Re: [Haskell-cafe] double existential type

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 wrote:

On Wed, Mar 24, 2010 at 6:31 PM, Ozgur Akgun 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