are not meaningful. | |
741 | @end defun | |
742 | ||
f99ed2f8 SM |
743 | @defun syntax-ppss-flush-cache beg |
744 | This function flushes the cache used by @code{syntax-ppss}, starting at | |
745 | position @var{beg}. | |
746 | ||
747 | When @code{syntax-ppss} is called, it automatically hooks itself | |
748 | to @code{before-change-functions} to keep its cache consistent. | |
749 | But this can fail if @code{syntax-ppss} is called while | |
750 | @code{before-change-functions} is temporarily let-bound, or if the | |
751 | buffer is modified without obeying the hook, such as when using | |
752 | @code{inhibit-modification-hooks}. For this reason, it is sometimes | |
753 | necessary to flush the cache manually. | |
754 | @end defun | |
755 | ||
756 | @defvar syntax-begin-function | |
70aded15 RS |
757 | If this is non-@code{nil}, it should be a function that moves to an |
758 | earlier buffer position where the parser state is equivalent to | |
759 | @code{nil}---in other words, a position outside of any comment, | |
760 | string, or parenthesis. @code{syntax-ppss} uses it to supplement its | |
761 | cache. | |
f99ed2f8 SM |
762 | @end defvar |
763 | ||
7015aca4 RS |
764 | @defun scan-lists from count depth |
765 | This function scans forward @var{count} balanced parenthetical groupings | |
f9f59935 RS |
766 | from position @var{from}. It returns the position where the scan stops. |
767 | If @var{count} is negative, the scan moves backwards. | |
7015aca4 RS |
768 | |
769 | If @var{depth} is nonzero, parenthesis depth counting begins from that | |
770 | value. The only candidates for stopping are places where the depth in | |
771 | parentheses becomes zero; @code{scan-lists} counts @var{count} such | |
772 | places and then stops. Thus, a positive value for @var{depth} means go | |
7fd1911a | 773 | out @var{depth} levels of parenthesis. |
7015aca4 RS |
774 | |
775 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
776 | non-@code{nil}. | |
777 | ||
7fd1911a RS |
778 | If the scan reaches the beginning or end of the buffer (or its |
779 | accessible portion), and the depth is not zero, an error is signaled. | |
780 | If the depth is zero but the count is not used up, @code{nil} is | |
781 | returned. | |
7015aca4 RS |
782 | @end defun |
783 | ||
784 | @defun scan-sexps from count | |
f9f59935 RS |
785 | This function scans forward @var{count} sexps from position @var{from}. |
786 | It returns the position where the scan stops. If @var{count} is | |
787 | negative, the scan moves backwards. | |
7015aca4 RS |
788 | |
789 | Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
790 | non-@code{nil}. | |
791 | ||
7fd1911a | 792 | If the scan reaches the beginning or end of (the accessible part of) the |
f9f59935 RS |
793 | buffer while in the middle of a parenthetical grouping, an error is |
794 | signaled. If it reaches the beginning or end between groupings but | |
795 | before count is used up, @code{nil} is returned. | |
7015aca4 RS |
796 | @end defun |
797 | ||
3357a32f RS |
798 | @defvar multibyte-syntax-as-symbol |
799 | @tindex multibyte-syntax-as-symbol | |
800 | If this variable is non-@code{nil}, @code{scan-sexps} treats all | |
ad800164 | 801 | non-@acronym{ASCII} characters as symbol constituents regardless |
3357a32f RS |
802 | of what the syntax table says about them. (However, text properties |
803 | can still override the syntax.) | |
804 | @end defvar | |
805 | ||
9c5609e8 | 806 | @defopt parse-sexp-ignore-comments |
7015aca4 RS |
807 | @cindex skipping comments |
808 | If the value is non-@code{nil}, then comments are treated as | |
809 | whitespace by the functions in this section and by @code{forward-sexp}. | |
