Mercurial > hg > xemacs-beta
annotate man/lispref/syntax.texi @ 5903:5afddd952c46
Return ratios in canonical form too, #'string-to-number
src/ChangeLog addition:
2015-05-08 Aidan Kehoe <kehoea@parhasard.net>
* data.c (Fstring_to_number):
Canonicalise ratios in this function, as we do bignums.
| author | Aidan Kehoe <kehoea@parhasard.net> |
|---|---|
| date | Fri, 08 May 2015 13:58:22 +0100 |
| parents | 9fae6227ede5 |
| children |
| rev | line source |
|---|---|
| 0 | 1 @c -*-texinfo-*- |
| 2 @c This is part of the XEmacs Lisp Reference Manual. | |
| 444 | 3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. |
| 0 | 4 @c See the file lispref.texi for copying conditions. |
| 5 @setfilename ../../info/syntax.info | |
| 6 @node Syntax Tables, Abbrevs, Searching and Matching, Top | |
| 7 @chapter Syntax Tables | |
| 8 @cindex parsing | |
| 9 @cindex syntax table | |
| 10 @cindex text parsing | |
| 11 | |
| 12 A @dfn{syntax table} specifies the syntactic textual function of each | |
| 13 character. This information is used by the parsing commands, the | |
| 14 complex movement commands, and others to determine where words, symbols, | |
| 15 and other syntactic constructs begin and end. The current syntax table | |
| 16 controls the meaning of the word motion functions (@pxref{Word Motion}) | |
| 17 and the list motion functions (@pxref{List Motion}) as well as the | |
| 18 functions in this chapter. | |
| 19 | |
| 20 @menu | |
| 21 * Basics: Syntax Basics. Basic concepts of syntax tables. | |
| 22 * Desc: Syntax Descriptors. How characters are classified. | |
| 23 * Syntax Table Functions:: How to create, examine and alter syntax tables. | |
| 24 * Motion and Syntax:: Moving over characters with certain syntaxes. | |
| 25 * Parsing Expressions:: Parsing balanced expressions | |
| 26 using the syntax table. | |
| 27 * Standard Syntax Tables:: Syntax tables used by various major modes. | |
| 28 * Syntax Table Internals:: How syntax table information is stored. | |
| 29 @end menu | |
| 30 | |
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31 @node Syntax Basics, Syntax Descriptors, Syntax Tables, Syntax Tables |
| 0 | 32 @section Syntax Table Concepts |
| 33 | |
| 34 @ifinfo | |
| 35 A @dfn{syntax table} provides Emacs with the information that | |
| 36 determines the syntactic use of each character in a buffer. This | |
| 37 information is used by the parsing commands, the complex movement | |
| 38 commands, and others to determine where words, symbols, and other | |
| 39 syntactic constructs begin and end. The current syntax table controls | |
| 40 the meaning of the word motion functions (@pxref{Word Motion}) and the | |
| 41 list motion functions (@pxref{List Motion}) as well as the functions in | |
| 42 this chapter. | |
| 43 @end ifinfo | |
| 44 | |
| 1024 | 45 Under XEmacs 20 and later, a syntax table is a particular subtype of the |
| 0 | 46 primitive char table type (@pxref{Char Tables}), and each element of the |
| 47 char table is an integer that encodes the syntax of the character in | |
| 48 question, or a cons of such an integer and a matching character (for | |
| 49 characters with parenthesis syntax). | |
| 50 | |
| 51 Under XEmacs 19, a syntax table is a vector of 256 elements; it | |
| 52 contains one entry for each of the 256 possible characters in an 8-bit | |
| 53 byte. Each element is an integer that encodes the syntax of the | |
| 54 character in question. (The matching character, if any, is embedded | |
| 55 in the bits of this integer.) | |
| 56 | |
| 57 Syntax tables are used only for moving across text, not for the Emacs | |
| 58 Lisp reader. XEmacs Lisp uses built-in syntactic rules when reading Lisp | |
| 59 expressions, and these rules cannot be changed. | |
| 60 | |
| 61 Each buffer has its own major mode, and each major mode has its own | |
| 62 idea of the syntactic class of various characters. For example, in Lisp | |
| 63 mode, the character @samp{;} begins a comment, but in C mode, it | |
| 64 terminates a statement. To support these variations, XEmacs makes the | |
| 65 choice of syntax table local to each buffer. Typically, each major | |
| 66 mode has its own syntax table and installs that table in each buffer | |
| 67 that uses that mode. Changing this table alters the syntax in all | |
| 68 those buffers as well as in any buffers subsequently put in that mode. | |
| 69 Occasionally several similar modes share one syntax table. | |
| 70 @xref{Example Major Modes}, for an example of how to set up a syntax | |
| 71 table. | |
| 72 | |
| 73 A syntax table can inherit the data for some characters from the | |
| 74 standard syntax table, while specifying other characters itself. The | |
| 75 ``inherit'' syntax class means ``inherit this character's syntax from | |
| 76 the standard syntax table.'' Most major modes' syntax tables inherit | |
| 77 the syntax of character codes 0 through 31 and 128 through 255. This is | |
| 78 useful with character sets such as ISO Latin-1 that have additional | |
