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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
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3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
4 | @c Free Software Foundation, Inc. | |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/sequences | |
8241495d | 7 | @node Sequences Arrays Vectors, Hash Tables, Lists, Top |
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8 | @chapter Sequences, Arrays, and Vectors |
9 | @cindex sequence | |
10 | ||
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11 | Recall that the @dfn{sequence} type is the union of two other Lisp |
12 | types: lists and arrays. In other words, any list is a sequence, and | |
13 | any array is a sequence. The common property that all sequences have is | |
14 | that each is an ordered collection of elements. | |
4672ee8f | 15 | |
79d11238 | 16 | An @dfn{array} is a single primitive object that has a slot for each |
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17 | of its elements. All the elements are accessible in constant time, but |
18 | the length of an existing array cannot be changed. Strings, vectors, | |
19 | char-tables and bool-vectors are the four types of arrays. | |
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20 | |
21 | A list is a sequence of elements, but it is not a single primitive | |
22 | object; it is made of cons cells, one cell per element. Finding the | |
23 | @var{n}th element requires looking through @var{n} cons cells, so | |
24 | elements farther from the beginning of the list take longer to access. | |
25 | But it is possible to add elements to the list, or remove elements. | |
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26 | |
27 | The following diagram shows the relationship between these types: | |
28 | ||
29 | @example | |
30 | @group | |
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31 | _____________________________________________ |
32 | | | | |
33 | | Sequence | | |
34 | | ______ ________________________________ | | |
35 | | | | | | | | |
36 | | | List | | Array | | | |
37 | | | | | ________ ________ | | | |
38 | | |______| | | | | | | | | |
39 | | | | Vector | | String | | | | |
40 | | | |________| |________| | | | |
41 | | | ____________ _____________ | | | |
42 | | | | | | | | | | |
43 | | | | Char-table | | Bool-vector | | | | |
44 | | | |____________| |_____________| | | | |
45 | | |________________________________| | | |
46 | |_____________________________________________| | |
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47 | @end group |
48 | @end example | |
49 | ||
50 | The elements of vectors and lists may be any Lisp objects. The | |
51 | elements of strings are all characters. | |
52 | ||
53 | @menu | |
54 | * Sequence Functions:: Functions that accept any kind of sequence. | |
55 | * Arrays:: Characteristics of arrays in Emacs Lisp. | |
56 | * Array Functions:: Functions specifically for arrays. | |
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57 | * Vectors:: Special characteristics of Emacs Lisp vectors. |
58 | * Vector Functions:: Functions specifically for vectors. | |
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59 | * Char-Tables:: How to work with char-tables. |
60 | * Bool-Vectors:: How to work with bool-vectors. | |
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61 | @end menu |
62 | ||
63 | @node Sequence Functions | |
64 | @section Sequences | |
65 | ||
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66 | In Emacs Lisp, a @dfn{sequence} is either a list or an array. The |
67 | common property of all sequences is that they are ordered collections of | |
68 | elements. This section describes functions that accept any kind of | |
69 | sequence. | |
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70 | |
71 | @defun sequencep object | |
72 | Returns @code{t} if @var{object} is a list, vector, or | |
73 | string, @code{nil} otherwise. | |