9c5609e8 | 810 | @end defopt |
7015aca4 | 811 | |
cf4ccadb | 812 | @vindex parse-sexp-lookup-properties |
4b53b8d7 | 813 | The behavior of @code{parse-partial-sexp} is also affected by |
075ec3c4 | 814 | @code{parse-sexp-lookup-properties} (@pxref{Syntax Properties}). |
cf4ccadb | 815 | |
7015aca4 RS |
816 | You can use @code{forward-comment} to move forward or backward over |
817 | one comment or several comments. | |
818 | ||
819 | @defun forward-comment count | |
47eda1bd RS |
820 | This function moves point forward across @var{count} complete comments |
821 | (that is, including the starting delimiter and the terminating | |
37778b63 RS |
822 | delimiter if any), plus any whitespace encountered on the way. It |
823 | moves backward if @var{count} is negative. If it encounters anything | |
824 | other than a comment or whitespace, it stops, leaving point at the | |
825 | place where it stopped. This includes (for instance) finding the end | |
826 | of a comment when moving forward and expecting the beginning of one. | |
827 | The function also stops immediately after moving over the specified | |
cf4ccadb | 828 | number of complete comments. If @var{count} comments are found as |
075ec3c4 RS |
829 | expected, with nothing except whitespace between them, it returns |
830 | @code{t}; otherwise it returns @code{nil}. | |
47eda1bd RS |
831 | |
832 | This function cannot tell whether the ``comments'' it traverses are | |
833 | embedded within a string. If they look like comments, it treats them | |
834 | as comments. | |
7015aca4 RS |
835 | @end defun |
836 | ||
837 | To move forward over all comments and whitespace following point, use | |
838 | @code{(forward-comment (buffer-size))}. @code{(buffer-size)} is a good | |
7fd1911a | 839 | argument to use, because the number of comments in the buffer cannot |
7015aca4 RS |
840 | exceed that many. |
841 | ||
842 | @node Standard Syntax Tables | |
843 | @section Some Standard Syntax Tables | |
844 | ||
bfe721d1 KH |
845 | Most of the major modes in Emacs have their own syntax tables. Here |
846 | are several of them: | |
7015aca4 RS |
847 | |
848 | @defun standard-syntax-table | |
849 | This function returns the standard syntax table, which is the syntax | |
850 | table used in Fundamental mode. | |
851 | @end defun | |
852 | ||
853 | @defvar text-mode-syntax-table | |
854 | The value of this variable is the syntax table used in Text mode. | |
855 | @end defvar | |
856 | ||
857 | @defvar c-mode-syntax-table | |
858 | The value of this variable is the syntax table for C-mode buffers. | |
859 | @end defvar | |
860 | ||
861 | @defvar emacs-lisp-mode-syntax-table | |
862 | The value of this variable is the syntax table used in Emacs Lisp mode | |
863 | by editing commands. (It has no effect on the Lisp @code{read} | |
864 | function.) | |
865 | @end defvar | |
866 | ||
867 | @node Syntax Table Internals | |
868 | @section Syntax Table Internals | |
869 | @cindex syntax table internals | |
870 | ||
f9f59935 | 871 | Lisp programs don't usually work with the elements directly; the |
7015aca4 | 872 | Lisp-level syntax table functions usually work with syntax descriptors |
f9f59935 | 873 | (@pxref{Syntax Descriptors}). Nonetheless, here we document the |
d1f08d85 SM |
874 | internal format. This format is used mostly when manipulating |
875 | syntax properties. | |
f9f59935 RS |
876 | |
877 | Each element of a syntax table is a cons cell of the form | |
878 | @code{(@var{syntax-code} . @var{matching-char})}. The @sc{car}, | |
879 | @var{syntax-code}, is an integer that encodes the syntax class, and any | |
880 | flags. The @sc{cdr}, @var{matching-char}, is non-@code{nil} if | |
