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| author | Stephen J. Turnbull <stephen@xemacs.org> |
|---|---|
| date | Sat, 29 Oct 2011 17:08:25 +0900 |
| parents | d9eb5ea14f65 |
| children | 6772ce4d982b |
| rev | line source |
|---|---|
| 428 | 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. |
| 428 | 4 @c See the file lispref.texi for copying conditions. |
| 5 @setfilename ../../info/strings.info | |
| 6 @node Strings and Characters, Lists, Numbers, Top | |
| 7 @chapter Strings and Characters | |
| 8 @cindex strings | |
| 9 @cindex character arrays | |
| 10 @cindex characters | |
| 11 @cindex bytes | |
| 12 | |
| 13 A string in XEmacs Lisp is an array that contains an ordered sequence | |
| 14 of characters. Strings are used as names of symbols, buffers, and | |
| 15 files, to send messages to users, to hold text being copied between | |
| 16 buffers, and for many other purposes. Because strings are so important, | |
| 17 XEmacs Lisp has many functions expressly for manipulating them. XEmacs | |
| 18 Lisp programs use strings more often than individual characters. | |
| 19 | |
| 20 @menu | |
| 440 | 21 * String Basics:: Basic properties of strings and characters. |
| 428 | 22 * Predicates for Strings:: Testing whether an object is a string or char. |
| 23 * Creating Strings:: Functions to allocate new strings. | |
| 24 * Predicates for Characters:: Testing whether an object is a character. | |
| 25 * Character Codes:: Each character has an equivalent integer. | |
| 26 * Text Comparison:: Comparing characters or strings. | |
| 27 * String Conversion:: Converting characters or strings and vice versa. | |
| 28 * Modifying Strings:: Changing characters in a string. | |
| 29 * String Properties:: Additional information attached to strings. | |
| 30 * Formatting Strings:: @code{format}: XEmacs's analog of @code{printf}. | |
| 31 * Character Case:: Case conversion functions. | |
| 32 * Case Tables:: Customizing case conversion. | |
| 33 * Char Tables:: Mapping from characters to Lisp objects. | |
| 34 @end menu | |
| 35 | |
| 36 @node String Basics | |
| 37 @section String and Character Basics | |
| 38 | |
| 39 Strings in XEmacs Lisp are arrays that contain an ordered sequence of | |
| 40 characters. Characters are their own primitive object type in XEmacs | |
| 41 20. However, in XEmacs 19, characters are represented in XEmacs Lisp as | |
| 42 integers; whether an integer was intended as a character or not is | |
| 43 determined only by how it is used. @xref{Character Type}. | |
| 44 | |
| 45 The length of a string (like any array) is fixed and independent of | |
| 46 the string contents, and cannot be altered. Strings in Lisp are | |
| 47 @emph{not} terminated by a distinguished character code. (By contrast, | |
| 48 strings in C are terminated by a character with @sc{ascii} code 0.) | |
| 49 This means that any character, including the null character (@sc{ascii} | |
| 50 code 0), is a valid element of a string.@refill | |
| 51 | |
| 52 Since strings are considered arrays, you can operate on them with the | |
| 53 general array functions. (@xref{Sequences Arrays Vectors}.) For | |
| 54 example, you can access or change individual characters in a string | |
| 55 using the functions @code{aref} and @code{aset} (@pxref{Array | |
| 56 Functions}). | |
| 57 | |
| 58 Strings use an efficient representation for storing the characters | |
| 59 in them, and thus take up much less memory than a vector of the same | |
| 60 length. | |
| 61 | |
| 62 Sometimes you will see strings used to hold key sequences. This | |
| 63 exists for backward compatibility with Emacs 18, but should @emph{not} | |
| 64 be used in new code, since many key chords can't be represented at | |
| 65 all and others (in particular meta key chords) are confused with | |
| 66 accented characters. | |
| 67 | |
| 68 @ignore @c Not accurate any more | |
| 69 Each character in a string is stored in a single byte. Therefore, | |
| 70 numbers not in the range 0 to 255 are truncated when stored into a | |
| 71 string. This means that a string takes up much less memory than a | |
| 72 vector of the same length. | |
| 73 | |
| 74 Sometimes key sequences are represented as strings. When a string is | |
| 75 a key sequence, string elements in the range 128 to 255 represent meta | |
| 76 characters (which are extremely large integers) rather than keyboard | |
| 77 events in the range 128 to 255. | |
| 78 | |
| 79 Strings cannot hold characters that have the hyper, super or alt | |
| 80 modifiers; they can hold @sc{ASCII} control characters, but no other | |
| 81 control characters. They do not distinguish case in @sc{ASCII} control | |
| 82 characters. @xref{Character Type}, for more information about | |
| 83 representation of meta and other modifiers for keyboard input | |
| 84 characters. | |
| 85 @end ignore | |
| 86 | |
| 87 Strings are useful for holding regular expressions. You can also | |
| 88 match regular expressions against strings (@pxref{Regexp Search}). The | |
| 89 functions @code{match-string} (@pxref{Simple Match Data}) and | |
| 90 @code{replace-match} (@pxref{Replacing Match}) are useful for | |
| 91 decomposing and modifying strings based on regular expression matching. | |
| 92 | |
| 93 Like a buffer, a string can contain extents in it. These extents are | |
| 94 created when a function such as @code{buffer-substring} is called on a | |
| 95 region with duplicable extents in it. When the string is inserted into | |
| 96 a buffer, the extents are inserted along with it. @xref{Duplicable | |
| 97 Extents}. | |
| 98 | |
| 99 @xref{Text}, for information about functions that display strings or | |
| 100 copy them into buffers. @xref{Character Type}, and @ref{String Type}, | |
| 101 for information about the syntax of characters and strings. | |
| 102 | |
| 103 @node Predicates for Strings | |
| 104 @section The Predicates for Strings | |
| 105 | |
| 106 For more information about general sequence and array predicates, | |
| 107 see @ref{Sequences Arrays Vectors}, and @ref{Arrays}. | |
| 108 | |
| 109 @defun stringp object | |
| 110 This function returns @code{t} if @var{object} is a string, @code{nil} | |
| 111 otherwise. | |
| 112 @end defun | |
| 113 | |
| 114 @defun char-or-string-p object | |
| 115 This function returns @code{t} if @var{object} is a string or a | |
| 116 character, @code{nil} otherwise. | |
| 117 | |
| 118 In XEmacs addition, this function also returns @code{t} if @var{object} | |
| 119 is an integer that can be represented as a character. This is because | |
| 120 of compatibility with previous XEmacs and should not be depended on. | |
| 121 @end defun | |
| 122 | |
| 123 @node Creating Strings | |
| 124 @section Creating Strings | |
| 125 | |
| 126 The following functions create strings, either from scratch, or by | |
| 127 putting strings together, or by taking them apart. | |
| 128 | |
| 129 @defun string &rest characters | |
| 130 This function returns a new string made up of @var{characters}. | |
| 131 | |
| 132 @example | |
| 133 (string ?X ?E ?m ?a ?c ?s) | |
| 134 @result{} "XEmacs" | |
| 135 (string) | |
