Existential types, object-orientation.

[Nick Kallen]

Existential types are a spiffy feature for psuedo-object orientation as is
clearly seen in the Clean book in the OO Drawing program chapter. I have a
few questions related to object-orientation as seen in some of the more
modern mixed languages like Java and Oberon:
    Can one can use inheritence or class polymorphism with Existential types
in Clean? If not, are these concepts even compatible?
    Could dynamic types be implemented in a functional language like clean?
Exactly how would it work? Could one simulate prototypes in a functional
language?

My only real use of existential types is seeing the Clean book (I'm pretty
new to functional programming). It is probable that their potential uses far
exceed the limited scope of usage in the book. If anyone can provide any
interesting problems or data structures implemented with existential types
(in a manner distinct from that of the Clean book), I'd be appreciative.
Furthermore, if anyone can provide any critical information, relating
existential types to object-orientation, their limitations, etc.--I'd be
appreciative.

-Nick