881 | a character to match was specified. | |
7015aca4 | 882 | |
f9f59935 RS |
883 | This table gives the value of @var{syntax-code} which corresponds |
884 | to each syntactic type. | |
7015aca4 | 885 | |
fb056bef | 886 | @multitable @columnfractions .05 .3 .3 .31 |
a9f0a989 RS |
887 | @item |
888 | @tab | |
969fe9b5 RS |
889 | @i{Integer} @i{Class} |
890 | @tab | |
891 | @i{Integer} @i{Class} | |
892 | @tab | |
893 | @i{Integer} @i{Class} | |
a9f0a989 RS |
894 | @item |
895 | @tab | |
969fe9b5 RS |
896 | 0 @ @ whitespace |
897 | @tab | |
898 | 5 @ @ close parenthesis | |
899 | @tab | |
900 | 10 @ @ character quote | |
a9f0a989 RS |
901 | @item |
902 | @tab | |
969fe9b5 RS |
903 | 1 @ @ punctuation |
904 | @tab | |
905 | 6 @ @ expression prefix | |
906 | @tab | |
907 | 11 @ @ comment-start | |
a9f0a989 RS |
908 | @item |
909 | @tab | |
969fe9b5 RS |
910 | 2 @ @ word |
911 | @tab | |
912 | 7 @ @ string quote | |
913 | @tab | |
914 | 12 @ @ comment-end | |
a9f0a989 RS |
915 | @item |
916 | @tab | |
969fe9b5 RS |
917 | 3 @ @ symbol |
918 | @tab | |
919 | 8 @ @ paired delimiter | |
920 | @tab | |
921 | 13 @ @ inherit | |
a9f0a989 RS |
922 | @item |
923 | @tab | |
969fe9b5 RS |
924 | 4 @ @ open parenthesis |
925 | @tab | |
926 | 9 @ @ escape | |
927 | @tab | |
85c7ceaa | 928 | 14 @ @ generic comment |
a9f0a989 RS |
929 | @item |
930 | @tab | |
85c7ceaa | 931 | 15 @ generic string |
969fe9b5 | 932 | @end multitable |
7015aca4 | 933 | |
f9f59935 RS |
934 | For example, the usual syntax value for @samp{(} is @code{(4 . 41)}. |
935 | (41 is the character code for @samp{)}.) | |
936 | ||
937 | The flags are encoded in higher order bits, starting 16 bits from the | |
938 | least significant bit. This table gives the power of two which | |
939 | corresponds to each syntax flag. | |
940 | ||
969fe9b5 | 941 | @multitable @columnfractions .05 .3 .3 .3 |
a9f0a989 RS |
942 | @item |
943 | @tab | |
969fe9b5 RS |
944 | @i{Prefix} @i{Flag} |
945 | @tab | |
946 | @i{Prefix} @i{Flag} | |
947 | @tab | |
948 | @i{Prefix} @i{Flag} | |
a9f0a989 RS |
949 | @item |
950 | @tab | |
969fe9b5 RS |
951 | @samp{1} @ @ @code{(lsh 1 16)} |
952 | @tab | |
79ddc9c9 | 953 | @samp{4} @ @ @code{(lsh 1 19)} |
969fe9b5 | 954 | @tab |
79ddc9c9 | 955 | @samp{b} @ @ @code{(lsh 1 21)} |
a9f0a989 RS |
956 | @item |
957 | @tab | |
969fe9b5 RS |
958 | @samp{2} @ @ @code{(lsh 1 17)} |
959 | @tab | |
79ddc9c9 | 960 | @samp{p} @ @ @code{(lsh 1 20)} |
969fe9b5 | 961 | @tab |
79ddc9c9 GM |
962 | @samp{n} @ @ @code{(lsh 1 22)} |
963 | @item | |
964 | @tab | |
965 | @samp{3} @ @ @code{(lsh 1 18)} | |
969fe9b5 | 966 | @end multitable |
f9f59935 | 967 | |
d1f08d85 SM |
968 | @defun string-to-syntax @var{desc} |
969 | This function returns the internal form @code{(@var{syntax-code} . | |
970 | @var{matching-char})} corresponding to the syntax descriptor @var{desc}. | |
40153606 | 971 | @end defun |
d1f08d85 | 972 | |
8a2f014e RS |
973 | @defun syntax-after pos |
974 | This function returns the syntax code of the character in the buffer | |
975 | after position @var{pos}, taking account of syntax properties as well | |
92426d9c EZ |
976 | as the syntax table. If @var{pos} is outside the buffer's accessible |
977 | portion (@pxref{Narrowing, accessible portion}), this function returns | |
978 | @code{nil}. | |
8a2f014e RS |
979 | @end defun |
980 | ||
137a5ef2 | 981 | @defun syntax-class syntax |
92426d9c EZ |
982 | This function returns the syntax class of the syntax code |
983 | @var{syntax}. (It masks off the high 16 bits that hold the flags | |
984 | encoded in the syntax descriptor.) If @var{syntax} is @code{nil}, it | |
985 | returns @code{nil}; this is so evaluating the expression | |
