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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, | |
6ed161e1 | 4 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
b8d4c8d0 | 5 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 6 | @setfilename ../../info/strings |
b8d4c8d0 GM |
7 | @node Strings and Characters, Lists, Numbers, Top |
8 | @comment node-name, next, previous, up | |
9 | @chapter Strings and Characters | |
10 | @cindex strings | |
11 | @cindex character arrays | |
12 | @cindex characters | |
13 | @cindex bytes | |
14 | ||
15 | A string in Emacs Lisp is an array that contains an ordered sequence | |
16 | of characters. Strings are used as names of symbols, buffers, and | |
17 | files; to send messages to users; to hold text being copied between | |
18 | buffers; and for many other purposes. Because strings are so important, | |
19 | Emacs Lisp has many functions expressly for manipulating them. Emacs | |
20 | Lisp programs use strings more often than individual characters. | |
21 | ||
22 | @xref{Strings of Events}, for special considerations for strings of | |
23 | keyboard character events. | |
24 | ||
25 | @menu | |
26 | * Basics: String Basics. Basic properties of strings and characters. | |
27 | * Predicates for Strings:: Testing whether an object is a string or char. | |
28 | * Creating Strings:: Functions to allocate new strings. | |
29 | * Modifying Strings:: Altering the contents of an existing string. | |
30 | * Text Comparison:: Comparing characters or strings. | |
31 | * String Conversion:: Converting to and from characters and strings. | |
32 | * Formatting Strings:: @code{format}: Emacs's analogue of @code{printf}. | |
33 | * Case Conversion:: Case conversion functions. | |
34 | * Case Tables:: Customizing case conversion. | |
35 | @end menu | |
36 | ||
37 | @node String Basics | |
38 | @section String and Character Basics | |
39 | ||
40 | Characters are represented in Emacs Lisp as integers; | |
41 | whether an integer is a character or not is determined only by how it is | |
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42 | used. Thus, strings really contain integers. @xref{Character Codes}, |
43 | for details about character representation in Emacs. | |
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44 | |
45 | The length of a string (like any array) is fixed, and cannot be | |
46 | altered once the string exists. Strings in Lisp are @emph{not} | |
47 | terminated by a distinguished character code. (By contrast, strings in | |
48 | C are terminated by a character with @acronym{ASCII} code 0.) | |
49 | ||
50 | Since strings are arrays, and therefore sequences as well, you can | |
51 | operate on them with the general array and sequence functions. | |
52 | (@xref{Sequences Arrays Vectors}.) For example, you can access or | |
53 | change individual characters in a string using the functions @code{aref} | |
54 | and @code{aset} (@pxref{Array Functions}). | |
55 | ||
56 | There are two text representations for non-@acronym{ASCII} characters in | |
57 | Emacs strings (and in buffers): unibyte and multibyte (@pxref{Text | |
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58 | Representations}). For most Lisp programming, you don't need to be |
59 | concerned with these two representations. | |
b8d4c8d0 | 60 | |
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61 | Sometimes key sequences are represented as unibyte strings. When a |
62 | unibyte string is a key sequence, string elements in the range 128 to | |
63 | 255 represent meta characters (which are large integers) rather than | |
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64 | character codes in the range 128 to 255. Strings cannot hold |
65 | characters that have the hyper, super or alt modifiers; they can hold | |
66 | @acronym{ASCII} control characters, but no other control characters. | |
67 | They do not distinguish case in @acronym{ASCII} control characters. | |
68 | If you want to store such characters in a sequence, such as a key | |
69 | sequence, you must use a vector instead of a string. @xref{Character | |
70 | Type}, for more information about keyboard input characters. | |
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71 | |
72 | Strings are useful for holding regular expressions. You can also | |
73 | match regular expressions against strings with @code{string-match} | |
74 | (@pxref{Regexp Search}). The functions @code{match-string} | |
75 | (@pxref{Simple Match Data}) and @code{replace-match} (@pxref{Replacing | |
76 | Match}) are useful for decomposing and modifying strings after | |
77 | matching regular expressions against them. | |
78 | ||
79 | Like a buffer, a string can contain text properties for the characters | |
80 | in it, as well as the characters themselves. @xref{Text Properties}. | |
81 | All the Lisp primitives that copy text from strings to buffers or other | |
82 | strings also copy the properties of the characters being copied. | |
83 | ||
84 | @xref{Text}, for information about functions that display strings or | |
85 | copy them into buffers. @xref{Character Type}, and @ref{String Type}, | |
86 | for information about the syntax of characters and strings. | |
87 | @xref{Non-ASCII Characters}, for functions to convert between text | |
88 | representations and to encode and decode character codes. | |
89 | ||
90 | @node Predicates for Strings | |
91 | @section The Predicates for Strings | |
92 | ||
93 | For more information about general sequence and array predicates, | |
94 | see @ref{Sequences Arrays Vectors}, and @ref{Arrays}. | |
95 | ||
96 | @defun stringp object | |
97 | This function returns @code{t} if @var{object} is a string, @code{nil} | |
98 | otherwise. | |
99 | @end defun | |
100 | ||
101 | @defun string-or-null-p object | |
8c641f06 | 102 | This function returns @code{t} if @var{object} is a string or |
638a2457 | 103 | @code{nil}. It returns @code{nil} otherwise. |
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104 | @end defun |
105 | ||
106 | @defun char-or-string-p object | |
107 | This function returns @code{t} if @var{object} is a string or a | |
108 | character (i.e., an integer), @code{nil} otherwise. | |
109 | @end defun | |
110 | ||
111 | @node Creating Strings | |
112 | @section Creating Strings | |
113 | ||
114 | The following functions create strings, either from scratch, or by | |
115 | putting strings together, or by taking them apart. | |
116 | ||
117 | @defun make-string count character | |
118 | This function returns a string made up of @var{count} repetitions of | |
119 | @var{character}. If @var{count} is negative, an error is signaled. | |
120 | ||
121 | @example | |
122 | (make-string 5 ?x) | |
123 | @result{} "xxxxx" | |
124 | (make-string 0 ?x) | |
125 | @result{} "" | |
126 | @end example | |
127 | ||