| 79 alphabetic characters in the range 128 to 255. Just changing the | |
| 80 standard syntax for these characters affects all major modes. | |
| 81 | |
| 82 @defun syntax-table-p object | |
| 83 This function returns @code{t} if @var{object} is a vector of length 256 | |
| 84 elements. This means that the vector may be a syntax table. However, | |
| 85 according to this test, any vector of length 256 is considered to be a | |
| 86 syntax table, no matter what its contents. | |
| 87 @end defun | |
| 88 | |
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89 @node Syntax Descriptors, Syntax Table Functions, Syntax Basics, Syntax Tables |
| 0 | 90 @section Syntax Descriptors |
| 91 @cindex syntax classes | |
| 92 | |
| 93 This section describes the syntax classes and flags that denote the | |
| 94 syntax of a character, and how they are represented as a @dfn{syntax | |
| 95 descriptor}, which is a Lisp string that you pass to | |
| 96 @code{modify-syntax-entry} to specify the desired syntax. | |
| 97 | |
| 98 XEmacs defines a number of @dfn{syntax classes}. Each syntax table | |
| 99 puts each character into one class. There is no necessary relationship | |
| 100 between the class of a character in one syntax table and its class in | |
| 101 any other table. | |
| 102 | |
| 103 Each class is designated by a mnemonic character, which serves as the | |
| 104 name of the class when you need to specify a class. Usually the | |
| 105 designator character is one that is frequently in that class; however, | |
| 106 its meaning as a designator is unvarying and independent of what syntax | |
| 107 that character currently has. | |
| 108 | |
| 109 @cindex syntax descriptor | |
| 110 A syntax descriptor is a Lisp string that specifies a syntax class, a | |
| 111 matching character (used only for the parenthesis classes) and flags. | |
| 112 The first character is the designator for a syntax class. The second | |
| 113 character is the character to match; if it is unused, put a space there. | |
| 114 Then come the characters for any desired flags. If no matching | |
| 115 character or flags are needed, one character is sufficient. | |
| 116 | |
| 117 For example, the descriptor for the character @samp{*} in C mode is | |
| 118 @samp{@w{. 23}} (i.e., punctuation, matching character slot unused, | |
| 119 second character of a comment-starter, first character of an | |
| 120 comment-ender), and the entry for @samp{/} is @samp{@w{. 14}} (i.e., | |
| 121 punctuation, matching character slot unused, first character of a | |
| 122 comment-starter, second character of a comment-ender). | |
| 123 | |
| 124 @menu | |
| 125 * Syntax Class Table:: Table of syntax classes. | |
| 126 * Syntax Flags:: Additional flags each character can have. | |
| 127 @end menu | |
| 128 | |
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129 @node Syntax Class Table, Syntax Flags, Syntax Descriptors, Syntax Descriptors |
| 0 | 130 @subsection Table of Syntax Classes |
| 131 | |
| 132 Here is a table of syntax classes, the characters that stand for them, | |
| 133 their meanings, and examples of their use. | |
| 134 | |
| 135 @deffn {Syntax class} @w{whitespace character} | |
| 1024 | 136 @dfn{Whitespace characters} (designated with @samp{-}) |
| 0 | 137 separate symbols and words from each other. Typically, whitespace |
| 138 characters have no other syntactic significance, and multiple whitespace | |
| 139 characters are syntactically equivalent to a single one. Space, tab, | |
| 1024 | 140 newline and formfeed are almost always classified as whitespace. (The |
| 141 designator @w{@samp{@ }} is accepted for backwards compatibility with | |
| 142 older versions of XEmacs, but is deprecated. It is invalid in GNU Emacs.) | |
| 0 | 143 @end deffn |
| 144 | |
| 145 @deffn {Syntax class} @w{word constituent} | |
| 146 @dfn{Word constituents} (designated with @samp{w}) are parts of normal | |
| 147 English words and are typically used in variable and command names in | |
| 148 programs. All upper- and lower-case letters, and the digits, are typically | |
| 149 word constituents. | |
| 150 @end deffn | |
| 151 | |
| 152 @deffn {Syntax class} @w{symbol constituent} | |
| 153 @dfn{Symbol constituents} (designated with @samp{_}) are the extra | |
| 154 characters that are used in variable and command names along with word | |
| 155 constituents. For example, the symbol constituents class is used in | |
| 156 Lisp mode to indicate that certain characters may be part of symbol | |
| 157 names even though they are not part of English words. These characters | |
| 158 are @samp{$&*+-_<>}. In standard C, the only non-word-constituent | |
| 159 character that is valid in symbols is underscore (@samp{_}). | |
| 160 @end deffn | |
| 161 | |
| 162 @deffn {Syntax class} @w{punctuation character} | |
| 163 @dfn{Punctuation characters} (@samp{.}) are those characters that are | |
| 164 used as punctuation in English, or are used in some way in a programming | |