74 | @end defun | |
75 | ||
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76 | @defun length sequence |
77 | @cindex string length | |
78 | @cindex list length | |
79 | @cindex vector length | |
80 | @cindex sequence length | |
81 | This function returns the number of elements in @var{sequence}. If | |
82 | @var{sequence} is a cons cell that is not a list (because the final | |
83 | @sc{cdr} is not @code{nil}), a @code{wrong-type-argument} error is | |
84 | signaled. | |
85 | ||
a9f0a989 | 86 | @xref{List Elements}, for the related function @code{safe-length}. |
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87 | |
88 | @example | |
89 | @group | |
90 | (length '(1 2 3)) | |
91 | @result{} 3 | |
92 | @end group | |
93 | @group | |
94 | (length ()) | |
95 | @result{} 0 | |
96 | @end group | |
97 | @group | |
98 | (length "foobar") | |
99 | @result{} 6 | |
100 | @end group | |
101 | @group | |
102 | (length [1 2 3]) | |
103 | @result{} 3 | |
104 | @end group | |
105 | @group | |
106 | (length (make-bool-vector 5 nil)) | |
107 | @result{} 5 | |
108 | @end group | |
109 | @end example | |
110 | @end defun | |
111 | ||
112 | @defun elt sequence index | |
113 | @cindex elements of sequences | |
114 | This function returns the element of @var{sequence} indexed by | |
115 | @var{index}. Legitimate values of @var{index} are integers ranging from | |
116 | 0 up to one less than the length of @var{sequence}. If @var{sequence} | |
117 | is a list, then out-of-range values of @var{index} return @code{nil}; | |
118 | otherwise, they trigger an @code{args-out-of-range} error. | |
119 | ||
120 | @example | |
121 | @group | |
122 | (elt [1 2 3 4] 2) | |
123 | @result{} 3 | |
124 | @end group | |
125 | @group | |
126 | (elt '(1 2 3 4) 2) | |
127 | @result{} 3 | |
128 | @end group | |
129 | @group | |
130 | ;; @r{We use @code{string} to show clearly which character @code{elt} returns.} | |
131 | (string (elt "1234" 2)) | |
132 | @result{} "3" | |
133 | @end group | |
134 | @group | |
135 | (elt [1 2 3 4] 4) | |
a9f0a989 | 136 | @error{} Args out of range: [1 2 3 4], 4 |
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137 | @end group |
138 | @group | |
139 | (elt [1 2 3 4] -1) | |
a9f0a989 | 140 | @error{} Args out of range: [1 2 3 4], -1 |
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141 | @end group |
142 | @end example | |
143 | ||
144 | This function generalizes @code{aref} (@pxref{Array Functions}) and | |
145 | @code{nth} (@pxref{List Elements}). | |
146 | @end defun | |
147 | ||
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148 | @defun copy-sequence sequence |
149 | @cindex copying sequences | |
150 | Returns a copy of @var{sequence}. The copy is the same type of object | |
151 | as the original sequence, and it has the same elements in the same order. | |
152 | ||
153 | Storing a new element into the copy does not affect the original | |
154 | @var{sequence}, and vice versa. However, the elements of the new | |
155 | sequence are not copies; they are identical (@code{eq}) to the elements | |
156 | of the original. Therefore, changes made within these elements, as | |
157 | found via the copied sequence, are also visible in the original | |
158 | sequence. | |
159 | ||
160 | If the sequence is a string with text properties, the property list in | |
161 | the copy is itself a copy, not shared with the original's property | |
162 | list. However, the actual values of the properties are shared. | |
163 | @xref{Text Properties}. | |
164 | ||
165 | See also @code{append} in @ref{Building Lists}, @code{concat} in | |
d699a7ad | 166 | @ref{Creating Strings}, and @code{vconcat} in @ref{Vectors}, for other |
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167 | ways to copy sequences. |
168 | ||
169 | @example | |
170 | @group | |
171 | (setq bar '(1 2)) | |
172 | @result{} (1 2) | |
173 | @end group | |
174 | @group | |
175 | (setq x (vector 'foo bar)) | |
176 | @result{} [foo (1 2)] | |
177 | @end group | |
