On Thu, Jun 05, 2008 at 10:39:16AM +0200, Thomas Davie wrote: > Even deriving an instance of Functor seems rather implausable, what > should it do for > > data 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?
Generic Haskell can do all that. Read Ralf Hinze's "Generic Programs and Proofs" for the theory: http://www.informatik.uni-bonn.de/~ralf/publications/habilitation.pdf Edsko _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
