mirryi/regexp2

Toy regular expressions implementation using finite automata.

RegExp2

A toy regular expressions implementation.

Usage

The following operators are supported:

• * : the Kleene star
• + : the "plus" operator, where a+ is equivalent to aa* or a*a
• ? : the optional operator
• | : the union operator
• ( and ) : grouping
• \  : escaping meta-characters
• [abc] : character classes with character ranges [A-Z0-9]
• [^abc] : negation of character classes
• \n : newline
• \d, \D : all Unicode decimal number characters and all non-decimal number characters, respectively
• \w, \W : all word characters (alphanumeric and _) and non-word characters, respectively
• \s, \S : all whitespace and non-whitespace characters, respectively
• . : any character except newline (\n)

A fairly arbitrary usage example:

use regexp2::RegExp;

fn main() {
    // Any sequence of a's and b's ending in abb.
    let mut re = RegExp::new("(a|b)*abb").unwrap();
    assert!(re.is_match("abb"));
    assert!(re.is_match("aababb"));

    // Any sequence of characters that are not B, C, D, E, F or any lowercase
    // letter.
    re = RegExp::new("[^B-Fa-z]*").unwrap();
    assert!(re.is_match("AGAQR"));

    // Any sequence of at least one digit followed by nothing or an
    // alphanumeric or underscore.
    re = RegExp::new(r"\d+\w?").unwrap();
    assert!(re.is_match("3a"));
    assert!(re.is_match("08m"));
    assert!(re.is_match("999_"));
}