178 | @group | |
179 | (setq y (copy-sequence x)) | |
180 | @result{} [foo (1 2)] | |
181 | @end group | |
182 | ||
183 | @group | |
184 | (eq x y) | |
185 | @result{} nil | |
186 | @end group | |
187 | @group | |
188 | (equal x y) | |
189 | @result{} t | |
190 | @end group | |
191 | @group | |
192 | (eq (elt x 1) (elt y 1)) | |
193 | @result{} t | |
194 | @end group | |
195 | ||
196 | @group | |
197 | ;; @r{Replacing an element of one sequence.} | |
198 | (aset x 0 'quux) | |
199 | x @result{} [quux (1 2)] | |
200 | y @result{} [foo (1 2)] | |
201 | @end group | |
202 | ||
203 | @group | |
204 | ;; @r{Modifying the inside of a shared element.} | |
205 | (setcar (aref x 1) 69) | |
206 | x @result{} [quux (69 2)] | |
207 | y @result{} [foo (69 2)] | |
208 | @end group | |
209 | @end example | |
210 | @end defun | |
211 | ||
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212 | @node Arrays |
213 | @section Arrays | |
214 | @cindex array | |
215 | ||
79d11238 | 216 | An @dfn{array} object has slots that hold a number of other Lisp |
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217 | objects, called the elements of the array. Any element of an array may |
218 | be accessed in constant time. In contrast, an element of a list | |
219 | requires access time that is proportional to the position of the element | |
220 | in the list. | |
221 | ||
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222 | Emacs defines four types of array, all one-dimensional: @dfn{strings}, |
223 | @dfn{vectors}, @dfn{bool-vectors} and @dfn{char-tables}. A vector is a | |
224 | general array; its elements can be any Lisp objects. A string is a | |
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225 | specialized array; its elements must be characters. Each type of array |
226 | has its own read syntax. | |
a9f0a989 | 227 | @xref{String Type}, and @ref{Vector Type}. |
4672ee8f | 228 | |
969fe9b5 | 229 | All four kinds of array share these characteristics: |
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230 | |
231 | @itemize @bullet | |
232 | @item | |
233 | The first element of an array has index zero, the second element has | |
234 | index 1, and so on. This is called @dfn{zero-origin} indexing. For | |
235 | example, an array of four elements has indices 0, 1, 2, @w{and 3}. | |
236 | ||
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237 | @item |
238 | The length of the array is fixed once you create it; you cannot | |
239 | change the length of an existing array. | |
240 | ||
241 | @item | |
242 | The array is a constant, for evaluation---in other words, it evaluates | |
243 | to itself. | |
244 | ||
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245 | @item |
246 | The elements of an array may be referenced or changed with the functions | |
247 | @code{aref} and @code{aset}, respectively (@pxref{Array Functions}). | |
248 | @end itemize | |
249 | ||
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250 | When you create an array, other than a char-table, you must specify |
251 | its length. You cannot specify the length of a char-table, because that | |
252 | is determined by the range of character codes. | |
253 | ||
254 | In principle, if you want an array of text characters, you could use | |
255 | either a string or a vector. In practice, we always choose strings for | |
256 | such applications, for four reasons: | |
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257 | |
258 | @itemize @bullet | |
259 | @item | |
260 | They occupy one-fourth the space of a vector of the same elements. | |
261 | ||
262 | @item | |
263 | Strings are printed in a way that shows the contents more clearly | |
f9f59935 | 264 | as text. |
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265 | |
266 | @item | |
267 | Strings can hold text properties. @xref{Text Properties}. | |
268 | ||
269 | @item | |
270 | Many of the specialized editing and I/O facilities of Emacs accept only | |
