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Subject: [Caml-list] accessing the type of a polymorphic parameter

Hello.

Is it possible in OCaml for a polymorphic function to somehow have
access to the concrete type of an actual parameter used in a call of
the function?

For example, is there some way of writing a polymorphic function 'foo'
list this:

     let foo x =3D
        match (type_of x) with
          Int    -> ....
        | String -> ....

where 'type_of' is some function that returns a representation of the
concrete type of its argument.

I want this because I want to implement an ad-hoc polymorphic
function.  I know this is outside the bounds of "normal" OCaml, but is
there some nasty part of the language like Obj.magic that I could use
to achieve this?

Mark.