问题
Hask looks like a subcategory of the SET - category of all sets and single-argument functions between them. However, seems like it fails to preserve id when it comes down to the undefined: seq undefined () fails with exception as it suppose to, however seq (undefined . id) () = seq (id . undefined) () = (). Obviously, id acts wrongly.
Is there a way to (theoretically at least) resolve this issue and make Hask a category indeed? Except throwing undefined away?
来源：https://stackoverflow.com/questions/51331179/does-hask-form-a-theoretically-valid-category-or-it-just-pretends-to-be-one