aboutsummaryrefslogblamecommitdiffstats
path: root/lib/stdlib/doc/src/string.xml
blob: 7ee38e496d256f9b92b18fbadab59a9ace887010 (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415






























































































































































































































































































































































































































                                                                                                                 
<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1996</year><year>2009</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.
    
      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.
    
    </legalnotice>

    <title>string</title>
    <prepared>Robert Virding</prepared>
    <responsible>Bjarne Dacker</responsible>
    <docno>1</docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked></checked>
    <date>96-09-28</date>
    <rev>A</rev>
    <file>string.sgml</file>
  </header>
  <module>string</module>
  <modulesummary>String Processing Functions</modulesummary>
  <description>
    <p>This module contains functions for string processing.</p>
  </description>
  <funcs>
    <func>
      <name>len(String) -> Length</name>
      <fsummary>Return the length of a string</fsummary>
      <type>
        <v>String = string()</v>
        <v>Length = integer()</v>
      </type>
      <desc>
        <p>Returns the number of characters in the string.</p>
      </desc>
    </func>
    <func>
      <name>equal(String1, String2) -> bool()</name>
      <fsummary>Test string equality</fsummary>
      <type>
        <v>String1 = String2 = string()</v>
      </type>
      <desc>
        <p>Tests whether two strings are equal. Returns <c>true</c> if
          they are, otherwise <c>false</c>.</p>
      </desc>
    </func>
    <func>
      <name>concat(String1, String2) -> String3</name>
      <fsummary>Concatenate two strings</fsummary>
      <type>
        <v>String1 = String2 = String3 = string()</v>
      </type>
      <desc>
        <p>Concatenates two strings to form a new string. Returns the
          new string.</p>
      </desc>
    </func>
    <func>
      <name>chr(String, Character) -> Index</name>
      <name>rchr(String, Character) -> Index</name>
      <fsummary>Return the index of the first/last occurrence of<c>Character</c>in <c>String</c></fsummary>
      <type>
        <v>String = string()</v>
        <v>Character = char()</v>
        <v>Index = integer()</v>
      </type>
      <desc>
        <p>Returns the index of the first/last occurrence of
          <c>Character</c> in <c>String</c>. <c>0</c> is returned if <c>Character</c> does not
          occur.</p>
      </desc>
    </func>
    <func>
      <name>str(String, SubString) -> Index</name>
      <name>rstr(String, SubString) -> Index</name>
      <fsummary>Find the index of a substring</fsummary>
      <type>
        <v>String = SubString = string()</v>
        <v>Index = integer()</v>
      </type>
      <desc>
        <p>Returns the position where the first/last occurrence of
          <c>SubString</c> begins in <c>String</c>. <c>0</c> is returned if <c>SubString</c>
          does not exist in <c>String</c>.
          For example:</p>
        <code type="none">
> string:str(" Hello Hello World World ", "Hello World").
8        </code>
      </desc>
    </func>
    <func>
      <name>span(String, Chars) -> Length </name>
      <name>cspan(String, Chars) -> Length</name>
      <fsummary>Span characters at start of string</fsummary>
      <type>
        <v>String = Chars = string()</v>
        <v>Length = integer()</v>
      </type>
      <desc>
        <p>Returns the length of the maximum initial segment of
          String, which consists entirely of characters from (not
          from) Chars.</p>
        <p>For example:</p>
        <code type="none">
> string:span("\\t    abcdef", " \\t").
5
> string:cspan("\\t    abcdef", " \\t").
0        </code>
      </desc>
    </func>
    <func>
      <name>substr(String, Start) -> SubString</name>
      <name>substr(String, Start, Length) -> Substring</name>
      <fsummary>Return a substring of <c>String</c></fsummary>
      <type>
        <v>String = SubString = string()</v>
        <v>Start = Length = integer()</v>
      </type>
      <desc>
        <p>Returns a substring of <c>String</c>, starting at the
          position <c>Start</c>, and ending at the end of the string or
          at length <c>Length</c>.</p>
        <p>For example:</p>
        <code type="none">
> substr("Hello World", 4, 5).
