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

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.