Not just with generics, but also with dynamic dispatch on the runtime class of the K type which implements Ordered interface. ML traditionally doesn't have dyna

Not just with generics, but also with dynamic dispatch on the runtime class of the K type which implements Ordered interface. ML traditionally doesn't have dynamic dispatch, so it uses the static mechanism of building a map type specialized to a given key type. The value type is completely generic, though. I said 'traditionally' above because OCaml actually has dynamic dispatch now; it has a powerful and feature-complete OOP implementation, and a way to pass around modules at runtime as first-class objects. And in fact people take advantage of these capabilities to build more 'modern' APIs. But I would argue that the functor approach is one of, if not the best, overall.