Comment by lindig

OCaml modules and Haskell type classes are quite separate, too. I would make more sense to compare OCaml and Haskell modules. Haskell type classes implement ad-hoc polymorphism and OCaml doesn't have that at all. You can't implement in OCaml something like a show function that works on integers and strings and list of integers and so on like in Haskell using the Show type class.