Hi, I have probably a very simple question, but I wasn't able to figure it out myself.
Consider a two-parameter data type: > data X a b = X a b If I want to make it a functor in the last type variable (b), I can just define > instance Functor (X a) where > fmap f (X a b) = X a (f b) But how do I write it if I want X to be a functor in its first type variable? Is that possible at all? Something like: > instance Functor ??? where > fmap f (X a b) = X (f a) b Thanks in advance, Petr _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
