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);

Execute matches the compiled regular expression x against string s. It returns 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 flag was 0, there are no more elements. If 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 nth element gives the position of the last match to the nth parenthesized subexpression, or (-1,-1) if the subexpression does not participate in the overall match.

Executese is similar to execute but allows the start and end points in the string to be specified, as tuple se: (start , end), where start is the index in s of the initial character to be matched, and end is the index in s of the first character beyond the substring to be matched (and can be the length of s). If bol is non-zero, the initial character is at the beginning of a line, allowing an initial match by the regular expression operator `^'; if eol is non-zero, the last character is at the end of a line, allowing a match by the operator `$'.

(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);