"lo Wo"        </code>
      </desc>
    </func>
    <func>
      <name>tokens(String, SeparatorList) -> Tokens</name>
      <fsummary>Split string into tokens</fsummary>
      <type>
        <v>String = SeparatorList = string()</v>
        <v>Tokens = [string()]</v>
      </type>
      <desc>
        <p>Returns a list of tokens in <c>String</c>, separated by the
          characters in <c>SeparatorList</c>.</p>
        <p>For example:</p>
        <code type="none">
> tokens("abc defxxghix jkl", "x ").
["abc", "def", "ghi", "jkl"]        </code>
      </desc>
    </func>
    <func>
      <name>join(StringList, Separator) -> String</name>
      <fsummary>Join a list of strings with separator</fsummary>
      <type>
	<v>StringList = [string()]</v>
	<v>Separator = string()</v>
      </type>
      <desc>
	<p>Returns a string with the elements of <c>StringList</c>
	  separated by the string in <c>Seperator</c>.</p>
	<p>For example:</p>
	<code type="none">
> join(["one", "two", "three"], ", ").
"one, two, three"        </code>
      </desc>
    </func>
    <func>
      <name>chars(Character, Number) -> String</name>
      <name>chars(Character, Number, Tail) -> String</name>
      <fsummary>Returns a string consisting of numbers of characters</fsummary>
      <type>
        <v>Character = char()</v>
        <v>Number = integer()</v>
        <v>String = string()</v>
      </type>
      <desc>
        <p>Returns a string consisting of <c>Number</c> of characters
          <c>Character</c>. Optionally, the string can end with the
          string <c>Tail</c>.</p>
      </desc>
    </func>
    <func>
      <name>copies(String, Number) -> Copies</name>
      <fsummary>Copy a string</fsummary>
      <type>
        <v>String = Copies = string()</v>
        <v>Number = integer()</v>
      </type>
      <desc>
        <p>Returns a string containing <c>String</c> repeated
          <c>Number</c> times.</p>
      </desc>
    </func>
    <func>
      <name>words(String) -> Count</name>
      <name>words(String, Character) -> Count</name>
      <fsummary>Count blank separated words</fsummary>
      <type>
        <v>String = string()</v>
        <v>Character = char()</v>
        <v>Count = integer()</v>
      </type>
      <desc>
        <p>Returns the number of words in <c>String</c>, separated by
          blanks or <c>Character</c>.</p>
        <p>For example:</p>
        <code type="none">
> words(" Hello old boy!", $o).
4        </code>
      </desc>
    </func>
    <func>
      <name>sub_word(String, Number) -> Word</name>
      <name>sub_word(String, Number, Character) -> Word</name>
      <fsummary>Extract subword</fsummary>
      <type>
        <v>String = Word = string()</v>
        <v>Character = char()</v>
        <v>Number = integer()</v>
      </type>
      <desc>
        <p>Returns the word in position <c>Number</c> of <c>String</c>.
          Words are separated by blanks or <c>Character</c>s.</p>
        <p>For example:</p>
        <code type="none">
> string:sub_word(" Hello old boy !",3,$o).
"ld b"        </code>
      </desc>
    </func>
    <func>
      <name>strip(String) -> Stripped</name>
      <name>strip(String, Direction) -> Stripped</name>
      <name>strip(String, Direction, Character) -> Stripped</name>
      <fsummary>Strip leading or trailing characters</fsummary>
      <type>
        <v>String = Stripped = string()</v>
        <v>Direction = left | right | both</v>
        <v>Character = char()</v>
      </type>
      <desc>
        <p>Returns a string, where leading and/or trailing blanks or a
          number of <c>Character</c> have been removed.
          <c>Direction</c> can be <c>left</c>, <c>right</c>, or
          <c>both</c> and indicates from which direction blanks are to be
          removed. The function <c>strip/1</c> is equivalent to
          <c>strip(String, both)</c>.</p>
        <p>For example:</p>
        <code type="none">
> string:strip("...Hello.....", both, $.).
"Hello"        </code>
      </desc>
    </func>
    <func>
      <name>left(String, Number) -> Left</name>
      <name>left(String, Number, Character) -> Left</name>
      <fsummary>Adjust left end of string</fsummary>
      <type>
        <v>String = Left = string()</v>
        <v>Character = char</v>
        <v>Number = integer()</v>
      </type>
      <desc>
        <p>Returns the <c>String</c> with the length adjusted in
          accordance with <c>Number</c>. The left margin is
          fixed. If the <c>length(String)</c> &lt; <c>Number</c>,
          <c>String</c> is padded with blanks or <c>Character</c>s.</p>
        <p>For example:</p>
        <code type="none">
> string:left("Hello",10,$.).