| 165 language to separate symbols from one another. Most programming | |
| 166 language modes, including Emacs Lisp mode, have no characters in this | |
| 167 class since the few characters that are not symbol or word constituents | |
| 168 all have other uses. | |
| 169 @end deffn | |
| 170 | |
| 171 @deffn {Syntax class} @w{open parenthesis character} | |
| 172 @deffnx {Syntax class} @w{close parenthesis character} | |
| 173 @cindex parenthesis syntax | |
| 174 Open and close @dfn{parenthesis characters} are characters used in | |
| 175 dissimilar pairs to surround sentences or expressions. Such a grouping | |
| 176 is begun with an open parenthesis character and terminated with a close. | |
| 177 Each open parenthesis character matches a particular close parenthesis | |
| 178 character, and vice versa. Normally, XEmacs indicates momentarily the | |
| 179 matching open parenthesis when you insert a close parenthesis. | |
| 180 @xref{Blinking}. | |
| 181 | |
| 182 The class of open parentheses is designated with @samp{(}, and that of | |
| 183 close parentheses with @samp{)}. | |
| 184 | |
| 185 In English text, and in C code, the parenthesis pairs are @samp{()}, | |
| 186 @samp{[]}, and @samp{@{@}}. In XEmacs Lisp, the delimiters for lists and | |
| 187 vectors (@samp{()} and @samp{[]}) are classified as parenthesis | |
| 188 characters. | |
| 189 @end deffn | |
| 190 | |
| 191 @deffn {Syntax class} @w{string quote} | |
| 192 @dfn{String quote characters} (designated with @samp{"}) are used in | |
| 193 many languages, including Lisp and C, to delimit string constants. The | |
| 194 same string quote character appears at the beginning and the end of a | |
| 195 string. Such quoted strings do not nest. | |
| 196 | |
| 197 The parsing facilities of XEmacs consider a string as a single token. | |
| 198 The usual syntactic meanings of the characters in the string are | |
| 199 suppressed. | |
| 200 | |
| 201 The Lisp modes have two string quote characters: double-quote (@samp{"}) | |
| 202 and vertical bar (@samp{|}). @samp{|} is not used in XEmacs Lisp, but it | |
| 203 is used in Common Lisp. C also has two string quote characters: | |
| 204 double-quote for strings, and single-quote (@samp{'}) for character | |
| 205 constants. | |
| 206 | |
| 207 English text has no string quote characters because English is not a | |
| 208 programming language. Although quotation marks are used in English, | |
| 209 we do not want them to turn off the usual syntactic properties of | |
| 210 other characters in the quotation. | |
| 211 @end deffn | |
| 212 | |
| 213 @deffn {Syntax class} @w{escape} | |
| 214 An @dfn{escape character} (designated with @samp{\}) starts an escape | |
| 215 sequence such as is used in C string and character constants. The | |
| 216 character @samp{\} belongs to this class in both C and Lisp. (In C, it | |
| 217 is used thus only inside strings, but it turns out to cause no trouble | |
| 218 to treat it this way throughout C code.) | |
| 219 | |
| 220 Characters in this class count as part of words if | |
| 221 @code{words-include-escapes} is non-@code{nil}. @xref{Word Motion}. | |
| 222 @end deffn | |
| 223 | |
| 224 @deffn {Syntax class} @w{character quote} | |
| 225 A @dfn{character quote character} (designated with @samp{/}) quotes the | |
| 226 following character so that it loses its normal syntactic meaning. This | |
| 227 differs from an escape character in that only the character immediately | |
| 228 following is ever affected. | |
| 229 | |
| 230 Characters in this class count as part of words if | |
| 231 @code{words-include-escapes} is non-@code{nil}. @xref{Word Motion}. | |
| 232 | |
| 233 This class is used for backslash in @TeX{} mode. | |
| 234 @end deffn | |
| 235 | |
| 236 @deffn {Syntax class} @w{paired delimiter} | |
| 237 @dfn{Paired delimiter characters} (designated with @samp{$}) are like | |
| 238 string quote characters except that the syntactic properties of the | |
| 239 characters between the delimiters are not suppressed. Only @TeX{} mode | |
| 240 uses a paired delimiter presently---the @samp{$} that both enters and | |
| 241 leaves math mode. | |
| 242 @end deffn | |
| 243 | |
| 244 @deffn {Syntax class} @w{expression prefix} | |
| 245 An @dfn{expression prefix operator} (designated with @samp{'}) is used | |
| 246 for syntactic operators that are part of an expression if they appear | |
| 247 next to one. These characters in Lisp include the apostrophe, @samp{'} | |
| 248 (used for quoting), the comma, @samp{,} (used in macros), and @samp{#} | |
| 249 (used in the read syntax for certain data types). | |
| 250 @end deffn | |
| 251 | |
| 252 @deffn {Syntax class} @w{comment starter} | |
| 253 @deffnx {Syntax class} @w{comment ender} | |
| 254 @cindex comment syntax | |
| 255 The @dfn{comment starter} and @dfn{comment ender} characters are used in | |
| 256 various languages to delimit comments. These classes are designated | |
| 257 with @samp{<} and @samp{>}, respectively. | |
| 258 | |
