Re: [Caml-list] passing object to a function fails to compile (lablgtk2 involved)

[Olivier Andrieu <oandrieu@nerim.net>]

On Tue, Jul 17, 2012 at 10:32 AM, Ivan <ivg@ieee.org> wrote:
> Method set (which I'm suspecting as a cause of a failure) has type, that contains type quantifier:
> "'a. row:Gtk.tree_iter -> column:'a column -> 'a -> unit". Right now, type quantifiers are out of my ocaml's
> active vocabulary. In other words I do not know, how to handle them properly.

Yes, the GTree.list_store has a polymorphic method #set. Such methods
usually need a type annotation otherwise
the type inference will give you a regular non-polymorphic type for the method.

In your case the simple solution would be to constrain your model argument :
    let fill_model (model : GTree.list_store) name_col value_col =

(not tested :)

> Moreover, I still have no insight on the variable 'b. Why do the compiler refers to some 'b, without even mentioning it in the types it inferred? It's very strange for me.

This 'b variable is hidden in GTree.list_store I think.
A class name such as GTree.list_store acts like an alias for the
corresponding object type, here something like < ... set : 'b.
row:Gtk.tree_iter -> column:'b  GTree.column-> 'b -> unit ... >.

-- 
  Olivier