Cale Gibbard wrote:
apfelmus wrote:
Unfortunately, the identity functor currently can't be overloaded, although I think it would be unambiguous.
Unfortunately, it would be quite ambiguous -- the identity functor overlaps with basically any other. Consider the case:
reverse . [[1,2,3],[4,5]]
which if (.) is fmap would normally mean [[3,2,1],[5,4]], but if the identity functor is used instead would mean [[4,5],[1,2,3]].
Whoops, what I did think here? I somehow thought that the argument of the function applied ( reverse in this case) would fix the functor. But this only works if the function is monomorphic: (reverse :: [[Int]] -> [[Int]]) . [[1,2,3],[4,5]] (reverse :: [Int] -> [Int]) . [[1,2,3],[4,5]] not if it's polymorphic. Regards, apfelmus