Some time ago I wrote to this list linking to a regular expression engine I was writing in order to learn the Haskell programming language. I had noted the ability to send a single functions output into it as the its input and had tried using this property of the language in a rather winding way to transform a string regular expression into an integer based array of rules approximating DFAs. At the time I just smashed the stack as mutually dependent functions called one another recursively, each depending on the output of the other to execute. I didn't know a way around this, or even if Haskell provided a way around this. Yesterday a link from reddit to a site concerning `irrefutable patterns` caused me to jump back to the code and see if they allowed for what I wanted. They did. The working code can be found here : http://rx-haskell.googlecode.com/svn/trunk/rx.hs The link goes to a simple regular expression matcher a little under 200 lines long that can accept a regex string with operands (*), (*?), (?), (??), (+) and grouping using parenthesis. I hope to update the code with bracketed ranges and things soon. Any comments, questions, or criticisms from the list would be highly appreciated. - Michael Speer .