The str library: regular expressions and string processing
The str library provides high-level string processing functions,
some based on regular expressions. It is intended to support the kind
of file processing that is usually performed with scripting languages
such as awk, perl or sed.
- Unix:
-
Programs that use the str library must be linked in ``custom
runtime'' mode, as follows:
ocamlc -custom other options str.cma other files -cclib -lstr
ocamlopt other options str.cmxa other files -cclib -lstr
For interactive use of the str library, do:
ocamlmktop -custom -o mytop str.cma -cclib -lstr
./mytop
- Windows:
-
Programs that use the str library must be linked in ``custom
runtime'' mode, as follows:
ocamlc -custom other options str.cma other files %CAMLLIB%/libstr.lib
ocamlopt other options str.cmxa other files %CAMLLIB%/libstr.lib
For interactive use of the str library, do:
ocamlmktop -custom -o mytop.exe str.cma %CAMLLIB%/libstr.lib
./mytop.exe
Module Str: regular expressions and high-level string processing
Regular expressions
type regexp
-
The type of compiled regular expressions.
val regexp: string -> regexp
-
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.
val regexp_case_fold: string -> regexp
-
Same as regexp, but the compiled expression will match text
in a case-insensitive way: uppercase and lowercase letters will
be considered equivalent.
String matching and searching
val string_match: regexp -> string -> int -> bool
-
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.
val search_forward: regexp -> string -> int -> int
-
search_forward r s start searchs 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.
val search_backward: regexp -> string -> int -> int
-
Same as search_forward, but the search proceeds towards the
beginning of the string.
val matched_string: string -> string
-
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.
val match_beginning: unit -> int
val match_end: unit -> int
-
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.
val matched_group: int -> string -> string
-
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.
val group_beginning: int -> int
val group_end: int -> int
-
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.
Replacement
val global_replace: regexp -> string -> string -> string
-
global_replace regexp repl s returns a string identical to s,
except that all substrings of s that match regexp have been
replaced by repl. The replacement text repl 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.
val replace_first: regexp -> string -> string -> string
-
Same as global_replace, except that only the first substring
matching the regular expression is replaced.
val global_substitute: regexp -> (string -> string) -> string -> string
-
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.
val substitute_first: regexp -> (string -> string) -> string -> string
-
Same as global_substitute, except that only the first substring
matching the regular expression is replaced.
Splitting
val split: regexp -> string -> string list
-
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.
val bounded_split: regexp -> string -> int -> string list
-
Same as split, but splits into at most n substrings,
where n is the extra integer parameter.
Extracting substrings
val string_before: string -> int -> string
-
string_before s n returns the substring of all characters of s
that precede position n (excluding the character at
position n).
val string_after: string -> int -> string
-
string_after s n returns the substring of all characters of s
that follow position n (including the character at
position n).
val first_chars: string -> int -> string
-
first_chars s n returns the first n characters of s.
This is the same function as string_before.
val last_chars: string -> int -> string
-
last_chars s n returns the last n characters of s.