Am Montag, den 19.01.2009, 14:47 +0100 schrieb Daniel Fischer: > Am Montag, 19. Januar 2009 14:31 schrieb Antoine Latter: > > 2009/1/19 Luke Palmer <lrpal...@gmail.com>: > > > As a side curiosity, I would love to see an example of any data structure > > > which has more than one Functor instance. Especially those which have > > > more than one useful functor instance. > > > > (,) ? > > > > -Antoine > > Wrong kind. And > (,) a > has only one useful instance.
What about instance Functor ((,) a) where fmap f (x,y) = (x, f y) and instance Functor (, a) where fmap f (x, y) = (f x, y) ? Of course, the latter is not legal Haskell. But if it was, then it might be useful. Is there any way to declare this Functor instance, possibly with some GHC extensions? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe