Here's a short implementation (with explanation) in Scheme: http://matt.might.net/articles/implementation-of-regular-expression-matching-in-scheme-with-derivat

Here's a short implementation (with explanation) in Scheme: http://matt.might.net/articles/implementation-of-regular-expression-matching-in-scheme-with-derivatives/ http://matt.might.net/articles/implementation-of-regular-exp...