From: Vitaly Lugovsky <vsl@ontil.ihep.su>
> > In particular, I think that the question ``What means '_a ?''
> > from the
> > "EXPERT" FAQ could be relevant to your problem :)
> 
>  No. Sorry. I still don't understand. Why there is a *wrong* type
> specification in .cmi? If it's '_a, why it's 'a in .cmi?

Did you read my answer?
http://caml.inria.fr/archives/200301/msg00120.html

What I believe is happening is that, the way you define it, execute
cannot be given a polymorphic type. This has become more confused
because you wrote a .mli.  Just erase the .mli (or get it out of the
way) and compile lisp.ml. You should get a "this type variable is not
bound" error, which is what Pierre Weis is referring to.

Also note that '_a is only meaningful in output from the compiler.
If you write it in a .mli it will only be interpreted as a normal type
variable, in particular _it cannot match a non-generalizable one_
(only a closed type can).

Jacques Garrigue
-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners