[Haskell-cafe] Are arbitrary rank types and existentials equivalent?

[Loup Vaillant]

Maybe one subsumes the other?

What I want to know is if there is an easy way to emulate one with the
other, and how much convenience is lost in doing so.

For instance, is it possible to implement stream fusion with rank2
types, or the ST monad with existantials?

Is there any paper discussing this kind of things?

Thanks,
Loup