Is it possible in Haskell + GHC extensions to use reflection techniques to determine typeclass membership? I'm thinking of things like the following:
Idea 1: > data MaybeEq a = NoEq a | Eq a => HasEq a > checkEq :: (some typeclass constraint) => a -> MaybeEq a (such that checkEq x returns HasEq x if and only if x has an Eq instance.) Idea 2: > data HTrue > data HFalse > class MaybeEq a b | a -> b > instance Eq a => MaybeEq a HTrue > instance (otherwise) => MaybeEq a HFalse -- ryan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
