[Haskell-cafe] ANNOUNCE: Utrecht Haskell Compiler (UHC) -- first release

wren ng thornton wren at freegeek.org
Sun Apr 19 16:56:29 EDT 2009

Bulat Ziganshin wrote:
> Hello R.A.,
> Sunday, April 19, 2009, 11:46:53 PM, you wrote:
>> Does anybody know if there are any plans to incorporate some of
>> these extensions into GHC - specifically the existential typing ?
> it is already here, but you should use "forall" keyword instead odf
> "exists"

More particularly, enable Rank2Types and then for any type lambda F and 
for any type Y which does not capture @a@:

(x :: exists a. F a) ==> (x :: forall a. F a)

(f :: exists a. (F a -> Y)) ==> (f :: (forall a. F a) -> Y)

Live well,

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