[Haskell-cafe] What does the `forall` mean ?
ryani.spam at gmail.com
Thu Nov 12 14:48:58 EST 2009
On Thu, Nov 12, 2009 at 2:50 AM, Eugene Kirpichov <ekirpichov at gmail.com> wrote:
> But that's not an issue of semantics of forall, just of which part of
> the rather broad and universal semantics is captured by which language
The forall for existential type quantification is wierd.
> data Top = forall a. Any a -- existential
> data Bottom = All (forall a. a) -- rank 2
I think it makes much more sense in GADT syntax:
> data Top where
> Any :: forall a. a -> Top
> data Bottom where
> All :: (forall a. a) -> Bottom
where it's clear the forall is scoping the type of the constructor.
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