| 136 @result{} "" | |
| 137 @end example | |
| 138 | |
| 139 Analogous functions operating on other data types include @code{list}, | |
| 140 @code{cons} (@pxref{Building Lists}), @code{vector} (@pxref{Vectors}) | |
| 444 | 141 and @code{bit-vector} (@pxref{Bit Vectors}). This function has not been |
| 428 | 142 available in XEmacs prior to 21.0 and FSF Emacs prior to 20.3. |
| 143 @end defun | |
| 144 | |
| 444 | 145 @defun make-string length character |
| 146 This function returns a new string consisting entirely of @var{length} | |
| 147 successive copies of @var{character}. @var{length} must be a | |
| 148 non-negative integer. | |
| 428 | 149 |
| 150 @example | |
| 151 (make-string 5 ?x) | |
| 152 @result{} "xxxxx" | |
| 153 (make-string 0 ?x) | |
| 154 @result{} "" | |
| 155 @end example | |
| 156 | |
| 157 Other functions to compare with this one include @code{char-to-string} | |
| 158 (@pxref{String Conversion}), @code{make-vector} (@pxref{Vectors}), and | |
| 159 @code{make-list} (@pxref{Building Lists}). | |
| 160 @end defun | |
| 161 | |
| 162 @defun substring string start &optional end | |
| 163 This function returns a new string which consists of those characters | |
| 164 from @var{string} in the range from (and including) the character at the | |
| 165 index @var{start} up to (but excluding) the character at the index | |
| 166 @var{end}. The first character is at index zero. | |
| 167 | |
| 168 @example | |
| 169 @group | |
| 170 (substring "abcdefg" 0 3) | |
| 171 @result{} "abc" | |
| 172 @end group | |
| 173 @end example | |
| 174 | |
| 175 @noindent | |
| 176 Here the index for @samp{a} is 0, the index for @samp{b} is 1, and the | |
| 177 index for @samp{c} is 2. Thus, three letters, @samp{abc}, are copied | |
| 178 from the string @code{"abcdefg"}. The index 3 marks the character | |
| 179 position up to which the substring is copied. The character whose index | |
| 180 is 3 is actually the fourth character in the string. | |
| 181 | |
| 182 A negative number counts from the end of the string, so that @minus{}1 | |
| 444 | 183 signifies the index of the last character of the string. For example: |
| 428 | 184 |
| 185 @example | |
| 186 @group | |
| 187 (substring "abcdefg" -3 -1) | |
| 188 @result{} "ef" | |
| 189 @end group | |
| 190 @end example | |
| 191 | |
| 192 @noindent | |
| 193 In this example, the index for @samp{e} is @minus{}3, the index for | |
| 194 @samp{f} is @minus{}2, and the index for @samp{g} is @minus{}1. | |
| 195 Therefore, @samp{e} and @samp{f} are included, and @samp{g} is excluded. | |
| 196 | |
| 197 When @code{nil} is used as an index, it stands for the length of the | |
| 198 string. Thus, | |
| 199 | |
| 200 @example | |
| 201 @group | |
| 202 (substring "abcdefg" -3 nil) | |
| 203 @result{} "efg" | |
| 204 @end group | |
| 205 @end example | |
| 206 | |
| 207 Omitting the argument @var{end} is equivalent to specifying @code{nil}. | |
| 208 It follows that @code{(substring @var{string} 0)} returns a copy of all | |
| 209 of @var{string}. | |
| 210 | |
| 211 @example | |
| 212 @group | |
| 213 (substring "abcdefg" 0) | |
| 214 @result{} "abcdefg" | |
| 215 @end group | |
| 216 @end example | |
| 217 | |
| 218 @noindent | |
| 219 But we recommend @code{copy-sequence} for this purpose (@pxref{Sequence | |
| 220 Functions}). | |
| 221 | |
| 222 If the characters copied from @var{string} have duplicable extents or | |
| 223 text properties, those are copied into the new string also. | |
| 224 @xref{Duplicable Extents}. | |
| 225 | |
| 226 A @code{wrong-type-argument} error is signaled if either @var{start} or | |
| 227 @var{end} is not an integer or @code{nil}. An @code{args-out-of-range} | |
| 228 error is signaled if @var{start} indicates a character following | |
| 229 @var{end}, or if either integer is out of range for @var{string}. | |
| 230 | |
| 231 Contrast this function with @code{buffer-substring} (@pxref{Buffer | |
| 232 Contents}), which returns a string containing a portion of the text in | |
| 233 the current buffer. The beginning of a string is at index 0, but the | |
| 234 beginning of a buffer is at index 1. | |
| 235 @end defun | |
| 236 | |
| 237 @defun concat &rest sequences | |
| 238 @cindex copying strings | |
| 239 @cindex concatenating strings | |
| 240 This function returns a new string consisting of the characters in the | |
| 241 arguments passed to it (along with their text properties, if any). The | |
| 242 arguments may be strings, lists of numbers, or vectors of numbers; they | |
| 243 are not themselves changed. If @code{concat} receives no arguments, it | |
| 244 returns an empty string. | |
| 245 | |
| 246 @example | |
| 247 (concat "abc" "-def") | |
| 248 @result{} "abc-def" | |
| 249 (concat "abc" (list 120 (+ 256 121)) [122]) | |
| 250 @result{} "abcxyz" | |
| 251 ;; @r{@code{nil} is an empty sequence.} | |
| 252 (concat "abc" nil "-def") | |
| 253 @result{} "abc-def" | |
| 254 (concat "The " "quick brown " "fox.") | |
| 255 @result{} "The quick brown fox." | |
| 256 (concat) | |
| 257 @result{} "" | |
| 258 @end example | |
| 259 | |
| 260 @noindent | |
| 261 The second example above shows how characters stored in strings are | |
| 262 taken modulo 256. In other words, each character in the string is | |
| 263 stored in one byte. | |
| 264 | |
| 265 The @code{concat} function always constructs a new string that is | |
| 266 not @code{eq} to any existing string. | |
| 267 | |
| 268 When an argument is an integer (not a sequence of integers), it is | |
| 269 converted to a string of digits making up the decimal printed | |
| 270 representation of the integer. @strong{Don't use this feature; we plan | |
| 271 to eliminate it. If you already use this feature, change your programs | |
| 272 now!} The proper way to convert an integer to a decimal number in this | |
| 273 way is with @code{format} (@pxref{Formatting Strings}) or | |
| 274 @code{number-to-string} (@pxref{String Conversion}). | |
| 275 | |
| 276 @example | |
| 277 @group | |
| 278 (concat 137) | |
| 279 @result{} "137" | |
| 280 (concat 54 321) | |
| 281 @result{} "54321" | |
| 282 @end group | |
| 283 @end example | |
| 284 | |
| 285 For information about other concatenation functions, see the description | |
| 286 of @code{mapconcat} in @ref{Mapping Functions}, @code{vconcat} in | |
| 287 @ref{Vectors}, @code{bvconcat} in @ref{Bit Vectors}, and @code{append} | |
| 288 in @ref{Building Lists}. | |
| 289 @end defun | |
| 290 | |
| 1495 | 291 The function @code{split-string}, in @ref{Regexp Search}, generates a |
| 292 list of strings by splitting a string on occurances of a regular | |
| 293 expression. | |
| 294 | |
| 428 | 295 @node Predicates for Characters |
| 296 @section The Predicates for Characters | |
| 297 | |
| 298 @defun characterp object | |
| 299 This function returns @code{t} if @var{object} is a character. | |
| 300 | |
| 301 Some functions that work on integers (e.g. the comparison functions | |
| 302 <, <=, =, /=, etc. and the arithmetic functions +, -, *, etc.) | |
| 303 accept characters and implicitly convert them into integers. In | |
