(sorry for any double-posting) The problem is that in your declaration of h, the inferred type for f is of the form (unit -> unit -> ...), and you use it with the different type (unit -> ?a:'a -> unit -> ...).
Changing ?a to be the first parameter of f change f's type to (?a:'a -> unit -> unit -> ...). OCaml knows that it can implicitly coerce functions when the optional parameters appear in the first position. This is explained in the manual : http://caml.inria.fr/pub/docs/manual-ocaml/manual006.html#htoc39 > However, in the specific case where the expected type > is a non-labeled function type, and the argument is > a function expecting optional parameters, the compiler > will attempt to transform the argument to have it match > the expected type, by passing None for all optional parameters. A fix is to add an annotation when defining h : let h (f : _ -> ?a:_ -> _) = f () () # let () = h f;; bouh! bouh! _______________________________________________ Caml-list mailing list. Subscription management: http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list Archives: http://caml.inria.fr Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs
