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 JAA11577 for caml-redistribution; Tue, 8 Sep 1998 09:08:53 +0200 (MET DST)
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id RAA12433 for <caml-list@pauillac.inria.fr>; Mon, 7 Sep 1998 17:12:45 +0200 (MET DST)
Received: from margaux.inria.fr (margaux.inria.fr [128.93.8.2])
	by concorde.inria.fr (8.8.7/8.8.7) with ESMTP id RAA12031
	for <caml-list@pauillac.inria.fr>; Mon, 7 Sep 1998 17:12:44 +0200 (MET DST)
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by margaux.inria.fr (8.7.6/8.7.3) with ESMTP id RAA28626 for <caml-list@margaux.inria.fr>; Mon, 7 Sep 1998 17:12:44 +0200 (MET DST)
Received: from front1.grolier.fr (front1.grolier.fr [194.158.96.51])
	by concorde.inria.fr (8.8.7/8.8.7) with ESMTP id RAA12027
	for <caml-list@margaux.inria.fr>; Mon, 7 Sep 1998 17:12:43 +0200 (MET DST)
Received: from [194.158.109.186] (ppp-109-186.villette.club-internet.fr [194.158.109.186])
	by front1.grolier.fr (8.9.1/MGC-980407-Frontal-No_Relay) with SMTP id RAA29199
	for <caml-list@margaux.inria.fr>; Mon, 7 Sep 1998 17:12:40 +0200 (MET DST)
Message-Id: <199809071512.RAA29199@front1.grolier.fr>
Subject: right hand side of let rec
Date: Mon, 7 Sep 98 17:15:05 +0200
x-sender: lcheno@pop3.club-internet.fr
x-mailer: Claris Emailer 2.0Fv1 , 3 juillet 1997
From: Laurent Ch=?ISO-8859-1?Q?éno?= <lcheno@club-internet.fr>
To: "Caml list" <caml-list@margaux.inria.fr>
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-transfer-encoding: quoted-printable
Sender: weis

Sorry : poor-english version at the end.

Je ne comprends pas ce qui se passe avec le programme suivant :

(*****)
let ignore _ = () ;;

type 'a cycle = {	mutable val : 'a ;
					mutable pred : 'a cycle ;
					mutable succ : 'a cycle } ;;

let ajoute_au_cycle c x =
	let p = c.pred
	and s = c.succ
	in
	let r =	{ val = x ; pred = p ; succ = c }
	in
	p.succ <- r ;
	c.pred <- r ;
	r ;;

let cycle_of_list l =
	let rec r = { val = hd l ; succ = r ; pred = r }
	in
	do_list (function x -> ignore (ajoute_au_cycle r x)) (tl l) ;
	r ;;
(*****)

Caml me renvoie un message d'erreur :

#Entrée interactive:
>	let rec r = { val = hd l ; succ = r ; pred = r }
>	                    ^^^^
Ce genre d'expressions n'est pas autorisé comme membre droit d'un =
"let rec".


Bien s=FBr, j'ai contourné la difficulté en écrivant

let cycle_of_list l =
     let hd_l = hd l
     in
     let rec r = { val = hd_l ; succ = r ; pred = r }
     in
     do_list (function x -> ignore (ajoute_au_cycle r x)) (tl l) ;
     r ;;

Mais pourquoi Caml est-il si malheureux ?

Cordialement, Laurent Chéno

------- poor english

the later program causes an error : unauthorised expression in rhs of =
"let rec"
why ?