From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12861 invoked from network); 17 Jun 2008 11:38:46 -0000 X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on f.primenet.com.au X-Spam-Level: X-Spam-Status: No, score=-2.6 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.2.4 Received: from news.dotsrc.org (HELO a.mx.sunsite.dk) (130.225.247.88) by ns1.primenet.com.au with SMTP; 17 Jun 2008 11:38:46 -0000 Received-SPF: none (ns1.primenet.com.au: domain at sunsite.dk does not designate permitted sender hosts) Received: (qmail 73376 invoked from network); 17 Jun 2008 11:38:43 -0000 Received: from sunsite.dk (130.225.247.90) by a.mx.sunsite.dk with SMTP; 17 Jun 2008 11:38:43 -0000 Received: (qmail 18088 invoked by alias); 17 Jun 2008 11:38:40 -0000 Mailing-List: contact zsh-workers-help@sunsite.dk; run by ezmlm Precedence: bulk X-No-Archive: yes X-Seq: 25182 Received: (qmail 18070 invoked from network); 17 Jun 2008 11:38:39 -0000 Received: from bifrost.dotsrc.org (130.225.254.106) by sunsite.dk with SMTP; 17 Jun 2008 11:38:39 -0000 Received: from prunille.vinc17.org (vinc17.pck.nerim.net [213.41.242.187]) by bifrost.dotsrc.org (Postfix) with ESMTP id 20B948028AC3 for ; Tue, 17 Jun 2008 13:38:32 +0200 (CEST) Received: by prunille.vinc17.org (Postfix, from userid 501) id 807C7235015B; Tue, 17 Jun 2008 13:38:32 +0200 (CEST) Date: Tue, 17 Jun 2008 13:38:32 +0200 From: Vincent Lefevre To: Zsh hackers list Cc: Richard Hartmann , Peter Stephenson Subject: Re: arithmetic operator precedence Message-ID: <20080617113832.GG10734@prunille.vinc17.org> Mail-Followup-To: Zsh hackers list , Richard Hartmann , Peter Stephenson References: <20080612095723.GF5113@sc.homeunix.net> <20080616080726.GP10734@prunille.vinc17.org> <20080616144211.276fb0e3@pws-pc> <2d460de70806170219k12ff4cadn441b52c48bf8076f@mail.gmail.com> <20080617094509.GC5016@sc.homeunix.net> <2d460de70806170324o5a44609x9383cc2445d67dd6@mail.gmail.com> <20080617103829.GD5016@sc.homeunix.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20080617103829.GD5016@sc.homeunix.net> X-Mailer-Info: http://www.vinc17.org/mutt/ User-Agent: Mutt/1.5.18-vl-r22984 (2008-06-11) X-Virus-Scanned: ClamAV 0.92.1/7494/Tue Jun 17 06:46:03 2008 on bifrost X-Virus-Status: Clean On 2008-06-17 11:38:29 +0100, Stephane Chazelas wrote: > What I meant is that ^ reminds of the /human/ (as opposed to > /computer/) representation as it indicates that follows must be > raised up as in 3². So, one can understand that it should follow > the same rules (that is -3^2 should be the same as -3², even > though that's not what POSIX decided for bc). But given that ** > has more the shape of the * operator, I'm not sure we can tell > the same thing. Note that in math, -(a * b) and (-a) * b are equivalent (even in the general case of a ring), and I'd say that most people regard - a * b more like -(a * b) than (-a) * b. So, you can't really compare to * without confusion. Also ** is merely a replacement for the more conventional (and shorter) ^ when ^ can't be used (e.g. because it already has another meaning). Math writing asside, the fact that -3**2 and 0-3**2 return different results is quite confusing too. -- Vincent Lefèvre - Web: 100% accessible validated (X)HTML - Blog: Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)