128 | Other functions to compare with this one include @code{char-to-string} | |
129 | (@pxref{String Conversion}), @code{make-vector} (@pxref{Vectors}), and | |
130 | @code{make-list} (@pxref{Building Lists}). | |
131 | @end defun | |
132 | ||
133 | @defun string &rest characters | |
134 | This returns a string containing the characters @var{characters}. | |
135 | ||
136 | @example | |
137 | (string ?a ?b ?c) | |
138 | @result{} "abc" | |
139 | @end example | |
140 | @end defun | |
141 | ||
142 | @defun substring string start &optional end | |
143 | This function returns a new string which consists of those characters | |
144 | from @var{string} in the range from (and including) the character at the | |
145 | index @var{start} up to (but excluding) the character at the index | |
146 | @var{end}. The first character is at index zero. | |
147 | ||
148 | @example | |
149 | @group | |
150 | (substring "abcdefg" 0 3) | |
151 | @result{} "abc" | |
152 | @end group | |
153 | @end example | |
154 | ||
155 | @noindent | |
8f88eb24 CY |
156 | In the above example, the index for @samp{a} is 0, the index for |
157 | @samp{b} is 1, and the index for @samp{c} is 2. The index 3---which | |
158 | is the the fourth character in the string---marks the character | |
159 | position up to which the substring is copied. Thus, @samp{abc} is | |
160 | copied from the string @code{"abcdefg"}. | |
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161 | |
162 | A negative number counts from the end of the string, so that @minus{}1 | |
163 | signifies the index of the last character of the string. For example: | |
164 | ||
165 | @example | |
166 | @group | |
167 | (substring "abcdefg" -3 -1) | |
168 | @result{} "ef" | |
169 | @end group | |
170 | @end example | |
171 | ||
172 | @noindent | |
173 | In this example, the index for @samp{e} is @minus{}3, the index for | |
174 | @samp{f} is @minus{}2, and the index for @samp{g} is @minus{}1. | |
175 | Therefore, @samp{e} and @samp{f} are included, and @samp{g} is excluded. | |
176 | ||
177 | When @code{nil} is used for @var{end}, it stands for the length of the | |
178 | string. Thus, | |
179 | ||
180 | @example | |
181 | @group | |
182 | (substring "abcdefg" -3 nil) | |
183 | @result{} "efg" | |
184 | @end group | |
185 | @end example | |
186 | ||
187 | Omitting the argument @var{end} is equivalent to specifying @code{nil}. | |
188 | It follows that @code{(substring @var{string} 0)} returns a copy of all | |
189 | of @var{string}. | |
190 | ||
191 | @example | |
192 | @group | |
193 | (substring "abcdefg" 0) | |
194 | @result{} "abcdefg" | |
195 | @end group | |
196 | @end example | |
197 | ||
198 | @noindent | |
199 | But we recommend @code{copy-sequence} for this purpose (@pxref{Sequence | |
200 | Functions}). | |
201 | ||
202 | If the characters copied from @var{string} have text properties, the | |
203 | properties are copied into the new string also. @xref{Text Properties}. | |
204 | ||
205 | @code{substring} also accepts a vector for the first argument. | |
206 | For example: | |
207 | ||
208 | @example | |
209 | (substring [a b (c) "d"] 1 3) | |
210 | @result{} [b (c)] | |
211 | @end example | |
212 | ||
213 | A @code{wrong-type-argument} error is signaled if @var{start} is not | |
214 | an integer or if @var{end} is neither an integer nor @code{nil}. An | |
215 | @code{args-out-of-range} error is signaled if @var{start} indicates a | |
216 | character following @var{end}, or if either integer is out of range | |
217 | for @var{string}. | |
218 | ||
219 | Contrast this function with @code{buffer-substring} (@pxref{Buffer | |
220 | Contents}), which returns a string containing a portion of the text in | |
221 | the current buffer. The beginning of a string is at index 0, but the | |
222 | beginning of a buffer is at index 1. | |
223 | @end defun | |
224 | ||
225 | @defun substring-no-properties string &optional start end | |
226 | This works like @code{substring} but discards all text properties from | |
227 | the value. Also, @var{start} may be omitted or @code{nil}, which is | |
228 | equivalent to 0. Thus, @w{@code{(substring-no-properties | |
229 | @var{string})}} returns a copy of @var{string}, with all text | |
230 | properties removed. | |
231 | @end defun | |
232 | ||
233 | @defun concat &rest sequences | |
234 | @cindex copying strings | |
235 | @cindex concatenating strings | |
236 | This function returns a new string consisting of the characters in the | |
237 | arguments passed to it (along with their text properties, if any). The | |
238 | arguments may be strings, lists of numbers, or vectors of numbers; they | |
239 | are not themselves changed. If @code{concat} receives no arguments, it | |
240 | returns an empty string. | |
241 | ||
242 | @example | |
243 | (concat "abc" "-def") | |
244 | @result{} "abc-def" | |
245 | (concat "abc" (list 120 121) [122]) | |
246 | @result{} "abcxyz" | |
247 | ;; @r{@code{nil} is an empty sequence.} | |
248 | (concat "abc" nil "-def") | |
249 | @result{} "abc-def" | |
250 | (concat "The " "quick brown " "fox.") | |
251 | @result{} "The quick brown fox." | |
252 | (concat) | |
253 | @result{} "" | |
254 | @end example | |
255 | ||
256 | @noindent | |
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257 | This function always constructs a new string that is not @code{eq} to |
258 | any existing string, except when the result is the empty string (to | |
259 | save space, Emacs makes only one empty multibyte string). | |
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260 | |
261 | For information about other concatenation functions, see the | |
262 | description of @code{mapconcat} in @ref{Mapping Functions}, | |
263 | @code{vconcat} in @ref{Vector Functions}, and @code{append} in @ref{Building | |
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264 | Lists}. For concatenating individual command-line arguments into a |
265 | string to be used as a shell command, see @ref{Shell Arguments, | |
266 | combine-and-quote-strings}. | |
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267 | @end defun |
268 | ||
269 | @defun split-string string &optional separators omit-nulls | |
8f88eb24 CY |
270 | This function splits @var{string} into substrings based on the regular |
271 | expression @var{separators} (@pxref{Regular Expressions}). Each match | |
272 | for @var{separators} defines a splitting point; the substrings between | |
273 | splitting points are made into a list, which is returned. | |
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275 | If @var{omit-nulls} is @code{nil} (or omitted), the result contains |
276 | null strings whenever there are two consecutive matches for | |
277 | @var{separators}, or a match is adjacent to the beginning or end of | |
278 | @var{string}. If @var{omit-nulls} is @code{t}, these null strings are | |
279 | omitted from the result. | |