986 | ||
987 | @example | |
988 | (syntax-class (syntax-after pos)) | |
989 | @end example | |
990 | ||
991 | @noindent | |
992 | where @code{pos} is outside the buffer's accessible portion, will | |
993 | yield @code{nil} without throwing errors or producing wrong syntax | |
994 | class codes. | |
137a5ef2 SM |
995 | @end defun |
996 | ||
f9f59935 RS |
997 | @node Categories |
998 | @section Categories | |
999 | @cindex categories of characters | |
1000 | ||
1001 | @dfn{Categories} provide an alternate way of classifying characters | |
969fe9b5 RS |
1002 | syntactically. You can define several categories as needed, then |
1003 | independently assign each character to one or more categories. Unlike | |
f9f59935 RS |
1004 | syntax classes, categories are not mutually exclusive; it is normal for |
1005 | one character to belong to several categories. | |
1006 | ||
1007 | Each buffer has a @dfn{category table} which records which categories | |
1008 | are defined and also which characters belong to each category. Each | |
969fe9b5 RS |
1009 | category table defines its own categories, but normally these are |
1010 | initialized by copying from the standard categories table, so that the | |
1011 | standard categories are available in all modes. | |
1012 | ||
ad800164 | 1013 | Each category has a name, which is an @acronym{ASCII} printing character in |
969fe9b5 RS |
1014 | the range @w{@samp{ }} to @samp{~}. You specify the name of a category |
1015 | when you define it with @code{define-category}. | |
f9f59935 RS |
1016 | |
1017 | The category table is actually a char-table (@pxref{Char-Tables}). | |
1018 | The element of the category table at index @var{c} is a @dfn{category | |
1019 | set}---a bool-vector---that indicates which categories character @var{c} | |
1020 | belongs to. In this category set, if the element at index @var{cat} is | |
1021 | @code{t}, that means category @var{cat} is a member of the set, and that | |
1022 | character @var{c} belongs to category @var{cat}. | |
1023 | ||
9c5609e8 LT |
1024 | For the next three functions, the optional argument @var{table} |
1025 | defaults to the current buffer's category table. | |
1026 | ||
f9f59935 RS |
1027 | @defun define-category char docstring &optional table |
1028 | This function defines a new category, with name @var{char} and | |
8a2f014e | 1029 | documentation @var{docstring}, for the category table @var{table}. |
f9f59935 RS |
1030 | @end defun |
1031 | ||
1032 | @defun category-docstring category &optional table | |
1033 | This function returns the documentation string of category @var{category} | |
1034 | in category table @var{table}. | |
1035 | ||
1036 | @example | |
1037 | (category-docstring ?a) | |
1038 | @result{} "ASCII" | |
1039 | (category-docstring ?l) | |
1040 | @result{} "Latin" | |
1041 | @end example | |
1042 | @end defun | |
1043 | ||
9c5609e8 | 1044 | @defun get-unused-category &optional table |
f9f59935 | 1045 | This function returns a category name (a character) which is not |
969fe9b5 | 1046 | currently defined in @var{table}. If all possible categories are in use |
1911e6e5 | 1047 | in @var{table}, it returns @code{nil}. |
f9f59935 RS |
1048 | @end defun |
1049 | ||
1050 | @defun category-table | |
1051 | This function returns the current buffer's category table. | |
1052 | @end defun | |
1053 | ||
1054 | @defun category-table-p object | |
1055 | This function returns @code{t} if @var{object} is a category table, | |
1056 | otherwise @code{nil}. | |
1057 | @end defun | |
1058 | ||
1059 | @defun standard-category-table | |
1060 | This function returns the standard category table. | |
1061 | @end defun | |
