[Haskell-cafe] Predicate Library?

Hi, I'm trying to manipulate predicates in Haskell, and was wondering if there was a predicate library available that I could use? My predicates consist of `and` and `or` over some constraints. I have various rules which can be used to collapse certain constraints. Currently I have written my own predicate code, but its not great, and the simplification is overly hacky. The main facility I want out of the predicate library is some simplification. Thanks Neil