| 304 general, functions that work on characters also accept char-ints and | |
| 305 implicitly convert them into characters. WARNING: Neither of these | |
| 306 behaviors is very desirable, and they are maintained for backward | |
| 307 compatibility with old E-Lisp programs that confounded characters and | |
| 308 integers willy-nilly. These behaviors may change in the future; therefore, | |
| 309 do not rely on them. Instead, convert the characters explicitly | |
| 310 using @code{char-int}. | |
| 311 @end defun | |
| 312 | |
| 313 @defun integer-or-char-p object | |
| 314 This function returns @code{t} if @var{object} is an integer or character. | |
| 315 @end defun | |
| 316 | |
| 317 @node Character Codes | |
| 318 @section Character Codes | |
| 319 | |
| 444 | 320 @defun char-int character |
| 428 | 321 This function converts a character into an equivalent integer. |
| 322 The resulting integer will always be non-negative. The integers in | |
| 323 the range 0 - 255 map to characters as follows: | |
| 324 | |
| 325 @table @asis | |
| 326 @item 0 - 31 | |
| 327 Control set 0 | |
| 328 @item 32 - 127 | |
| 329 @sc{ascii} | |
| 330 @item 128 - 159 | |
| 331 Control set 1 | |
| 332 @item 160 - 255 | |
| 333 Right half of ISO-8859-1 | |
| 334 @end table | |
| 335 | |
| 336 If support for @sc{mule} does not exist, these are the only valid | |
| 337 character values. When @sc{mule} support exists, the values assigned to | |
| 338 other characters may vary depending on the particular version of XEmacs, | |
| 339 the order in which character sets were loaded, etc., and you should not | |
| 340 depend on them. | |
| 341 @end defun | |
| 342 | |
| 343 @defun int-char integer | |
| 344 This function converts an integer into the equivalent character. Not | |
| 345 all integers correspond to valid characters; use @code{char-int-p} to | |
| 346 determine whether this is the case. If the integer cannot be converted, | |
| 347 @code{nil} is returned. | |
| 348 @end defun | |
| 349 | |
| 350 @defun char-int-p object | |
| 351 This function returns @code{t} if @var{object} is an integer that can be | |
| 352 converted into a character. | |
| 353 @end defun | |
| 354 | |
| 355 @defun char-or-char-int-p object | |
| 356 This function returns @code{t} if @var{object} is a character or an | |
| 357 integer that can be converted into one. | |
| 358 @end defun | |
| 359 | |
| 360 @need 2000 | |
| 361 @node Text Comparison | |
| 362 @section Comparison of Characters and Strings | |
| 363 @cindex string equality | |
| 364 | |
| 444 | 365 @defun char-equal character1 character2 &optional buffer |
| 428 | 366 This function returns @code{t} if the arguments represent the same |
| 367 character, @code{nil} otherwise. This function ignores differences | |
| 444 | 368 in case if the value of @code{case-fold-search} is non-@code{nil} in |
| 369 @var{buffer}, which defaults to the current buffer. | |
| 428 | 370 |
| 371 @example | |
| 372 (char-equal ?x ?x) | |
| 373 @result{} t | |
| 374 (let ((case-fold-search t)) | |
| 375 (char-equal ?x ?X)) | |
| 376 @result{} t | |
| 377 (let ((case-fold-search nil)) | |
| 378 (char-equal ?x ?X)) | |
| 379 @result{} nil | |
| 380 @end example | |
| 381 @end defun | |
| 382 | |
| 383 @defun char= character1 character2 | |
| 384 This function returns @code{t} if the arguments represent the same | |
| 385 character, @code{nil} otherwise. Case is significant. | |
| 386 | |
| 387 @example | |
| 388 (char= ?x ?x) | |
| 389 @result{} t | |
| 390 (char= ?x ?X) | |
| 391 @result{} nil | |
| 392 (let ((case-fold-search t)) | |
| 393 (char-equal ?x ?X)) | |
| 394 @result{} nil | |
| 395 (let ((case-fold-search nil)) | |
| 396 (char-equal ?x ?X)) | |
| 397 @result{} nil | |
| 398 @end example | |
| 399 @end defun | |
| 400 | |
| 401 @defun string= string1 string2 | |
| 402 This function returns @code{t} if the characters of the two strings | |
| 403 match exactly; case is significant. | |
| 404 | |
| 405 @example | |
| 406 (string= "abc" "abc") | |
| 407 @result{} t | |
| 408 (string= "abc" "ABC") | |
| 409 @result{} nil | |
| 410 (string= "ab" "ABC") | |
| 411 @result{} nil | |
| 412 @end example | |
| 413 | |
| 414 @ignore @c `equal' in XEmacs does not compare text properties | |
| 415 The function @code{string=} ignores the text properties of the | |
| 416 two strings. To compare strings in a way that compares their text | |
| 417 properties also, use @code{equal} (@pxref{Equality Predicates}). | |
| 418 @end ignore | |
| 419 @end defun | |
| 420 | |
| 421 @defun string-equal string1 string2 | |
| 422 @code{string-equal} is another name for @code{string=}. | |
| 423 @end defun | |
| 424 | |
| 425 @cindex lexical comparison | |
| 426 @defun string< string1 string2 | |
| 427 @c (findex string< causes problems for permuted index!!) | |
| 428 This function compares two strings a character at a time. First it | |
| 429 scans both the strings at once to find the first pair of corresponding | |
| 430 characters that do not match. If the lesser character of those two is | |
| 431 the character from @var{string1}, then @var{string1} is less, and this | |
| 432 function returns @code{t}. If the lesser character is the one from | |
| 433 @var{string2}, then @var{string1} is greater, and this function returns | |
| 434 @code{nil}. If the two strings match entirely, the value is @code{nil}. | |
| 435 | |
| 436 Pairs of characters are compared by their @sc{ascii} codes. Keep in | |
| 437 mind that lower case letters have higher numeric values in the | |
| 438 @sc{ascii} character set than their upper case counterparts; numbers and | |
| 439 many punctuation characters have a lower numeric value than upper case | |
| 440 letters. | |
| 441 | |
| 442 @example | |
| 443 @group | |
| 444 (string< "abc" "abd") | |
| 445 @result{} t | |
| 446 (string< "abd" "abc") | |
| 447 @result{} nil | |
| 448 (string< "123" "abc") | |
| 449 @result{} t | |
| 450 @end group | |
| 451 @end example | |
| 452 | |
| 453 When the strings have different lengths, and they match up to the | |
| 454 length of @var{string1}, then the result is @code{t}. If they match up | |
| 455 to the length of @var{string2}, the result is @code{nil}. A string of | |
| 456 no characters is less than any other string. | |
| 457 | |
| 458 @example | |
| 459 @group | |
| 460 (string< "" "abc") | |
| 461 @result{} t | |
| 462 (string< "ab" "abc") | |
| 463 @result{} t | |
| 464 (string< "abc" "") | |
| 465 @result{} nil | |
| 466 (string< "abc" "ab") | |
| 467 @result{} nil | |
| 468 (string< "" "") | |
| 444 | 469 @result{} nil |
| 428 | 470 @end group |
| 471 @end example | |
| 472 @end defun | |
| 473 | |
| 474 @defun string-lessp string1 string2 | |
| 475 @code{string-lessp} is another name for @code{string<}. | |
| 476 @end defun | |
| 477 | |
| 478 See also @code{compare-buffer-substrings} in @ref{Comparing Text}, for | |
| 479 a way to compare text in buffers. The function @code{string-match}, | |
| 480 which matches a regular expression against a string, can be used | |
| 481 for a kind of string comparison; see @ref{Regexp Search}. | |
| 482 | |
