[Haskell-cafe] Context for type parameters of type constructors

[Henning Thielemann]

On Tue, 30 Mar 2004, Dylan Thurston wrote:

> If you use multi-parameter type classes, then in your instance
> declaration you can specify exactly what requirements you need.  For
> instance: 
>
> > class VectorSpace v a where
> >   zero :: v
> >   add :: v -> v -> v
> >   scale :: a -> v -> v

Multi-parameter type classes aren't Haskell 98, are they? I tried to stay
away from them. I didn't get the point yet why the context for 'data'
is not sufficient for the 'instance' method definition.