271 | strings. For example, you cannot insert a vector of characters into a | |
272 | buffer the way you can insert a string. @xref{Strings and Characters}. | |
273 | @end itemize | |
274 | ||
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275 | By contrast, for an array of keyboard input characters (such as a key |
276 | sequence), a vector may be necessary, because many keyboard input | |
277 | characters are outside the range that will fit in a string. @xref{Key | |
278 | Sequence Input}. | |
279 | ||
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280 | @node Array Functions |
281 | @section Functions that Operate on Arrays | |
282 | ||
f9f59935 RS |
283 | In this section, we describe the functions that accept all types of |
284 | arrays. | |
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285 | |
286 | @defun arrayp object | |
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287 | This function returns @code{t} if @var{object} is an array (i.e., a |
288 | vector, a string, a bool-vector or a char-table). | |
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289 | |
290 | @example | |
291 | @group | |
292 | (arrayp [a]) | |
969fe9b5 | 293 | @result{} t |
4672ee8f | 294 | (arrayp "asdf") |
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295 | @result{} t |
296 | (arrayp (syntax-table)) ;; @r{A char-table.} | |
297 | @result{} t | |
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298 | @end group |
299 | @end example | |
300 | @end defun | |
301 | ||
302 | @defun aref array index | |
303 | @cindex array elements | |
304 | This function returns the @var{index}th element of @var{array}. The | |
305 | first element is at index zero. | |
306 | ||
307 | @example | |
308 | @group | |
309 | (setq primes [2 3 5 7 11 13]) | |
310 | @result{} [2 3 5 7 11 13] | |
311 | (aref primes 4) | |
312 | @result{} 11 | |
4672ee8f | 313 | @end group |
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314 | @group |
315 | (aref "abcdefg" 1) | |
8241495d | 316 | @result{} 98 ; @r{@samp{b} is @sc{ascii} code 98.} |
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317 | @end group |
318 | @end example | |
319 | ||
320 | See also the function @code{elt}, in @ref{Sequence Functions}. | |
321 | @end defun | |
322 | ||
323 | @defun aset array index object | |
324 | This function sets the @var{index}th element of @var{array} to be | |
325 | @var{object}. It returns @var{object}. | |
326 | ||
327 | @example | |
328 | @group | |
329 | (setq w [foo bar baz]) | |
330 | @result{} [foo bar baz] | |
331 | (aset w 0 'fu) | |
332 | @result{} fu | |
333 | w | |
334 | @result{} [fu bar baz] | |
335 | @end group | |
336 | ||
337 | @group | |
338 | (setq x "asdfasfd") | |
339 | @result{} "asdfasfd" | |
340 | (aset x 3 ?Z) | |
341 | @result{} 90 | |
342 | x | |
343 | @result{} "asdZasfd" | |
344 | @end group | |
345 | @end example | |
346 | ||
347 | If @var{array} is a string and @var{object} is not a character, a | |
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348 | @code{wrong-type-argument} error results. The function converts a |
349 | unibyte string to multibyte if necessary to insert a character. | |
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350 | @end defun |
351 | ||
352 | @defun fillarray array object | |
79d11238 RS |
353 | This function fills the array @var{array} with @var{object}, so that |
354 | each element of @var{array} is @var{object}. It returns @var{array}. | |
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355 | |
356 | @example | |
357 | @group | |
358 | (setq a [a b c d e f g]) | |
359 | @result{} [a b c d e f g] | |
360 | (fillarray a 0) | |
361 | @result{} [0 0 0 0 0 0 0] | |
362 | a | |
363 | @result{} [0 0 0 0 0 0 0] | |
364 | @end group | |
365 | @group | |
366 | (setq s "When in the course") | |
367 | @result{} "When in the course" | |
368 | (fillarray s ?-) | |
369 | @result{} "------------------" | |
370 | @end group | |
371 | @end example | |
372 | ||
373 | If @var{array} is a string and @var{object} is not a character, a | |