| 483 @node String Conversion | |
| 484 @section Conversion of Characters and Strings | |
| 485 @cindex conversion of strings | |
| 486 | |
| 487 This section describes functions for conversions between characters, | |
| 488 strings and integers. @code{format} and @code{prin1-to-string} | |
| 489 (@pxref{Output Functions}) can also convert Lisp objects into strings. | |
| 490 @code{read-from-string} (@pxref{Input Functions}) can ``convert'' a | |
| 491 string representation of a Lisp object into an object. | |
| 492 | |
| 493 @xref{Documentation}, for functions that produce textual descriptions | |
| 494 of text characters and general input events | |
| 495 (@code{single-key-description} and @code{text-char-description}). These | |
| 496 functions are used primarily for making help messages. | |
| 497 | |
| 498 @defun char-to-string character | |
| 499 @cindex character to string | |
| 500 This function returns a new string with a length of one character. | |
| 501 The value of @var{character}, modulo 256, is used to initialize the | |
| 502 element of the string. | |
| 503 | |
| 504 This function is similar to @code{make-string} with an integer argument | |
| 505 of 1. (@xref{Creating Strings}.) This conversion can also be done with | |
| 506 @code{format} using the @samp{%c} format specification. | |
| 507 (@xref{Formatting Strings}.) | |
| 508 | |
| 509 @example | |
| 510 (char-to-string ?x) | |
| 511 @result{} "x" | |
| 512 (char-to-string (+ 256 ?x)) | |
| 513 @result{} "x" | |
| 514 (make-string 1 ?x) | |
| 515 @result{} "x" | |
| 516 @end example | |
| 517 @end defun | |
| 518 | |
| 519 @defun string-to-char string | |
| 520 @cindex string to character | |
| 521 This function returns the first character in @var{string}. If the | |
| 522 string is empty, the function returns 0. (Under XEmacs 19, the value is | |
| 523 also 0 when the first character of @var{string} is the null character, | |
| 524 @sc{ascii} code 0.) | |
| 525 | |
| 526 @example | |
| 527 (string-to-char "ABC") | |
| 528 @result{} ?A ;; @r{Under XEmacs 20.} | |
| 529 @result{} 65 ;; @r{Under XEmacs 19.} | |
| 530 (string-to-char "xyz") | |
| 531 @result{} ?x ;; @r{Under XEmacs 20.} | |
| 532 @result{} 120 ;; @r{Under XEmacs 19.} | |
| 533 (string-to-char "") | |
| 534 @result{} 0 | |
| 535 (string-to-char "\000") | |
| 536 @result{} ?\^@ ;; @r{Under XEmacs 20.} | |
| 537 @result{} 0 ;; @r{Under XEmacs 20.} | |
| 538 @end example | |
| 539 | |
| 540 This function may be eliminated in the future if it does not seem useful | |
| 541 enough to retain. | |
| 542 @end defun | |
| 543 | |
| 544 @defun number-to-string number | |
| 545 @cindex integer to string | |
| 546 @cindex integer to decimal | |
| 547 This function returns a string consisting of the printed | |
| 548 representation of @var{number}, which may be an integer or a floating | |
| 549 point number. The value starts with a sign if the argument is | |
| 550 negative. | |
| 551 | |
| 552 @example | |
| 553 (number-to-string 256) | |
| 554 @result{} "256" | |
| 555 (number-to-string -23) | |
| 556 @result{} "-23" | |
| 557 (number-to-string -23.5) | |
| 558 @result{} "-23.5" | |
| 559 @end example | |
| 560 | |
| 561 @cindex int-to-string | |
| 562 @code{int-to-string} is a semi-obsolete alias for this function. | |
| 563 | |
| 564 See also the function @code{format} in @ref{Formatting Strings}. | |
| 565 @end defun | |
| 566 | |
| 567 @defun string-to-number string &optional base | |
| 568 @cindex string to number | |
| 444 | 569 This function returns the numeric value represented by @var{string}, |
| 570 read in @var{base}. It skips spaces and tabs at the beginning of | |
| 571 @var{string}, then reads as much of @var{string} as it can interpret as | |
| 572 a number. (On some systems it ignores other whitespace at the | |
| 573 beginning, not just spaces and tabs.) If the first character after the | |
| 574 ignored whitespace is not a digit or a minus sign, this function returns | |
| 575 0. | |
| 428 | 576 |
| 577 If @var{base} is not specified, it defaults to ten. With @var{base} | |
| 578 other than ten, only integers can be read. | |
| 579 | |
| 580 @example | |
| 581 (string-to-number "256") | |
| 582 @result{} 256 | |
| 583 (string-to-number "25 is a perfect square.") | |
| 584 @result{} 25 | |
| 585 (string-to-number "X256") | |
| 586 @result{} 0 | |
| 587 (string-to-number "-4.5") | |
| 588 @result{} -4.5 | |
| 589 (string-to-number "ffff" 16) | |
| 590 @result{} 65535 | |
| 591 @end example | |
| 592 | |
| 593 @findex string-to-int | |
| 594 @code{string-to-int} is an obsolete alias for this function. | |
| 595 @end defun | |
| 596 | |
| 597 @node Modifying Strings | |
| 598 @section Modifying Strings | |
| 599 @cindex strings, modifying | |
| 600 | |
| 601 You can modify a string using the general array-modifying primitives. | |
| 602 @xref{Arrays}. The function @code{aset} modifies a single character; | |
| 603 the function @code{fillarray} sets all characters in the string to | |
| 604 a specified character. | |
| 605 | |
| 606 Each string has a tick counter that starts out at zero (when the string | |
| 607 is created) and is incremented each time a change is made to that | |
| 608 string. | |
| 609 | |
| 610 @defun string-modified-tick string | |
| 611 This function returns the tick counter for @samp{string}. | |
| 612 @end defun | |
| 613 | |
| 614 @node String Properties | |
| 615 @section String Properties | |
| 616 @cindex string properties | |
| 617 @cindex properties of strings | |
| 618 | |
| 442 | 619 Just as with symbols, extents, faces, and glyphs, you can attach |
| 428 | 620 additional information to strings in the form of @dfn{string |
| 621 properties}. These differ from text properties, which are logically | |
| 622 attached to particular characters in the string. | |
| 623 | |
| 624 To attach a property to a string, use @code{put}. To retrieve a property | |
| 625 from a string, use @code{get}. You can also use @code{remprop} to remove | |
| 442 | 626 a property from a string and @code{object-plist} to retrieve a list of |
| 428 | 627 all the properties in a string. |
| 628 | |
| 629 @node Formatting Strings | |
| 630 @section Formatting Strings | |
| 631 @cindex formatting strings | |
| 632 @cindex strings, formatting them | |
| 633 | |
| 634 @dfn{Formatting} means constructing a string by substitution of | |
| 635 computed values at various places in a constant string. This string | |
| 636 controls how the other values are printed as well as where they appear; | |
| 637 it is called a @dfn{format string}. | |
| 638 | |
| 639 Formatting is often useful for computing messages to be displayed. In | |
| 640 fact, the functions @code{message} and @code{error} provide the same | |
| 641 formatting feature described here; they differ from @code{format} only | |
| 642 in how they use the result of formatting. | |
| 643 | |
| 644 @defun format string &rest objects | |
| 645 This function returns a new string that is made by copying | |
| 444 | 646 @var{string} and then replacing any format specification |
| 428 | 647 in the copy with encodings of the corresponding @var{objects}. The |
