In fact, the solution

  module V3 : module type of Vector3

does not work completely, because, the equality between Vector3 and V3
is lost, which poses problem with the types defined by Vector 3. What
works is:

  include module type of struct module V3 = Vector3 end

Here is a full example:

module M : sig

  module Vector3 : sig type t end
  (* module V3 : module type of Vector3 *)
  include module type of struct module V3 = Vector3 end

end = struct

  module Vector3 = struct type t end
  module V3 = Vector3

end 

open M
let id (x : Vector3.t) : V3.t = x


Regards,

Tiphaine


On 11/19/12 13:44, Paolo Donadeo wrote:
>
> Actually this is not true, Martin explained how. :-)
>
>
> -- 
> Paolo
> Sent by Gmail from Android
>
> Il giorno 19/nov/2012 11:35, "David House" <dhouse@janestreet.com
> <mailto:dhouse@janestreet.com>> ha scritto:
>
>     Annoyingly though, there is no way to create a module alias in an mli.
>
>     If, in an ml file, you have to refer often to
>     Some_very_long_module_name, it can quite convenient to define an alias
>     by doing "module Mod = Some_very_long_module_name" (or, locally, "let
>     module Mod = Some_very_long_module_name in"). But there is no way of
>     doing this in an mli: you have to use the long name every time.
>
>     This is especially annoying if you have some big type that you want to
>     expose in the mli. You really just want to copy-paste out of the ml
>     file and stick it into the mli, but then you have to expand all the
>     module aliases. (It's just a couple of goes with M-%, but still...)
>
>     On Mon, Nov 19, 2012 at 6:36 AM, Francois Berenger
>     <berenger@riken.jp <mailto:berenger@riken.jp>> wrote:
>     > On 11/19/2012 03:02 PM, Martin Jambon wrote:
>     >>
>     >> On Sun 18 Nov 2012 09:29:31 PM PST, Francois Berenger wrote:
>     >>>
>     >>> Hello,
>     >>>
>     >>> Here is my stupid question of the day:
>     >>> can't I declare the following in a .mli file?
>     >>>
>     >>> module V3 = Vector3
>     >>
>     >>
>     >> No, because "= Vector3" specifies an implementation.
>     >> An mli file is a module interface, and module interfaces never
>     contain
>     >> implementations.
>     >>
>     >> However, you may want to do this, which does what it says:
>     >>
>     >>   module V3 : module type of Vector3
>     >
>     >
>     > Thanks a lot! That's exactly what I needed. :)
>     >
>     >
>     >
>     >
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