luckasranarison / regex-potata

Potata regex engine

Regex-potata

A basic regex engine, built as a practical application of automata theory, implements an E-NFA using Thompson construction and BFS for NFA simulation.

Usage

use regex_potata::Regex;

fn main() {
    let re = Regex::new("hello (w|w)orld!*").unwrap();
    let result = re.test("hello world!!!");

    println!("{}", result); // true

    let re = Regex::new(r#"(?<day>\d{2})-(?<month>\d{2})-(?<year>\d{4})"#).unwrap();
    let captures = re.captures("07-01-2024").unwrap();

    println!("{:?}", captures.get_name("day"));
    println!("{:?}", captures.get_name("month"));
    println!("{:?}", captures.get_name("year"));

    let re = Regex::new("(T|t)h(e|(e|o)se)").unwrap();
    let matches = re.find_all("the These those The");

    println!("{:?}", matches);
}

TODOs

• Basic regex foo (bar) | .
• Quantifiers + ? * {x} {x,y} {x,}
• Character classes [a-z] [^x] \d \D \w \W \s \S
• Captures (foo) (:?bar) (?<named>foo)
• Anchors ^ $
• NFA visualizer

regex-potata's Issues

Quantified capture groups

When quantifiers are applied to expressions inside parentheses, the last match should be the captured one. Like in the following:

const re = /(hi)+(ha)+/;
const input = "hihiha";
console log(input.match(re));
// [ 'hihiha', 'hi', 'ha', index: 0, input: 'hihiha', groups: undefined ]

The matched hi is the last one, i.e the second one. But it doesn't work in the current implementation.