RE: forall and class contexts

| I want to define something like | class (Eq (forall a. T a), Monad T) => C T | where the context shall mean that T has to be an instance of Monad and | that for every type a the type T a has to be an instance of Eq. | Is such a thing possible with some Haskell implementation? Not currently, but I think it makes sense, and I'll implement it if enough people ask. Presumably you mean 'instance' not 'class'? A class decl always has a type variable after the =>; thus ...=> C a. There aren't many type constructors T for which T a is an equality type... Simon