1Str(3) OCaml library Str(3)
2
6 Str - Regular expressions and high-level string processing
7
9 Module Str
10
12 Module Str
13 : sig end
14 Regular expressions and high-level string processing
17 Regular expressions
25 type regexp
26 The type of compiled regular expressions.
29 val regexp : string -> regexp
33 Compile a regular expression. The following constructs are recognized:
35 - . Matches any character except newline.
37 - * (postfix) Matches the preceding expression zero, one or several
39 times
40 - + (postfix) Matches the preceding expression one or several times
42 - ? (postfix) Matches the preceding expression once or not at all
44 - [..] Character set. Ranges are denoted with - , as in [a-z] . An
46 initial ^ , as in [^0-9] , complements the set. To include a ] charac‐
47 ter in a set, make it the first character of the set. To include a -
48 character in a set, make it the first or the last character of the set.
49 - ^ Matches at beginning of line: either at the beginning of the
51 matched string, or just after a '\n' character.
52 - $ Matches at end of line: either at the end of the matched string, or
54 just before a '\n' character.
55 - \| (infix) Alternative between two expressions.
57 - \(..\) Grouping and naming of the enclosed expression.
59 - \1 The text matched by the first \(...\) expression ( \2 for the sec‐
61 ond expression, and so on up to \9 ).
62 - \b Matches word boundaries.
64 - \ Quotes special characters. The special characters are $^\.*+?[] .
66 Note: the argument to regexp is usually a string literal. In this case,
68 any backslash character in the regular expression must be doubled to
69 make it past the OCaml string parser. For example, the following
70 expression: let r = Str.regexp hello \\([A-Za-z]+\\) in
71 Str.replace_first r \\1 hello world returns the string world .
72 In particular, if you want a regular expression that matches a single
74 backslash character, you need to quote it in the argument to regexp
75 (according to the last item of the list above) by adding a second back‐
76 slash. Then you need to quote both backslashes (according to the syntax
77 of string constants in OCaml) by doubling them again, so you need to
78 write four backslash characters: Str.regexp \\\\ .
79 val regexp_case_fold : string -> regexp
83 Same as regexp , but the compiled expression will match text in a
85 case-insensitive way: uppercase and lowercase letters will be consid‐
86 ered equivalent.
87 val quote : string -> string
91 Str.quote s returns a regexp string that matches exactly s and nothing
94 else.
95 val regexp_string : string -> regexp
99 Str.regexp_string s returns a regular expression that matches exactly s
102 and nothing else.
103 val regexp_string_case_fold : string -> regexp
107 Str.regexp_string_case_fold is similar to Str.regexp_string , but the
110 regexp matches in a case-insensitive way.
111 String matching and searching
116 val string_match : regexp -> string -> int -> bool
117 string_match r s start tests whether a substring of s that starts at
120 position start matches the regular expression r . The first character
121 of a string has position 0 , as usual.
122 val search_forward : regexp -> string -> int -> int
126 search_forward r s start searches the string s for a substring matching
129 the regular expression r . The search starts at position start and pro‐
130 ceeds towards the end of the string. Return the position of the first
131 character of the matched substring.
132 Raises Not_found if no substring matches.
135 val search_backward : regexp -> string -> int -> int
139 search_backward r s last searches the string s for a substring matching
142 the regular expression r . The search first considers substrings that
143 start at position last and proceeds towards the beginning of string.
144 Return the position of the first character of the matched substring.
145 Raises Not_found if no substring matches.
148 val string_partial_match : regexp -> string -> int -> bool
152 Similar to Str.string_match , but also returns true if the argument
154 string is a prefix of a string that matches. This includes the case of
155 a true complete match.
156 val matched_string : string -> string
160 matched_string s returns the substring of s that was matched by the
163 last call to one of the following matching or searching functions:
164 - Str.string_match
166 - Str.search_forward
169 - Str.search_backward
172 - Str.string_partial_match
175 - Str.global_substitute
178 - Str.substitute_first
181 provided that none of the following functions was called in between:
183 - Str.global_replace
185 - Str.replace_first
188 - Str.split
191 - Str.bounded_split
194 - Str.split_delim
197 - Str.bounded_split_delim
200 - Str.full_split
203 - Str.bounded_full_split
206 Note: in the case of global_substitute and substitute_first , a call to
208 matched_string is only valid within the subst argument, not after
209 global_substitute or substitute_first returns.
210 The user must make sure that the parameter s is the same string that
212 was passed to the matching or searching function.
213 val match_beginning : unit -> int
217 match_beginning() returns the position of the first character of the
220 substring that was matched by the last call to a matching or searching
221 function (see Str.matched_string for details).
222 val match_end : unit -> int
226 match_end() returns the position of the character following the last
229 character of the substring that was matched by the last call to a
230 matching or searching function (see Str.matched_string for details).