| 648 arguments @var{objects} are the computed values to be formatted. | |
| 649 @end defun | |
| 650 | |
| 651 @cindex @samp{%} in format | |
| 652 @cindex format specification | |
| 653 A format specification is a sequence of characters beginning with a | |
| 654 @samp{%}. Thus, if there is a @samp{%d} in @var{string}, the | |
| 655 @code{format} function replaces it with the printed representation of | |
| 656 one of the values to be formatted (one of the arguments @var{objects}). | |
| 657 For example: | |
| 658 | |
| 659 @example | |
| 660 @group | |
| 661 (format "The value of fill-column is %d." fill-column) | |
| 662 @result{} "The value of fill-column is 72." | |
| 663 @end group | |
| 664 @end example | |
| 665 | |
| 666 If @var{string} contains more than one format specification, the | |
| 667 format specifications correspond with successive values from | |
| 668 @var{objects}. Thus, the first format specification in @var{string} | |
| 669 uses the first such value, the second format specification uses the | |
| 670 second such value, and so on. Any extra format specifications (those | |
| 671 for which there are no corresponding values) cause unpredictable | |
| 672 behavior. Any extra values to be formatted are ignored. | |
| 673 | |
| 674 Certain format specifications require values of particular types. | |
| 675 However, no error is signaled if the value actually supplied fails to | |
| 676 have the expected type. Instead, the output is likely to be | |
| 677 meaningless. | |
| 678 | |
| 679 Here is a table of valid format specifications: | |
| 680 | |
| 681 @table @samp | |
| 682 @item %s | |
| 683 Replace the specification with the printed representation of the object, | |
| 684 made without quoting. Thus, strings are represented by their contents | |
| 685 alone, with no @samp{"} characters, and symbols appear without @samp{\} | |
| 686 characters. This is equivalent to printing the object with @code{princ}. | |
| 687 | |
| 688 If there is no corresponding object, the empty string is used. | |
| 689 | |
| 690 @item %S | |
| 691 Replace the specification with the printed representation of the object, | |
| 692 made with quoting. Thus, strings are enclosed in @samp{"} characters, | |
| 693 and @samp{\} characters appear where necessary before special characters. | |
| 694 This is equivalent to printing the object with @code{prin1}. | |
| 695 | |
| 696 If there is no corresponding object, the empty string is used. | |
| 697 | |
| 698 @item %o | |
| 699 @cindex integer to octal | |
| 700 Replace the specification with the base-eight representation of an | |
| 701 integer. | |
| 702 | |
| 703 @item %d | |
| 704 @itemx %i | |
| 705 Replace the specification with the base-ten representation of an | |
| 706 integer. | |
| 707 | |
| 708 @item %x | |
| 709 @cindex integer to hexadecimal | |
| 710 Replace the specification with the base-sixteen representation of an | |
| 711 integer, using lowercase letters. | |
| 712 | |
| 713 @item %X | |
| 714 @cindex integer to hexadecimal | |
| 715 Replace the specification with the base-sixteen representation of an | |
| 716 integer, using uppercase letters. | |
| 717 | |
|
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718 @item %b |
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719 @cindex integer to binary |
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720 Replace the specification with the base-two representation of an |
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721 integer. |
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722 |
| 428 | 723 @item %c |
| 724 Replace the specification with the character which is the value given. | |
| 725 | |
| 726 @item %e | |
| 727 Replace the specification with the exponential notation for a floating | |
| 728 point number (e.g. @samp{7.85200e+03}). | |
| 729 | |
| 730 @item %f | |
| 731 Replace the specification with the decimal-point notation for a floating | |
| 732 point number. | |
| 733 | |
| 734 @item %g | |
| 735 Replace the specification with notation for a floating point number, | |
| 736 using a ``pretty format''. Either exponential notation or decimal-point | |
| 737 notation will be used (usually whichever is shorter), and trailing | |
| 738 zeroes are removed from the fractional part. | |
| 739 | |
| 740 @item %% | |
| 741 A single @samp{%} is placed in the string. This format specification is | |
| 742 unusual in that it does not use a value. For example, @code{(format "%% | |
| 743 %d" 30)} returns @code{"% 30"}. | |
| 744 @end table | |
| 745 | |
| 746 Any other format character results in an @samp{Invalid format | |
| 747 operation} error. | |
| 748 | |
| 749 Here are several examples: | |
| 750 | |
| 751 @example | |
| 752 @group | |
| 753 (format "The name of this buffer is %s." (buffer-name)) | |
| 754 @result{} "The name of this buffer is strings.texi." | |
| 755 | |
| 756 (format "The buffer object prints as %s." (current-buffer)) | |
| 757 @result{} "The buffer object prints as #<buffer strings.texi>." | |
| 758 | |
| 444 | 759 (format "The octal value of %d is %o, |
| 428 | 760 and the hex value is %x." 18 18 18) |
| 444 | 761 @result{} "The octal value of 18 is 22, |
| 428 | 762 and the hex value is 12." |
| 763 @end group | |
| 764 @end example | |
| 765 | |
| 766 There are many additional flags and specifications that can occur | |
| 767 between the @samp{%} and the format character, in the following order: | |
| 768 | |
| 769 @enumerate | |
| 770 @item | |
| 771 An optional repositioning specification, which is a positive | |
| 772 integer followed by a @samp{$}. | |
| 773 | |
| 774 @item | |
| 775 Zero or more of the optional flag characters @samp{-}, @samp{+}, | |
| 776 @samp{ }, @samp{0}, and @samp{#}. | |
| 777 | |
| 778 @item | |
| 779 An asterisk (@samp{*}, meaning that the field width is now assumed to | |
| 780 have been specified as an argument. | |
| 781 | |
| 782 @item | |
| 783 An optional minimum field width. | |
| 784 | |
| 785 @item | |
| 786 An optional precision, preceded by a @samp{.} character. | |
| 787 @end enumerate | |
| 788 | |
| 789 @cindex repositioning format arguments | |
| 790 @cindex multilingual string formatting | |
| 791 A @dfn{repositioning} specification changes which argument to | |
| 792 @code{format} is used by the current and all following format | |
| 793 specifications. Normally the first specification uses the first | |
| 794 argument, the second specification uses the second argument, etc. Using | |
| 795 a repositioning specification, you can change this. By placing a number | |
| 444 | 796 @var{n} followed by a @samp{$} between the @samp{%} and the format |
| 797 character, you cause the specification to use the @var{n}th argument. | |
| 798 The next specification will use the @var{n}+1'th argument, etc. | |
| 428 | 799 |
| 800 For example: | |
| 801 | |
| 802 @example | |
| 803 @group | |
| 804 (format "Can't find file `%s' in directory `%s'." | |
| 805 "ignatius.c" "loyola/") | |
| 806 @result{} "Can't find file `ignatius.c' in directory `loyola/'." | |
| 807 | |
