On Fri, 2004-08-06 at 15:54, MR K P SCHUPKE wrote: > class OnlyInt a > instance OnlyInt Int > instance Fail () => OnlyInt x > > Where Fail is a class with no instances, that is not exported! > > If you try and add an instance to OnlyInt the program will fail > with overlapping instances.
Very nice. However I think I still need to use allow-overlapping-instances because [Char] and GConfPrimitiveValue a => [a] still overlap. If closes classes were a language feature the typechecker would see that the do not overlap since there is no instance GConfPrimitiveValue Char. Duncan _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
