Mercurial > hg > xemacs-beta
annotate man/lispref/strings.texi @ 5917:ffb5abc8dc4e
Fix a bug in the #'equalp compiler macro.
lisp/ChangeLog addition:
2015-06-11 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (equalp):
Fix a bug in this compiler macro when passed constants in a
certain order.
tests/ChangeLog addition:
2015-06-11 Aidan Kehoe <kehoea@parhasard.net>
* automated/lisp-tests.el:
Add a test looking for a bug just fixed in the equalp compiler
macro.
| author | Aidan Kehoe <kehoea@parhasard.net> |
|---|---|
| date | Thu, 11 Jun 2015 16:09:11 +0100 |
| parents | e0f1dfaa821e |
| children |
| 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 | |
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36 @node String Basics, Predicates for Strings, Strings and Characters, Strings and Characters |
| 428 | 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 | |
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103 @node Predicates for Strings, Creating Strings, String Basics, Strings and Characters |
| 428 | 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 | |
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123 @node Creating Strings, Predicates for Characters, Predicates for Strings, Strings and Characters |
| 428 | 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 | |
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148 non-negative fixnum. |
| 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 | |
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168 In this implementation, @code{substring} is an alias for @code{subseq}, |
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169 so @var{string} can be any sequence. In GNU Emacs, @var{string} can be |
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170 a string or a vector, and in older XEmacs it can only be a string. |
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171 |
| 428 | 172 @example |
| 173 @group | |
| 174 (substring "abcdefg" 0 3) | |
| 175 @result{} "abc" | |
| 176 @end group | |
| 177 @end example | |
| 178 | |
| 179 @noindent | |
| 180 Here the index for @samp{a} is 0, the index for @samp{b} is 1, and the | |
| 181 index for @samp{c} is 2. Thus, three letters, @samp{abc}, are copied | |
| 182 from the string @code{"abcdefg"}. The index 3 marks the character | |
| 183 position up to which the substring is copied. The character whose index | |
| 184 is 3 is actually the fourth character in the string. | |
| 185 | |
| 186 A negative number counts from the end of the string, so that @minus{}1 | |
| 444 | 187 signifies the index of the last character of the string. For example: |
| 428 | 188 |
| 189 @example | |
| 190 @group | |
| 191 (substring "abcdefg" -3 -1) | |
| 192 @result{} "ef" | |
| 193 @end group | |
| 194 @end example | |
| 195 | |
| 196 @noindent | |
| 197 In this example, the index for @samp{e} is @minus{}3, the index for | |
| 198 @samp{f} is @minus{}2, and the index for @samp{g} is @minus{}1. | |
| 199 Therefore, @samp{e} and @samp{f} are included, and @samp{g} is excluded. | |
| 200 | |
| 201 When @code{nil} is used as an index, it stands for the length of the | |
| 202 string. Thus, | |
| 203 | |
| 204 @example | |
| 205 @group | |
| 206 (substring "abcdefg" -3 nil) | |
| 207 @result{} "efg" | |
| 208 @end group | |
| 209 @end example | |
| 210 | |
| 211 Omitting the argument @var{end} is equivalent to specifying @code{nil}. | |
| 212 It follows that @code{(substring @var{string} 0)} returns a copy of all | |
| 213 of @var{string}. | |
| 214 | |
| 215 @example | |
| 216 @group | |
| 217 (substring "abcdefg" 0) | |
| 218 @result{} "abcdefg" | |
| 219 @end group | |
| 220 @end example | |
| 221 | |
| 222 @noindent | |
| 223 But we recommend @code{copy-sequence} for this purpose (@pxref{Sequence | |
| 224 Functions}). | |
| 225 | |
| 226 If the characters copied from @var{string} have duplicable extents or | |
| 227 text properties, those are copied into the new string also. | |
| 228 @xref{Duplicable Extents}. | |
| 229 | |
| 230 A @code{wrong-type-argument} error is signaled if either @var{start} or | |
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231 @var{end} is not a fixnum or @code{nil}. An @code{args-out-of-range} |
| 428 | 232 error is signaled if @var{start} indicates a character following |
| 233 @var{end}, or if either integer is out of range for @var{string}. | |
| 234 | |
| 235 Contrast this function with @code{buffer-substring} (@pxref{Buffer | |
| 236 Contents}), which returns a string containing a portion of the text in | |
| 237 the current buffer. The beginning of a string is at index 0, but the | |
| 238 beginning of a buffer is at index 1. | |
| 239 @end defun | |
| 240 | |
| 241 @defun concat &rest sequences | |
| 242 @cindex copying strings | |
| 243 @cindex concatenating strings | |
| 244 This function returns a new string consisting of the characters in the | |
| 245 arguments passed to it (along with their text properties, if any). The | |
| 246 arguments may be strings, lists of numbers, or vectors of numbers; they | |
| 247 are not themselves changed. If @code{concat} receives no arguments, it | |
| 248 returns an empty string. | |
| 249 | |
| 250 @example | |
| 251 (concat "abc" "-def") | |
| 252 @result{} "abc-def" | |
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253 (equal (concat "abc" (list 120 (+ 256 121)) [122]) (format "abcx%cz" 377)) |
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254 @result{} t |
| 428 | 255 ;; @r{@code{nil} is an empty sequence.} |
| 256 (concat "abc" nil "-def") | |
| 257 @result{} "abc-def" | |
| 258 (concat "The " "quick brown " "fox.") | |
| 259 @result{} "The quick brown fox." | |
| 260 (concat) | |
| 261 @result{} "" | |
| 262 @end example | |
| 263 | |
| 264 @noindent | |
| 265 The @code{concat} function always constructs a new string that is | |
| 266 not @code{eq} to any existing string. | |
| 267 | |
| 268 For information about other concatenation functions, see the description | |
| 269 of @code{mapconcat} in @ref{Mapping Functions}, @code{vconcat} in | |
| 270 @ref{Vectors}, @code{bvconcat} in @ref{Bit Vectors}, and @code{append} | |
| 271 in @ref{Building Lists}. | |
| 272 @end defun | |
| 273 | |
| 1495 | 274 The function @code{split-string}, in @ref{Regexp Search}, generates a |
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275 list of strings by splitting a string on occurrences of a regular |
| 1495 | 276 expression. |
| 277 | |
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278 @node Predicates for Characters, Character Codes, Creating Strings, Strings and Characters |
| 428 | 279 @section The Predicates for Characters |
| 280 | |
| 281 @defun characterp object | |
| 282 This function returns @code{t} if @var{object} is a character. | |
| 283 | |
| 284 Some functions that work on integers (e.g. the comparison functions | |
| 285 <, <=, =, /=, etc. and the arithmetic functions +, -, *, etc.) | |
| 286 accept characters and implicitly convert them into integers. In | |
| 287 general, functions that work on characters also accept char-ints and | |
| 288 implicitly convert them into characters. WARNING: Neither of these | |
| 289 behaviors is very desirable, and they are maintained for backward | |