1062 | ||
1063 | @defun copy-category-table &optional table | |
1064 | This function constructs a copy of @var{table} and returns it. If | |
1065 | @var{table} is not supplied (or is @code{nil}), it returns a copy of the | |
9c5609e8 | 1066 | standard category table. Otherwise, an error is signaled if @var{table} |
f9f59935 RS |
1067 | is not a category table. |
1068 | @end defun | |
1069 | ||
1070 | @defun set-category-table table | |
1071 | This function makes @var{table} the category table for the current | |
1072 | buffer. It returns @var{table}. | |
1073 | @end defun | |
1074 | ||
3f26d1e6 | 1075 | @defun make-category-table |
2468d0c0 | 1076 | @tindex make-category-table |
3f26d1e6 GM |
1077 | This creates and returns an empty category table. In an empty category |
1078 | table, no categories have been allocated, and no characters belong to | |
1079 | any categories. | |
2468d0c0 DL |
1080 | @end defun |
1081 | ||
f9f59935 RS |
1082 | @defun make-category-set categories |
1083 | This function returns a new category set---a bool-vector---whose initial | |
1084 | contents are the categories listed in the string @var{categories}. The | |
1085 | elements of @var{categories} should be category names; the new category | |
1086 | set has @code{t} for each of those categories, and @code{nil} for all | |
1087 | other categories. | |
1088 | ||
1089 | @example | |
1090 | (make-category-set "al") | |
1091 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1092 | @end example | |
1093 | @end defun | |
1094 | ||
1095 | @defun char-category-set char | |
9c5609e8 LT |
1096 | This function returns the category set for character @var{char} in the |
1097 | current buffer's category table. This is the bool-vector which | |
1098 | records which categories the character @var{char} belongs to. The | |
1099 | function @code{char-category-set} does not allocate storage, because | |
1100 | it returns the same bool-vector that exists in the category table. | |
f9f59935 RS |
1101 | |
1102 | @example | |
1103 | (char-category-set ?a) | |
1104 | @result{} #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0" | |
1105 | @end example | |
1106 | @end defun | |
1107 | ||
1108 | @defun category-set-mnemonics category-set | |
1109 | This function converts the category set @var{category-set} into a string | |
2468d0c0 DL |
1110 | containing the characters that designate the categories that are members |
1111 | of the set. | |
f9f59935 RS |
1112 | |
1113 | @example | |
1114 | (category-set-mnemonics (char-category-set ?a)) | |
1115 | @result{} "al" | |
1116 | @end example | |
1117 | @end defun | |
1118 | ||
1119 | @defun modify-category-entry character category &optional table reset | |
1120 | This function modifies the category set of @var{character} in category | |
1121 | table @var{table} (which defaults to the current buffer's category | |
1122 | table). | |
1123 | ||
1124 | Normally, it modifies the category set by adding @var{category} to it. | |
1125 | But if @var{reset} is non-@code{nil}, then it deletes @var{category} | |
1126 | instead. | |
1127 | @end defun | |
a57092e8 | 1128 | |
9c5609e8 | 1129 | @deffn Command describe-categories &optional buffer-or-name |
a57092e8 | 1130 | This function describes the category specifications in the current |
9c5609e8 LT |
1131 | category table. It inserts the descriptions in a buffer, and then |
1132 | displays that buffer. If @var{buffer-or-name} is non-@code{nil}, it | |
1133 | describes the category table of that buffer instead. | |
a57092e8 | 1134 | @end deffn |
ab5796a9 MB |
1135 | |
1136 | @ignore | |
1137 | arch-tag: 4d914e96-0283-445c-9233-75d33662908c | |
1138 | @end ignore |