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Its riding the haskell bandwagon to some degree. By borrowing ideas from category theory they have some really nice abstractions in practical code. But then it gets more confusing so you want to loop back and see what the actual definition of a "monoid" is, or understand "functors". Even if haskell's idea of functor isn't 1 to 1 with category theory's.

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The only thing I can think of that's wrong with Haskell's functors is that they're more specifically endofunctors, or am I missing something else?

And Hask is arguably not a proper category

Can you expand on this? I'm genuinely curious.

My understanding is that it's not a proper category due to the presence of Bottom - https://wiki.haskell.org/Bottom

> Bottom is a member of any type, even the trivial type () [...] If it were not, the compiler could solve the halting problem and statically determine whether any computation terminated

You can imagine function composition and identity don't work too well on things that never complete.

Ah yes, you're right. I always forget about bottom.

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