| 808 (format "In directory `%2$s', the file `%1$s' was not found." | |
| 809 "ignatius.c" "loyola/") | |
| 810 @result{} "In directory `loyola/', the file `ignatius.c' was not found." | |
| 811 | |
| 812 (format | |
| 813 "The numbers %d and %d are %1$x and %x in hex and %1$o and %o in octal." | |
| 814 37 12) | |
| 815 @result{} "The numbers 37 and 12 are 25 and c in hex and 45 and 14 in octal." | |
| 816 @end group | |
| 817 @end example | |
| 818 | |
| 819 As you can see, this lets you reprocess arguments more than once or | |
| 820 reword a format specification (thereby moving the arguments around) | |
| 821 without having to actually reorder the arguments. This is especially | |
| 822 useful in translating messages from one language to another: Different | |
| 823 languages use different word orders, and this sometimes entails changing | |
| 824 the order of the arguments. By using repositioning specifications, | |
| 825 this can be accomplished without having to embed knowledge of particular | |
| 826 languages into the location in the program's code where the message is | |
| 827 displayed. | |
| 828 | |
| 829 @cindex numeric prefix | |
| 830 @cindex field width | |
| 831 @cindex padding | |
| 832 All the specification characters allow an optional numeric prefix | |
| 833 between the @samp{%} and the character, and following any repositioning | |
| 834 specification or flag. The optional numeric prefix defines the minimum | |
| 835 width for the object. If the printed representation of the object | |
| 836 contains fewer characters than this, then it is padded. The padding is | |
| 837 normally on the left, but will be on the right if the @samp{-} flag | |
| 838 character is given. The padding character is normally a space, but if | |
| 839 the @samp{0} flag character is given, zeros are used for padding. | |
| 840 | |
| 841 @example | |
| 842 (format "%06d is padded on the left with zeros" 123) | |
| 843 @result{} "000123 is padded on the left with zeros" | |
| 844 | |
| 845 (format "%-6d is padded on the right" 123) | |
| 846 @result{} "123 is padded on the right" | |
| 847 @end example | |
| 848 | |
| 849 @code{format} never truncates an object's printed representation, no | |
| 850 matter what width you specify. Thus, you can use a numeric prefix to | |
| 851 specify a minimum spacing between columns with no risk of losing | |
| 852 information. | |
| 853 | |
| 854 In the following three examples, @samp{%7s} specifies a minimum width | |
| 855 of 7. In the first case, the string inserted in place of @samp{%7s} has | |
| 856 only 3 letters, so 4 blank spaces are inserted for padding. In the | |
| 857 second case, the string @code{"specification"} is 13 letters wide but is | |
| 858 not truncated. In the third case, the padding is on the right. | |
| 859 | |
| 444 | 860 @smallexample |
| 428 | 861 @group |
| 862 (format "The word `%7s' actually has %d letters in it." | |
| 863 "foo" (length "foo")) | |
| 444 | 864 @result{} "The word ` foo' actually has 3 letters in it." |
| 428 | 865 @end group |
| 866 | |
| 867 @group | |
| 868 (format "The word `%7s' actually has %d letters in it." | |
| 444 | 869 "specification" (length "specification")) |
| 870 @result{} "The word `specification' actually has 13 letters in it." | |
| 428 | 871 @end group |
| 872 | |
| 873 @group | |
| 874 (format "The word `%-7s' actually has %d letters in it." | |
| 875 "foo" (length "foo")) | |
| 444 | 876 @result{} "The word `foo ' actually has 3 letters in it." |
| 428 | 877 @end group |
| 878 @end smallexample | |
| 879 | |
| 880 @cindex format precision | |
| 881 @cindex precision of formatted numbers | |
| 882 After any minimum field width, a precision may be specified by | |
| 883 preceding it with a @samp{.} character. The precision specifies the | |
| 884 minimum number of digits to appear in @samp{%d}, @samp{%i}, @samp{%o}, | |
| 885 @samp{%x}, and @samp{%X} conversions (the number is padded on the left | |
| 886 with zeroes as necessary); the number of digits printed after the | |
| 887 decimal point for @samp{%f}, @samp{%e}, and @samp{%E} conversions; the | |
| 888 number of significant digits printed in @samp{%g} and @samp{%G} | |
| 889 conversions; and the maximum number of non-padding characters printed in | |
| 890 @samp{%s} and @samp{%S} conversions. The default precision for | |
| 891 floating-point conversions is six. | |
| 892 | |
| 893 The other flag characters have the following meanings: | |
| 894 | |
| 895 @itemize @bullet | |
| 896 @item | |
| 897 The @samp{ } flag means prefix non-negative numbers with a space. | |
| 898 | |
| 899 @item | |
| 900 The @samp{+} flag means prefix non-negative numbers with a plus sign. | |
| 901 | |
| 902 @item | |
| 903 The @samp{#} flag means print numbers in an alternate, more verbose | |
| 904 format: octal numbers begin with zero; hex numbers begin with a | |
| 905 @samp{0x} or @samp{0X}; a decimal point is printed in @samp{%f}, | |
| 906 @samp{%e}, and @samp{%E} conversions even if no numbers are printed | |
| 907 after it; and trailing zeroes are not omitted in @samp{%g} and @samp{%G} | |
| 908 conversions. | |
| 909 @end itemize | |
| 910 | |
| 911 @node Character Case | |
| 912 @section Character Case | |
| 444 | 913 @cindex upper case |
| 914 @cindex lower case | |
| 915 @cindex character case | |
| 428 | 916 |
| 917 The character case functions change the case of single characters or | |
| 918 of the contents of strings. The functions convert only alphabetic | |
| 919 characters (the letters @samp{A} through @samp{Z} and @samp{a} through | |
| 920 @samp{z}); other characters are not altered. The functions do not | |
| 921 modify the strings that are passed to them as arguments. | |
| 922 | |
| 923 The examples below use the characters @samp{X} and @samp{x} which have | |
| 924 @sc{ascii} codes 88 and 120 respectively. | |
| 925 | |
| 444 | 926 @defun downcase string-or-char &optional buffer |
| 428 | 927 This function converts a character or a string to lower case. |
| 928 | |
| 929 When the argument to @code{downcase} is a string, the function creates | |
| 930 and returns a new string in which each letter in the argument that is | |
| 931 upper case is converted to lower case. When the argument to | |
| 932 @code{downcase} is a character, @code{downcase} returns the | |
| 933 corresponding lower case character. (This value is actually an integer | |
| 934 under XEmacs 19.) If the original character is lower case, or is not a | |
| 935 letter, then the value equals the original character. | |
| 936 | |
| 444 | 937 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 938 use, and defaults to the current buffer. | |
| 939 | |
| 428 | 940 @example |
| 941 (downcase "The cat in the hat") | |
| 942 @result{} "the cat in the hat" | |
| 943 | |
| 944 (downcase ?X) | |
| 945 @result{} ?x ;; @r{Under XEmacs 20.} | |
| 946 @result{} 120 ;; @r{Under XEmacs 19.} | |
| 947 | |
| 948 @end example | |
| 949 @end defun | |
| 950 | |
| 444 | 951 @defun upcase string-or-char &optional buffer |
| 428 | 952 This function converts a character or a string to upper case. |
| 953 | |
