ref: 6bb619c8db2867ddd9cd19c0aec05065f5ee0cae
dir: /man/2/regex/
.TH REGEX 2
.SH NAME
regex \- regular expression recognizer module
.SH SYNOPSIS
.EX
include "regex.m";
regex := load Regex Regex->PATH;
compile: fn(e: string, flag: int): (Re, string);
execute: fn(x: Re; s: string): array of (int,int);
executese: fn(x: Re, s: string, se: (int, int), bol: int, eol: int):
array of (int, int);
.EE
.SH DESCRIPTION
Regular expressions are defined by
.IR regexp (6).
.B Compile
returns (as the first element of the result tuple)
a compiled form of the regular expression given in string
.IR e .
If
.I e
is not a valid regular expression,
.B compile
returns the tuple
.BI "(nil" ", diag" )
where
.I diag
is a diagnostic string.
The effect of
.I flag
is described below.
.PP
.B Execute
matches the compiled regular expression
.I x
against string
.I s.
It returns
.B nil
on no match, otherwise it returns an array.
The element with index 0 gives the character positions
of the first character of some longest leftmost match and
the first character beyond the match.
If the compilation
.I flag
was 0, there are no more elements.
If
.I flag
was 1, there is one element for each pair of
parentheses in the regular expression, counting
left parentheses left to right starting at 1.
The
.IR n th
element gives the position of the last match to the
.IR n th
parenthesized subexpression, or (\-1,\-1) if the subexpression
does not participate in the overall match.
.PP
.B Executese
is similar to
.B execute
but allows the start and end points in the string to be specified,
as tuple
.IR se :
.BI ( "start , end" ) ,
where
.I start
is the index in
.I s
of the initial character to be matched,
and
.I end
is the index in
.I s
of the first character beyond the substring to be matched
(and can be the length of
.IR s ).
If
.I bol
is non-zero, the
initial character is at the beginning of a line,
allowing an initial match by the regular expression operator
.RB ` ^ ';
if
.I eol
is non-zero, the
last character is at the end of a line, allowing a match
by the operator `\f5$\fP'.
.SH EXAMPLES
.EX
(re, nil) := regex->compile("(thick )*(chocolate |raspberry )?"+
"(topp|fill)ing", 0);
(re, nil) := regex->compile("[ABCb-z]+", 0);
a := regex->execute(re, s:="aAbBcCdD");
(beg, end) := a[0];
s[beg:end] == "AbBcCd";
(re, nil) := regex->compile("a*b*", 0);
a := regex->execute(re, "bbaabb");
(beg, end) := a[0];
(beg, end) == (0,2);
.EE
.SH SOURCE
.B /appl/lib/regex.b
.SH SEE ALSO
.IR regexp (6)