From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from weis@localhost) by pauillac.inria.fr (8.6.10/8.6.6) id LAA11846 for caml-redistribution; Tue, 5 Mar 1996 11:36:21 +0100
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.6.10/8.6.6) with ESMTP id KAA10138 for <caml-list@pauillac.inria.fr>; Tue, 5 Mar 1996 10:05:48 +0100
Received: from cherub.hd.ibm.de (cherub.hd.ibm.de [192.101.197.10]) by concorde.inria.fr (8.7.1/8.7.1) with SMTP id KAA15103 for <caml-list@pauillac.inria.fr>; Tue, 5 Mar 1996 10:04:28 +0100 (MET)
Received: from kaa.heidelbg.ibm.com by cherub.hd.ibm.de (AIX 3.2/UCB 5.64/4.03/chkV1.0)
          id AA66138; Tue, 5 Mar 1996 10:04:02 +0100
Received: from idse.heidelbg.ibm.com by kaa.heidelbg.ibm.com (AIX 3.2/UCB 5.64/4.03)
          id AA31350; Tue, 5 Mar 1996 10:03:35 +0100
Received: by idse.heidelbg.ibm.com (AIX 3.2/UCB 5.64/4.03)
          id AA36425; Tue, 5 Mar 1996 10:03:34 +0100
Message-Id: <9603050903.AA36425@idse.heidelbg.ibm.com>
To: Xavier Leroy <Xavier.Leroy@inria.fr>
Cc: Guy.Cousineau@ens.fr, caml-list@pauillac.inria.fr
Subject: Re: CSL modules 
In-Reply-To: (Your message of Mon, 04 Mar 96 15:05:49 N.)
             <199603041405.PAA26261@pauillac.inria.fr> 
Date: Tue, 05 Mar 96 10:03:33 +0100
From: Wolfgang Lux <lux@heidelbg.ibm.com>
Sender: weis


> This is easily done using a signature constraint to specify exactly
> how much of C should remain visible:
> 
> module type SIGA =
>   sig
>     type ta = A | B of int
>     val xa : ta
>   end
> module type SIGB =
>   sig
>     type tb = C | D of string
>     val xb : tb
>   end
> 

[ alternate (and better) definition of SIGC and F deleted]

> module type SIGC =
>   sig
>     type ta = A.ta              (* concrete *)
>     type tb                     (* abstract *)
>     val xa : ta
>     val xb : tb
>   end
> module F(A: SIGA)(B: SIGB) =
>   (struct
>      type ta = A.ta
>      type tb = B.tb
>      let xa = A.xa
>      let xb = B.xb
>    end : SIGC)
> module C = F(A)(B)
> 

Being curious I tried this and got an error from CSL 1.14, which I
really don't understand. After defining SIGA and SIGB and the
following two sample modules

module A : SIGA =
  struct
    type ta = A | B of int
    let xa = B 4
  end
module B : SIGB =
  struct
    type tb = C | D of string
    let xb = D "hello"
  end

I can define SIGC, but when I enter the definition of F, CSL returns
the following error:

Signature mismatch:
Modules do not match:
  sig type ta = A.ta type tb = B.tb val xa : A.ta val xb : B.tb end
is not included in
  SIGC
Type declarations do not match:
  type ta = A.ta
is not included in
  type ta = A.ta

Any clues?

Wolfgang

----
Wolfgang Lux
WZH Heidelberg, IBM Germany             Internet: lux@heidelbg.ibm.com
+49-6221-59-4546                        VNET:     LUX at HEIDELBG
+49-6221-59-3500 (fax)	                EARN:     LUX at DHDIBMIP