[Haskell-cafe] Re: Rank-2-polymorphism problem

[Bulat Ziganshin]

Hello Martin,

Friday, March 23, 2007, 11:37:16 PM, you wrote:

>> readValue' :: Field -> Maybe (forall s. SqlBind s => s) -> Value

> Thank you very much, that's exactly what I wanted. After reading in the
> GHC users guide about rank 2 polymorphism I thought that this is not 
> possible. Chapter "7.4.8. Arbitrary-rank polymorphism" says:

"impredicative polymorphism" is new in ghc 6.6. look for this word in
ghc docs and in spj's papers


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com