[Haskell-cafe] double existential type

[Ozgur Akgun]

I tried forall a,b. Binary' a b and the *what was I thinking* comment was
for that.

And I absulutely agree with you on the nesting part. That's what came to my
mind at the first glance for obvious reasons.

On 24 March 2010 20:27, Bas van Dijk <v.dijk.bas at gmail.com> wrote:

> On Wed, Mar 24, 2010 at 6:31 PM, Ozgur Akgun <ozgurakgun at gmail.com> wrote:
> > What was I thinking?
>
> A sensible thought if you asked me.
>
> It's certainly a surprise to me that this isn't allowed. Because in
> any other context binders, like lambdas and foralls, may be freely
> nested. For example:
>
> {-# LANGUAGE RankNTypes #-}
> swap :: forall a. forall b. a -> b -> (a, b)
> swap = \x -> \y -> (x,y)
>
> {-# LANGUAGE PolymorphicComponents #-}
> data Foo = Foo (forall a. forall b. a)
>
> regards,
>
> Bas
>



-- 
Ozgur Akgun
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