From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Jay Belanger Newsgroups: gmane.emacs.help Subject: Re: Non-Commutative calculations in Calc, Revisited Date: Thu, 06 Oct 2005 11:17:09 -0500 Organization: Posted via Supernews, http://www.supernews.com Message-ID: <87ek6y4o3e.fsf@vh213602.truman.edu> References: <878xx66b1c.fsf@vh213602.truman.edu> <851x2yu5gv.fsf@lola.goethe.zz> Reply-To: belanger@truman.edu NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1128615782 23913 80.91.229.2 (6 Oct 2005 16:23:02 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 6 Oct 2005 16:23:02 +0000 (UTC) Cc: belanger@truman.edu Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Oct 06 18:23:00 2005 Return-path: Original-Received: from lists.gnu.org ([199.232.76.165]) by ciao.gmane.org with esmtp (Exim 4.43) id 1ENYUT-0000Wx-Us for geh-help-gnu-emacs@m.gmane.org; Thu, 06 Oct 2005 18:21:06 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ENYUT-0005of-7z for geh-help-gnu-emacs@m.gmane.org; Thu, 06 Oct 2005 12:21:05 -0400 Original-Path: shelby.stanford.edu!newsfeed.stanford.edu!newsfeed.berkeley.edu!ucberkeley!sn-xit-02!sn-xit-06!sn-post-01!supernews.com!corp.supernews.com!not-for-mail Original-Newsgroups: gnu.emacs.help User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux) Cancel-Lock: sha1:17cU6/iWE0OI15i+/YxVaa5Insg= Original-X-Complaints-To: abuse@supernews.com Original-Lines: 22 Original-Xref: shelby.stanford.edu gnu.emacs.help:134407 Original-To: help-gnu-emacs@gnu.org X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:29982 Archived-At: David Kastrup writes: > Jay Belanger writes: > >> Neon Absentius writes: >> >>> When in non-commutative (aka `matrix') mode calc calculates >>> (a b)^-1 to be a^-1 b^-1 instead of the correct b^-1 a^-1. > > Uh, what's correct about b^-1 a^-1? > > Set a=[1,1], b=[1;0], then (a b)^-1 = [1], and neither b^-1 nor a^-1 > exist. > > This only works with a and b being square matrices. Oops; you're right. Of course, the proper fix will no longer give the general non-commutative operations that Neon wants to work with. Perhaps a square matrix option should be made to the Calc matrix modes. Jay