The type of compiled regular expressions.

Compile a regular expression. The syntax for regular expressions is the same as in Gnu Emacs. The special characters are $^.*+?[]. The following constructs are recognized:

• . matches any character except newline
• * (postfix) matches the previous expression zero, one or several times
• + (postfix) matches the previous expression one or several times
• ? (postfix) matches the previous expression once or not at all
• [..] character set; ranges are denoted with -, as in [a-z]; an initial ^, as in [^0-9], complements the set
• ^ matches at beginning of line
• $ matches at end of line
• \| (infix) alternative between two expressions
• \(..\) grouping and naming of the enclosed expression
• \1 the text matched by the first \(...\) expression (\2 for the second expression, etc)
• \b matches word boundaries
• \ quotes special characters.

Same as regexp, but the compiled expression will match text in a case-insensitive way: uppercase and lowercase letters will be considered equivalent.

Str.quote s returns a regexp string that matches exactly s and nothing else.

Str.regexp_string s returns a regular expression that matches exactly s and nothing else. Str.regexp_string_case_fold is similar, but the regexp matches in a case-insensitive way.

string_match r s start tests whether the characters in s starting at position start match the regular expression r. The first character of a string has position 0, as usual.

search_forward r s start searches the string s for a substring matching the regular expression r. The search starts at position start and proceeds towards the end of the string. Return the position of the first character of the matched substring, or raise Not_found if no substring matches.

Same as search_forward, but the search proceeds towards the beginning of the string.

Similar to string_match, but succeeds whenever the argument string is a prefix of a string that matches. This includes the case of a true complete match.

matched_string s returns the substring of s that was matched by the latest string_match, search_forward or search_backward. The user must make sure that the parameter s is the same string that was passed to the matching or searching function.

match_beginning () returns the position of the first character of the substring that was matched by string_match, search_forward or search_backward. match_end () returns the position of the character following the last character of the matched substring.

matched_group n s returns the substring of s that was matched by the nth group \(...\) of the regular expression during the latest string_match, search_forward or search_backward. The user must make sure that the parameter s is the same string that was passed to the matching or searching function. matched_group n s raises Not_found if the nth group of the regular expression was not matched. This can happen with groups inside alternatives \|, options ? or repetitions *. For instance, the empty string will match \(a\)*, but matched_group 1 "" will raise Not_found because the first group itself was not matched.

group_beginning n returns the position of the first character of the substring that was matched by the nth group of the regular expression. group_end n returns the position of the character following the last character of the matched substring. Both functions raise Not_found if the nth group of the regular expression was not matched.

global_replace regexp templ s returns a string identical to s, except that all substrings of s that match regexp have been replaced by templ. The replacement template templ can contain \1, \2, etc; these sequences will be replaced by the text matched by the corresponding group in the regular expression. \0 stands for the text matched by the whole regular expression.

Same as global_replace, except that only the first substring matching the regular expression is replaced.

global_substitute regexp subst s returns a string identical to s, except that all substrings of s that match regexp have been replaced by the result of function subst. The function subst is called once for each matching substring, and receives s (the whole text) as argument.

Same as global_substitute, except that only the first substring matching the regular expression is replaced.

replace_matched repl s returns the replacement text repl in which \1, \2, etc. have been replaced by the text matched by the corresponding groups in the most recent matching operation. s must be the same string that was matched during this matching operation.

split r s splits s into substrings, taking as delimiters the substrings that match r, and returns the list of substrings. For instance, split (regexp "[ \t]+") s splits s into blank-separated words. An occurrence of the delimiter at the beginning and at the end of the string is ignored.

Same as split, but splits into at most n substrings, where n is the extra integer parameter.

Same as split and bounded_split, but occurrences of the delimiter at the beginning and at the end of the string are recognized and returned as empty strings in the result. For instance, split_delim (regexp " ") " abc " returns [""; "abc"; ""], while split with the same arguments returns ["abc"].

Same as split_delim and bounded_split_delim, but returns the delimiters as well as the substrings contained between delimiters. The former are tagged Delim in the result list; the latter are tagged Text. For instance, full_split (regexp "[{}]") "{ab}" returns [Delim "{"; Text "ab"; Delim "}"].

string_before s n returns the substring of all characters of s that precede position n (excluding the character at position n).

string_after s n returns the substring of all characters of s that follow position n (including the character at position n).

first_chars s n returns the first n characters of s. This is the same function as string_before.

last_chars s n returns the last n characters of s.