From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11043 invoked by alias); 8 Apr 2005 22:16:33 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 9751 invoked by uid 48); 8 Apr 2005 22:14:10 -0000 Date: Fri, 08 Apr 2005 22:16:00 -0000 Message-ID: <20050408221410.9750.qmail@sourceware.org> From: "kreckel at ginac dot de" To: gcc-bugs@gcc.gnu.org In-Reply-To: <20050404213802.20758.kreckel@ginac.de> References: <20050404213802.20758.kreckel@ginac.de> Reply-To: gcc-bugzilla@gcc.gnu.org Subject: [Bug libstdc++/20758] operator-(const T&, const complex&) vs operator-(const complex&, const complex&) X-Bugzilla-Reason: CC X-SW-Source: 2005-04/txt/msg01089.txt.bz2 List-Id: ------- Additional Comments From kreckel at ginac dot de 2005-04-08 22:14 ------- (In reply to comment #20) > Thatis the mathematical question/answer. The real issue is this: > > * in operator-(const T&, const complex&), should the imaginary > part eve be touched? > > there are vairous ansewrs. And, yes we've been using our brains. I don't understand. What definition of "touched" is meant here? Of course, some sort of "touching" needs to be done because at least for imag(rhs)!=0 we want to flip the sign bit. > | BTW: I've always tought that systems that distinguish between 0.0 and -0.0, but > | not between 0.0 and +0.0 are slightly broken from a mathematical point of view. > > If you ask me, any system with signed zeros is broken, to start with. Actually, I'm surprised to hear that from you since I was under the impression that all numerical analysis folks have been smoking Kahan's crack pipe. :-) BTW, I can't find my copy of Kahan's old "Much Ado..." paper. Does anyone know of a downloadable copy? I tried to google for it, but had no luck. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20758