From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from weis@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id XAA11122 for caml-red; Sun, 16 Jul 2000 23:59:52 +0200 (MET DST)
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id NAA20630 for <caml-list@pauillac.inria.fr>; Tue, 11 Jul 2000 13:32:44 +0200 (MET DST)
Received: from air.irisa.fr (air.irisa.fr [131.254.60.130])
	by nez-perce.inria.fr (8.10.0/8.10.0) with ESMTP id e6BBWib23717
	for <caml-list@inria.fr>; Tue, 11 Jul 2000 13:32:44 +0200 (MET DST)
Received: from parate.irisa.fr (parate.irisa.fr [131.254.12.25])
	by air.irisa.fr (8.9.3/8.9.3) with ESMTP id NAA17280
	for <caml-list@inria.fr>; Tue, 11 Jul 2000 13:32:40 +0200 (MET DST)
To: caml-list@inria.fr
Subject: [newbie] Define and use records in sum types
From: David.Mentre@irisa.fr (David=?iso-8859-1?q?_Mentr=E9?=)
Date: 11 Jul 2000 13:32:40 +0200
Message-ID: <wd8d7kkewbr.fsf@parate.irisa.fr>
User-Agent: Gnus/5.0805 (Gnus v5.8.5) Emacs/20.6
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: weis@pauillac.inria.fr

Hello dear camlists,

I have problems with basic record and sum types use.

I would like to define a sum type with records as constructor
parameters, records with the same field names. 

I have tried the follwing definition:

<ocaml>
# type asp = A of { name : string } | B of { name : string ; ext : int };;
                  -
Syntax error
</ocaml>

However, I can use intermediate names:

<ocaml>
# type a_rec = { name : string };;
type a_rec = { name : string; } 
# type b_rec = { name : string ; ext : int };;
type b_rec = { name : string; ext : int; } 
# type asp = A of a_rec | B of b_rec ;;
type asp = A of a_rec | B of b_rec
</ocaml>

It *seems* to work but, in fact, the a_rec definition is masked by b_rec
definition:

<ocaml>
# let a_b = B({name = "n" ; ext=3 }) ;;
val a_b : asp = B {name="n"; ext=3}
# let an_a = A({name="n"});;
               ----------
Some record field labels are undefined
</ocaml>

So my question is: is it possible to define a sum of records with the
same field names? 


The rationale behind this question: I find records more clear that
tuples in source code.


Best regards,
david
-- 
 David.Mentre@irisa.fr -- http://www.irisa.fr/prive/dmentre/
 Opinions expressed here are only mine.