Am Donnerstag, 12. Juli 2007 20:14 schrieb Andrew Coppin: > The only thing the libraries provide, as far as I can tell, is the fact > that tuples are all Functors. (In other words, you can apply some > function to all the elements to get a new tuple.) I think that's about > it. I doubt you can use that to define lifting functions...
Actually, they aren't (Functors). (,) takes two type arguments, (,,) takes three, etc. class Functor f requires f to take one type argument. So something like instance Functor (,) where ... won't compile. Besides, what should fmap (+1) (3, 4, "foo") do? (Somewhere in the libraries there is an instance Functor (,) a where fmap f (x, y) = (x, f y) but that's probably not what you expected.) HTH, Lukas _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe