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
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