b8d4c8d0 | 280 | |
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281 | If @var{separators} is @code{nil} (or omitted), the default is the |
282 | value of @code{split-string-default-separators}. | |
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283 | |
284 | As a special case, when @var{separators} is @code{nil} (or omitted), | |
285 | null strings are always omitted from the result. Thus: | |
286 | ||
287 | @example | |
288 | (split-string " two words ") | |
289 | @result{} ("two" "words") | |
290 | @end example | |
291 | ||
292 | The result is not @code{("" "two" "words" "")}, which would rarely be | |
293 | useful. If you need such a result, use an explicit value for | |
294 | @var{separators}: | |
295 | ||
296 | @example | |
297 | (split-string " two words " | |
298 | split-string-default-separators) | |
299 | @result{} ("" "two" "words" "") | |
300 | @end example | |
301 | ||
302 | More examples: | |
303 | ||
304 | @example | |
305 | (split-string "Soup is good food" "o") | |
306 | @result{} ("S" "up is g" "" "d f" "" "d") | |
307 | (split-string "Soup is good food" "o" t) | |
308 | @result{} ("S" "up is g" "d f" "d") | |
309 | (split-string "Soup is good food" "o+") | |
310 | @result{} ("S" "up is g" "d f" "d") | |
311 | @end example | |
312 | ||
313 | Empty matches do count, except that @code{split-string} will not look | |
314 | for a final empty match when it already reached the end of the string | |
315 | using a non-empty match or when @var{string} is empty: | |
316 | ||
317 | @example | |
318 | (split-string "aooob" "o*") | |
319 | @result{} ("" "a" "" "b" "") | |
320 | (split-string "ooaboo" "o*") | |
321 | @result{} ("" "" "a" "b" "") | |
322 | (split-string "" "") | |
323 | @result{} ("") | |
324 | @end example | |
325 | ||
326 | However, when @var{separators} can match the empty string, | |
327 | @var{omit-nulls} is usually @code{t}, so that the subtleties in the | |
328 | three previous examples are rarely relevant: | |
329 | ||
330 | @example | |
331 | (split-string "Soup is good food" "o*" t) | |
332 | @result{} ("S" "u" "p" " " "i" "s" " " "g" "d" " " "f" "d") | |
333 | (split-string "Nice doggy!" "" t) | |
334 | @result{} ("N" "i" "c" "e" " " "d" "o" "g" "g" "y" "!") | |
335 | (split-string "" "" t) | |
336 | @result{} nil | |
337 | @end example | |
338 | ||
339 | Somewhat odd, but predictable, behavior can occur for certain | |
340 | ``non-greedy'' values of @var{separators} that can prefer empty | |
341 | matches over non-empty matches. Again, such values rarely occur in | |
342 | practice: | |
343 | ||
344 | @example | |
345 | (split-string "ooo" "o*" t) | |
346 | @result{} nil | |
347 | (split-string "ooo" "\\|o+" t) | |
348 | @result{} ("o" "o" "o") | |
349 | @end example | |
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350 | |
351 | If you need to split a string that is a shell command, where | |
352 | individual arguments could be quoted, see @ref{Shell Arguments, | |
353 | split-string-and-unquote}. | |
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354 | @end defun |
355 | ||
356 | @defvar split-string-default-separators | |
357 | The default value of @var{separators} for @code{split-string}. Its | |
358 | usual value is @w{@code{"[ \f\t\n\r\v]+"}}. | |
359 | @end defvar | |
360 | ||
361 | @node Modifying Strings | |
362 | @section Modifying Strings | |
363 | ||
364 | The most basic way to alter the contents of an existing string is with | |
365 | @code{aset} (@pxref{Array Functions}). @code{(aset @var{string} | |
366 | @var{idx} @var{char})} stores @var{char} into @var{string} at index | |
367 | @var{idx}. Each character occupies one or more bytes, and if @var{char} | |
368 | needs a different number of bytes from the character already present at | |
369 | that index, @code{aset} signals an error. | |
370 | ||
371 | A more powerful function is @code{store-substring}: | |
372 | ||
373 | @defun store-substring string idx obj | |
374 | This function alters part of the contents of the string @var{string}, by | |
375 | storing @var{obj} starting at index @var{idx}. The argument @var{obj} | |
376 | may be either a character or a (smaller) string. | |
377 | ||
378 | Since it is impossible to change the length of an existing string, it is | |
379 | an error if @var{obj} doesn't fit within @var{string}'s actual length, | |
380 | or if any new character requires a different number of bytes from the | |
381 | character currently present at that point in @var{string}. | |
382 | @end defun | |
383 | ||
384 | To clear out a string that contained a password, use | |
385 | @code{clear-string}: | |
386 | ||
387 | @defun clear-string string | |
388 | This makes @var{string} a unibyte string and clears its contents to | |
389 | zeros. It may also change @var{string}'s length. | |
390 | @end defun | |
391 | ||
392 | @need 2000 | |
393 | @node Text Comparison | |
394 | @section Comparison of Characters and Strings | |
395 | @cindex string equality | |
396 | ||
397 | @defun char-equal character1 character2 | |
398 | This function returns @code{t} if the arguments represent the same | |
399 | character, @code{nil} otherwise. This function ignores differences | |
400 | in case if @code{case-fold-search} is non-@code{nil}. | |
401 | ||
402 | @example | |
403 | (char-equal ?x ?x) | |
404 | @result{} t | |
405 | (let ((case-fold-search nil)) | |
406 | (char-equal ?x ?X)) | |
407 | @result{} nil | |
408 | @end example | |
409 | @end defun | |
410 | ||
411 | @defun string= string1 string2 | |
412 | This function returns @code{t} if the characters of the two strings | |
413 | match exactly. Symbols are also allowed as arguments, in which case | |
414 | their print names are used. | |
415 | Case is always significant, regardless of @code{case-fold-search}. | |
416 | ||
417 | @example | |
418 | (string= "abc" "abc") | |
419 | @result{} t | |
420 | (string= "abc" "ABC") | |
421 | @result{} nil | |
422 | (string= "ab" "ABC") | |
423 | @result{} nil | |
424 | @end example | |
425 | ||
426 | The function @code{string=} ignores the text properties of the two | |
427 | strings. When @code{equal} (@pxref{Equality Predicates}) compares two | |
428 | strings, it uses @code{string=}. | |
429 | ||
430 | For technical reasons, a unibyte and a multibyte string are | |
431 | @code{equal} if and only if they contain the same sequence of | |
432 | character codes and all these codes are either in the range 0 through | |
433 | 127 (@acronym{ASCII}) or 160 through 255 (@code{eight-bit-graphic}). | |
8f88eb24 CY |
434 | However, when a unibyte string is converted to a multibyte string, all |
435 | characters with codes in the range 160 through 255 are converted to | |
436 | characters with higher codes, whereas @acronym{ASCII} characters | |
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437 | remain unchanged. Thus, a unibyte string and its conversion to |
