On Sun, Aug 22, 2010 at 7:47 PM, Daniel Peebles <[email protected]> wrote:
> You could also do some (in my opinion) fairly nasty stuff with
> Dynamic or Typeable, adding a constraint to the Eq and
> attempting to cast at runtime (returning False if the cast
> returns Nothing).
This is what he's talking about:
> {-# LANGUAGE GADTs #-}
>
> import Data.Typeable (Typeable, cast)
>
> data Foo where
> Foo :: (Typeable t, Eq t) => t -> Foo
>
> instance Eq Foo where
> (Foo a) == (Foo b) = maybe False (== b) (cast a)
Cheers,
--
Felipe.
_______________________________________________
Haskell-Cafe mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/haskell-cafe
