>Am I right in thinking that the following holds ?
>
>polymorphic  = has type 'a  = for all
>monomorphic  = has type '_a = exists

not in the type-theoretic sense of the word. Exists normally refers to
data abstraction, whereas the '_a here is a "hack" of the ocaml
interactive environment. As soon as it gets a type, you cannot
"re"-instantiate it.  SML doesn't have the '_a at all and returns a dummy
type-variable. I think (but I am not sure about this) that the batch
compiler doesn't deal with '_a at all. 

cheers,

	Simon