On Fri, Jul 5, 2013 at 11:03 PM, Ömer Sinan Ağacan <omeragacan@gmail.com> wrote:

There's an implicit quantifier in type of `f`, like this: `f :: forall
a. a -> ListF a a`. When I add `ScopedTypeVariables` and `forall a.
...` in top level definition, it's like all `a`s in scope of top level
definition are same, except when explicitly defined as `forall a.
...`.

Is my intuition correct?

Yes it is ! :)

ScopedTypeVariables is a very nice and non problematic extension, it may even be made part of some future Haskell standard.

Jedaï