[onlydnaq]

I don't really agree with the premise that not having type classes is as big of a problem that the author thinks, but to answer your question OCaml has functors which are basically higher order modules. A functor in OCaml is a module defined over abstract types and you instantiate it with concrete types.

A lot of people in the Haskell community have yearned for this as well, and the latest version of the Haskell compiler will support something similar called Backpack.