| 259 English text has no comment characters. In Lisp, the semicolon | |
| 260 (@samp{;}) starts a comment and a newline or formfeed ends one. | |
| 261 @end deffn | |
| 262 | |
| 263 @deffn {Syntax class} @w{inherit} | |
| 264 This syntax class does not specify a syntax. It says to look in the | |
| 265 standard syntax table to find the syntax of this character. The | |
| 266 designator for this syntax code is @samp{@@}. | |
| 267 @end deffn | |
| 268 | |
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269 @node Syntax Flags, , Syntax Class Table, Syntax Descriptors |
| 0 | 270 @subsection Syntax Flags |
| 271 @cindex syntax flags | |
| 272 | |
| 1024 | 273 @c This is a bit inaccurate, the ``a'' and ``b'' flags actually don't |
| 274 @c exist in the internal implementation. AFAICT it doesn't affect the | |
| 275 @c semantics as perceived by the LISP programmer. | |
| 0 | 276 In addition to the classes, entries for characters in a syntax table |
| 1024 | 277 can include flags. There are eleven possible flags, represented by the |
| 278 digits @samp{1}--@samp{8}, and the lowercase letters @samp{a}, @samp{b}, | |
| 279 and @samp{p}. | |
| 0 | 280 |
| 1024 | 281 All the flags except @samp{p} are used to describe comment delimiters. |
| 282 The digit flags indicate that a character can @emph{also} be part of a | |
| 283 multi-character comment sequence, in addition to the syntactic | |
| 284 properties associated with its character class. The flags must be | |
| 0 | 285 independent of the class and each other for the sake of characters such |
| 286 as @samp{*} in C mode, which is a punctuation character, @emph{and} the | |
| 287 second character of a start-of-comment sequence (@samp{/*}), @emph{and} | |
| 288 the first character of an end-of-comment sequence (@samp{*/}). | |
| 289 | |
| 290 Emacs supports two comment styles simultaneously in any one syntax | |
| 291 table. This is for the sake of C++. Each style of comment syntax has | |
| 292 its own comment-start sequence and its own comment-end sequence. Each | |
| 293 comment must stick to one style or the other; thus, if it starts with | |
| 294 the comment-start sequence of style ``b'', it must also end with the | |
| 295 comment-end sequence of style ``b''. | |
| 296 | |
| 1024 | 297 @c #### Compatibility note; index here. |
| 298 As an extension to GNU Emacs 19 and 20, XEmacs supports two arbitrary | |
| 299 comment-start sequences and two arbitrary comment-end sequences. (Thus | |
| 300 the need for 8 flags.) GNU Emacs restricts the comment-start sequences | |
| 301 to start with the same character, XEmacs does not. This means that for | |
| 302 two-character sequences, where GNU Emacs uses the @samp{b} flag, XEmacs | |
| 303 uses the digit flags @samp{5}--@samp{8}. | |
| 0 | 304 |
| 1024 | 305 A one character comment-end sequence applies to the ``b'' style if its |
| 306 first character has the @samp{b} flag set; otherwise, it applies to the | |
| 307 ``a'' style. The @samp{a} flag is optional. These flags have no effect | |
| 308 on non-comment characters; two-character styles are determined by the | |
| 309 digit flags. | |
| 310 | |
| 311 The flags for a character @var{c} are: | |
| 0 | 312 |
| 1024 | 313 @itemize @bullet |
| 314 @item | |
| 315 @samp{1} means @var{c} is the start of a two-character comment-start | |
| 316 sequence of style ``a''. | |
| 317 | |
| 318 @item | |
| 319 @samp{2} means @var{c} is the second character of such a sequence. | |
| 0 | 320 |
| 1024 | 321 @item |
| 322 @samp{3} means @var{c} is the start of a two-character comment-end | |
| 323 sequence of style ``a''. | |
| 324 | |
| 325 @item | |
| 326 @samp{4} means @var{c} is the second character of such a sequence. | |
| 0 | 327 |
| 1024 | 328 @item |
| 329 @samp{5} means @var{c} is the start of a two-character comment-start | |
| 330 sequence of style ``b''. | |
| 331 | |
| 332 @item | |
| 333 @samp{6} means @var{c} is the second character of such a sequence. | |
| 0 | 334 |
| 1024 | 335 @item |
| 336 @samp{7} means @var{c} is the start of a two-character comment-end | |
| 337 sequence of style ``b''. | |
| 338 | |
| 339 @item | |
| 340 @samp{8} means @var{c} is the second character of such a sequence. | |
| 0 | 341 |
| 1024 | 342 @item |
| 343 @samp{a} means that @var{c} as a comment delimiter belongs to the | |
| 344 default ``a'' comment style. (This flag is optional.) | |
| 0 | 345 |
| 1024 | 346 @item |
| 347 @c Emacs 19 feature | |
| 348 @samp{b} means that @var{c} as a comment delimiter belongs to the | |
| 349 alternate ``b'' comment style. | |
| 0 | 350 |
| 351 @item | |
| 352 @c Emacs 19 feature | |
| 353 @samp{p} identifies an additional ``prefix character'' for Lisp syntax. | |
| 354 These characters are treated as whitespace when they appear between | |
| 355 expressions. When they appear within an expression, they are handled | |
| 356 according to their usual syntax codes. | |
| 357 | |
| 358 The function @code{backward-prefix-chars} moves back over these | |
