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src
README.md
lfa.go

README.md

Regex

This is a very simple regular expression engine, created for learning purposes. It supports parantheses, the Kleene star, and the OR operator.

It works by turning a regular expression into a λ-NFA, turns that into a simple NFA, then into a DFA, then minimizes the DFA. A word is then matched by the regular expression if it's recognized by the resulting DFA.

The package is written in golang and it doesn't have any external dependencies. Also, it doesn't rely on the regexp package.

What's this all about

If you want to learn about Finite Automata, this package should be hacking material.

How do I use this

go run lfa.go -- it will prompt you for a regular expression and a word to match against that expression.

It then prints whether the word matches or not, and also prints out the minimized DFA as a directed graph with characters on edges.

You can use UTF-8 for the word/regex, though don't use the lambda character.

Example regular expressions:

a*b
(a|b)*c
(word)*|anotherword