374 | @code{wrong-type-argument} error results. | |
375 | @end defun | |
376 | ||
377 | The general sequence functions @code{copy-sequence} and @code{length} | |
378 | are often useful for objects known to be arrays. @xref{Sequence Functions}. | |
379 | ||
380 | @node Vectors | |
381 | @section Vectors | |
382 | @cindex vector | |
383 | ||
384 | Arrays in Lisp, like arrays in most languages, are blocks of memory | |
385 | whose elements can be accessed in constant time. A @dfn{vector} is a | |
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386 | general-purpose array of specified length; its elements can be any Lisp |
387 | objects. (By contrast, a string can hold only characters as elements.) | |
388 | Vectors in Emacs are used for obarrays (vectors of symbols), and as part | |
389 | of keymaps (vectors of commands). They are also used internally as part | |
390 | of the representation of a byte-compiled function; if you print such a | |
f9f59935 | 391 | function, you will see a vector in it. |
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392 | |
393 | In Emacs Lisp, the indices of the elements of a vector start from zero | |
394 | and count up from there. | |
395 | ||
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396 | Vectors are printed with square brackets surrounding the elements. |
397 | Thus, a vector whose elements are the symbols @code{a}, @code{b} and | |
398 | @code{a} is printed as @code{[a b a]}. You can write vectors in the | |
399 | same way in Lisp input. | |
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400 | |
401 | A vector, like a string or a number, is considered a constant for | |
402 | evaluation: the result of evaluating it is the same vector. This does | |
403 | not evaluate or even examine the elements of the vector. | |
404 | @xref{Self-Evaluating Forms}. | |
405 | ||
f9f59935 | 406 | Here are examples illustrating these principles: |
4672ee8f RS |
407 | |
408 | @example | |
409 | @group | |
410 | (setq avector [1 two '(three) "four" [five]]) | |
411 | @result{} [1 two (quote (three)) "four" [five]] | |
412 | (eval avector) | |
413 | @result{} [1 two (quote (three)) "four" [five]] | |
414 | (eq avector (eval avector)) | |
415 | @result{} t | |
416 | @end group | |
417 | @end example | |
418 | ||
79d11238 | 419 | @node Vector Functions |
969fe9b5 | 420 | @section Functions for Vectors |
79d11238 | 421 | |
4672ee8f RS |
422 | Here are some functions that relate to vectors: |
423 | ||
424 | @defun vectorp object | |
425 | This function returns @code{t} if @var{object} is a vector. | |
426 | ||
427 | @example | |
428 | @group | |
429 | (vectorp [a]) | |
430 | @result{} t | |
431 | (vectorp "asdf") | |
432 | @result{} nil | |
433 | @end group | |
434 | @end example | |
435 | @end defun | |
436 | ||
437 | @defun vector &rest objects | |
438 | This function creates and returns a vector whose elements are the | |
439 | arguments, @var{objects}. | |
440 | ||
441 | @example | |
442 | @group | |
443 | (vector 'foo 23 [bar baz] "rats") | |
444 | @result{} [foo 23 [bar baz] "rats"] | |
445 | (vector) | |
446 | @result{} [] | |
447 | @end group | |
448 | @end example | |
449 | @end defun | |
450 | ||
451 | @defun make-vector length object | |
452 | This function returns a new vector consisting of @var{length} elements, | |
453 | each initialized to @var{object}. | |
454 | ||
455 | @example | |
456 | @group | |
457 | (setq sleepy (make-vector 9 'Z)) | |
458 | @result{} [Z Z Z Z Z Z Z Z Z] | |
459 | @end group | |
460 | @end example | |
461 | @end defun | |
462 | ||
463 | @defun vconcat &rest sequences | |
464 | @cindex copying vectors | |
465 | This function returns a new vector containing all the elements of the | |
f9f59935 RS |
466 | @var{sequences}. The arguments @var{sequences} may be any kind of |
467 | arrays, including lists, vectors, or strings. If no @var{sequences} are | |
468 | given, an empty vector is returned. | |