438 | multibyte are only @code{equal} if the string is all @acronym{ASCII}. | |
439 | Character codes 160 through 255 are not entirely proper in multibyte | |
440 | text, even though they can occur. As a consequence, the situation | |
441 | where a unibyte and a multibyte string are @code{equal} without both | |
442 | being all @acronym{ASCII} is a technical oddity that very few Emacs | |
443 | Lisp programmers ever get confronted with. @xref{Text | |
444 | Representations}. | |
445 | @end defun | |
446 | ||
447 | @defun string-equal string1 string2 | |
448 | @code{string-equal} is another name for @code{string=}. | |
449 | @end defun | |
450 | ||
451 | @cindex lexical comparison | |
452 | @defun string< string1 string2 | |
453 | @c (findex string< causes problems for permuted index!!) | |
454 | This function compares two strings a character at a time. It | |
455 | scans both the strings at the same time to find the first pair of corresponding | |
456 | characters that do not match. If the lesser character of these two is | |
457 | the character from @var{string1}, then @var{string1} is less, and this | |
458 | function returns @code{t}. If the lesser character is the one from | |
459 | @var{string2}, then @var{string1} is greater, and this function returns | |
460 | @code{nil}. If the two strings match entirely, the value is @code{nil}. | |
461 | ||
462 | Pairs of characters are compared according to their character codes. | |
463 | Keep in mind that lower case letters have higher numeric values in the | |
464 | @acronym{ASCII} character set than their upper case counterparts; digits and | |
465 | many punctuation characters have a lower numeric value than upper case | |
466 | letters. An @acronym{ASCII} character is less than any non-@acronym{ASCII} | |
467 | character; a unibyte non-@acronym{ASCII} character is always less than any | |
468 | multibyte non-@acronym{ASCII} character (@pxref{Text Representations}). | |
469 | ||
470 | @example | |
471 | @group | |
472 | (string< "abc" "abd") | |
473 | @result{} t | |
474 | (string< "abd" "abc") | |
475 | @result{} nil | |
476 | (string< "123" "abc") | |
477 | @result{} t | |
478 | @end group | |
479 | @end example | |
480 | ||
481 | When the strings have different lengths, and they match up to the | |
482 | length of @var{string1}, then the result is @code{t}. If they match up | |
483 | to the length of @var{string2}, the result is @code{nil}. A string of | |
484 | no characters is less than any other string. | |
485 | ||
486 | @example | |
487 | @group | |
488 | (string< "" "abc") | |
489 | @result{} t | |
490 | (string< "ab" "abc") | |
491 | @result{} t | |
492 | (string< "abc" "") | |
493 | @result{} nil | |
494 | (string< "abc" "ab") | |
495 | @result{} nil | |
496 | (string< "" "") | |
497 | @result{} nil | |
498 | @end group | |
499 | @end example | |
500 | ||
501 | Symbols are also allowed as arguments, in which case their print names | |
502 | are used. | |
503 | @end defun | |
504 | ||
505 | @defun string-lessp string1 string2 | |
506 | @code{string-lessp} is another name for @code{string<}. | |
507 | @end defun | |
508 | ||
509 | @defun compare-strings string1 start1 end1 string2 start2 end2 &optional ignore-case | |
510 | This function compares the specified part of @var{string1} with the | |
511 | specified part of @var{string2}. The specified part of @var{string1} | |
512 | runs from index @var{start1} up to index @var{end1} (@code{nil} means | |
513 | the end of the string). The specified part of @var{string2} runs from | |
514 | index @var{start2} up to index @var{end2} (@code{nil} means the end of | |
515 | the string). | |
516 | ||
517 | The strings are both converted to multibyte for the comparison | |
518 | (@pxref{Text Representations}) so that a unibyte string and its | |
519 | conversion to multibyte are always regarded as equal. If | |
520 | @var{ignore-case} is non-@code{nil}, then case is ignored, so that | |
521 | upper case letters can be equal to lower case letters. | |
522 | ||
523 | If the specified portions of the two strings match, the value is | |
524 | @code{t}. Otherwise, the value is an integer which indicates how many | |
525 | leading characters agree, and which string is less. Its absolute value | |
526 | is one plus the number of characters that agree at the beginning of the | |
527 | two strings. The sign is negative if @var{string1} (or its specified | |
528 | portion) is less. | |
529 | @end defun | |
530 | ||
531 | @defun assoc-string key alist &optional case-fold | |
532 | This function works like @code{assoc}, except that @var{key} must be a | |
533 | string or symbol, and comparison is done using @code{compare-strings}. | |
534 | Symbols are converted to strings before testing. | |
535 | If @var{case-fold} is non-@code{nil}, it ignores case differences. | |
536 | Unlike @code{assoc}, this function can also match elements of the alist | |
537 | that are strings or symbols rather than conses. In particular, @var{alist} can | |
538 | be a list of strings or symbols rather than an actual alist. | |
539 | @xref{Association Lists}. | |
540 | @end defun | |
541 | ||
8f88eb24 | 542 | See also the function @code{compare-buffer-substrings} in |
b8d4c8d0 GM |
543 | @ref{Comparing Text}, for a way to compare text in buffers. The |
544 | function @code{string-match}, which matches a regular expression | |
545 | against a string, can be used for a kind of string comparison; see | |
546 | @ref{Regexp Search}. | |
547 | ||
548 | @node String Conversion | |
549 | @comment node-name, next, previous, up | |
550 | @section Conversion of Characters and Strings | |
551 | @cindex conversion of strings | |
552 | ||
8f88eb24 CY |
553 | This section describes functions for converting between characters, |
554 | strings and integers. @code{format} (@pxref{Formatting Strings}) and | |
555 | @code{prin1-to-string} (@pxref{Output Functions}) can also convert | |
556 | Lisp objects into strings. @code{read-from-string} (@pxref{Input | |
557 | Functions}) can ``convert'' a string representation of a Lisp object | |
558 | into an object. The functions @code{string-make-multibyte} and | |
559 | @code{string-make-unibyte} convert the text representation of a string | |
560 | (@pxref{Converting Representations}). | |
b8d4c8d0 GM |
561 | |
562 | @xref{Documentation}, for functions that produce textual descriptions | |
563 | of text characters and general input events | |
564 | (@code{single-key-description} and @code{text-char-description}). These | |
565 | are used primarily for making help messages. | |
566 | ||
567 | @defun char-to-string character | |
568 | @cindex character to string | |
569 | This function returns a new string containing one character, | |
570 | @var{character}. This function is semi-obsolete because the function | |
