Am 18.06.2014 um 12:09 schrieb Yitzchak Gale:
In my opinion, Richard missed the most important reason:
3) Gratuitous polymorphism makes code much less readable and much costlier to maintain, usually for almost no gain.
One of the biggest strengths of Haskell is semantic clarity. You can often look at a Haskell expression, recognize its type, and then immediately understand exactly what the expression is doing. That is immensely valuable, not only for writing code, but for maintaining and refactoring it over the lifetime of an application, often by people other than the original author.
I have to strongly agree. I have already written things like fmap (fmap (fmap (fmap f))) and find it hard to find out later, which fmap refers to Maybe, which one to List, and which one to Map. That is, I prefer 'map' even if there is an 'fmap'.