Hi Philip, On 28 August 2011 23:44, Philip Holzenspies <p...@st-andrews.ac.uk> wrote: > > import Data.Typeable > > data MyADT m = MyADT (m ()) > > instance (Typeable1 m, Monad m) => Typeable (MyADT m) where > typeOf t@(MyADT _) > = mkTyCon "MyADT" > `mkTyConApp` > [typeOf1 ((return :: Monad m => MyADT m -> m (MyADT m)) t)] >
IIRC, typeOf is supposed to work with undefined as the argument. Try: typeOf (undefined :: Int) See: http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Typeable.html#v:typeOf I think the undefined is merely because the pattern matching you use in the instance declaration fails. Hope this helps, Ozgur
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
