From: "Jon Fairbairn"
To reinforce what Aaron said, if a programme works now, it'll still work if map suddenly means fmap.
Well, this isn't quite true, is it? Here's an example: class Foldable f where fold :: (a -> a -> a) -> a -> f a -> a instance Foldable [] where fold = foldr example = fold (+) 0 (map (+1) (return 2)) example has the value 3 (of course), but if you replace map by fmap then the code no longer compiles. In any case, I'm dubious about this as a criterion. I would guess that the majority if compiler runs for beginners (and perhaps for the rest of us too!) end in a type error, not a successful compilation, so arguably the quality of error messages when a type-check fails is more important than which programs compile. John