| 359 characters, as well as over characters whose primary syntax class is | |
| 360 prefix (@samp{'}). @xref{Motion and Syntax}. | |
| 361 @end itemize | |
| 362 | |
| 1024 | 363 Lisp (as you would expect) has a simple comment syntax. |
| 364 | |
| 365 @table @asis | |
| 366 @item @samp{;} | |
| 367 @samp{<} | |
| 368 @item newline | |
| 369 @samp{>} | |
| 370 @end table | |
| 371 | |
| 372 Note that no flags are used. | |
| 373 This defines two comment-delimiting sequences: | |
| 374 | |
| 375 @table @asis | |
| 376 @item @samp{;} | |
| 377 This is a single-character comment-start sequence because the syntax | |
| 378 class is @samp{<}. | |
| 379 | |
| 380 @item newline | |
| 381 This is a single character comment-end sequence because the syntax class | |
| 382 is @samp{>} and the @samp{b} flag is not set. | |
| 383 @end table | |
| 384 | |
| 385 C++ (again, as you would expect) has a baroque, overrich, and | |
| 386 excessively complex comment syntax. | |
| 387 | |
| 388 @table @asis | |
| 389 @item @samp{/} | |
| 390 @samp{1456} | |
| 391 @item @samp{*} | |
| 392 @samp{23} | |
| 393 @item newline | |
| 394 @samp{>b} | |
| 395 @end table | |
| 396 | |
| 397 Note that the ``b'' style mixes one-character and two-character | |
| 398 sequences. The table above defines four comment-delimiting sequences: | |
| 399 | |
| 400 @table @asis | |
| 401 @item @samp{/*} | |
| 402 This is a comment-start sequence for ``a'' style because the @samp{1} | |
| 403 flag is set on @samp{/} and the @samp{2} flag is set on @samp{*}. | |
| 404 | |
| 405 @item @samp{//} | |
| 406 This is a comment-start sequence for ``b'' style because both the @samp{5} | |
| 407 and the @samp{6} flags are set on @samp{/}. | |
| 408 | |
| 409 @item @samp{*/} | |
| 410 This is a comment-end sequence for ``a'' style because the @samp{3} | |
| 411 flag is set on @samp{*} and the @samp{4} flag is set on @samp{/}. | |
| 412 | |
| 413 @item newline | |
| 414 This is a comment-end sequence for ``b'' style, because the newline | |
| 415 character has the @samp{b} flag. | |
| 416 @end table | |
| 417 | |
| 418 | |
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419 @node Syntax Table Functions, Motion and Syntax, Syntax Descriptors, Syntax Tables |
| 0 | 420 @section Syntax Table Functions |
| 421 | |
| 422 In this section we describe functions for creating, accessing and | |
| 423 altering syntax tables. | |
| 424 | |
| 444 | 425 @defun make-syntax-table &optional oldtable |
| 0 | 426 This function creates a new syntax table. Character codes 0 through |
| 427 31 and 128 through 255 are set up to inherit from the standard syntax | |
| 428 table. The other character codes are set up by copying what the | |
| 429 standard syntax table says about them. | |
| 430 | |
| 431 Most major mode syntax tables are created in this way. | |
| 432 @end defun | |
| 433 | |
| 444 | 434 @defun copy-syntax-table &optional syntax-table |
| 435 This function constructs a copy of @var{syntax-table} and returns it. | |
| 436 If @var{syntax-table} is not supplied (or is @code{nil}), it returns a | |
| 437 copy of the current syntax table. Otherwise, an error is signaled if | |
| 438 @var{syntax-table} is not a syntax table. | |
| 0 | 439 @end defun |
| 440 | |
| 444 | 441 @deffn Command modify-syntax-entry char-range syntax-descriptor &optional syntax-table |
| 442 This function sets the syntax entry for @var{char-range} according to | |
| 443 @var{syntax-descriptor}. @var{char-range} is either a single character | |
| 444 or a range of characters, as used with @code{put-char-table}. The syntax | |
| 445 is changed only for @var{syntax-table}, which defaults to the current | |
| 446 buffer's syntax table, and not in any other syntax table. The argument | |
| 447 @var{syntax-descriptor} specifies the desired syntax; this is a string | |
| 448 beginning with a class designator character, and optionally containing a | |
| 449 matching character and flags as well. @xref{Syntax Descriptors}. | |
| 0 | 450 |
| 451 This function always returns @code{nil}. The old syntax information in | |
| 444 | 452 the table for @var{char-range} is discarded. |
| 0 | 453 |
| 454 An error is signaled if the first character of the syntax descriptor is not | |
| 444 | 455 one of the twelve syntax class designator characters. |
| 0 | 456 |
| 457 @example | |
| 458 @group | |
| 459 @exdent @r{Examples:} | |
| 460 | |
| 461 ;; @r{Put the space character in class whitespace.} | |
| 462 (modify-syntax-entry ?\ " ") | |
| 463 @result{} nil | |
| 464 @end group | |
| 465 | |
| 466 @group | |
| 467 ;; @r{Make @samp{$} an open parenthesis character,} | |
| 468 ;; @r{with @samp{^} as its matching close.} | |
| 469 (modify-syntax-entry ?$ "(^") | |
| 470 @result{} nil | |
| 471 @end group | |
| 472 | |
| 473 @group | |
| 474 ;; @r{Make @samp{^} a close parenthesis character,} | |
| 475 ;; @r{with @samp{$} as its matching open.} | |
| 476 (modify-syntax-entry ?^ ")$") | |
| 477 @result{} nil | |
| 478 @end group | |
| 479 | |
| 480 @group | |
