Re: [Caml-list] Re: "module type of" on sub-module of functor result

[Gabriel Scherer <gabriel.scherer@gmail.com>]

You could use the following work-around, which introduces an
additional layer to have some space to name the functor application:
  module Map = struct
    module Make (Ord : BatInterfaces.OrderedType) = struct
      module M = BatMap.Make(Ord)
      module Result : module type of M.Labels = struct
        include M.Labels
      end
    end
  end

I suppose that may not suit your need -- you probably want to mimic an
existing hierarchy without changing it -- but it's difficult to do
better with such a reduced example, where you don't even need the
signature anyway.


2012/2/22 Ashish Agarwal <agarwal1975@gmail.com>:
> Here's an example I still don't know how to accomplish:
>
> module Map = struct
>   module Make (Ord : BatInterfaces.OrderedType) : sig
>     include module type of BatMap.Make(Ord).Labels (* this line is invalid
> *)
>   end = struct
>     include BatMap.Make(Ord)
>     include Labels
>   end
> end
>
> The idea is I only want "module type of Labels" for the functor's output,
> but I need BatMap.Make(Ord) within the implementation (perhaps to implement
> some other functions).
>
> I thought I can simply replace the line "include BatMap.Make(Ord)" with
> "open BatMap.Make(Ord)", and then not provide the explicit signature. But
> "open BatMap.Make(Ord)" gives a syntax error.
>
>
> 2012/2/22 Till Varoquaux <till@pps.jussieu.fr>
>>
>> 2012/2/22 Milan Stanojević <milanst@gmail.com>d
>> > On Tue, Feb 21, 2012 at 3:32 PM, Hezekiah M. Carty <hez@0ok.org> wrote:
>> >> On Tue, Feb 21, 2012 at 2:37 PM, Ashish Agarwal <agarwal1975@gmail.com>
>> >> wrote:
>> >>> I must've accidentally deleted part of my email before hitting send.
>> >>> The
>> >>> point was to make the first code sample compile after removing the
>> >>> commented
>> >>> line. But that is not allowed; I get a syntax error:
>> >>>
>> >>> $ ocamlfind ocamlc -c -package batteries a.ml
>> >>> File "a.ml", line 6, characters 38-39:
>> >>> Error: Syntax error: 'end' expected
>> >>> File "a.ml", line 4, characters 16-19:
>> >>> Error: This 'sig' might be unmatched
>> >>>
>> >>> I'm wondering if there is a better solution than my second code
>> >>> sample.
>> >>>
>> >
>> > I would consider this a bug. I think than any module expression than
>> > can be used with "include" should be usable with "include module type
>> > of"
>> >
>> > --
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>> >
>>
>> Milan is right: the language grammar does say that both [include] and
>> [module type of] should work on module_expr. However, based upon the
>> manual(*),  [A(B)] and  [A.B] are syntacticly valid module_expr's but
>> [A(B).C] isn't. Is this because of an inherent limitation in the
>> module system?
>>
>> [*]http://caml.inria.fr/pub/docs/manual-ocaml/manual019.html#module-expr
>
>