Question about using higher order polymorphism.

[Johannes Waldmann]

> My question is, in which version of Haskell can I use higher order
> polymorphism features (including first class polymorphic and first class
> existential types), and how to use them (what's the syntax).  

for ghc, check this:
http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html
(i think) most of this is implemented in hugs as well.

with ghc, you need `ghc -fglasgow-exts', with hugs, use `hugs -98'.
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