"Hello....."        </code>
      </desc>
    </func>
    <func>
      <name>right(String, Number) -> Right</name>
      <name>right(String, Number, Character) -> Right</name>
      <fsummary>Adjust right end of string</fsummary>
      <type>
        <v>String = Right = string()</v>
        <v>Character = char</v>
        <v>Number = integer()</v>
      </type>
      <desc>
        <p>Returns the <c>String</c> with the length adjusted in
          accordance with <c>Number</c>. The right margin is
          fixed. If the length of <c>(String)</c> &lt; <c>Number</c>,
          <c>String</c> is padded with blanks or <c>Character</c>s.</p>
        <p>For example:</p>
        <code type="none">
> string:right("Hello", 10, $.).
".....Hello"        </code>
      </desc>
    </func>
    <func>
      <name>centre(String, Number) -> Centered</name>
      <name>centre(String, Number, Character) -> Centered</name>
      <fsummary>Center a string</fsummary>
      <type>
        <v>String = Centered = string()</v>
        <v>Character = char</v>
        <v>Number = integer()</v>
      </type>
      <desc>
        <p>Returns a string, where <c>String</c> is centred in the
          string and surrounded by blanks or characters. The resulting
          string will have the length <c>Number</c>.</p>
      </desc>
    </func>
    <func>
      <name>sub_string(String, Start) -> SubString</name>
      <name>sub_string(String, Start, Stop) -> SubString</name>
      <fsummary>Extract a substring</fsummary>
      <type>
        <v>String = SubString = string()</v>
        <v>Start = Stop = integer()</v>
      </type>
      <desc>
        <p>Returns a substring of <c>String</c>, starting at the
          position <c>Start</c> to the end of the string, or to and
          including the <c>Stop</c> position.</p>
        <p>For example:</p>
        <code type="none">
sub_string("Hello World", 4, 8).
"lo Wo"        </code>
      </desc>
    </func>
    <func>
      <name>to_float(String) -> {Float,Rest} | {error,Reason} </name>
      <fsummary>Returns a float whose text representation is the integers (ASCII values) in String.</fsummary>
      <type>
        <v>String = string()</v>
        <v>Float = float()</v>
        <v>Rest = string()</v>
        <v>Reason = no_float | not_a_list</v>
      </type>
      <desc>
        <p>Argument <c>String</c> is expected to start with a valid text
          represented float (the digits being ASCII values). Remaining characters 
          in the string after the float are returned in <c>Rest</c>.</p>
        <p>Example:</p>
        <code type="none">
          > {F1,Fs} = string:to_float("1.0-1.0e-1"),
          > {F2,[]} = string:to_float(Fs),
          > F1+F2.
          0.9
          > string:to_float("3/2=1.5").
          {error,no_float}
          > string:to_float("-1.5eX").
          {-1.5,"eX"}</code>
      </desc>
    </func>
    <func>
      <name>to_integer(String) -> {Int,Rest} | {error,Reason} </name>
      <fsummary>Returns an integer whose text representation is the integers (ASCII values) in String.</fsummary>
      <type>
        <v>String = string()</v>
        <v>Int = integer()</v>
        <v>Rest = string()</v>
        <v>Reason = no_integer | not_a_list</v>
      </type>
      <desc>
        <p>Argument <c>String</c> is expected to start with a valid text
          represented integer (the digits being ASCII values). Remaining characters 
          in the string after the integer are returned in <c>Rest</c>.</p>
        <p>Example:</p>
        <code type="none">
          > {I1,Is} = string:to_integer("33+22"),
          > {I2,[]} = string:to_integer(Is),
          > I1-I2.
          11
          > string:to_integer("0.5").
          {0,".5"}
          > string:to_integer("x=2").
          {error,no_integer}</code>
      </desc>
    </func>
    <func>
      <name>to_lower(String) -> Result</name>
      <name>to_lower(Char) -> CharResult</name>
      <name>to_upper(String) -> Result</name>
      <name>to_upper(Char) -> CharResult</name>
      <fsummary>Convert case of string (ISO/IEC 8859-1)</fsummary>
      <type>
        <v>String = Result = string()</v>
        <v>Char = CharResult = integer()</v>
      </type>
      <desc>
        <p>The given string or character is case-converted. Note that
          the supported character set is ISO/IEC 8859-1 (a.k.a. Latin 1),
          all values outside this set is unchanged</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>Notes</title>
    <p>Some of the general string functions may seem to overlap each
      other. The reason for this is that this string package is the
      combination of two earlier packages and all the functions of
      both packages have been retained.
      </p>
    <note>
      <p>Any undocumented functions in <c>string</c> should not be used.</p>
    </note>
  </section>
</erlref>