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Message-ID: <4BF46D09.1000206@frisch.fr>
Date: Thu, 20 May 2010 00:58:17 +0200
From: Alain Frisch <alain@frisch.fr>
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To: caml-list <caml-list@yquem.inria.fr>
Subject: Re: [Caml-list] recursive module and types
References: <4BF3D87D.6010805@univ-savoie.fr>
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X-Spam: no; 0.00; frisch:01 frisch:01 recursive:01 christophe:01 raffalli:01 sig:01 val:01 struct:01 node:01 node:01 elt:01 sig:01 wrote:01 rec:01 caml-list:01 

On 05/19/2010 02:24 PM, Christophe Raffalli wrote:
> Does anyone see a way to avoid it

I propose:


module rec T : sig
   type t = U.t
   val compare : t -> t -> int
end = struct
   include U

   let compare u v = match u, v with
     Leaf, Leaf -> 0
   | Node u', Node v' -> S.compare u' v'
   | Leaf, Node _ -> -1
   | Node _, Leaf -> 1
end

and S : Set.S with type elt = T.t = Set.Make(T)

and U : sig
   type t =
     Node of S.t
   | Leaf
end = U


The type definition is given only once.


-- Alain