From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: * X-Spam-Status: No, score=1.4 required=5.0 tests=AWL,DNS_FROM_RFC_ABUSE, DNS_FROM_RFC_POST autolearn=disabled version=3.1.3 X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from mail1-relais-roc.national.inria.fr (mail1-relais-roc.national.inria.fr [192.134.164.82]) by yquem.inria.fr (Postfix) with ESMTP id A11A8BBAF for ; Tue, 10 Mar 2009 09:48:27 +0100 (CET) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhQCAJfGtUmYTQLKmWdsb2JhbACVKwEBAQEBCAsKBxGsa49mhAUG X-IronPort-AV: E=Sophos;i="4.38,335,1233529200"; d="scan'208";a="25329627" Received: from amazone2.ujf-grenoble.fr ([152.77.2.202]) by mail1-smtp-roc.national.inria.fr with ESMTP; 10 Mar 2009 09:48:27 +0100 Received: from tana1.ujf-grenoble.fr (tana1.ujf-grenoble.fr [152.77.18.74]) by amazone2.ujf-grenoble.fr (8.13.7/8.13.7/Configured by JE 21 07 2006) with ESMTP id n2A8m5N9035877; Tue, 10 Mar 2009 09:48:05 +0100 (CET) Received: from localhost (unknown [127.0.0.1]) by tana1.ujf-grenoble.fr (Postfix) with ESMTP id BF91E5642B; Tue, 10 Mar 2009 09:48:05 +0100 (CET) X-UJF-AV: Scanned on tana1.ujf-grenoble.fr Received: from tibre1.ujf-grenoble.fr (tibre1.ujf-grenoble.fr [152.77.18.86]) by tana1.ujf-grenoble.fr (Postfix) with ESMTP id 957965641A; Tue, 10 Mar 2009 09:48:05 +0100 (CET) Received: from fourier.ujf-grenoble.fr (fourier.ujf-grenoble.fr [152.77.212.18]) by tibre1.ujf-grenoble.fr (8.14.2/8.14.2) with ESMTP id n2A8m3bY020562; Tue, 10 Mar 2009 09:48:05 +0100 (CET) (envelope-from michaelgrunewald@yahoo.fr) Received: from localhost (localhost [127.0.0.1]) by fourier.ujf-grenoble.fr (Postfix) with ESMTP id 49022D0713; Tue, 10 Mar 2009 09:48:05 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at fourier.ujf-grenoble.fr Received: from fourier.ujf-grenoble.fr ([127.0.0.1]) by localhost (fourier.ujf-grenoble.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id WD653PBgKBiY; Tue, 10 Mar 2009 09:48:05 +0100 (CET) Received: from ifpoolext1.ujf-grenoble.fr (ifpoolext1.ujf-grenoble.fr [193.48.255.244]) by fourier.ujf-grenoble.fr (Postfix) with ESMTP id 2EA3CD01CF; Tue, 10 Mar 2009 09:48:05 +0100 (CET) Cc: David Rajchenbach-Teller , Su Zhang , caml-list@yquem.inria.fr Message-Id: <89C1F57E-4FCC-4FA6-B600-B426A2CAC326@yahoo.fr> From: =?ISO-8859-1?Q?Gr=FCnewald_Micha=EBl?= To: AUGER Cedric In-Reply-To: <49B51619.9010306@lri.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed; delsp=yes Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Apple Message framework v930.3) Subject: Re: [Caml-list] how can I express empty element? Date: Tue, 10 Mar 2009 09:47:38 +0100 References: <1236603817.18569.4.camel@Blefuscu> <49B51619.9010306@lri.fr> X-Mailer: Apple Mail (2.930.3) X-Spam: no; 0.00; cheers:01 wrote:01 caml-list:01 constructor:01 constructor:01 define:02 algebraic:03 unit:03 unit:03 element:03 element:03 ecrit:06 topological:07 probably:07 space:07 Le 9 mars 09 =E0 14:14, AUGER Cedric a =E9crit : > > David Rajchenbach-Teller wrote: >> No, that's not possible. :: is an algebraic constructor, which means, >> among other things, that it accepts no neutral element (well, except >> when the list is infinite, but that's probably not what you're =20 >> looking >> for). >> > And even if the list is infinite, I don't see any way to do it; > but you can always define: If `l' is only infinite list with type `unit list', then `l' is a =20 neutral element for `::' constructor, but only for `unit list'. (Well, that is reminiscent of your favourite =ABconsider a topological =20= space with two points, one open and one closed=BB-example, but I did not = =20 find a better one!) --=20 Cheers, Micha=EBl G.