[polityagent]

Polymorphism doesn't require anything to do with OOP or objects themselves, see clojure multi methods as an extremely pure example that involves nothing even close to an object.

Protocols or typeclasses are also ways to implement functionality over (usually) immutable data. I don't see the relation to a mutable object with a closed set of methods defined at compile time.

[sifoobar]

I didn't make the distinction, the post sort of did between the lines.

Go back to my original comment and you'll see that multiple dispatch is what got us here.

I never said anything about mutable/immutable data, I'm talking about polymorphism. But I did mention type classes as an alternative.

I frankly fail to see how this is leading anywhere.