Re: [Caml-list] module alias in a .mli file

[Francois Berenger <berenger@riken.jp>]

On 11/20/2012 10:38 AM, Francois Berenger wrote:
> On 11/20/2012 12:46 AM, Tiphaine Turpin wrote:
>> 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
>
> It's a little verbose but might be closer to what I was looking for.

Indeed, now I can write (and compile) a .mli file with:

---
include module type of struct module BA  = Bigarray        end
include module type of struct module BA3 = Bigarray.Array3 end
[...]
mutable grid : (int, BA.int8_unsigned_elt, BA.c_layout) BA3.t
[...]
---

Which is more compact than what I had previously.

Thanks! :)
F.

>> 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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>>>
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>>>
>>
>
>