Hi, I'm looking for a type class which checks whether two types are the same or not. My first guess is: class Same a b where same :: a -> b -> Bool instance Same a a where same _ _ = True instance Same a b where same _ _ = False In Hugs this seems to work with overlapping instances (not requiring unsafe overlapping instances). GHC requires {-# LANGUAGE MultiParamTypeClasses, IncoherentInstances #-} So my question is if this is safe? Will the compiler always pick the "right one"? Is there a better way to do this? The alternative I thought of is using Typeable, but this is not supported particularly well on Hugs (no deriving Typeable) and would require modifications to the existing data structures (additional derivings) so is not such a good choice. Thanks Neil