571 | @code{string} is more general. @xref{Creating Strings}. | |
572 | @end defun | |
573 | ||
574 | @defun string-to-char string | |
575 | @cindex string to character | |
576 | This function returns the first character in @var{string}. If the | |
577 | string is empty, the function returns 0. The value is also 0 when the | |
578 | first character of @var{string} is the null character, @acronym{ASCII} code | |
579 | 0. | |
580 | ||
581 | @example | |
582 | (string-to-char "ABC") | |
583 | @result{} 65 | |
584 | ||
585 | (string-to-char "xyz") | |
586 | @result{} 120 | |
587 | (string-to-char "") | |
588 | @result{} 0 | |
589 | @group | |
590 | (string-to-char "\000") | |
591 | @result{} 0 | |
592 | @end group | |
593 | @end example | |
594 | ||
595 | This function may be eliminated in the future if it does not seem useful | |
596 | enough to retain. | |
597 | @end defun | |
598 | ||
599 | @defun number-to-string number | |
600 | @cindex integer to string | |
601 | @cindex integer to decimal | |
602 | This function returns a string consisting of the printed base-ten | |
603 | representation of @var{number}, which may be an integer or a floating | |
604 | point number. The returned value starts with a minus sign if the argument is | |
605 | negative. | |
606 | ||
607 | @example | |
608 | (number-to-string 256) | |
609 | @result{} "256" | |
610 | @group | |
611 | (number-to-string -23) | |
612 | @result{} "-23" | |
613 | @end group | |
614 | (number-to-string -23.5) | |
615 | @result{} "-23.5" | |
616 | @end example | |
617 | ||
618 | @cindex int-to-string | |
619 | @code{int-to-string} is a semi-obsolete alias for this function. | |
620 | ||
621 | See also the function @code{format} in @ref{Formatting Strings}. | |
622 | @end defun | |
623 | ||
624 | @defun string-to-number string &optional base | |
625 | @cindex string to number | |
626 | This function returns the numeric value of the characters in | |
627 | @var{string}. If @var{base} is non-@code{nil}, it must be an integer | |
628 | between 2 and 16 (inclusive), and integers are converted in that base. | |
629 | If @var{base} is @code{nil}, then base ten is used. Floating point | |
630 | conversion only works in base ten; we have not implemented other | |
631 | radices for floating point numbers, because that would be much more | |
632 | work and does not seem useful. If @var{string} looks like an integer | |
633 | but its value is too large to fit into a Lisp integer, | |
634 | @code{string-to-number} returns a floating point result. | |
635 | ||
636 | The parsing skips spaces and tabs at the beginning of @var{string}, | |
637 | then reads as much of @var{string} as it can interpret as a number in | |
638 | the given base. (On some systems it ignores other whitespace at the | |
639 | beginning, not just spaces and tabs.) If the first character after | |
640 | the ignored whitespace is neither a digit in the given base, nor a | |
641 | plus or minus sign, nor the leading dot of a floating point number, | |
642 | this function returns 0. | |
643 | ||
644 | @example | |
645 | (string-to-number "256") | |
646 | @result{} 256 | |
647 | (string-to-number "25 is a perfect square.") | |
648 | @result{} 25 | |
649 | (string-to-number "X256") | |
650 | @result{} 0 | |
651 | (string-to-number "-4.5") | |
652 | @result{} -4.5 | |
653 | (string-to-number "1e5") | |
654 | @result{} 100000.0 | |
655 | @end example | |
656 | ||
657 | @findex string-to-int | |
658 | @code{string-to-int} is an obsolete alias for this function. | |
659 | @end defun | |
660 | ||
661 | Here are some other functions that can convert to or from a string: | |
662 | ||
663 | @table @code | |
664 | @item concat | |
665 | @code{concat} can convert a vector or a list into a string. | |
666 | @xref{Creating Strings}. | |
667 | ||
668 | @item vconcat | |
669 | @code{vconcat} can convert a string into a vector. @xref{Vector | |
670 | Functions}. | |
671 | ||
672 | @item append | |
673 | @code{append} can convert a string into a list. @xref{Building Lists}. | |
674 | @end table | |
675 | ||
676 | @node Formatting Strings | |
677 | @comment node-name, next, previous, up | |
678 | @section Formatting Strings | |
679 | @cindex formatting strings | |
680 | @cindex strings, formatting them | |
681 | ||
8f88eb24 CY |
682 | @dfn{Formatting} means constructing a string by substituting |
683 | computed values at various places in a constant string. This constant | |
684 | string controls how the other values are printed, as well as where | |
685 | they appear; it is called a @dfn{format string}. | |
b8d4c8d0 GM |
686 | |
687 | Formatting is often useful for computing messages to be displayed. In | |
688 | fact, the functions @code{message} and @code{error} provide the same | |
689 | formatting feature described here; they differ from @code{format} only | |
690 | in how they use the result of formatting. | |
691 | ||
692 | @defun format string &rest objects | |
693 | This function returns a new string that is made by copying | |
694 | @var{string} and then replacing any format specification | |
695 | in the copy with encodings of the corresponding @var{objects}. The | |
696 | arguments @var{objects} are the computed values to be formatted. | |
697 | ||
698 | The characters in @var{string}, other than the format specifications, | |
699 | are copied directly into the output, including their text properties, | |
700 | if any. | |
701 | @end defun | |
702 | ||
703 | @cindex @samp{%} in format | |
704 | @cindex format specification | |
705 | A format specification is a sequence of characters beginning with a | |
706 | @samp{%}. Thus, if there is a @samp{%d} in @var{string}, the | |
707 | @code{format} function replaces it with the printed representation of | |
708 | one of the values to be formatted (one of the arguments @var{objects}). | |
709 | For example: | |
710 | ||
711 | @example | |
712 | @group | |
713 | (format "The value of fill-column is %d." fill-column) | |
714 | @result{} "The value of fill-column is 72." | |
715 | @end group | |
716 | @end example | |
717 | ||
718 | Since @code{format} interprets @samp{%} characters as format | |
719 | specifications, you should @emph{never} pass an arbitrary string as | |
720 | the first argument. This is particularly true when the string is | |
721 | generated by some Lisp code. Unless the string is @emph{known} to | |
722 | never include any @samp{%} characters, pass @code{"%s"}, described | |
723 | below, as the first argument, and the string as the second, like this: | |
724 | ||
725 | @example | |
726 | (format "%s" @var{arbitrary-string}) | |
727 | @end example | |
728 | ||
729 | If @var{string} contains more than one format specification, the | |
730 | format specifications correspond to successive values from | |
731 | @var{objects}. Thus, the first format specification in @var{string} | |
