Re: [Caml-list] Unpacked module parameterized type escaping

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

On Thu, Apr 18, 2013 at 1:12 PM, John Carr <jfc@mit.edu> wrote:
>
> I have a function of two arguments:
>
> 1. A packed module implementing Map.S.
>
> 2. A value of the module's Map.S.t.
>
> I can't find a way to prevent a "type constructor ... would escape its
> scope" error.

I think you may just want to wrap both the map module to be used and
the value on which its functions should operate in another first-class
module, e.g.:

  module type Arg = sig
    module M : Map.S with type key = int
    val v : 'a M.t
  end

Then you can write:

  let is_empty (module Arg : Arg) = Arg.M.is_empty Arg.v

This admittedly doesn't look particularly elegant, but should solve the problem.

Regards,
Markus

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