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From: Goswin von Brederlow <goswin-v-b@web.de>
To: caml-list@inria.fr
Subject: RFH: Values do not match: val bar1 : Foo.foo_t is not included in val bar1 : Foo.foo_t
Date: Mon, 24 May 2010 00:03:01 +0200
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X-Spam: no; 0.00; val:01 foo:01 foo:01 val:01 cmx:01 mli:01 sig:01 extern:01 sig:01 intern:01 homeip:01 makefile:01 ocamlopt:01 -for-pack:01 ocamlopt:01 

Hi,

I'm playing around with packs and ways to avoid having to duplicate
module signatures all over the place. So I came up with the following
idea: Each module declares an external and internal module type and
restricts itself to the internal type. The pack then further restricts
the module to the external type.

But then I get a type error I can't make heads or tails of:

File "pack.cmx", line 1, characters 0-1:
Error: The implementation (obtained by packing)
       does not match the interface pack.mli:
       Modules do not match:
         sig
           module type Extern = sig val bar1 : Foo.foo_t end
           module type Intern =
             sig val bar1 : Foo.foo_t val bar2 : Foo.foo_t end
           module I : sig val bar1 : Foo.foo_t val bar2 : Foo.foo_t end
           val bar1 : Foo.foo_t
           val bar2 : Foo.foo_t
         end
       is not included in
         sig val bar1 : Foo.foo_t end
       Values do not match:
         val bar1 : Foo.foo_t
       is not included in
         val bar1 : Foo.foo_t
make: *** [all] Error 2


Can anyone explain that to me?

MfG
        Goswin
--

Here is a simple example that gives the above error:
(also on http://mrvn.homeip.net/t/)

---------------[ Makefile ]---------------
all:
        ocamlopt -for-pack Pack -c foo.ml
        ocamlopt -for-pack Pack -c bar.ml
        ocamlopt -c pack.mli
        ocamlopt -pack -o pack.cmx foo.cmx bar.cmx

clean:
        rm -f *.o *.cmx *.cmi *~

---------------[ bar.ml ]---------------
module type Extern = sig
  val bar1 : Foo.foo_t
end

module type Intern = sig
  include Extern
  val bar2 : Foo.foo_t
end

module I : Intern = struct
  let bar1 = Foo.foo2
  let bar2 = Foo.BAZ
  let bar3 = Foo.BLUB
end

include I

---------------[ foo.ml ]---------------
module type Extern = sig
  type foo_t = FOO | BAR | BAZ | BLUB
  val foo1 : foo_t
end

module type Intern = sig
  include Extern
  val foo2 : foo_t
end

module I : Intern = struct
  type foo_t = FOO | BAR | BAZ | BLUB
  let foo1 = FOO
  let foo2 = BAR
  let foo3 = BLUB
end

include I

---------------[ pack.mli ]---------------
module Foo : sig
  include Foo.Extern
end

module Bar : sig
  include Bar.Extern
end

-----------------------------------