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From: "Andreas Rossberg" <AndreasRossberg@web.de>
To: "John F. Hughes" <jfh@cs.brown.edu>, <caml-list@inria.fr>
References: <20041120041446.JDEC13256.lakermmtao10.cox.net@SPIKESHOMEPC>
Subject: Re: [Caml-list] A second functor question
Date: Sat, 20 Nov 2004 15:48:06 +0100
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John F. Hughes <jfh@cs.brown.edu> wrote:
> 
> module type COMBINE =
>    sig
>       module A : P
>       module B : P
>    end;;
>  with A.t = B.t;;
> 
> [...]
> 
> module Fun = 
>    functor (Z : COMBINE) -> 
>      struct
>         let f x:Z.A.t = Z.B.foo x 
>      end;;
> 
> This will fail because Z.B.foo expects a B.t, but is being handed an
> A.t. 

It works when you define COMBINE as

 module type COMBINE =
    sig
       module A : P
       module B : P with type t = A.t
    end

Hope this helps,

    - Andreas