From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <d@doomeer.com>
X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr
X-Spam-Level: 
X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled 
	version=3.1.3
Received: from discorde.inria.fr (discorde.inria.fr [192.93.2.38])
	by yquem.inria.fr (Postfix) with ESMTP id 72415BC0A
	for <caml-list@yquem.inria.fr>; Thu, 24 May 2007 13:31:30 +0200 (CEST)
Received: from ext.lri.fr (ext.lri.fr [129.175.15.4])
	by discorde.inria.fr (8.13.6/8.13.6) with ESMTP id l4OBVUkw030647
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO)
	for <caml-list@yquem.inria.fr>; Thu, 24 May 2007 13:31:30 +0200
Received: from smtp.lri.fr (serveur3-5 [129.175.3.5])
	by ext.lri.fr (Postfix) with ESMTP id D40132020D7;
	Thu, 24 May 2007 13:31:29 +0200 (CEST)
Received: from [129.175.4.129] (lri4-129 [129.175.4.129])
	by smtp.lri.fr (Postfix) with ESMTP
	id 25376CED98; Thu, 24 May 2007 13:31:29 +0200 (CEST)
Message-ID: <46557792.5090207@doomeer.com>
Date: Thu, 24 May 2007 13:31:30 +0200
From: Romain <d@doomeer.com>
User-Agent: Thunderbird 1.5.0.9 (X11/20070104)
MIME-Version: 1.0
To: Niko Matsakis <niko@alum.mit.edu>
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Extracting common information
References: <E7A015DC-1733-4752-BE63-78113DBA3D5B@alum.mit.edu>
In-Reply-To: <E7A015DC-1733-4752-BE63-78113DBA3D5B@alum.mit.edu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Virus-Scanned: by amavisd-new at lri.fr
X-Miltered: at discorde with ID 46557792.000 by Joe's j-chkmail (http://j-chkmail . ensmp . fr)!
X-Spam: no; 0.00; pointer:01 node:01 node:01 pointer:01 expr:01 expr:01 userdata:98 userdata:98 caml-list:01 binary:01 data:02 data:02 tree:02 tree:02 match:02 

Hi,

Note that you can replace your pattern-matching with something like:

let ud_type type =
   match type with
     Primitive(ud,_)
   | Pointer(ud,_) -> ud

But although it is more factorized (which is good) it doesn't solve your 
problem.

One solution which I like better is something like:

type userdata = ... whatever you want (code location...) ...
type 'a node = {
   user_data: userdata;
   node: 'a;
}
type type_tree =
   Primitive of string
| Pointer of type_tree node
type expr_tree =
   Unary of string * expr_tree node
| Binary of string * expr_tree node * expr_tree node

Now instead of matching on a type_tree x, you'll match on x.node. And if 
you want the user data you just use x.user_data.

Hope it helps.

-- 
Romain Bardou