231 val matched_group : int -> string -> string
235 matched_group n s returns the substring of s that was matched by the n
238 th group \(...\) of the regular expression that was matched by the last
239 call to a matching or searching function (see Str.matched_string for
240 details). The user must make sure that the parameter s is the same
241 string that was passed to the matching or searching function.
242 Raises Not_found if the n th group of the regular expression was not
245 matched. This can happen with groups inside alternatives \| , options
246 ? or repetitions * . For instance, the empty string will match \(a\)*
247 , but matched_group 1 will raise Not_found because the first group
248 itself was not matched.
249 val group_beginning : int -> int
253 group_beginning n returns the position of the first character of the
256 substring that was matched by the n th group of the regular expression
257 that was matched by the last call to a matching or searching function
258 (see Str.matched_string for details).
259 Raises Not_found if the n th group of the regular expression was not
262 matched.
263 Raises Invalid_argument if there are fewer than n groups in the regular
266 expression.
267 val group_end : int -> int
271 group_end n returns the position of the character following the last
274 character of substring that was matched by the n th group of the regu‐
275 lar expression that was matched by the last call to a matching or
276 searching function (see Str.matched_string for details).
277 Raises Not_found if the n th group of the regular expression was not
280 matched.
281 Raises Invalid_argument if there are fewer than n groups in the regular
284 expression.
285 Replacement
290 val global_replace : regexp -> string -> string -> string
291 global_replace regexp templ s returns a string identical to s , except
294 that all substrings of s that match regexp have been replaced by templ
295 . The replacement template templ can contain \1 , \2 , etc; these
296 sequences will be replaced by the text matched by the corresponding
297 group in the regular expression. \0 stands for the text matched by the
298 whole regular expression.
299 val replace_first : regexp -> string -> string -> string
303 Same as Str.global_replace , except that only the first substring
305 matching the regular expression is replaced.
306 val global_substitute : regexp -> (string -> string) -> string ->
310 string
311 global_substitute regexp subst s returns a string identical to s ,
314 except that all substrings of s that match regexp have been replaced by
315 the result of function subst . The function subst is called once for
316 each matching substring, and receives s (the whole text) as argument.
317 val substitute_first : regexp -> (string -> string) -> string -> string
321 Same as Str.global_substitute , except that only the first substring
323 matching the regular expression is replaced.
324 val replace_matched : string -> string -> string
328 replace_matched repl s returns the replacement text repl in which \1 ,
331 \2 , etc. have been replaced by the text matched by the corresponding
332 groups in the regular expression that was matched by the last call to a
333 matching or searching function (see Str.matched_string for details). s
334 must be the same string that was passed to the matching or searching
335 function.
336 Splitting
341 val split : regexp -> string -> string list
342 split r s splits s into substrings, taking as delimiters the substrings
345 that match r , and returns the list of substrings. For instance, split
346 (regexp [ \t]+ ) s splits s into blank-separated words. An occurrence
347 of the delimiter at the beginning or at the end of the string is
348 ignored.
349 val bounded_split : regexp -> string -> int -> string list
353 Same as Str.split , but splits into at most n substrings, where n is
355 the extra integer parameter.
356 val split_delim : regexp -> string -> string list
360 Same as Str.split but occurrences of the delimiter at the beginning and
362 at the end of the string are recognized and returned as empty strings
363 in the result. For instance, split_delim (regexp ) abc returns ["";
364 abc ; ] , while split with the same arguments returns ["abc"] .
365 val bounded_split_delim : regexp -> string -> int -> string list
369 Same as Str.bounded_split , but occurrences of the delimiter at the
371 beginning and at the end of the string are recognized and returned as
372 empty strings in the result.
373 type split_result =
376 | Text of string
377 | Delim of string
378 val full_split : regexp -> string -> split_result list
384 Same as Str.split_delim , but returns the delimiters as well as the
386 substrings contained between delimiters. The former are tagged Delim
387 in the result list; the latter are tagged Text . For instance,
388 full_split (regexp [{}] ) {ab} returns [Delim { ; Text ab ; Delim } ] .
389 val bounded_full_split : regexp -> string -> int -> split_result list
393 Same as Str.bounded_split_delim , but returns the delimiters as well as
395 the substrings contained between delimiters. The former are tagged
396 Delim in the result list; the latter are tagged Text .
397 Extracting substrings
402 val string_before : string -> int -> string
403 string_before s n returns the substring of all characters of s that
406 precede position n (excluding the character at position n ).
407 val string_after : string -> int -> string
411 string_after s n returns the substring of all characters of s that fol‐
414 low position n (including the character at position n ).
415 val first_chars : string -> int -> string
419 first_chars s n returns the first n characters of s . This is the same
422 function as Str.string_before .
423 val last_chars : string -> int -> string
427 last_chars s n returns the last n characters of s .
430OCamldoc 2019-07-30 Str(3)