| 481 ;; @r{Make @samp{/} a punctuation character,} | |
| 482 ;; @r{the first character of a start-comment sequence,} | |
| 483 ;; @r{and the second character of an end-comment sequence.} | |
| 484 ;; @r{This is used in C mode.} | |
| 485 (modify-syntax-entry ?/ ". 14") | |
| 486 @result{} nil | |
| 487 @end group | |
| 488 @end example | |
| 489 @end deffn | |
| 490 | |
| 444 | 491 @defun char-syntax character &optional syntax-table |
| 0 | 492 This function returns the syntax class of @var{character}, represented |
| 493 by its mnemonic designator character. This @emph{only} returns the | |
| 494 class, not any matching parenthesis or flags. | |
| 495 | |
| 444 | 496 An error is signaled if @var{character} is not a character. |
| 497 | |
| 498 The characters that correspond to various syntax codes | |
| 499 are listed in the documentation of @code{modify-syntax-entry}. | |
| 500 | |
| 501 Optional second argument @var{syntax-table} is the syntax table to be | |
| 502 used, and defaults to the current buffer's syntax table. | |
| 0 | 503 |
| 504 The following examples apply to C mode. The first example shows that | |
| 505 the syntax class of space is whitespace (represented by a space). The | |
| 506 second example shows that the syntax of @samp{/} is punctuation. This | |
| 507 does not show the fact that it is also part of comment-start and -end | |
| 508 sequences. The third example shows that open parenthesis is in the class | |
| 509 of open parentheses. This does not show the fact that it has a matching | |
| 510 character, @samp{)}. | |
| 511 | |
| 512 @example | |
| 513 @group | |
| 514 (char-to-string (char-syntax ?\ )) | |
| 515 @result{} " " | |
| 516 @end group | |
| 517 | |
| 518 @group | |
| 519 (char-to-string (char-syntax ?/)) | |
| 520 @result{} "." | |
| 521 @end group | |
| 522 | |
| 523 @group | |
| 524 (char-to-string (char-syntax ?\()) | |
| 525 @result{} "(" | |
| 526 @end group | |
| 527 @end example | |
| 528 @end defun | |
| 529 | |
| 444 | 530 @defun set-syntax-table syntax-table &optional buffer |
| 531 This function makes @var{syntax-table} the syntax table for @var{buffer}, which | |
| 532 defaults to the current buffer if omitted. It returns @var{syntax-table}. | |
| 0 | 533 @end defun |
| 534 | |
| 535 @defun syntax-table &optional buffer | |
| 536 This function returns the syntax table for @var{buffer}, which defaults | |
| 537 to the current buffer if omitted. | |
| 538 @end defun | |
| 539 | |
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540 @node Motion and Syntax, Parsing Expressions, Syntax Table Functions, Syntax Tables |
| 0 | 541 @section Motion and Syntax |
| 542 | |
| 543 This section describes functions for moving across characters in | |
| 544 certain syntax classes. None of these functions exists in Emacs | |
| 545 version 18 or earlier. | |
| 546 | |
| 547 @defun skip-syntax-forward syntaxes &optional limit buffer | |
| 548 This function moves point forward across characters having syntax classes | |
| 549 mentioned in @var{syntaxes}. It stops when it encounters the end of | |
| 550 the buffer, or position @var{limit} (if specified), or a character it is | |
| 551 not supposed to skip. Optional argument @var{buffer} defaults to the | |
| 552 current buffer if omitted. | |
| 553 @ignore @c may want to change this. | |
| 554 The return value is the distance traveled, which is a nonnegative | |
| 555 integer. | |
| 556 @end ignore | |
| 557 @end defun | |
| 558 | |
| 559 @defun skip-syntax-backward syntaxes &optional limit buffer | |
| 560 This function moves point backward across characters whose syntax | |
| 561 classes are mentioned in @var{syntaxes}. It stops when it encounters | |
| 562 the beginning of the buffer, or position @var{limit} (if specified), or a | |
| 563 character it is not supposed to skip. Optional argument @var{buffer} | |
| 564 defaults to the current buffer if omitted. | |
| 565 | |
| 566 @ignore @c may want to change this. | |
| 567 The return value indicates the distance traveled. It is an integer that | |
| 568 is zero or less. | |
| 569 @end ignore | |
| 570 @end defun | |
| 571 | |
| 572 @defun backward-prefix-chars &optional buffer | |
| 573 This function moves point backward over any number of characters with | |
| 574 expression prefix syntax. This includes both characters in the | |
| 575 expression prefix syntax class, and characters with the @samp{p} flag. | |
| 576 Optional argument @var{buffer} defaults to the current buffer if | |
| 577 omitted. | |
| 578 @end defun | |
| 579 | |
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580 @node Parsing Expressions, Standard Syntax Tables, Motion and Syntax, Syntax Tables |
| 0 | 581 @section Parsing Balanced Expressions |
| 582 | |
| 583 Here are several functions for parsing and scanning balanced | |
| 584 expressions, also known as @dfn{sexps}, in which parentheses match in | |
| 585 pairs. The syntax table controls the interpretation of characters, so | |
