I suspect you probably just need more experience with the base language. And I don't mean that in a bad way -- Haskell is a bit of a weird language, and it's so

I suspect you probably just need more experience with the base language. And I don't mean that in a bad way -- Haskell is a bit of a weird language, and it's something that you'll need to spend some time with. But indeed that's a fairly standard sort of type signature that you'll process at a glance if you've used the language a fair bit.