Contexts in Existential Types

[Ashley Yakeley]

At 2001-03-13 19:36, I wrote:

>Would it be appropriate for Haskell to be able to remember contexts in 
>existential types? For instance, currently this does not work in Hugs:
>
>--
>class Charable a where
>	obtainChar :: a -> Char
>
>instance Charable Char where
>	obtainChar c = c
>
>data AnyCharable = forall c. (Charable c) => MkAnyCharable c
>
>anyA = MkAnyCharable 'a'
>recoverA = obtainChar ((\(MkAnyCharable c) -> c) anyA)
>--

Whoops, my error. It is possible to do this:

--
recoverA = (\(MkAnyCharable c) -> obtainChar c) anyA
--

Sorry...

-- 
Ashley Yakeley, Seattle WA