| 290 compatibility with old E-Lisp programs that confounded characters and | |
| 291 integers willy-nilly. These behaviors may change in the future; therefore, | |
| 292 do not rely on them. Instead, convert the characters explicitly | |
| 293 using @code{char-int}. | |
| 294 @end defun | |
| 295 | |
| 296 @defun integer-or-char-p object | |
| 297 This function returns @code{t} if @var{object} is an integer or character. | |
| 298 @end defun | |
| 299 | |
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300 @defun digit-char-p character &optional (radix 10) radix-table |
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301 This function returns non-nil if @var{character} represents a digit in base |
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302 @var{radix}. The non-nil value returned is the integer value associated with |
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303 @var{character}. @var{radix} defaults to @code{10}. |
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304 |
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305 @var{radix-table}, if non-nil, specifies a character table mapping from |
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306 characters to their digit values. See the function @code{parse-integer} in |
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307 @ref{String Conversion}. |
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308 @end defun |
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309 |
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310 @defun digit-char weight &optional (radix 10) radix-table |
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311 This function is the inverse of @code{digit-char-p}. Given an integer |
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312 @var{weight}, it returns a character representing @var{weight} when read with |
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313 base @var{radix}. If no such character exists, it returns @code{nil}. |
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314 @end defun |
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315 |
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316 @node Character Codes, Text Comparison, Predicates for Characters, Strings and Characters |
| 428 | 317 @section Character Codes |
| 318 | |
| 444 | 319 @defun char-int character |
| 428 | 320 This function converts a character into an equivalent integer. |
| 321 The resulting integer will always be non-negative. The integers in | |
| 322 the range 0 - 255 map to characters as follows: | |
| 323 | |
| 324 @table @asis | |
| 325 @item 0 - 31 | |
| 326 Control set 0 | |
| 327 @item 32 - 127 | |
| 328 @sc{ascii} | |
| 329 @item 128 - 159 | |
| 330 Control set 1 | |
| 331 @item 160 - 255 | |
| 332 Right half of ISO-8859-1 | |
| 333 @end table | |
| 334 | |
| 335 If support for @sc{mule} does not exist, these are the only valid | |
| 336 character values. When @sc{mule} support exists, the values assigned to | |
| 337 other characters may vary depending on the particular version of XEmacs, | |
| 338 the order in which character sets were loaded, etc., and you should not | |
| 339 depend on them. | |
| 340 @end defun | |
| 341 | |
| 342 @defun int-char integer | |
| 343 This function converts an integer into the equivalent character. Not | |
| 344 all integers correspond to valid characters; use @code{char-int-p} to | |
| 345 determine whether this is the case. If the integer cannot be converted, | |
| 346 @code{nil} is returned. | |
| 347 @end defun | |
| 348 | |
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349 @defvar char-code-limit |
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350 This is a constant integer describing an exclusive upper bound on the |
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351 results return by @code{char-int} and that set of integers (fixnums) for |
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352 which @code{int-char} will give non-nil. Without @sc{mule} |
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353 (internationalization) support this will be @code{#x100}, as described |
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354 under @code{char-int}, but with @sc{mule} support the range of values is |
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355 much bigger, at least 21 bits' worth. If an integer is less than |
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356 @var{char-code-limit}, it may still not have an associated character, it |
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357 is still necessary to check with the next function, @code{char-int-p}. |
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358 @end defvar |
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359 |
| 428 | 360 @defun char-int-p object |
| 361 This function returns @code{t} if @var{object} is an integer that can be | |
| 362 converted into a character. | |
| 363 @end defun | |
| 364 | |
| 365 @defun char-or-char-int-p object | |
| 366 This function returns @code{t} if @var{object} is a character or an | |
| 367 integer that can be converted into one. | |
| 368 @end defun | |
| 369 | |
| 370 @need 2000 | |
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371 @node Text Comparison, String Conversion, Character Codes, Strings and Characters |
| 428 | 372 @section Comparison of Characters and Strings |
| 373 @cindex string equality | |
| 374 | |
| 444 | 375 @defun char-equal character1 character2 &optional buffer |
| 428 | 376 This function returns @code{t} if the arguments represent the same |
| 377 character, @code{nil} otherwise. This function ignores differences | |
| 444 | 378 in case if the value of @code{case-fold-search} is non-@code{nil} in |
| 379 @var{buffer}, which defaults to the current buffer. | |
| 428 | 380 |
| 381 @example | |
| 382 (char-equal ?x ?x) | |
| 383 @result{} t | |
| 384 (let ((case-fold-search t)) | |
| 385 (char-equal ?x ?X)) | |
| 386 @result{} t | |
| 387 (let ((case-fold-search nil)) | |
| 388 (char-equal ?x ?X)) | |
| 389 @result{} nil | |
| 390 @end example | |
| 391 @end defun | |
| 392 | |
| 393 @defun char= character1 character2 | |
| 394 This function returns @code{t} if the arguments represent the same | |
| 395 character, @code{nil} otherwise. Case is significant. | |
| 396 | |
| 397 @example | |
| 398 (char= ?x ?x) | |
| 399 @result{} t | |
| 400 (char= ?x ?X) | |
| 401 @result{} nil | |
| 402 (let ((case-fold-search t)) | |
| 403 (char-equal ?x ?X)) | |
| 404 @result{} nil | |
| 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; case is significant. | |
| 414 | |
| 415 @example | |
| 416 (string= "abc" "abc") | |
| 417 @result{} t | |
| 418 (string= "abc" "ABC") | |
| 419 @result{} nil | |
| 420 (string= "ab" "ABC") | |
| 421 @result{} nil | |
| 422 @end example | |
| 423 | |
| 424 @ignore @c `equal' in XEmacs does not compare text properties | |
| 425 The function @code{string=} ignores the text properties of the | |
| 426 two strings. To compare strings in a way that compares their text | |
| 427 properties also, use @code{equal} (@pxref{Equality Predicates}). | |
| 428 @end ignore | |
| 429 @end defun | |
