I wrote:
> You may find these handy:
> class SubType a b where
> inj :: a -> b
> prj :: b -> Maybe a
>
> instance SubType a (Either a b) where
> inj a = Left a
> prj (Left a) = a
> prj (_) = Nothing
This should be:
instance SubType a (Either a b) where
inj a = Left a
prj (Left a) = a
prj (Right b) = prj b
instance SubType Pow (Either Pro Pow)
inj a = Right a
prj (Right Pow) = Pow
prj _ = Nothing
Regards,
John Hörnkvist
--
ToastedMarshmallow, the perfect Cocoa companion
http://www.toastedmarshmallow.com
