Re: [Caml-list] Include question

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

If you want some module of your system to be parametrized by another
module (to be able to pass either a concrete module or a mockup
module), you should use a functor.

  http://caml.inria.fr/pub/docs/manual-ocaml/manual004.html#toc15

in logic.ml
  module Make (Net_lib : Net_interface) = struct
    ...
  end

in main.ml:
  module Logic = Logic.Make(Net_lib)
  ..

in main_mockup.ml:
  module Logic = Logic.Make(Net_mockup)
  ...

On Tue, Nov 8, 2011 at 4:03 PM, Hans Ole Rafaelsen <hrafaelsen@gmail.com> wrote:
> Hi,
>
> I'm trying to create a mockup module to replace a network module when doing
> testing.
>
> The application consists of basically 3 parts. Some user interaction. This
> calls some logic of the application, and the logic module might need to call
> some other functions over the network. For testing I want to make a mockup
> of the network module, in addition to synthesize the user interaction. I
> want to test the logic module. The application has the following files:
>
> net_lib.ml:
> let util_fun a = a
> let foo a b = a + b
> let bar a b = a - b
>
> logic.ml:
> let state = ref 0
> let get_state () = !state
> let do_op a b =
>   incr state;
>   (Net_lib.foo a b) * (Net_lib.bar (Net_lib.util_fun a) b )
>
> main_appl.ml:
> let () =
>   let a, b  = Scanf.scanf  "%d %d\n" (fun a b -> a,b) in
>   Printf.printf "Foo %d %d\n%!" (Logic.get_state ()) (Logic.do_op a b)
>
> let () =
>   let a, b  = Scanf.scanf  "%d %d\n" (fun a b -> a,b) in
>   Printf.printf "Foo %d %d\n%!" (Logic.get_state ()) (Logic.do_op a b)
>
>
> For testing I have the following modules:
> net_lib_mockup.ml
> include Net_lib
> let foo a b = 1
> let bar a b = 1
>
> logic_mockup.ml:
> module Net_lib = Net_lib_mockup
> include Logic
>
> main_test.ml:
> module Logic = Logic_mockup
>
> let () =
>   let a, b = (1, 1) in
>   Printf.printf "Test %d %d\n%!" (Logic.get_state ()) (Logic.do_op a b)
>
> let () =
>   let a, b = (10, 1) in
>   Printf.printf "Test %d %d\n%!" (Logic.get_state ()) (Logic.do_op a b)
>
> The problem is that the "include Logic" has already 'bound' the functions in
> Logic to the Net_lib module and will not use the Net_lib_mockup that I try
> to use through a moudle alias. If i replace the 'include Logic' with the
> actual content of the logic.ml file, then the functions get bound to the
> Logic_mockup functions, and the test works as they should.
>
> Are there some trick to get the 'include Logic', in logic_mockup.ml, to use
> to the Net_lib_mockup module and not the Net_lib module, so that I don't
> have to do copy and paste between the two files?
>
>
> Regards,
>
> Hans Ole Rafaelsen
>
>