| 586 these functions can be used for Lisp expressions when in Lisp mode and | |
| 587 for C expressions when in C mode. @xref{List Motion}, for convenient | |
| 588 higher-level functions for moving over balanced expressions. | |
| 589 | |
| 590 @defun parse-partial-sexp start limit &optional target-depth stop-before state stop-comment buffer | |
| 591 This function parses a sexp in the current buffer starting at | |
| 592 @var{start}, not scanning past @var{limit}. It stops at position | |
| 593 @var{limit} or when certain criteria described below are met, and sets | |
| 594 point to the location where parsing stops. It returns a value | |
| 595 describing the status of the parse at the point where it stops. | |
| 596 | |
| 597 If @var{state} is @code{nil}, @var{start} is assumed to be at the top | |
| 598 level of parenthesis structure, such as the beginning of a function | |
| 599 definition. Alternatively, you might wish to resume parsing in the | |
| 600 middle of the structure. To do this, you must provide a @var{state} | |
| 601 argument that describes the initial status of parsing. | |
| 602 | |
| 603 @cindex parenthesis depth | |
| 604 If the third argument @var{target-depth} is non-@code{nil}, parsing | |
| 605 stops if the depth in parentheses becomes equal to @var{target-depth}. | |
| 606 The depth starts at 0, or at whatever is given in @var{state}. | |
| 607 | |
| 608 If the fourth argument @var{stop-before} is non-@code{nil}, parsing | |
| 609 stops when it comes to any character that starts a sexp. If | |
| 610 @var{stop-comment} is non-@code{nil}, parsing stops when it comes to the | |
| 611 start of a comment. | |
| 612 | |
| 613 @cindex parse state | |
| 614 The fifth argument @var{state} is an eight-element list of the same | |
| 615 form as the value of this function, described below. The return value | |
| 616 of one call may be used to initialize the state of the parse on another | |
| 617 call to @code{parse-partial-sexp}. | |
| 618 | |
| 619 The result is a list of eight elements describing the final state of | |
| 620 the parse: | |
| 621 | |
| 622 @enumerate 0 | |
| 444 | 623 @item |
| 0 | 624 The depth in parentheses, counting from 0. |
| 625 | |
| 444 | 626 @item |
| 0 | 627 @cindex innermost containing parentheses |
| 628 The character position of the start of the innermost parenthetical | |
| 629 grouping containing the stopping point; @code{nil} if none. | |
| 630 | |
| 444 | 631 @item |
| 0 | 632 @cindex previous complete subexpression |
| 633 The character position of the start of the last complete subexpression | |
| 634 terminated; @code{nil} if none. | |
| 635 | |
| 444 | 636 @item |
| 0 | 637 @cindex inside string |
| 638 Non-@code{nil} if inside a string. More precisely, this is the | |
| 639 character that will terminate the string. | |
| 640 | |
| 444 | 641 @item |
| 0 | 642 @cindex inside comment |
| 643 @code{t} if inside a comment (of either style). | |
| 644 | |
| 444 | 645 @item |
| 0 | 646 @cindex quote character |
| 647 @code{t} if point is just after a quote character. | |
| 648 | |
| 444 | 649 @item |
| 0 | 650 The minimum parenthesis depth encountered during this scan. |
| 651 | |
| 652 @item | |
| 653 @code{t} if inside a comment of style ``b''. | |
| 654 @end enumerate | |
| 655 | |
| 656 Elements 0, 3, 4, 5 and 7 are significant in the argument @var{state}. | |
| 657 | |
| 658 @cindex indenting with parentheses | |
| 659 This function is most often used to compute indentation for languages | |
| 660 that have nested parentheses. | |
| 661 @end defun | |
| 662 | |
| 663 @defun scan-lists from count depth &optional buffer noerror | |
| 664 This function scans forward @var{count} balanced parenthetical groupings | |
| 665 from character number @var{from}. It returns the character position | |
| 666 where the scan stops. | |
| 667 | |
| 668 If @var{depth} is nonzero, parenthesis depth counting begins from that | |
| 669 value. The only candidates for stopping are places where the depth in | |
| 670 parentheses becomes zero; @code{scan-lists} counts @var{count} such | |
| 671 places and then stops. Thus, a positive value for @var{depth} means go | |
| 672 out @var{depth} levels of parenthesis. | |
| 673 | |
| 674 Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
| 675 non-@code{nil}. | |
| 676 | |
| 677 If the scan reaches the beginning or end of the buffer (or its | |
| 678 accessible portion), and the depth is not zero, an error is signaled. | |
| 679 If the depth is zero but the count is not used up, @code{nil} is | |
| 680 returned. | |
| 681 | |
| 682 If optional arg @var{buffer} is non-@code{nil}, scanning occurs in that | |
| 683 buffer instead of in the current buffer. | |
| 684 | |
| 685 If optional arg @var{noerror} is non-@code{nil}, @code{scan-lists} | |
| 686 will return @code{nil} instead of signalling an error. | |
| 687 @end defun | |
| 688 | |
| 689 @defun scan-sexps from count &optional buffer noerror | |
| 690 This function scans forward @var{count} sexps from character position | |
