[l_dopa]

You just described parametric polymorphism, which has nothing to do with objects or runtime type information.

[kazinator]

"has nothing to do" ... says you! I didn't describe static parametric polymorphism. Some of the things I described are doable with static parametric polymorphism in some limited circumstances.

[l_dopa]

Well, you described parametric polymorphism (a generic Nth function) and then switched to talking about dispatching on tags at runtime. You are mistaken; those really are completely unrelated concepts.

[asuffield]

Please, identify which things can't be done with parametric polymorphism. It is not clear what you are referring to.