- Solid arrows point from the general to the specific; that is, if there is an arrow from Foo to Bar it means that every Bar is (or should be, or can be made into) a Foo.
- Dotted arrows indicate some other sort of relationship.
- Monad and ArrowApply are equivalent.
- Semigroup, Apply and Comonad are greyed out since they are not actually (yet?) in the standard Haskell libraries.
