On 1/21/13 1:40 AM, Shachaf Ben-Kiki wrote:
For example:{-# LANGUAGE TypeFamilies #-} import Unsafe.Coerce newtype Id a = MkId { unId :: a } {-# RULES "fmap unId" fmap unId = unsafeCoerce #-} data family Foo x y a data instance Foo x y (Id a) = FooI x data instance Foo x y Bool = FooB { unB :: y } instance Functor (Foo x y) where fmap = undefined
You can define instances for type functions? Eek! -- Live well, ~wren _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