| 430 | |
| 431 @defun string-equal string1 string2 | |
| 432 @code{string-equal} is another name for @code{string=}. | |
| 433 @end defun | |
| 434 | |
| 435 @cindex lexical comparison | |
| 436 @defun string< string1 string2 | |
| 437 @c (findex string< causes problems for permuted index!!) | |
| 438 This function compares two strings a character at a time. First it | |
| 439 scans both the strings at once to find the first pair of corresponding | |
| 440 characters that do not match. If the lesser character of those two is | |
| 441 the character from @var{string1}, then @var{string1} is less, and this | |
| 442 function returns @code{t}. If the lesser character is the one from | |
| 443 @var{string2}, then @var{string1} is greater, and this function returns | |
| 444 @code{nil}. If the two strings match entirely, the value is @code{nil}. | |
| 445 | |
| 446 Pairs of characters are compared by their @sc{ascii} codes. Keep in | |
| 447 mind that lower case letters have higher numeric values in the | |
| 448 @sc{ascii} character set than their upper case counterparts; numbers and | |
| 449 many punctuation characters have a lower numeric value than upper case | |
| 450 letters. | |
| 451 | |
| 452 @example | |
| 453 @group | |
| 454 (string< "abc" "abd") | |
| 455 @result{} t | |
| 456 (string< "abd" "abc") | |
| 457 @result{} nil | |
| 458 (string< "123" "abc") | |
| 459 @result{} t | |
| 460 @end group | |
| 461 @end example | |
| 462 | |
| 463 When the strings have different lengths, and they match up to the | |
| 464 length of @var{string1}, then the result is @code{t}. If they match up | |
| 465 to the length of @var{string2}, the result is @code{nil}. A string of | |
| 466 no characters is less than any other string. | |
| 467 | |
| 468 @example | |
| 469 @group | |
| 470 (string< "" "abc") | |
| 471 @result{} t | |
| 472 (string< "ab" "abc") | |
| 473 @result{} t | |
| 474 (string< "abc" "") | |
| 475 @result{} nil | |
| 476 (string< "abc" "ab") | |
| 477 @result{} nil | |
| 478 (string< "" "") | |
| 444 | 479 @result{} nil |
| 428 | 480 @end group |
| 481 @end example | |
| 482 @end defun | |
| 483 | |
| 484 @defun string-lessp string1 string2 | |
| 485 @code{string-lessp} is another name for @code{string<}. | |
| 486 @end defun | |
| 487 | |
| 488 See also @code{compare-buffer-substrings} in @ref{Comparing Text}, for | |
| 489 a way to compare text in buffers. The function @code{string-match}, | |
| 490 which matches a regular expression against a string, can be used | |
| 491 for a kind of string comparison; see @ref{Regexp Search}. | |
| 492 | |
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493 @node String Conversion, Modifying Strings, Text Comparison, Strings and Characters |
| 428 | 494 @section Conversion of Characters and Strings |
| 495 @cindex conversion of strings | |
| 496 | |
| 497 This section describes functions for conversions between characters, | |
| 498 strings and integers. @code{format} and @code{prin1-to-string} | |
| 499 (@pxref{Output Functions}) can also convert Lisp objects into strings. | |
| 500 @code{read-from-string} (@pxref{Input Functions}) can ``convert'' a | |
| 501 string representation of a Lisp object into an object. | |
| 502 | |
| 503 @xref{Documentation}, for functions that produce textual descriptions | |
| 504 of text characters and general input events | |
| 505 (@code{single-key-description} and @code{text-char-description}). These | |
| 506 functions are used primarily for making help messages. | |
| 507 | |
| 508 @defun char-to-string character | |
| 509 @cindex character to string | |
| 510 This function returns a new string with a length of one character. | |
| 511 The value of @var{character}, modulo 256, is used to initialize the | |
| 512 element of the string. | |
| 513 | |
| 514 This function is similar to @code{make-string} with an integer argument | |
| 515 of 1. (@xref{Creating Strings}.) This conversion can also be done with | |
| 516 @code{format} using the @samp{%c} format specification. | |
| 517 (@xref{Formatting Strings}.) | |
| 518 | |
| 519 @example | |
| 520 (char-to-string ?x) | |
| 521 @result{} "x" | |
| 522 (char-to-string (+ 256 ?x)) | |
| 523 @result{} "x" | |
| 524 (make-string 1 ?x) | |
| 525 @result{} "x" | |
| 526 @end example | |
| 527 @end defun | |
| 528 | |
| 529 @defun string-to-char string | |
| 530 @cindex string to character | |
| 531 This function returns the first character in @var{string}. If the | |
| 532 string is empty, the function returns 0. (Under XEmacs 19, the value is | |
| 533 also 0 when the first character of @var{string} is the null character, | |
| 534 @sc{ascii} code 0.) | |
| 535 | |
| 536 @example | |
| 537 (string-to-char "ABC") | |
| 538 @result{} ?A ;; @r{Under XEmacs 20.} | |
| 539 @result{} 65 ;; @r{Under XEmacs 19.} | |
| 540 (string-to-char "xyz") | |
| 541 @result{} ?x ;; @r{Under XEmacs 20.} | |
| 542 @result{} 120 ;; @r{Under XEmacs 19.} | |
| 543 (string-to-char "") | |
| 544 @result{} 0 | |
| 545 (string-to-char "\000") | |
| 546 @result{} ?\^@ ;; @r{Under XEmacs 20.} | |
| 547 @result{} 0 ;; @r{Under XEmacs 20.} | |
| 548 @end example | |
| 549 | |
| 550 This function may be eliminated in the future if it does not seem useful | |
| 551 enough to retain. | |
| 552 @end defun | |
| 553 | |
| 554 @defun number-to-string number | |
| 555 @cindex integer to string | |
| 556 @cindex integer to decimal | |
| 557 This function returns a string consisting of the printed | |
| 558 representation of @var{number}, which may be an integer or a floating | |
| 559 point number. The value starts with a sign if the argument is | |
| 560 negative. | |
| 561 | |
| 562 @example | |
| 563 (number-to-string 256) | |
| 564 @result{} "256" | |
| 565 (number-to-string -23) | |
| 566 @result{} "-23" | |
| 567 (number-to-string -23.5) | |
| 568 @result{} "-23.5" | |
| 569 @end example | |
| 570 | |
| 571 @cindex int-to-string | |
| 572 @code{int-to-string} is a semi-obsolete alias for this function. | |
| 573 | |
| 574 See also the function @code{format} in @ref{Formatting Strings}. | |
| 575 @end defun | |
| 576 | |
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577 @defun parse-integer string &key (start 0) end (radix 10) junk-allowed radix-table) |
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578 @cindex parse-integer |
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579 This function returns the fixnum or bignum value represented by @var{string} |
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580 in base @var{radix}. If @var{start} or @var{end} are specified, they describe |
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581 a subsequence of @var{string} to examine. @xref{Sequence Basics, Sequence |
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582 Basics, Sequences, cl}. It skips whitespace at the beginning and end of the |
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583 digits seen. Leading @code{?+} and @code{?-} are accepted and have the usual |
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584 meaning; there is no provision for recognition of a leading @code{#x} or |
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585 @code{#o} to indicate a non-default @var{radix}, and there is no special |
