On 5 Jun 2008, at 1:39 AM, Thomas Davie wrote:
Even deriving an instance of Functor seems rather implausable, what should it do fordata Wierd a b = Nil | A a (Wierd a b) | B b (Wierd a b) Should fmap's function argument operate on 'a's, 'b's, or both?
class Functor (f :: * -> *) where ... so, 'b's. jcc PS Why isn't Functor derivable? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe