[Haskell-cafe] advanced class constraints in Haskell 98?

[Ross Paterson]

On Thu, Jan 08, 2009 at 09:59:19PM +0100, Henning Thielemann wrote:
>
> GHC accepts a class declaration like
>   class Monad (m Maybe) => C m where
>      ...
>  without having any language extension switched on. But it isn't Haskell  
> 98, is it? Hugs 2005 also accepts this.

Yes, it is.  The Report is a good reference for questions like this.