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586 provision for a trailing @code{.}. |
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587 |
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588 If @var{junk-allowed} is non-nil, @code{parse-integer} allows non-digit, |
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589 non-whitespace characters before or after the number to be parsed. Otherwise, |
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590 it errors when presented with anything other than an optional series of |
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591 whitespace characters, followed by a non-optional series of digit characters, |
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592 followed by an optional series of whitespace characters. |
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593 |
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594 @code{parse-integer} returns two values, the second of which can be accessed |
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595 by, e.g. @xref{Multiple values, multiple-value-bind, ,}. If |
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596 @var{junk-allowed} is nil, the second value is always the length of that |
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597 subsequence of @var{string} specified. Otherwise, it is the index of the |
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598 first non-digit trailing character encountered. |
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599 |
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600 Normally, the digit values for each character encountered are those returned |
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601 by @code{digit-char-p}. Specifying @var{radix-table} allows this to be |
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602 overridden; if it is specified, it is a character table (@pxref{Char Tables}) |
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603 mapping from characters to fixnum digit values. If a given character has both |
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604 a digit value and a whitespace value, the digit value overrides. However, if a |
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605 @code{?-} both has a digit value and is the first character examined, its |
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606 digit value is ignored, it is treated as indicating the number is negative. |
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607 A work-around is to prepend a character having digit value zero to positive |
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608 integers and to double the leading @code{?-} for negative integers. |
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609 @end defun |
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610 |
| 428 | 611 @defun string-to-number string &optional base |
| 612 @cindex string to number | |
| 444 | 613 This function returns the numeric value represented by @var{string}, |
| 614 read in @var{base}. It skips spaces and tabs at the beginning of | |
| 615 @var{string}, then reads as much of @var{string} as it can interpret as | |
| 616 a number. (On some systems it ignores other whitespace at the | |
| 617 beginning, not just spaces and tabs.) If the first character after the | |
| 618 ignored whitespace is not a digit or a minus sign, this function returns | |
| 619 0. | |
| 428 | 620 |
| 621 If @var{base} is not specified, it defaults to ten. With @var{base} | |
| 622 other than ten, only integers can be read. | |
| 623 | |
| 624 @example | |
| 625 (string-to-number "256") | |
| 626 @result{} 256 | |
| 627 (string-to-number "25 is a perfect square.") | |
| 628 @result{} 25 | |
| 629 (string-to-number "X256") | |
| 630 @result{} 0 | |
| 631 (string-to-number "-4.5") | |
| 632 @result{} -4.5 | |
| 633 (string-to-number "ffff" 16) | |
| 634 @result{} 65535 | |
| 635 @end example | |
| 636 | |
| 637 @findex string-to-int | |
| 638 @code{string-to-int} is an obsolete alias for this function. | |
| 639 @end defun | |
| 640 | |
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641 @node Modifying Strings, String Properties, String Conversion, Strings and Characters |
| 428 | 642 @section Modifying Strings |
| 643 @cindex strings, modifying | |
| 644 | |
| 645 You can modify a string using the general array-modifying primitives. | |
| 646 @xref{Arrays}. The function @code{aset} modifies a single character; | |
| 647 the function @code{fillarray} sets all characters in the string to | |
| 648 a specified character. | |
| 649 | |
| 650 Each string has a tick counter that starts out at zero (when the string | |
| 651 is created) and is incremented each time a change is made to that | |
| 652 string. | |
| 653 | |
| 654 @defun string-modified-tick string | |
| 655 This function returns the tick counter for @samp{string}. | |
| 656 @end defun | |
| 657 | |
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658 @node String Properties, Formatting Strings, Modifying Strings, Strings and Characters |
| 428 | 659 @section String Properties |
| 660 @cindex string properties | |
| 661 @cindex properties of strings | |
| 662 | |
| 442 | 663 Just as with symbols, extents, faces, and glyphs, you can attach |
| 428 | 664 additional information to strings in the form of @dfn{string |
| 665 properties}. These differ from text properties, which are logically | |
| 666 attached to particular characters in the string. | |
| 667 | |
| 668 To attach a property to a string, use @code{put}. To retrieve a property | |
| 669 from a string, use @code{get}. You can also use @code{remprop} to remove | |
| 442 | 670 a property from a string and @code{object-plist} to retrieve a list of |
| 428 | 671 all the properties in a string. |
| 672 | |
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673 @node Formatting Strings, Character Case, String Properties, Strings and Characters |
| 428 | 674 @section Formatting Strings |
| 675 @cindex formatting strings | |
| 676 @cindex strings, formatting them | |
| 677 | |
| 678 @dfn{Formatting} means constructing a string by substitution of | |
| 679 computed values at various places in a constant string. This string | |
| 680 controls how the other values are printed as well as where they appear; | |
| 681 it is called a @dfn{format string}. | |
| 682 | |
| 683 Formatting is often useful for computing messages to be displayed. In | |
| 684 fact, the functions @code{message} and @code{error} provide the same | |
| 685 formatting feature described here; they differ from @code{format} only | |
| 686 in how they use the result of formatting. | |
| 687 | |
| 688 @defun format string &rest objects | |
| 689 This function returns a new string that is made by copying | |
| 444 | 690 @var{string} and then replacing any format specification |
| 428 | 691 in the copy with encodings of the corresponding @var{objects}. The |
| 692 arguments @var{objects} are the computed values to be formatted. | |
| 693 @end defun | |
| 694 | |
| 695 @cindex @samp{%} in format | |
| 696 @cindex format specification | |