| 954 When the argument to @code{upcase} is a string, the function creates | |
| 955 and returns a new string in which each letter in the argument that is | |
| 956 lower case is converted to upper case. | |
| 957 | |
| 958 When the argument to @code{upcase} is a character, @code{upcase} returns | |
| 959 the corresponding upper case character. (This value is actually an | |
| 960 integer under XEmacs 19.) If the original character is upper case, or | |
| 961 is not a letter, then the value equals the original character. | |
| 962 | |
| 444 | 963 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 964 use, and defaults to the current buffer. | |
| 965 | |
| 428 | 966 @example |
| 967 (upcase "The cat in the hat") | |
| 968 @result{} "THE CAT IN THE HAT" | |
| 969 | |
| 970 (upcase ?x) | |
| 971 @result{} ?X ;; @r{Under XEmacs 20.} | |
| 972 @result{} 88 ;; @r{Under XEmacs 19.} | |
| 973 @end example | |
| 974 @end defun | |
| 975 | |
| 444 | 976 @defun capitalize string-or-char &optional buffer |
| 428 | 977 @cindex capitalization |
| 978 This function capitalizes strings or characters. If | |
| 979 @var{string-or-char} is a string, the function creates and returns a new | |
| 980 string, whose contents are a copy of @var{string-or-char} in which each | |
| 981 word has been capitalized. This means that the first character of each | |
| 982 word is converted to upper case, and the rest are converted to lower | |
| 983 case. | |
| 984 | |
| 985 The definition of a word is any sequence of consecutive characters that | |
| 986 are assigned to the word constituent syntax class in the current syntax | |
| 987 table (@pxref{Syntax Class Table}). | |
| 988 | |
| 989 When the argument to @code{capitalize} is a character, @code{capitalize} | |
| 990 has the same result as @code{upcase}. | |
| 991 | |
| 444 | 992 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 993 use, and defaults to the current buffer. | |
| 994 | |
| 428 | 995 @example |
| 996 (capitalize "The cat in the hat") | |
| 997 @result{} "The Cat In The Hat" | |
| 998 | |
| 999 (capitalize "THE 77TH-HATTED CAT") | |
| 1000 @result{} "The 77th-Hatted Cat" | |
| 1001 | |
| 1002 @group | |
| 1003 (capitalize ?x) | |
| 1004 @result{} ?X ;; @r{Under XEmacs 20.} | |
| 1005 @result{} 88 ;; @r{Under XEmacs 19.} | |
| 1006 @end group | |
| 1007 @end example | |
| 1008 @end defun | |
| 1009 | |
| 1010 @node Case Tables | |
| 1011 @section The Case Table | |
| 1012 | |
| 1013 You can customize case conversion by installing a special @dfn{case | |
| 1014 table}. A case table specifies the mapping between upper case and lower | |
| 1015 case letters. It affects both the string and character case conversion | |
| 1016 functions (see the previous section) and those that apply to text in the | |
| 1017 buffer (@pxref{Case Changes}). You need a case table if you are using a | |
| 1018 language which has letters other than the standard @sc{ascii} letters. | |
| 1019 | |
| 1020 A case table is a list of this form: | |
| 1021 | |
| 1022 @example | |
| 1023 (@var{downcase} @var{upcase} @var{canonicalize} @var{equivalences}) | |
| 1024 @end example | |
| 1025 | |
| 1026 @noindent | |
| 1027 where each element is either @code{nil} or a string of length 256. The | |
| 1028 element @var{downcase} says how to map each character to its lower-case | |
| 1029 equivalent. The element @var{upcase} maps each character to its | |
| 1030 upper-case equivalent. If lower and upper case characters are in | |
| 1031 one-to-one correspondence, use @code{nil} for @var{upcase}; then XEmacs | |
| 1032 deduces the upcase table from @var{downcase}. | |
| 1033 | |
| 1034 For some languages, upper and lower case letters are not in one-to-one | |
| 1035 correspondence. There may be two different lower case letters with the | |
| 1036 same upper case equivalent. In these cases, you need to specify the | |
| 1037 maps for both directions. | |
| 1038 | |
| 1039 The element @var{canonicalize} maps each character to a canonical | |
| 1040 equivalent; any two characters that are related by case-conversion have | |
| 1041 the same canonical equivalent character. | |
| 1042 | |
| 1043 The element @var{equivalences} is a map that cyclicly permutes each | |
| 1044 equivalence class (of characters with the same canonical equivalent). | |
| 1045 (For ordinary @sc{ascii}, this would map @samp{a} into @samp{A} and | |
| 1046 @samp{A} into @samp{a}, and likewise for each set of equivalent | |
| 1047 characters.) | |
| 1048 | |
| 1049 When you construct a case table, you can provide @code{nil} for | |
| 1050 @var{canonicalize}; then Emacs fills in this string from @var{upcase} | |
| 1051 and @var{downcase}. You can also provide @code{nil} for | |
| 1052 @var{equivalences}; then Emacs fills in this string from | |
| 1053 @var{canonicalize}. In a case table that is actually in use, those | |
| 1054 components are non-@code{nil}. Do not try to specify @var{equivalences} | |
| 1055 without also specifying @var{canonicalize}. | |
| 1056 | |
| 1057 Each buffer has a case table. XEmacs also has a @dfn{standard case | |
| 1058 table} which is copied into each buffer when you create the buffer. | |
| 1059 Changing the standard case table doesn't affect any existing buffers. | |
| 1060 | |
| 1061 Here are the functions for working with case tables: | |
| 1062 | |
| 1063 @defun case-table-p object | |
| 1064 This predicate returns non-@code{nil} if @var{object} is a valid case | |
| 1065 table. | |
| 1066 @end defun | |
| 1067 | |
| 444 | 1068 @defun set-standard-case-table case-table |
| 1069 This function makes @var{case-table} the standard case table, so that it | |
| 1070 will apply to any buffers created subsequently. | |
| 428 | 1071 @end defun |
| 1072 | |
| 1073 @defun standard-case-table | |
| 1074 This returns the standard case table. | |
| 1075 @end defun | |
| 1076 | |
| 444 | 1077 @defun current-case-table &optional buffer |
| 1078 This function returns the case table of @var{buffer}, which defaults to | |
| 1079 the current buffer. | |
| 428 | 1080 @end defun |
| 1081 | |
| 444 | 1082 @defun set-case-table case-table |
| 1083 This sets the current buffer's case table to @var{case-table}. | |
| 428 | 1084 @end defun |
| 1085 | |
| 1086 The following three functions are convenient subroutines for packages | |
| 1087 that define non-@sc{ascii} character sets. They modify a string | |
| 1088 @var{downcase-table} provided as an argument; this should be a string to | |
| 1089 be used as the @var{downcase} part of a case table. They also modify | |
| 1090 the standard syntax table. @xref{Syntax Tables}. | |
| 1091 | |
| 1092 @defun set-case-syntax-pair uc lc downcase-table | |
| 1093 This function specifies a pair of corresponding letters, one upper case | |
| 1094 and one lower case. | |
| 1095 @end defun | |
| 1096 | |
| 1097 @defun set-case-syntax-delims l r downcase-table | |
| 1098 This function makes characters @var{l} and @var{r} a matching pair of | |
| 1099 case-invariant delimiters. | |
| 1100 @end defun | |
| 1101 | |
| 1102 @defun set-case-syntax char syntax downcase-table | |
| 1103 This function makes @var{char} case-invariant, with syntax | |