732 | uses the first such value, the second format specification uses the | |
733 | second such value, and so on. Any extra format specifications (those | |
734 | for which there are no corresponding values) cause an error. Any | |
735 | extra values to be formatted are ignored. | |
736 | ||
737 | Certain format specifications require values of particular types. If | |
738 | you supply a value that doesn't fit the requirements, an error is | |
739 | signaled. | |
740 | ||
741 | Here is a table of valid format specifications: | |
742 | ||
743 | @table @samp | |
744 | @item %s | |
745 | Replace the specification with the printed representation of the object, | |
746 | made without quoting (that is, using @code{princ}, not | |
747 | @code{prin1}---@pxref{Output Functions}). Thus, strings are represented | |
748 | by their contents alone, with no @samp{"} characters, and symbols appear | |
749 | without @samp{\} characters. | |
750 | ||
751 | If the object is a string, its text properties are | |
752 | copied into the output. The text properties of the @samp{%s} itself | |
753 | are also copied, but those of the object take priority. | |
754 | ||
755 | @item %S | |
756 | Replace the specification with the printed representation of the object, | |
757 | made with quoting (that is, using @code{prin1}---@pxref{Output | |
758 | Functions}). Thus, strings are enclosed in @samp{"} characters, and | |
759 | @samp{\} characters appear where necessary before special characters. | |
760 | ||
761 | @item %o | |
762 | @cindex integer to octal | |
763 | Replace the specification with the base-eight representation of an | |
764 | integer. | |
765 | ||
766 | @item %d | |
767 | Replace the specification with the base-ten representation of an | |
768 | integer. | |
769 | ||
770 | @item %x | |
771 | @itemx %X | |
772 | @cindex integer to hexadecimal | |
773 | Replace the specification with the base-sixteen representation of an | |
774 | integer. @samp{%x} uses lower case and @samp{%X} uses upper case. | |
775 | ||
776 | @item %c | |
777 | Replace the specification with the character which is the value given. | |
778 | ||
779 | @item %e | |
780 | Replace the specification with the exponential notation for a floating | |
781 | point number. | |
782 | ||
783 | @item %f | |
784 | Replace the specification with the decimal-point notation for a floating | |
785 | point number. | |
786 | ||
787 | @item %g | |
788 | Replace the specification with notation for a floating point number, | |
789 | using either exponential notation or decimal-point notation, whichever | |
790 | is shorter. | |
791 | ||
792 | @item %% | |
793 | Replace the specification with a single @samp{%}. This format | |
794 | specification is unusual in that it does not use a value. For example, | |
795 | @code{(format "%% %d" 30)} returns @code{"% 30"}. | |
796 | @end table | |
797 | ||
798 | Any other format character results in an @samp{Invalid format | |
799 | operation} error. | |
800 | ||
801 | Here are several examples: | |
802 | ||
803 | @example | |
804 | @group | |
805 | (format "The name of this buffer is %s." (buffer-name)) | |
806 | @result{} "The name of this buffer is strings.texi." | |
807 | ||
808 | (format "The buffer object prints as %s." (current-buffer)) | |
809 | @result{} "The buffer object prints as strings.texi." | |
810 | ||
811 | (format "The octal value of %d is %o, | |
812 | and the hex value is %x." 18 18 18) | |
813 | @result{} "The octal value of 18 is 22, | |
814 | and the hex value is 12." | |
815 | @end group | |
816 | @end example | |
817 | ||
818 | @cindex field width | |
819 | @cindex padding | |
b20e7c7d CY |
820 | A specification can have a @dfn{width}, which is a decimal number |
821 | between the @samp{%} and the specification character. If the printed | |
822 | representation of the object contains fewer characters than this | |
823 | width, @code{format} extends it with padding. The width specifier is | |
824 | ignored for the @samp{%%} specification. Any padding introduced by | |
825 | the width specifier normally consists of spaces inserted on the left: | |
b8d4c8d0 GM |
826 | |
827 | @example | |
b20e7c7d CY |
828 | (format "%5d is padded on the left with spaces" 123) |
829 | @result{} " 123 is padded on the left with spaces" | |
b8d4c8d0 GM |
830 | @end example |
831 | ||
832 | @noindent | |
833 | If the width is too small, @code{format} does not truncate the | |
834 | object's printed representation. Thus, you can use a width to specify | |
835 | a minimum spacing between columns with no risk of losing information. | |
b20e7c7d CY |
836 | In the following three examples, @samp{%7s} specifies a minimum width |
837 | of 7. In the first case, the string inserted in place of @samp{%7s} | |
838 | has only 3 letters, and needs 4 blank spaces as padding. In the | |
839 | second case, the string @code{"specification"} is 13 letters wide but | |
840 | is not truncated. | |
b8d4c8d0 | 841 | |
b20e7c7d | 842 | @example |
b8d4c8d0 GM |
843 | @group |
844 | (format "The word `%7s' actually has %d letters in it." | |
845 | "foo" (length "foo")) | |
846 | @result{} "The word ` foo' actually has 3 letters in it." | |
b8d4c8d0 GM |
847 | (format "The word `%7s' actually has %d letters in it." |
848 | "specification" (length "specification")) | |
849 | @result{} "The word `specification' actually has 13 letters in it." | |
850 | @end group | |
b20e7c7d CY |
851 | @end example |
852 | ||
853 | @cindex flags in format specifications | |
854 | Immediately after the @samp{%} and before the optional width | |
855 | specifier, you can also put certain @dfn{flag characters}. | |
856 | ||
857 | The flag @samp{+} inserts a plus sign before a positive number, so | |
858 | that it always has a sign. A space character as flag inserts a space | |
859 | before a positive number. (Otherwise, positive numbers start with the | |
860 | first digit.) These flags are useful for ensuring that positive | |
861 | numbers and negative numbers use the same number of columns. They are | |
862 | ignored except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}, and if | |
863 | both flags are used, @samp{+} takes precedence. | |
864 | ||
865 | The flag @samp{#} specifies an ``alternate form'' which depends on | |
866 | the format in use. For @samp{%o}, it ensures that the result begins | |
867 | with a @samp{0}. For @samp{%x} and @samp{%X}, it prefixes the result | |
868 | with @samp{0x} or @samp{0X}. For @samp{%e}, @samp{%f}, and @samp{%g}, | |
869 | the @samp{#} flag means include a decimal point even if the precision | |
870 | is zero. | |
871 | ||
872 | The flag @samp{-} causes the padding inserted by the width | |
873 | specifier, if any, to be inserted on the right rather than the left. | |
874 | The flag @samp{0} ensures that the padding consists of @samp{0} | |