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469 | |
470 | The value is a newly constructed vector that is not @code{eq} to any | |
471 | existing vector. | |
472 | ||
473 | @example | |
474 | @group | |
475 | (setq a (vconcat '(A B C) '(D E F))) | |
476 | @result{} [A B C D E F] | |
477 | (eq a (vconcat a)) | |
478 | @result{} nil | |
479 | @end group | |
480 | @group | |
481 | (vconcat) | |
482 | @result{} [] | |
483 | (vconcat [A B C] "aa" '(foo (6 7))) | |
484 | @result{} [A B C 97 97 foo (6 7)] | |
485 | @end group | |
486 | @end example | |
487 | ||
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488 | The @code{vconcat} function also allows byte-code function objects as |
489 | arguments. This is a special feature to make it easy to access the entire | |
490 | contents of a byte-code function object. @xref{Byte-Code Objects}. | |
491 | ||
22697dac KH |
492 | The @code{vconcat} function also allows integers as arguments. It |
493 | converts them to strings of digits, making up the decimal print | |
494 | representation of the integer, and then uses the strings instead of the | |
495 | original integers. @strong{Don't use this feature; we plan to eliminate | |
496 | it. If you already use this feature, change your programs now!} The | |
497 | proper way to convert an integer to a decimal number in this way is with | |
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498 | @code{format} (@pxref{Formatting Strings}) or @code{number-to-string} |
499 | (@pxref{String Conversion}). | |
500 | ||
501 | For other concatenation functions, see @code{mapconcat} in @ref{Mapping | |
502 | Functions}, @code{concat} in @ref{Creating Strings}, and @code{append} | |
503 | in @ref{Building Lists}. | |
504 | @end defun | |
505 | ||
506 | The @code{append} function provides a way to convert a vector into a | |
507 | list with the same elements (@pxref{Building Lists}): | |
508 | ||
509 | @example | |
510 | @group | |
511 | (setq avector [1 two (quote (three)) "four" [five]]) | |
512 | @result{} [1 two (quote (three)) "four" [five]] | |
513 | (append avector nil) | |
514 | @result{} (1 two (quote (three)) "four" [five]) | |
515 | @end group | |
516 | @end example | |
f9f59935 RS |
517 | |
518 | @node Char-Tables | |
519 | @section Char-Tables | |
520 | @cindex char-tables | |
a9f0a989 | 521 | @cindex extra slots of char-table |
f9f59935 RS |
522 | |
523 | A char-table is much like a vector, except that it is indexed by | |
524 | character codes. Any valid character code, without modifiers, can be | |
969fe9b5 | 525 | used as an index in a char-table. You can access a char-table's |
a9f0a989 RS |
526 | elements with @code{aref} and @code{aset}, as with any array. In |
527 | addition, a char-table can have @dfn{extra slots} to hold additional | |
528 | data not associated with particular character codes. Char-tables are | |
529 | constants when evaluated. | |
f9f59935 | 530 | |
f9f59935 | 531 | @cindex subtype of char-table |
a9f0a989 RS |
532 | Each char-table has a @dfn{subtype} which is a symbol. The subtype |
533 | has two purposes: to distinguish char-tables meant for different uses, | |
534 | and to control the number of extra slots. For example, display tables | |
535 | are char-tables with @code{display-table} as the subtype, and syntax | |
536 | tables are char-tables with @code{syntax-table} as the subtype. A valid | |
537 | subtype must have a @code{char-table-extra-slots} property which is an | |
538 | integer between 0 and 10. This integer specifies the number of | |
539 | @dfn{extra slots} in the char-table. | |
f9f59935 RS |
540 | |
541 | @cindex parent of char-table | |
4f790472 | 542 | A char-table can have a @dfn{parent}, which is another char-table. If |
f9f59935 RS |
543 | it does, then whenever the char-table specifies @code{nil} for a |
544 | particular character @var{c}, it inherits the value specified in the | |
545 | parent. In other words, @code{(aref @var{char-table} @var{c})} returns | |