| 697 A format specification is a sequence of characters beginning with a | |
| 698 @samp{%}. Thus, if there is a @samp{%d} in @var{string}, the | |
| 699 @code{format} function replaces it with the printed representation of | |
| 700 one of the values to be formatted (one of the arguments @var{objects}). | |
| 701 For example: | |
| 702 | |
| 703 @example | |
| 704 @group | |
| 705 (format "The value of fill-column is %d." fill-column) | |
| 706 @result{} "The value of fill-column is 72." | |
| 707 @end group | |
| 708 @end example | |
| 709 | |
| 710 If @var{string} contains more than one format specification, the | |
| 711 format specifications correspond with successive values from | |
| 712 @var{objects}. Thus, the first format specification in @var{string} | |
| 713 uses the first such value, the second format specification uses the | |
| 714 second such value, and so on. Any extra format specifications (those | |
| 715 for which there are no corresponding values) cause unpredictable | |
| 716 behavior. Any extra values to be formatted are ignored. | |
| 717 | |
| 718 Certain format specifications require values of particular types. | |
| 719 However, no error is signaled if the value actually supplied fails to | |
| 720 have the expected type. Instead, the output is likely to be | |
| 721 meaningless. | |
| 722 | |
| 723 Here is a table of valid format specifications: | |
| 724 | |
| 725 @table @samp | |
| 726 @item %s | |
| 727 Replace the specification with the printed representation of the object, | |
| 728 made without quoting. Thus, strings are represented by their contents | |
| 729 alone, with no @samp{"} characters, and symbols appear without @samp{\} | |
| 730 characters. This is equivalent to printing the object with @code{princ}. | |
| 731 | |
| 732 If there is no corresponding object, the empty string is used. | |
| 733 | |
| 734 @item %S | |
| 735 Replace the specification with the printed representation of the object, | |
| 736 made with quoting. Thus, strings are enclosed in @samp{"} characters, | |
| 737 and @samp{\} characters appear where necessary before special characters. | |
| 738 This is equivalent to printing the object with @code{prin1}. | |
| 739 | |
| 740 If there is no corresponding object, the empty string is used. | |
| 741 | |
| 742 @item %o | |
| 743 @cindex integer to octal | |
| 744 Replace the specification with the base-eight representation of an | |
| 745 integer. | |
| 746 | |
| 747 @item %d | |
| 748 @itemx %i | |
| 749 Replace the specification with the base-ten representation of an | |
| 750 integer. | |
| 751 | |
| 752 @item %x | |
| 753 @cindex integer to hexadecimal | |
| 754 Replace the specification with the base-sixteen representation of an | |
| 755 integer, using lowercase letters. | |
| 756 | |
| 757 @item %X | |
| 758 @cindex integer to hexadecimal | |
| 759 Replace the specification with the base-sixteen representation of an | |
| 760 integer, using uppercase letters. | |
| 761 | |
|
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762 @item %b |
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763 @cindex integer to binary |
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764 Replace the specification with the base-two representation of an |
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765 integer. |
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766 |
| 428 | 767 @item %c |
| 768 Replace the specification with the character which is the value given. | |
| 769 | |
| 770 @item %e | |
| 771 Replace the specification with the exponential notation for a floating | |
| 772 point number (e.g. @samp{7.85200e+03}). | |
| 773 | |
| 774 @item %f | |
| 775 Replace the specification with the decimal-point notation for a floating | |
| 776 point number. | |
| 777 | |
| 778 @item %g | |
| 779 Replace the specification with notation for a floating point number, | |
| 780 using a ``pretty format''. Either exponential notation or decimal-point | |
| 781 notation will be used (usually whichever is shorter), and trailing | |
| 782 zeroes are removed from the fractional part. | |
| 783 | |
| 784 @item %% | |
| 785 A single @samp{%} is placed in the string. This format specification is | |
| 786 unusual in that it does not use a value. For example, @code{(format "%% | |
| 787 %d" 30)} returns @code{"% 30"}. | |
| 788 @end table | |
| 789 | |
| 790 Any other format character results in an @samp{Invalid format | |
| 791 operation} error. | |
| 792 | |
| 793 Here are several examples: | |
| 794 | |
| 795 @example | |
| 796 @group | |
| 797 (format "The name of this buffer is %s." (buffer-name)) | |
| 798 @result{} "The name of this buffer is strings.texi." | |
| 799 | |
| 800 (format "The buffer object prints as %s." (current-buffer)) | |
| 801 @result{} "The buffer object prints as #<buffer strings.texi>." | |
| 802 | |
| 444 | 803 (format "The octal value of %d is %o, |
| 428 | 804 and the hex value is %x." 18 18 18) |
| 444 | 805 @result{} "The octal value of 18 is 22, |
| 428 | 806 and the hex value is 12." |
| 807 @end group | |
| 808 @end example | |
| 809 | |
| 810 There are many additional flags and specifications that can occur | |
| 811 between the @samp{%} and the format character, in the following order: | |
| 812 | |
| 813 @enumerate | |
| 814 @item | |
| 815 An optional repositioning specification, which is a positive | |
| 816 integer followed by a @samp{$}. | |
| 817 | |
| 818 @item | |
| 819 Zero or more of the optional flag characters @samp{-}, @samp{+}, | |
| 820 @samp{ }, @samp{0}, and @samp{#}. | |
| 821 | |
| 822 @item | |
| 823 An asterisk (@samp{*}, meaning that the field width is now assumed to | |
| 824 have been specified as an argument. | |
| 825 | |
| 826 @item | |
| 827 An optional minimum field width. | |
| 828 | |
| 829 @item | |
| 830 An optional precision, preceded by a @samp{.} character. | |
| 831 @end enumerate | |
| 832 | |
| 833 @cindex repositioning format arguments | |
| 834 @cindex multilingual string formatting | |
| 835 A @dfn{repositioning} specification changes which argument to | |
| 836 @code{format} is used by the current and all following format | |
| 837 specifications. Normally the first specification uses the first | |
| 838 argument, the second specification uses the second argument, etc. Using | |
| 839 a repositioning specification, you can change this. By placing a number | |
| 444 | 840 @var{n} followed by a @samp{$} between the @samp{%} and the format |
| 841 character, you cause the specification to use the @var{n}th argument. | |
| 842 The next specification will use the @var{n}+1'th argument, etc. | |
| 428 | 843 |
| 844 For example: | |
| 845 | |
| 846 @example | |
| 847 @group | |
| 848 (format "Can't find file `%s' in directory `%s'." | |
| 849 "ignatius.c" "loyola/") | |
| 850 @result{} "Can't find file `ignatius.c' in directory `loyola/'." | |
| 851 | |
| 852 (format "In directory `%2$s', the file `%1$s' was not found." | |
| 853 "ignatius.c" "loyola/") | |
| 854 @result{} "In directory `loyola/', the file `ignatius.c' was not found." | |
| 855 | |
| 856 (format | |
| 857 "The numbers %d and %d are %1$x and %x in hex and %1$o and %o in octal." | |
| 858 37 12) | |
