Re: [Caml-list] "with module" surprises

[Markus Mottl <markus.mottl@gmail.com>]

If "S" referred to "ARG" as signature for "Spec", too, then you are
right, and that's probably by far the usual case.  You could still
export anything in "ARG" that's not in the signature for "Spec"
imposed by "S".  But I agree this example is not nearly as useful as
it might seem.

Not sure I have ever depended on this feature in actual code.  If so,
this must be exceedingly rare, but semantically it still seems like
the right behavior to me.

Markus

On Mon, May 9, 2011 at 13:33, Andreas Rossberg <rossberg@mpi-sws.org> wrote:
> On May 9, 2011, at 19.21 h, Markus Mottl wrote:
>>
>> A use case for the intended semantics might be reexporting of functor
>> arguments:
>>
>>  module Make (Arg : ARG) : S with module Spec = Arg = struct
>>   module Spec = Arg
>>   ...
>>  end
>>
>> It could be bad from a design perspective to lose substructures in
>> "Spec" which were unknown to "S".
>
> If I understand your example correctly, then I don't think it does what you
> think it does. That is, if you apply Make to some M that is wider than ARG,
> you still won't have the additional components in F(M).Spec, because M gets
> narrowed to ARG by the functor application anyway.
>
> /Andreas
>
>



-- 
Markus Mottl        http://www.ocaml.info        markus.mottl@gmail.com