skaller writes:
 > Is it possible instantiate a functor with a module
 > containing a type variable? I have a Set with t = int,
 > and I now need 'a * int.. 

No it is not possible. This is a recurrent question on this
list. Various unsatisfying solutions have been proposed, among which

- to make a copy of Set with an additional type parameter eveywhere (I
  attach such a module below. Beware: this is an old version of Set)

- to make an unfunctorized version of Set that uses Pervasives.compare,
  thus polymorphic

regards,
-- 
Jean-Christophe Filliātre (http://www.lri.fr/~filliatr)