| 859 @result{} "The numbers 37 and 12 are 25 and c in hex and 45 and 14 in octal." | |
| 860 @end group | |
| 861 @end example | |
| 862 | |
| 863 As you can see, this lets you reprocess arguments more than once or | |
| 864 reword a format specification (thereby moving the arguments around) | |
| 865 without having to actually reorder the arguments. This is especially | |
| 866 useful in translating messages from one language to another: Different | |
| 867 languages use different word orders, and this sometimes entails changing | |
| 868 the order of the arguments. By using repositioning specifications, | |
| 869 this can be accomplished without having to embed knowledge of particular | |
| 870 languages into the location in the program's code where the message is | |
| 871 displayed. | |
| 872 | |
| 873 @cindex numeric prefix | |
| 874 @cindex field width | |
| 875 @cindex padding | |
| 876 All the specification characters allow an optional numeric prefix | |
| 877 between the @samp{%} and the character, and following any repositioning | |
| 878 specification or flag. The optional numeric prefix defines the minimum | |
| 879 width for the object. If the printed representation of the object | |
| 880 contains fewer characters than this, then it is padded. The padding is | |
| 881 normally on the left, but will be on the right if the @samp{-} flag | |
| 882 character is given. The padding character is normally a space, but if | |
| 883 the @samp{0} flag character is given, zeros are used for padding. | |
| 884 | |
| 885 @example | |
| 886 (format "%06d is padded on the left with zeros" 123) | |
| 887 @result{} "000123 is padded on the left with zeros" | |
| 888 | |
| 889 (format "%-6d is padded on the right" 123) | |
| 890 @result{} "123 is padded on the right" | |
| 891 @end example | |
| 892 | |
| 893 @code{format} never truncates an object's printed representation, no | |
| 894 matter what width you specify. Thus, you can use a numeric prefix to | |
| 895 specify a minimum spacing between columns with no risk of losing | |
| 896 information. | |
| 897 | |
| 898 In the following three examples, @samp{%7s} specifies a minimum width | |
| 899 of 7. In the first case, the string inserted in place of @samp{%7s} has | |
| 900 only 3 letters, so 4 blank spaces are inserted for padding. In the | |
| 901 second case, the string @code{"specification"} is 13 letters wide but is | |
| 902 not truncated. In the third case, the padding is on the right. | |
| 903 | |
| 444 | 904 @smallexample |
| 428 | 905 @group |
| 906 (format "The word `%7s' actually has %d letters in it." | |
| 907 "foo" (length "foo")) | |
| 444 | 908 @result{} "The word ` foo' actually has 3 letters in it." |
| 428 | 909 @end group |
| 910 | |
| 911 @group | |
| 912 (format "The word `%7s' actually has %d letters in it." | |
| 444 | 913 "specification" (length "specification")) |
| 914 @result{} "The word `specification' actually has 13 letters in it." | |
| 428 | 915 @end group |
| 916 | |
| 917 @group | |
| 918 (format "The word `%-7s' actually has %d letters in it." | |
| 919 "foo" (length "foo")) | |
| 444 | 920 @result{} "The word `foo ' actually has 3 letters in it." |
| 428 | 921 @end group |
| 922 @end smallexample | |
| 923 | |
| 924 @cindex format precision | |
| 925 @cindex precision of formatted numbers | |
| 926 After any minimum field width, a precision may be specified by | |
| 927 preceding it with a @samp{.} character. The precision specifies the | |
| 928 minimum number of digits to appear in @samp{%d}, @samp{%i}, @samp{%o}, | |
| 929 @samp{%x}, and @samp{%X} conversions (the number is padded on the left | |
| 930 with zeroes as necessary); the number of digits printed after the | |
| 931 decimal point for @samp{%f}, @samp{%e}, and @samp{%E} conversions; the | |
| 932 number of significant digits printed in @samp{%g} and @samp{%G} | |
| 933 conversions; and the maximum number of non-padding characters printed in | |
| 934 @samp{%s} and @samp{%S} conversions. The default precision for | |
| 935 floating-point conversions is six. | |
| 936 | |
| 937 The other flag characters have the following meanings: | |
| 938 | |
| 939 @itemize @bullet | |
| 940 @item | |
| 941 The @samp{ } flag means prefix non-negative numbers with a space. | |
| 942 | |
| 943 @item | |
| 944 The @samp{+} flag means prefix non-negative numbers with a plus sign. | |
| 945 | |
| 946 @item | |
| 947 The @samp{#} flag means print numbers in an alternate, more verbose | |
| 948 format: octal numbers begin with zero; hex numbers begin with a | |
| 949 @samp{0x} or @samp{0X}; a decimal point is printed in @samp{%f}, | |
| 950 @samp{%e}, and @samp{%E} conversions even if no numbers are printed | |
| 951 after it; and trailing zeroes are not omitted in @samp{%g} and @samp{%G} | |
| 952 conversions. | |
| 953 @end itemize | |
| 954 | |
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955 @node Character Case, Case Tables, Formatting Strings, Strings and Characters |
| 428 | 956 @section Character Case |
| 444 | 957 @cindex upper case |
| 958 @cindex lower case | |
| 959 @cindex character case | |
| 428 | 960 |
| 961 The character case functions change the case of single characters or | |
| 962 of the contents of strings. The functions convert only alphabetic | |
| 963 characters (the letters @samp{A} through @samp{Z} and @samp{a} through | |
| 964 @samp{z}); other characters are not altered. The functions do not | |
| 965 modify the strings that are passed to them as arguments. | |
| 966 | |
| 967 The examples below use the characters @samp{X} and @samp{x} which have | |
| 968 @sc{ascii} codes 88 and 120 respectively. | |
| 969 | |
| 444 | 970 @defun downcase string-or-char &optional buffer |
| 428 | 971 This function converts a character or a string to lower case. |
| 972 | |
| 973 When the argument to @code{downcase} is a string, the function creates | |
| 974 and returns a new string in which each letter in the argument that is | |
| 975 upper case is converted to lower case. When the argument to | |
| 976 @code{downcase} is a character, @code{downcase} returns the | |
| 977 corresponding lower case character. (This value is actually an integer | |
| 978 under XEmacs 19.) If the original character is lower case, or is not a | |
| 979 letter, then the value equals the original character. | |
| 980 | |
| 444 | 981 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 982 use, and defaults to the current buffer. | |
| 983 | |
| 428 | 984 @example |
| 985 (downcase "The cat in the hat") | |
| 986 @result{} "the cat in the hat" | |
| 987 | |
| 988 (downcase ?X) | |
| 989 @result{} ?x ;; @r{Under XEmacs 20.} | |
| 990 @result{} 120 ;; @r{Under XEmacs 19.} | |
| 991 | |
| 992 @end example | |
| 993 @end defun | |
| 994 | |
| 444 | 995 @defun upcase string-or-char &optional buffer |
| 428 | 996 This function converts a character or a string to upper case. |
| 997 | |
| 998 When the argument to @code{upcase} is a string, the function creates | |
| 999 and returns a new string in which each letter in the argument that is | |
| 1000 lower case is converted to upper case. | |
| 1001 | |
| 1002 When the argument to @code{upcase} is a character, @code{upcase} returns | |
