Parameterising Class Constraints in Existential Types
Fri, 30 Mar 2001 12:07:55 -0800
Hugs currently restricts the way constrained existential types
may be formed, for entirely internal, technical reasons. We're
currently looking over the implementation to see if it's
possible to lift the restriction without rewriting substantial
parts of the type checker.
On Thursday, March 29, 2001, at 01:46 AM, Ashley Yakeley wrote:
> Is this valid (extended) Haskell?
> class MyClass a b where
> foo :: a -> b -> Int
> data Special = forall b. (MyClass Int b)=> MkSpecial b
> data General a = forall b. (MyClass a b)=> MkGeneral b
> Hugs complains about the 'General' line but has no problem with the
> 'Special' line...
> Ashley Yakeley, Seattle WA
> Haskell mailing list