fa

https://github.com/lutter/ruby-fa

Bindings for libfa, a library to manipulate finite automata. Automata are constructed from regular expressions, using extended POSIX syntax, and make it possible to compute interesting things like the intersection of two regular expressions (all strings matched by both), or the complement of a regular expression (all strings _not_ matched by the regular expression). It is possible to convert from regular expression (compile) to finite automaton, and from finite automaton to regular expression (as_regexp)