546 | the value from the parent of @var{char-table} if @var{char-table} itself | |
547 | specifies @code{nil}. | |
548 | ||
549 | @cindex default value of char-table | |
550 | A char-table can also have a @dfn{default value}. If so, then | |
551 | @code{(aref @var{char-table} @var{c})} returns the default value | |
552 | whenever the char-table does not specify any other non-@code{nil} value. | |
553 | ||
f9f59935 RS |
554 | @defun make-char-table subtype &optional init |
555 | Return a newly created char-table, with subtype @var{subtype}. Each | |
556 | element is initialized to @var{init}, which defaults to @code{nil}. You | |
557 | cannot alter the subtype of a char-table after the char-table is | |
558 | created. | |
969fe9b5 RS |
559 | |
560 | There is no argument to specify the length of the char-table, because | |
561 | all char-tables have room for any valid character code as an index. | |
f9f59935 RS |
562 | @end defun |
563 | ||
f9f59935 | 564 | @defun char-table-p object |
969fe9b5 | 565 | This function returns @code{t} if @var{object} is a char-table, |
f9f59935 RS |
566 | otherwise @code{nil}. |
567 | @end defun | |
568 | ||
f9f59935 RS |
569 | @defun char-table-subtype char-table |
570 | This function returns the subtype symbol of @var{char-table}. | |
571 | @end defun | |
572 | ||
f9f59935 RS |
573 | @defun set-char-table-default char-table new-default |
574 | This function sets the default value of @var{char-table} to | |
575 | @var{new-default}. | |
576 | ||
577 | There is no special function to access the default value of a char-table. | |
578 | To do that, use @code{(char-table-range @var{char-table} nil)}. | |
579 | @end defun | |
580 | ||
f9f59935 RS |
581 | @defun char-table-parent char-table |
582 | This function returns the parent of @var{char-table}. The parent is | |
583 | always either @code{nil} or another char-table. | |
584 | @end defun | |
585 | ||
f9f59935 RS |
586 | @defun set-char-table-parent char-table new-parent |
587 | This function sets the parent of @var{char-table} to @var{new-parent}. | |
588 | @end defun | |
589 | ||
f9f59935 RS |
590 | @defun char-table-extra-slot char-table n |
591 | This function returns the contents of extra slot @var{n} of | |
592 | @var{char-table}. The number of extra slots in a char-table is | |
593 | determined by its subtype. | |
594 | @end defun | |
595 | ||
f9f59935 RS |
596 | @defun set-char-table-extra-slot char-table n value |
597 | This function stores @var{value} in extra slot @var{n} of | |
598 | @var{char-table}. | |
599 | @end defun | |
600 | ||
601 | A char-table can specify an element value for a single character code; | |
602 | it can also specify a value for an entire character set. | |
603 | ||
f9f59935 RS |
604 | @defun char-table-range char-table range |
605 | This returns the value specified in @var{char-table} for a range of | |
a9f0a989 | 606 | characters @var{range}. Here are the possibilities for @var{range}: |
f9f59935 RS |
607 | |
608 | @table @asis | |
609 | @item @code{nil} | |
610 | Refers to the default value. | |
611 | ||
612 | @item @var{char} | |
a9f0a989 RS |
613 | Refers to the element for character @var{char} |
614 | (supposing @var{char} is a valid character code). | |
f9f59935 RS |
615 | |
616 | @item @var{charset} | |
617 | Refers to the value specified for the whole character set | |
618 | @var{charset} (@pxref{Character Sets}). | |
a9f0a989 RS |
619 | |
620 | @item @var{generic-char} | |
621 | A generic character stands for a character set; specifying the generic | |
622 | character as argument is equivalent to specifying the character set | |
623 | name. @xref{Splitting Characters}, for a description of generic characters. | |
f9f59935 RS |
624 | @end table |
625 | @end defun | |
626 | ||
f9f59935 | 627 | @defun set-char-table-range char-table range value |
1911e6e5 | 628 | This function sets the value in @var{char-table} for a range of |
a9f0a989 | 629 | characters @var{range}. Here are the possibilities for @var{range}: |
f9f59935 RS |