| 691 @var{from}. It returns the character position where the scan stops. | |
| 692 | |
| 693 Scanning ignores comments if @code{parse-sexp-ignore-comments} is | |
| 694 non-@code{nil}. | |
| 695 | |
| 696 If the scan reaches the beginning or end of (the accessible part of) the | |
| 697 buffer in the middle of a parenthetical grouping, an error is signaled. | |
| 698 If it reaches the beginning or end between groupings but before count is | |
| 699 used up, @code{nil} is returned. | |
| 700 | |
| 701 If optional arg @var{buffer} is non-@code{nil}, scanning occurs in | |
| 702 that buffer instead of in the current buffer. | |
| 703 | |
| 704 If optional arg @var{noerror} is non-@code{nil}, @code{scan-sexps} | |
| 705 will return nil instead of signalling an error. | |
| 706 @end defun | |
| 707 | |
| 708 @defvar parse-sexp-ignore-comments | |
| 709 @cindex skipping comments | |
| 710 If the value is non-@code{nil}, then comments are treated as | |
| 711 whitespace by the functions in this section and by @code{forward-sexp}. | |
| 712 | |
| 713 In older Emacs versions, this feature worked only when the comment | |
| 714 terminator is something like @samp{*/}, and appears only to end a | |
| 715 comment. In languages where newlines terminate comments, it was | |
| 716 necessary make this variable @code{nil}, since not every newline is the | |
| 717 end of a comment. This limitation no longer exists. | |
| 718 @end defvar | |
| 719 | |
| 720 You can use @code{forward-comment} to move forward or backward over | |
| 721 one comment or several comments. | |
| 722 | |
| 446 | 723 @defun forward-comment &optional count buffer |
| 0 | 724 This function moves point forward across @var{count} comments (backward, |
| 725 if @var{count} is negative). If it finds anything other than a comment | |
| 726 or whitespace, it stops, leaving point at the place where it stopped. | |
| 446 | 727 It also stops after satisfying @var{count}. @var{count} defaults to @code{1}. |
| 0 | 728 |
| 446 | 729 Optional argument @var{buffer} defaults to the current buffer. |
| 0 | 730 @end defun |
| 731 | |
| 732 To move forward over all comments and whitespace following point, use | |
| 733 @code{(forward-comment (buffer-size))}. @code{(buffer-size)} is a good | |
| 734 argument to use, because the number of comments in the buffer cannot | |
| 735 exceed that many. | |
| 736 | |
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737 @node Standard Syntax Tables, Syntax Table Internals, Parsing Expressions, Syntax Tables |
| 0 | 738 @section Some Standard Syntax Tables |
| 739 | |
| 740 Most of the major modes in XEmacs have their own syntax tables. Here | |
| 741 are several of them: | |
| 742 | |
| 743 @defun standard-syntax-table | |
| 744 This function returns the standard syntax table, which is the syntax | |
| 745 table used in Fundamental mode. | |
| 746 @end defun | |
| 747 | |
| 748 @defvar text-mode-syntax-table | |
| 749 The value of this variable is the syntax table used in Text mode. | |
| 750 @end defvar | |
| 751 | |
| 752 @defvar c-mode-syntax-table | |
| 753 The value of this variable is the syntax table for C-mode buffers. | |
| 754 @end defvar | |
| 755 | |
| 756 @defvar emacs-lisp-mode-syntax-table | |
| 757 The value of this variable is the syntax table used in Emacs Lisp mode | |
| 758 by editing commands. (It has no effect on the Lisp @code{read} | |
| 759 function.) | |
| 760 @end defvar | |
| 761 | |
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762 @node Syntax Table Internals, , Standard Syntax Tables, Syntax Tables |
| 0 | 763 @section Syntax Table Internals |
| 764 @cindex syntax table internals | |
| 765 | |
| 766 Each element of a syntax table is an integer that encodes the syntax | |
| 767 of one character: the syntax class, possible matching character, and | |
| 768 flags. Lisp programs don't usually work with the elements directly; the | |
| 769 Lisp-level syntax table functions usually work with syntax descriptors | |
| 770 (@pxref{Syntax Descriptors}). | |
| 771 | |
| 772 The low 8 bits of each element of a syntax table indicate the | |
| 773 syntax class. | |
| 774 | |
| 775 @table @asis | |
| 776 @item @i{Integer} | |
| 777 @i{Class} | |
| 778 @item 0 | |
| 779 whitespace | |
| 780 @item 1 | |
| 781 punctuation | |
| 782 @item 2 | |
| 783 word | |
| 784 @item 3 | |
| 785 symbol | |
| 786 @item 4 | |
| 787 open parenthesis | |
| 788 @item 5 | |
| 789 close parenthesis | |
| 790 @item 6 | |
| 791 expression prefix | |
| 792 @item 7 | |
| 793 string quote | |
| 794 @item 8 | |
| 795 paired delimiter | |
| 796 @item 9 | |
| 797 escape | |
| 798 @item 10 | |
| 799 character quote | |
| 800 @item 11 | |
| 801 comment-start | |
| 802 @item 12 | |
| 803 comment-end | |
| 804 @item 13 | |
| 805 inherit | |
| 806 @end table | |
| 807 | |
| 808 The next 8 bits are the matching opposite parenthesis (if the | |
| 809 character has parenthesis syntax); otherwise, they are not meaningful. | |
| 810 The next 6 bits are the flags. |