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

Bulat Ziganshin bulat.ziganshin at gmail.com
Fri Mar 23 21:30:39 EDT 2007

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

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