1. Only for unconstrained parametric polymorphism. For constrained parametric polymorphism, ML requires functors (don't get me wrong, I think ML functors are br

1. Only for unconstrained parametric polymorphism. For constrained parametric polymorphism, ML requires functors (don't get me wrong, I think ML functors are brilliant, but they do require you to be rather explicit about your typing). 2. I wouldn't say that it's without problems even for unconstrained parametric polymorphism. Consider the value restriction [1] and the fact that if you add subtyping to the mix (as in OCaml), you're getting some really non-trivial issues (as Scala found out the hard way). [1] http://mlton.org/ValueRestriction http://mlton.org/ValueRestriction