Module Str
module Str: sig .. end
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 following constructs are
recognized:
. Matches any character except newline.* (postfix) Matches the preceding expression zero, one or
several times+ (postfix) Matches the preceding expression one or
several times? (postfix) Matches the preceding 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.
To include a ] character in a set, make it the first
character of the set. To include a - character in a set,
make it the first or the last character of the set.^ Matches at beginning of line (either at the beginning of
the matched string, or just after a newline character).$ Matches at end of line (either at the end of the matched
string, or just before a newline character).\| (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, and so on up to \9).\b Matches word boundaries.\ Quotes special characters. The special characters
are $^\.*+?[].
Note: the argument to
regexp is usually a string literal. In this
case, any backslash character in the regular expression must be
doubled to make it past the OCaml string parser. For example, the
following expression:
let r = Str.regexp "hello \\([A-Za-z]+\\)" in
Str.replace_first r "\\1" "hello world"
returns the string
"world".
In particular, if you want a regular expression that matches a single
backslash character, you need to quote it in the argument to
regexp
(according to the last item of the list above) by adding a second
backslash. Then you need to quote both backslashes (according to the
syntax of string constants in OCaml) by doubling them again, so you
need to write four backslash characters:
Str.regexp "\\\\".
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.
val quote : string -> string
Str.quote s returns a regexp string that matches exactly
s and nothing else.
val regexp_string : string -> regexp
Str.regexp_string s returns a regular expression
that matches exactly s and nothing else.
val regexp_string_case_fold : string -> regexp
Str.regexp_string_case_fold is similar to
Str.regexp_string,
but the regexp matches in a case-insensitive way.
String matching and searching
val string_match : regexp -> string -> int -> bool
string_match r s start tests whether a substring of s that
starts at position start matches 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 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.
Raises Not_found if no substring matches.
val search_backward : regexp -> string -> int -> int
search_backward r s last searches the string s for a
substring matching the regular expression r. The search first
considers substrings that start at position last and proceeds
towards the beginning of string. Return the position of the first
character of the matched substring.
Raises Not_found if no substring matches.
val string_partial_match : regexp -> string -> int -> bool
Similar to
Str.string_match, but also returns true if
the argument string is a prefix of a string that matches.
This includes the case of a true complete match.
val matched_string : string -> string
matched_string s returns the substring of
s that was matched
by the last call to one of the following matching or searching
functions:
Note: in the case of
global_substitute and
substitute_first,
a call to
matched_string is only valid within the
subst argument,
not after
global_substitute or
substitute_first returns.
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
match_beginning() returns the position of the first character
of the substring that was matched by the last call to a matching
or searching function (see
Str.matched_string for details).
val match_end : unit -> int
match_end() returns the position of the character following the
last character of the substring that was matched by the last call
to a matching or searching function (see
Str.matched_string for
details).
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 that was
matched by the last call to a matching or searching function (see
Str.matched_string for details).
The user must make sure that the parameter
s is the same string
that was passed to the matching or searching function.
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.
val group_beginning : 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 that was matched by the last call to a
matching or searching function (see
Str.matched_string for details).
RaisesNot_found if the nth group of the regular expression
was not matched.Invalid_argument if there are fewer than n groups in
the regular expression.
val group_end : int -> int
group_end n returns
the position of the character following the last character of
substring that was matched by the
nth group of the regular
expression that was matched by the last call to a matching or
searching function (see
Str.matched_string for details).
RaisesNot_found if the nth group of the regular expression
was not matched.Invalid_argument if there are fewer than n groups in
the regular expression.
Replacement
val global_replace : regexp -> string -> string -> string
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.
val replace_first : regexp -> string -> string -> string
Same as
Str.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
Str.global_substitute, except that only the first substring
matching the regular expression is replaced.
val replace_matched : string -> string -> string
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 regular expression
that was matched by the last call to a matching or searching
function (see
Str.matched_string for details).
s must be the same string that was passed to the matching or
searching function.
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. An occurrence of the delimiter at the
beginning or at the end of the string is ignored.
val bounded_split : regexp -> string -> int -> string list
Same as
Str.split, but splits into at most
n substrings,
where
n is the extra integer parameter.
val split_delim : regexp -> string -> string list
Same as
Str.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"].
val bounded_split_delim : regexp -> string -> int -> string list
Same as
Str.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.
type split_result =
|
| |
Text of string |
|
| |
Delim of string |
val full_split : regexp -> string -> split_result list
Same as
Str.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 "}"].
val bounded_full_split : regexp -> string -> int -> split_result list
Same as
Str.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.
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
Str.string_before.
val last_chars : string -> int -> string
last_chars s n returns the last n characters of s.