| 1003 the corresponding upper case character. (This value is actually an | |
| 1004 integer under XEmacs 19.) If the original character is upper case, or | |
| 1005 is not a letter, then the value equals the original character. | |
| 1006 | |
| 444 | 1007 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 1008 use, and defaults to the current buffer. | |
| 1009 | |
| 428 | 1010 @example |
| 1011 (upcase "The cat in the hat") | |
| 1012 @result{} "THE CAT IN THE HAT" | |
| 1013 | |
| 1014 (upcase ?x) | |
| 1015 @result{} ?X ;; @r{Under XEmacs 20.} | |
| 1016 @result{} 88 ;; @r{Under XEmacs 19.} | |
| 1017 @end example | |
| 1018 @end defun | |
| 1019 | |
| 444 | 1020 @defun capitalize string-or-char &optional buffer |
| 428 | 1021 @cindex capitalization |
| 1022 This function capitalizes strings or characters. If | |
| 1023 @var{string-or-char} is a string, the function creates and returns a new | |
| 1024 string, whose contents are a copy of @var{string-or-char} in which each | |
| 1025 word has been capitalized. This means that the first character of each | |
| 1026 word is converted to upper case, and the rest are converted to lower | |
| 1027 case. | |
| 1028 | |
| 1029 The definition of a word is any sequence of consecutive characters that | |
| 1030 are assigned to the word constituent syntax class in the current syntax | |
| 1031 table (@pxref{Syntax Class Table}). | |
| 1032 | |
| 1033 When the argument to @code{capitalize} is a character, @code{capitalize} | |
| 1034 has the same result as @code{upcase}. | |
| 1035 | |
| 444 | 1036 Optional second arg @var{buffer} specifies which buffer's case tables to |
| 1037 use, and defaults to the current buffer. | |
| 1038 | |
| 428 | 1039 @example |
| 1040 (capitalize "The cat in the hat") | |
| 1041 @result{} "The Cat In The Hat" | |
| 1042 | |
| 1043 (capitalize "THE 77TH-HATTED CAT") | |
| 1044 @result{} "The 77th-Hatted Cat" | |
| 1045 | |
| 1046 @group | |
| 1047 (capitalize ?x) | |
| 1048 @result{} ?X ;; @r{Under XEmacs 20.} | |
| 1049 @result{} 88 ;; @r{Under XEmacs 19.} | |
| 1050 @end group | |
| 1051 @end example | |
| 1052 @end defun | |
| 1053 | |
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1054 @node Case Tables, Char Tables, Character Case, Strings and Characters |
| 428 | 1055 @section The Case Table |
| 1056 | |
| 1057 You can customize case conversion by installing a special @dfn{case | |
| 1058 table}. A case table specifies the mapping between upper case and lower | |
| 1059 case letters. It affects both the string and character case conversion | |
| 1060 functions (see the previous section) and those that apply to text in the | |
| 1061 buffer (@pxref{Case Changes}). You need a case table if you are using a | |
| 1062 language which has letters other than the standard @sc{ascii} letters. | |
| 1063 | |
| 1064 A case table is a list of this form: | |
| 1065 | |
| 1066 @example | |
| 1067 (@var{downcase} @var{upcase} @var{canonicalize} @var{equivalences}) | |
| 1068 @end example | |
| 1069 | |
| 1070 @noindent | |
| 1071 where each element is either @code{nil} or a string of length 256. The | |
| 1072 element @var{downcase} says how to map each character to its lower-case | |
| 1073 equivalent. The element @var{upcase} maps each character to its | |
| 1074 upper-case equivalent. If lower and upper case characters are in | |
| 1075 one-to-one correspondence, use @code{nil} for @var{upcase}; then XEmacs | |
| 1076 deduces the upcase table from @var{downcase}. | |
| 1077 | |
| 1078 For some languages, upper and lower case letters are not in one-to-one | |
| 1079 correspondence. There may be two different lower case letters with the | |
| 1080 same upper case equivalent. In these cases, you need to specify the | |
| 1081 maps for both directions. | |
| 1082 | |
| 1083 The element @var{canonicalize} maps each character to a canonical | |
| 1084 equivalent; any two characters that are related by case-conversion have | |
| 1085 the same canonical equivalent character. | |
| 1086 | |
| 1087 The element @var{equivalences} is a map that cyclicly permutes each | |
| 1088 equivalence class (of characters with the same canonical equivalent). | |
| 1089 (For ordinary @sc{ascii}, this would map @samp{a} into @samp{A} and | |
| 1090 @samp{A} into @samp{a}, and likewise for each set of equivalent | |
| 1091 characters.) | |
| 1092 | |
| 1093 When you construct a case table, you can provide @code{nil} for | |
| 1094 @var{canonicalize}; then Emacs fills in this string from @var{upcase} | |
| 1095 and @var{downcase}. You can also provide @code{nil} for | |
| 1096 @var{equivalences}; then Emacs fills in this string from | |
| 1097 @var{canonicalize}. In a case table that is actually in use, those | |
| 1098 components are non-@code{nil}. Do not try to specify @var{equivalences} | |
| 1099 without also specifying @var{canonicalize}. | |
| 1100 | |
| 1101 Each buffer has a case table. XEmacs also has a @dfn{standard case | |
| 1102 table} which is copied into each buffer when you create the buffer. | |
| 1103 Changing the standard case table doesn't affect any existing buffers. | |
| 1104 | |
| 1105 Here are the functions for working with case tables: | |
| 1106 | |
| 1107 @defun case-table-p object | |
| 1108 This predicate returns non-@code{nil} if @var{object} is a valid case | |
| 1109 table. | |
| 1110 @end defun | |
| 1111 | |
| 444 | 1112 @defun set-standard-case-table case-table |
| 1113 This function makes @var{case-table} the standard case table, so that it | |
| 1114 will apply to any buffers created subsequently. | |
| 428 | 1115 @end defun |
| 1116 | |
| 1117 @defun standard-case-table | |
| 1118 This returns the standard case table. | |
| 1119 @end defun | |
| 1120 | |
| 444 | 1121 @defun current-case-table &optional buffer |
| 1122 This function returns the case table of @var{buffer}, which defaults to | |
| 1123 the current buffer. | |
| 428 | 1124 @end defun |
| 1125 | |
| 444 | 1126 @defun set-case-table case-table |
| 1127 This sets the current buffer's case table to @var{case-table}. | |
| 428 | 1128 @end defun |
| 1129 | |
| 1130 The following three functions are convenient subroutines for packages | |
| 1131 that define non-@sc{ascii} character sets. They modify a string | |
| 1132 @var{downcase-table} provided as an argument; this should be a string to | |
| 1133 be used as the @var{downcase} part of a case table. They also modify | |
| 1134 the standard syntax table. @xref{Syntax Tables}. | |
| 1135 | |
| 1136 @defun set-case-syntax-pair uc lc downcase-table | |
| 1137 This function specifies a pair of corresponding letters, one upper case | |
| 1138 and one lower case. | |
| 1139 @end defun | |
| 1140 | |
| 1141 @defun set-case-syntax-delims l r downcase-table | |
| 1142 This function makes characters @var{l} and @var{r} a matching pair of | |
| 1143 case-invariant delimiters. | |
| 1144 @end defun | |
| 1145 | |
| 1146 @defun set-case-syntax char syntax downcase-table | |
| 1147 This function makes @var{char} case-invariant, with syntax | |
| 1148 @var{syntax}. | |
| 1149 @end defun | |
| 1150 | |
| 1151 @deffn Command describe-buffer-case-table | |
| 1152 This command displays a description of the contents of the current | |
| 1153 buffer's case table. | |