630 | |
631 | @table @asis | |
632 | @item @code{nil} | |
633 | Refers to the default value. | |
634 | ||
635 | @item @code{t} | |
636 | Refers to the whole range of character codes. | |
637 | ||
638 | @item @var{char} | |
a9f0a989 RS |
639 | Refers to the element for character @var{char} |
640 | (supposing @var{char} is a valid character code). | |
f9f59935 RS |
641 | |
642 | @item @var{charset} | |
643 | Refers to the value specified for the whole character set | |
644 | @var{charset} (@pxref{Character Sets}). | |
a9f0a989 RS |
645 | |
646 | @item @var{generic-char} | |
647 | A generic character stands for a character set; specifying the generic | |
648 | character as argument is equivalent to specifying the character set | |
649 | name. @xref{Splitting Characters}, for a description of generic characters. | |
f9f59935 RS |
650 | @end table |
651 | @end defun | |
652 | ||
f9f59935 RS |
653 | @defun map-char-table function char-table |
654 | This function calls @var{function} for each element of @var{char-table}. | |
655 | @var{function} is called with two arguments, a key and a value. The key | |
a9f0a989 RS |
656 | is a possible @var{range} argument for @code{char-table-range}---either |
657 | a valid character or a generic character---and the value is | |
658 | @code{(char-table-range @var{char-table} @var{key})}. | |
f9f59935 | 659 | |
969fe9b5 | 660 | Overall, the key-value pairs passed to @var{function} describe all the |
f9f59935 | 661 | values stored in @var{char-table}. |
a9f0a989 RS |
662 | |
663 | The return value is always @code{nil}; to make this function useful, | |
664 | @var{function} should have side effects. For example, | |
665 | here is how to examine each element of the syntax table: | |
666 | ||
667 | @example | |
1911e6e5 RS |
668 | (let (accumulator) |
669 | (map-char-table | |
670 | #'(lambda (key value) | |
671 | (setq accumulator | |
672 | (cons (list key value) accumulator))) | |
673 | (syntax-table)) | |
674 | accumulator) | |
a9f0a989 RS |
675 | @result{} |
676 | ((475008 nil) (474880 nil) (474752 nil) (474624 nil) | |
677 | ... (5 (3)) (4 (3)) (3 (3)) (2 (3)) (1 (3)) (0 (3))) | |
678 | @end example | |
f9f59935 RS |
679 | @end defun |
680 | ||
681 | @node Bool-Vectors | |
682 | @section Bool-vectors | |
683 | @cindex Bool-vectors | |
684 | ||
685 | A bool-vector is much like a vector, except that it stores only the | |
686 | values @code{t} and @code{nil}. If you try to store any non-@code{nil} | |
969fe9b5 RS |
687 | value into an element of the bool-vector, the effect is to store |
688 | @code{t} there. As with all arrays, bool-vector indices start from 0, | |
689 | and the length cannot be changed once the bool-vector is created. | |
690 | Bool-vectors are constants when evaluated. | |
f9f59935 RS |
691 | |
692 | There are two special functions for working with bool-vectors; aside | |
693 | from that, you manipulate them with same functions used for other kinds | |
694 | of arrays. | |
695 | ||
f9f59935 | 696 | @defun make-bool-vector length initial |
db4413be | 697 | Return a new bool-vector of @var{length} elements, |
f9f59935 RS |
698 | each one initialized to @var{initial}. |
699 | @end defun | |
700 | ||
701 | @defun bool-vector-p object | |
702 | This returns @code{t} if @var{object} is a bool-vector, | |
703 | and @code{nil} otherwise. | |
704 | @end defun | |
705 | ||
5785f550 RS |
706 | Here is an example of creating, examining, and updating a |
707 | bool-vector. Note that the printed form represents up to 8 boolean | |
708 | values as a single character. | |
709 | ||
710 | @example | |
711 | (setq bv (make-bool-vector 5 t)) | |
712 | @result{} #&5"^_" | |
713 | (aref bv 1) | |
714 | @result{} t | |
715 | (aset bv 3 nil) | |
716 | @result{} nil | |
717 | bv | |
718 | @result{} #&5"^W" | |
719 | @end example | |
720 | ||
721 | @noindent | |
722 | These results make sense because the binary codes for control-_ and | |
723 | control-W are 11111 and 10111, respectively. | |
724 |