> You can't do it in standard Haskell, but with ghc extensions you can
> achieve the same effect. For example, the following program
>
> data Showable = forall a . Show a => Showable a
> instance Show Showable where
> show (Showable x) = show x
> example = map show [Showable 'a', Showable 5]
> main = print example
>
> produces the output
>
> ["'a'","5"]
And it isn't just ghc that has this extension. Hugs98 and nhc98
also implement it with this syntax. Hbc has the extension too (local
forall quantification), but uses a slightly different syntax, since
its implementation pre-dates all the others.
Regards,
Malcolm
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