From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20637 invoked from network); 17 Jun 2008 15:06:11 -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 15:06:11 -0000 Received-SPF: none (ns1.primenet.com.au: domain at sunsite.dk does not designate permitted sender hosts) Received: (qmail 73271 invoked from network); 17 Jun 2008 15:06:08 -0000 Received: from sunsite.dk (130.225.247.90) by a.mx.sunsite.dk with SMTP; 17 Jun 2008 15:06:08 -0000 Received: (qmail 15111 invoked by alias); 17 Jun 2008 15:06:06 -0000 Mailing-List: contact zsh-workers-help@sunsite.dk; run by ezmlm Precedence: bulk X-No-Archive: yes X-Seq: 25200 Received: (qmail 15100 invoked from network); 17 Jun 2008 15:06:05 -0000 Received: from bifrost.dotsrc.org (130.225.254.106) by sunsite.dk with SMTP; 17 Jun 2008 15:06:05 -0000 Received: from prunille.vinc17.org (vinc17.pck.nerim.net [213.41.242.187]) by bifrost.dotsrc.org (Postfix) with ESMTP id 32B6F8028AC3 for ; Tue, 17 Jun 2008 17:05:55 +0200 (CEST) Received: by prunille.vinc17.org (Postfix, from userid 501) id EDD812350CC8; Tue, 17 Jun 2008 17:05:54 +0200 (CEST) Date: Tue, 17 Jun 2008 17:05:54 +0200 From: Vincent Lefevre To: Zsh hackers list Cc: Richard Hartmann , Peter Stephenson Subject: Re: arithmetic operator precedence Message-ID: <20080617150554.GR10734@prunille.vinc17.org> Mail-Followup-To: Zsh hackers list , Richard Hartmann , Peter Stephenson References: <20080616144211.276fb0e3@pws-pc> <2d460de70806170219k12ff4cadn441b52c48bf8076f@mail.gmail.com> <20080617094509.GC5016@sc.homeunix.net> <20080617111934.GE10734@prunille.vinc17.org> <20080617115742.GE5016@sc.homeunix.net> <20080617123551.GJ10734@prunille.vinc17.org> <20080617124607.GH5016@sc.homeunix.net> <20080617130246.GL10734@prunille.vinc17.org> <20080617132039.GK5016@sc.homeunix.net> <20080617143559.GP5016@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: <20080617143559.GP5016@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 15:35:59 +0100, Stephane Chazelas wrote: > It can't be that simple though, as in > > x=-1; $((1 x)) > > which would be POSIX but fails in all shells. No, $((1 x)) is an invalid expression (unless the shell sees this as an extension), so POSIX requires it to fail. This is different from $((1 $x)), where the expansion of $x occurs first. > Or > > x=1; $((x = 1 + x)) > > which obviously is not meant to be the same as $(($x = 1 + $x)) So? What's the problem with them not being the same? Note that POSIX says: The shell shall expand all tokens in the expression for parameter ^^^^^^^^^ expansion, command substitution, and quote removal. ^^^^^^^^^ Next, the shell shall treat this as an arithmetic expression ^^^^ In the first case, the expression is x = 1 + x. In the second case, it is 1 = 1 + 1. > So that > > If the shell variable x contains a value that forms a valid > integer constant, then the arithmetic expansions "$((x))" and > "$(($x))" shall return the same value. > > says either too little or too much to be useful. I agree that this isn't perfect (BTW, see my mail in the Austin group when it appears -- I haven't received a copy yet). -- Vincent Lefèvre - Web: 100% accessible validated (X)HTML - Blog: Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)