| 1154 @end deffn | |
| 1155 | |
| 1156 @cindex ISO Latin 1 | |
| 1157 @pindex iso-syntax | |
| 1158 You can load the library @file{iso-syntax} to set up the standard syntax | |
| 1159 table and define a case table for the 8-bit ISO Latin 1 character set. | |
| 1160 | |
|
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1161 @node Char Tables, , Case Tables, Strings and Characters |
| 428 | 1162 @section The Char Table |
| 1163 | |
| 1164 A char table is a table that maps characters (or ranges of characters) | |
| 1165 to values. Char tables are specialized for characters, only allowing | |
| 1166 particular sorts of ranges to be assigned values. Although this | |
| 1167 loses in generality, it makes for extremely fast (constant-time) | |
| 1168 lookups, and thus is feasible for applications that do an extremely | |
| 1169 large number of lookups (e.g. scanning a buffer for a character in | |
| 1170 a particular syntax, where a lookup in the syntax table must occur | |
| 1171 once per character). | |
| 1172 | |
| 1173 Note that char tables as a primitive type, and all of the functions in | |
| 1174 this section, exist only in XEmacs 20. In XEmacs 19, char tables are | |
| 1175 generally implemented using a vector of 256 elements. | |
| 1176 | |
| 1177 When @sc{mule} support exists, the types of ranges that can be assigned | |
| 1178 values are | |
| 1179 | |
| 1180 @itemize @bullet | |
| 1181 @item | |
| 1182 all characters | |
| 1183 @item | |
| 1184 an entire charset | |
| 1185 @item | |
| 1186 a single row in a two-octet charset | |
| 1187 @item | |
| 1188 a single character | |
| 1189 @end itemize | |
| 1190 | |
| 1191 When @sc{mule} support is not present, the types of ranges that can be | |
| 1192 assigned values are | |
| 1193 | |
| 1194 @itemize @bullet | |
| 1195 @item | |
| 1196 all characters | |
| 1197 @item | |
| 1198 a single character | |
| 1199 @end itemize | |
| 1200 | |
| 1201 @defun char-table-p object | |
| 1202 This function returns non-@code{nil} if @var{object} is a char table. | |
| 1203 @end defun | |
| 1204 | |
| 1205 @menu | |
| 1206 * Char Table Types:: Char tables have different uses. | |
| 1207 * Working With Char Tables:: Creating and working with char tables. | |
| 1208 @end menu | |
| 1209 | |
|
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1210 @node Char Table Types, Working With Char Tables, Char Tables, Char Tables |
| 428 | 1211 @subsection Char Table Types |
| 1212 | |
| 1213 Each char table type is used for a different purpose and allows different | |
| 1214 sorts of values. The different char table types are | |
| 1215 | |
| 1216 @table @code | |
| 1217 @item category | |
| 1218 Used for category tables, which specify the regexp categories | |
| 1219 that a character is in. The valid values are @code{nil} or a | |
| 1220 bit vector of 95 elements. Higher-level Lisp functions are | |
| 1221 provided for working with category tables. Currently categories | |
| 1222 and category tables only exist when @sc{mule} support is present. | |
| 1223 @item char | |
| 1224 A generalized char table, for mapping from one character to | |
| 1225 another. Used for case tables, syntax matching tables, | |
| 1226 @code{keyboard-translate-table}, etc. The valid values are characters. | |
| 1227 @item generic | |
| 1228 An even more generalized char table, for mapping from a | |
| 1229 character to anything. | |
| 1230 @item display | |
| 1231 Used for display tables, which specify how a particular character | |
| 1232 is to appear when displayed. #### Not yet implemented. | |
| 1233 @item syntax | |
| 1234 Used for syntax tables, which specify the syntax of a particular | |
| 1235 character. Higher-level Lisp functions are provided for | |
|
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1236 working with syntax tables. The valid values are fixnums. |
| 428 | 1237 @end table |
| 1238 | |
| 444 | 1239 @defun char-table-type char-table |
| 1240 This function returns the type of char table @var{char-table}. | |
| 428 | 1241 @end defun |
| 1242 | |
| 1243 @defun char-table-type-list | |
| 1244 This function returns a list of the recognized char table types. | |
| 1245 @end defun | |
| 1246 | |
| 1247 @defun valid-char-table-type-p type | |
| 1248 This function returns @code{t} if @var{type} if a recognized char table type. | |
| 1249 @end defun | |
| 1250 | |
|
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1251 @node Working With Char Tables, , Char Table Types, Char Tables |
| 428 | 1252 @subsection Working With Char Tables |
| 1253 | |
| 1254 @defun make-char-table type | |
| 1255 This function makes a new, empty char table of type @var{type}. | |
| 1256 @var{type} should be a symbol, one of @code{char}, @code{category}, | |
| 1257 @code{display}, @code{generic}, or @code{syntax}. | |
| 1258 @end defun | |
| 1259 | |
| 444 | 1260 @defun put-char-table range value char-table |
| 1261 This function sets the value for chars in @var{range} to be @var{value} in | |
| 1262 @var{char-table}. | |
| 428 | 1263 |
| 1264 @var{range} specifies one or more characters to be affected and should be | |
| 1265 one of the following: | |
| 1266 | |
| 1267 @itemize @bullet | |
| 1268 @item | |
| 1269 @code{t} (all characters are affected) | |
| 1270 @item | |
| 1271 A charset (only allowed when @sc{mule} support is present) | |
| 1272 @item | |
| 1273 A vector of two elements: a two-octet charset and a row number | |
| 1274 (only allowed when @sc{mule} support is present) | |
| 1275 @item | |
| 1276 A single character | |
| 1277 @end itemize | |
| 1278 | |
| 444 | 1279 @var{value} must be a value appropriate for the type of @var{char-table}. |
| 428 | 1280 @end defun |
| 1281 | |
| 444 | 1282 @defun get-char-table character char-table |
| 1283 This function finds the value for @var{character} in @var{char-table}. | |
| 428 | 1284 @end defun |
| 1285 | |
| 444 | 1286 @defun get-range-char-table range char-table &optional multi |
| 1287 This function finds the value for a range in @var{char-table}. If there is | |
| 428 | 1288 more than one value, @var{multi} is returned (defaults to @code{nil}). |
| 1289 @end defun | |
| 1290 | |
| 444 | 1291 @defun reset-char-table char-table |
| 1292 This function resets @var{char-table} to its default state. | |
| 428 | 1293 @end defun |
| 1294 | |
| 444 | 1295 @defun map-char-table function char-table &optional range |
| 1296 This function maps @var{function} over entries in @var{char-table}, calling | |
| 428 | 1297 it with two args, each key and value in the table. |
| 1298 | |
| 1299 @var{range} specifies a subrange to map over and is in the same format | |
| 1300 as the @var{range} argument to @code{put-range-table}. If omitted or | |
| 1301 @code{t}, it defaults to the entire table. | |
| 1302 @end defun | |
| 1303 | |
| 1304 @defun valid-char-table-value-p value char-table-type | |
| 1305 This function returns non-@code{nil} if @var{value} is a valid value for | |
| 1306 @var{char-table-type}. | |
| 1307 @end defun | |
| 1308 | |
| 1309 @defun check-valid-char-table-value value char-table-type | |
| 1310 This function signals an error if @var{value} is not a valid value for | |
| 1311 @var{char-table-type}. | |
| 1312 @end defun |