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http://www.haskell.org/haskellwiki/Case

That link shows how to write a select function that offers functionality similar to a switch statement in C. ?Then you could use guards for the top-level switching and the select function for the second level.

Yikes - that idiom is rather horrible, vis packing cases into a list so they can be consumed by a function.

To solve the problem, I'd seek a more "mathy" description of the algorithm i.e. one that doesn't use conditionals so heavily and work from that rather than translate existing code.

Hi Stephen, I have solved the problem. I have made four functions instead of one.

Thanks

Thomas