Heirarchical name space allocation /Trees

[Johannes Waldmann FbIMN]

>   union :: (a -> a -> COrdering a) -> Set a -> Set a -> Set a

What we "really" want here is being able to write code like this:

    let instance Ord A where { ... }
    in  union (x :: Set A) (y :: Set A) 

It certainly needs some thinking to make this into
a consistent proposal for a language extension ... 

Best regards, J.