| 1104 @var{syntax}. | |
| 1105 @end defun | |
| 1106 | |
| 1107 @deffn Command describe-buffer-case-table | |
| 1108 This command displays a description of the contents of the current | |
| 1109 buffer's case table. | |
| 1110 @end deffn | |
| 1111 | |
| 1112 @cindex ISO Latin 1 | |
| 1113 @pindex iso-syntax | |
| 1114 You can load the library @file{iso-syntax} to set up the standard syntax | |
| 1115 table and define a case table for the 8-bit ISO Latin 1 character set. | |
| 1116 | |
| 1117 @node Char Tables | |
| 1118 @section The Char Table | |
| 1119 | |
| 1120 A char table is a table that maps characters (or ranges of characters) | |
| 1121 to values. Char tables are specialized for characters, only allowing | |
| 1122 particular sorts of ranges to be assigned values. Although this | |
| 1123 loses in generality, it makes for extremely fast (constant-time) | |
| 1124 lookups, and thus is feasible for applications that do an extremely | |
| 1125 large number of lookups (e.g. scanning a buffer for a character in | |
| 1126 a particular syntax, where a lookup in the syntax table must occur | |
| 1127 once per character). | |
| 1128 | |
| 1129 Note that char tables as a primitive type, and all of the functions in | |
| 1130 this section, exist only in XEmacs 20. In XEmacs 19, char tables are | |
| 1131 generally implemented using a vector of 256 elements. | |
| 1132 | |
| 1133 When @sc{mule} support exists, the types of ranges that can be assigned | |
| 1134 values are | |
| 1135 | |
| 1136 @itemize @bullet | |
| 1137 @item | |
| 1138 all characters | |
| 1139 @item | |
| 1140 an entire charset | |
| 1141 @item | |
| 1142 a single row in a two-octet charset | |
| 1143 @item | |
| 1144 a single character | |
| 1145 @end itemize | |
| 1146 | |
| 1147 When @sc{mule} support is not present, the types of ranges that can be | |
| 1148 assigned values are | |
| 1149 | |
| 1150 @itemize @bullet | |
| 1151 @item | |
| 1152 all characters | |
| 1153 @item | |
| 1154 a single character | |
| 1155 @end itemize | |
| 1156 | |
| 1157 @defun char-table-p object | |
| 1158 This function returns non-@code{nil} if @var{object} is a char table. | |
| 1159 @end defun | |
| 1160 | |
| 1161 @menu | |
| 1162 * Char Table Types:: Char tables have different uses. | |
| 1163 * Working With Char Tables:: Creating and working with char tables. | |
| 1164 @end menu | |
| 1165 | |
| 1166 @node Char Table Types | |
| 1167 @subsection Char Table Types | |
| 1168 | |
| 1169 Each char table type is used for a different purpose and allows different | |
| 1170 sorts of values. The different char table types are | |
| 1171 | |
| 1172 @table @code | |
| 1173 @item category | |
| 1174 Used for category tables, which specify the regexp categories | |
| 1175 that a character is in. The valid values are @code{nil} or a | |
| 1176 bit vector of 95 elements. Higher-level Lisp functions are | |
| 1177 provided for working with category tables. Currently categories | |
| 1178 and category tables only exist when @sc{mule} support is present. | |
| 1179 @item char | |
| 1180 A generalized char table, for mapping from one character to | |
| 1181 another. Used for case tables, syntax matching tables, | |
| 1182 @code{keyboard-translate-table}, etc. The valid values are characters. | |
| 1183 @item generic | |
| 1184 An even more generalized char table, for mapping from a | |
| 1185 character to anything. | |
| 1186 @item display | |
| 1187 Used for display tables, which specify how a particular character | |
| 1188 is to appear when displayed. #### Not yet implemented. | |
| 1189 @item syntax | |
| 1190 Used for syntax tables, which specify the syntax of a particular | |
| 1191 character. Higher-level Lisp functions are provided for | |
| 1192 working with syntax tables. The valid values are integers. | |
| 1193 @end table | |
| 1194 | |
| 444 | 1195 @defun char-table-type char-table |
| 1196 This function returns the type of char table @var{char-table}. | |
| 428 | 1197 @end defun |
| 1198 | |
| 1199 @defun char-table-type-list | |
| 1200 This function returns a list of the recognized char table types. | |
| 1201 @end defun | |
| 1202 | |
| 1203 @defun valid-char-table-type-p type | |
| 1204 This function returns @code{t} if @var{type} if a recognized char table type. | |
| 1205 @end defun | |
| 1206 | |
| 1207 @node Working With Char Tables | |
| 1208 @subsection Working With Char Tables | |
| 1209 | |
| 1210 @defun make-char-table type | |
| 1211 This function makes a new, empty char table of type @var{type}. | |
| 1212 @var{type} should be a symbol, one of @code{char}, @code{category}, | |
| 1213 @code{display}, @code{generic}, or @code{syntax}. | |
| 1214 @end defun | |
| 1215 | |
| 444 | 1216 @defun put-char-table range value char-table |
| 1217 This function sets the value for chars in @var{range} to be @var{value} in | |
| 1218 @var{char-table}. | |
| 428 | 1219 |
| 1220 @var{range} specifies one or more characters to be affected and should be | |
| 1221 one of the following: | |
| 1222 | |
| 1223 @itemize @bullet | |
| 1224 @item | |
| 1225 @code{t} (all characters are affected) | |
| 1226 @item | |
| 1227 A charset (only allowed when @sc{mule} support is present) | |
| 1228 @item | |
| 1229 A vector of two elements: a two-octet charset and a row number | |
| 1230 (only allowed when @sc{mule} support is present) | |
| 1231 @item | |
| 1232 A single character | |
| 1233 @end itemize | |
| 1234 | |
| 444 | 1235 @var{value} must be a value appropriate for the type of @var{char-table}. |
| 428 | 1236 @end defun |
| 1237 | |
| 444 | 1238 @defun get-char-table character char-table |
| 1239 This function finds the value for @var{character} in @var{char-table}. | |
| 428 | 1240 @end defun |
| 1241 | |
| 444 | 1242 @defun get-range-char-table range char-table &optional multi |
| 1243 This function finds the value for a range in @var{char-table}. If there is | |
| 428 | 1244 more than one value, @var{multi} is returned (defaults to @code{nil}). |
| 1245 @end defun | |
| 1246 | |
| 444 | 1247 @defun reset-char-table char-table |
| 1248 This function resets @var{char-table} to its default state. | |
| 428 | 1249 @end defun |
| 1250 | |
| 444 | 1251 @defun map-char-table function char-table &optional range |
| 1252 This function maps @var{function} over entries in @var{char-table}, calling | |
| 428 | 1253 it with two args, each key and value in the table. |
| 1254 | |
| 1255 @var{range} specifies a subrange to map over and is in the same format | |
| 1256 as the @var{range} argument to @code{put-range-table}. If omitted or | |
| 1257 @code{t}, it defaults to the entire table. | |
| 1258 @end defun | |
| 1259 | |
| 1260 @defun valid-char-table-value-p value char-table-type | |
| 1261 This function returns non-@code{nil} if @var{value} is a valid value for | |
| 1262 @var{char-table-type}. | |
| 1263 @end defun | |
| 1264 | |
| 1265 @defun check-valid-char-table-value value char-table-type | |
| 1266 This function signals an error if @var{value} is not a valid value for | |
| 1267 @var{char-table-type}. | |
| 1268 @end defun |