875 | characters instead of spaces, inserted on the left. These flags are | |
876 | ignored for specification characters for which they do not make sense: | |
877 | @samp{%s}, @samp{%S} and @samp{%c} accept the @samp{0} flag, but still | |
878 | pad with @emph{spaces} on the left. If both @samp{-} and @samp{0} are | |
879 | present and valid, @samp{-} takes precedence. | |
b8d4c8d0 | 880 | |
b20e7c7d | 881 | @example |
b8d4c8d0 | 882 | @group |
b20e7c7d CY |
883 | (format "%06d is padded on the left with zeros" 123) |
884 | @result{} "000123 is padded on the left with zeros" | |
885 | ||
886 | (format "%-6d is padded on the right" 123) | |
887 | @result{} "123 is padded on the right" | |
888 | ||
b8d4c8d0 GM |
889 | (format "The word `%-7s' actually has %d letters in it." |
890 | "foo" (length "foo")) | |
891 | @result{} "The word `foo ' actually has 3 letters in it." | |
892 | @end group | |
b20e7c7d | 893 | @end example |
b8d4c8d0 GM |
894 | |
895 | @cindex precision in format specifications | |
896 | All the specification characters allow an optional @dfn{precision} | |
897 | before the character (after the width, if present). The precision is | |
898 | a decimal-point @samp{.} followed by a digit-string. For the | |
899 | floating-point specifications (@samp{%e}, @samp{%f}, @samp{%g}), the | |
900 | precision specifies how many decimal places to show; if zero, the | |
901 | decimal-point itself is also omitted. For @samp{%s} and @samp{%S}, | |
902 | the precision truncates the string to the given width, so @samp{%.3s} | |
903 | shows only the first three characters of the representation for | |
904 | @var{object}. Precision has no effect for other specification | |
905 | characters. | |
906 | ||
b8d4c8d0 GM |
907 | @node Case Conversion |
908 | @comment node-name, next, previous, up | |
909 | @section Case Conversion in Lisp | |
910 | @cindex upper case | |
911 | @cindex lower case | |
912 | @cindex character case | |
913 | @cindex case conversion in Lisp | |
914 | ||
915 | The character case functions change the case of single characters or | |
916 | of the contents of strings. The functions normally convert only | |
917 | alphabetic characters (the letters @samp{A} through @samp{Z} and | |
918 | @samp{a} through @samp{z}, as well as non-@acronym{ASCII} letters); other | |
919 | characters are not altered. You can specify a different case | |
920 | conversion mapping by specifying a case table (@pxref{Case Tables}). | |
921 | ||
922 | These functions do not modify the strings that are passed to them as | |
923 | arguments. | |
924 | ||
925 | The examples below use the characters @samp{X} and @samp{x} which have | |
926 | @acronym{ASCII} codes 88 and 120 respectively. | |
927 | ||
928 | @defun downcase string-or-char | |
8f88eb24 CY |
929 | This function converts @var{string-or-char}, which should be either a |
930 | character or a string, to lower case. | |
b8d4c8d0 | 931 | |
8f88eb24 CY |
932 | When @var{string-or-char} is a string, this function returns a new |
933 | string in which each letter in the argument that is upper case is | |
934 | converted to lower case. When @var{string-or-char} is a character, | |
935 | this function returns the corresponding lower case character (an | |
936 | integer); if the original character is lower case, or is not a letter, | |
937 | the return value is equal to the original character. | |
b8d4c8d0 GM |
938 | |
939 | @example | |
940 | (downcase "The cat in the hat") | |
941 | @result{} "the cat in the hat" | |
942 | ||
943 | (downcase ?X) | |
944 | @result{} 120 | |
945 | @end example | |
946 | @end defun | |
947 | ||
948 | @defun upcase string-or-char | |
8f88eb24 CY |
949 | This function converts @var{string-or-char}, which should be either a |
950 | character or a string, to upper case. | |
b8d4c8d0 | 951 | |
8f88eb24 CY |
952 | When @var{string-or-char} is a string, this function returns a new |
953 | string in which each letter in the argument that is lower case is | |
954 | converted to upper case. When @var{string-or-char} is a character, | |
955 | this function returns the corresponding upper case character (an an | |
956 | integer); if the original character is upper case, or is not a letter, | |
957 | the return value is equal to the original character. | |
b8d4c8d0 GM |
958 | |
959 | @example | |
960 | (upcase "The cat in the hat") | |
961 | @result{} "THE CAT IN THE HAT" | |
962 | ||
963 | (upcase ?x) | |
964 | @result{} 88 | |
965 | @end example | |
966 | @end defun | |
967 | ||
968 | @defun capitalize string-or-char | |
969 | @cindex capitalization | |
970 | This function capitalizes strings or characters. If | |
8f88eb24 CY |
971 | @var{string-or-char} is a string, the function returns a new string |
972 | whose contents are a copy of @var{string-or-char} in which each word | |
973 | has been capitalized. This means that the first character of each | |
b8d4c8d0 GM |
974 | word is converted to upper case, and the rest are converted to lower |
975 | case. | |
976 | ||
977 | The definition of a word is any sequence of consecutive characters that | |
978 | are assigned to the word constituent syntax class in the current syntax | |
979 | table (@pxref{Syntax Class Table}). | |
980 | ||
8f88eb24 CY |
981 | When @var{string-or-char} is a character, this function does the same |
982 | thing as @code{upcase}. | |
b8d4c8d0 GM |
983 | |
984 | @example | |
985 | @group | |
986 | (capitalize "The cat in the hat") | |
987 | @result{} "The Cat In The Hat" | |
988 | @end group | |
989 | ||
990 | @group | |
991 | (capitalize "THE 77TH-HATTED CAT") | |
992 | @result{} "The 77th-Hatted Cat" | |
993 | @end group | |
994 | ||
995 | @group | |
996 | (capitalize ?x) | |
997 | @result{} 88 | |
998 | @end group | |
999 | @end example | |
1000 | @end defun | |
1001 | ||
1002 | @defun upcase-initials string-or-char | |
1003 | If @var{string-or-char} is a string, this function capitalizes the | |
1004 | initials of the words in @var{string-or-char}, without altering any | |
1005 | letters other than the initials. It returns a new string whose | |
1006 | contents are a copy of @var{string-or-char}, in which each word has | |
1007 | had its initial letter converted to upper case. | |
1008 | ||
1009 | The definition of a word is any sequence of consecutive characters that | |
1010 | are assigned to the word constituent syntax class in the current syntax | |
1011 | table (@pxref{Syntax Class Table}). | |
1012 | ||
1013 | When the argument to @code{upcase-initials} is a character, | |
1014 | @code{upcase-initials} has the same result as @code{upcase}. | |
1015 | ||
1016 | @example | |
1017 | @group | |
1018 | (upcase-initials "The CAT in the hAt") | |
1019 | @result{} "The CAT In The HAt" | |
1020 | @end group | |
1021 | @end example | |
1022 | @end defun | |
1023 | ||
1024 | @xref{Text Comparison}, for functions that compare strings; some of | |
