Contexts in Existential Types
Tue, 13 Mar 2001 19:36:42 -0800
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)
I believe allowing it to work would not amount to storing dynamic type
Is this an overlooked hole or would it break the spirit of the language?
Ashley Yakeley, Seattle WA