1025 | them ignore case differences, or can optionally ignore case differences. | |
1026 | ||
1027 | @node Case Tables | |
1028 | @section The Case Table | |
1029 | ||
1030 | You can customize case conversion by installing a special @dfn{case | |
1031 | table}. A case table specifies the mapping between upper case and lower | |
1032 | case letters. It affects both the case conversion functions for Lisp | |
1033 | objects (see the previous section) and those that apply to text in the | |
1034 | buffer (@pxref{Case Changes}). Each buffer has a case table; there is | |
1035 | also a standard case table which is used to initialize the case table | |
1036 | of new buffers. | |
1037 | ||
1038 | A case table is a char-table (@pxref{Char-Tables}) whose subtype is | |
1039 | @code{case-table}. This char-table maps each character into the | |
1040 | corresponding lower case character. It has three extra slots, which | |
1041 | hold related tables: | |
1042 | ||
1043 | @table @var | |
1044 | @item upcase | |
1045 | The upcase table maps each character into the corresponding upper | |
1046 | case character. | |
1047 | @item canonicalize | |
1048 | The canonicalize table maps all of a set of case-related characters | |
1049 | into a particular member of that set. | |
1050 | @item equivalences | |
1051 | The equivalences table maps each one of a set of case-related characters | |
1052 | into the next character in that set. | |
1053 | @end table | |
1054 | ||
1055 | In simple cases, all you need to specify is the mapping to lower-case; | |
1056 | the three related tables will be calculated automatically from that one. | |
1057 | ||
1058 | For some languages, upper and lower case letters are not in one-to-one | |
1059 | correspondence. There may be two different lower case letters with the | |
1060 | same upper case equivalent. In these cases, you need to specify the | |
1061 | maps for both lower case and upper case. | |
1062 | ||
1063 | The extra table @var{canonicalize} maps each character to a canonical | |
1064 | equivalent; any two characters that are related by case-conversion have | |
1065 | the same canonical equivalent character. For example, since @samp{a} | |
1066 | and @samp{A} are related by case-conversion, they should have the same | |
1067 | canonical equivalent character (which should be either @samp{a} for both | |
1068 | of them, or @samp{A} for both of them). | |
1069 | ||
1070 | The extra table @var{equivalences} is a map that cyclically permutes | |
1071 | each equivalence class (of characters with the same canonical | |
1072 | equivalent). (For ordinary @acronym{ASCII}, this would map @samp{a} into | |
1073 | @samp{A} and @samp{A} into @samp{a}, and likewise for each set of | |
1074 | equivalent characters.) | |
1075 | ||
8f88eb24 | 1076 | When constructing a case table, you can provide @code{nil} for |
b8d4c8d0 GM |
1077 | @var{canonicalize}; then Emacs fills in this slot from the lower case |
1078 | and upper case mappings. You can also provide @code{nil} for | |
1079 | @var{equivalences}; then Emacs fills in this slot from | |
1080 | @var{canonicalize}. In a case table that is actually in use, those | |
8f88eb24 CY |
1081 | components are non-@code{nil}. Do not try to specify |
1082 | @var{equivalences} without also specifying @var{canonicalize}. | |
b8d4c8d0 GM |
1083 | |
1084 | Here are the functions for working with case tables: | |
1085 | ||
1086 | @defun case-table-p object | |
1087 | This predicate returns non-@code{nil} if @var{object} is a valid case | |
1088 | table. | |
1089 | @end defun | |
1090 | ||
1091 | @defun set-standard-case-table table | |
1092 | This function makes @var{table} the standard case table, so that it will | |
1093 | be used in any buffers created subsequently. | |
1094 | @end defun | |
1095 | ||
1096 | @defun standard-case-table | |
1097 | This returns the standard case table. | |
1098 | @end defun | |
1099 | ||
1100 | @defun current-case-table | |
1101 | This function returns the current buffer's case table. | |
1102 | @end defun | |
1103 | ||
1104 | @defun set-case-table table | |
1105 | This sets the current buffer's case table to @var{table}. | |
1106 | @end defun | |
1107 | ||
1108 | @defmac with-case-table table body@dots{} | |
1109 | The @code{with-case-table} macro saves the current case table, makes | |
1110 | @var{table} the current case table, evaluates the @var{body} forms, | |
1111 | and finally restores the case table. The return value is the value of | |
1112 | the last form in @var{body}. The case table is restored even in case | |
1113 | of an abnormal exit via @code{throw} or error (@pxref{Nonlocal | |
1114 | Exits}). | |
1115 | @end defmac | |
1116 | ||
8f88eb24 | 1117 | Some language environments modify the case conversions of |
b8d4c8d0 GM |
1118 | @acronym{ASCII} characters; for example, in the Turkish language |
1119 | environment, the @acronym{ASCII} character @samp{I} is downcased into | |
1120 | a Turkish ``dotless i''. This can interfere with code that requires | |
1121 | ordinary ASCII case conversion, such as implementations of | |
1122 | @acronym{ASCII}-based network protocols. In that case, use the | |
1123 | @code{with-case-table} macro with the variable @var{ascii-case-table}, | |
1124 | which stores the unmodified case table for the @acronym{ASCII} | |
1125 | character set. | |
1126 | ||
1127 | @defvar ascii-case-table | |
1128 | The case table for the @acronym{ASCII} character set. This should not be | |
1129 | modified by any language environment settings. | |
1130 | @end defvar | |
1131 | ||
1132 | The following three functions are convenient subroutines for packages | |
1133 | that define non-@acronym{ASCII} character sets. They modify the specified | |
1134 | case table @var{case-table}; they also modify the standard syntax table. | |
1135 | @xref{Syntax Tables}. Normally you would use these functions to change | |
1136 | the standard case table. | |
1137 | ||
1138 | @defun set-case-syntax-pair uc lc case-table | |
1139 | This function specifies a pair of corresponding letters, one upper case | |
1140 | and one lower case. | |
1141 | @end defun | |
1142 | ||
1143 | @defun set-case-syntax-delims l r case-table | |
1144 | This function makes characters @var{l} and @var{r} a matching pair of | |
1145 | case-invariant delimiters. | |
1146 | @end defun | |
1147 | ||
1148 | @defun set-case-syntax char syntax case-table | |
1149 | This function makes @var{char} case-invariant, with syntax | |
1150 | @var{syntax}. | |
1151 | @end defun | |
1152 | ||
1153 | @deffn Command describe-buffer-case-table | |
1154 | This command displays a description of the contents of the current | |
1155 | buffer's case table. | |
1156 | @end deffn | |
1157 | ||
1158 | @ignore | |
1159 | arch-tag: 700b8e95-7aa5-4b52-9eb3-8f2e1ea152b4 | |
1160 | @end ignore |