From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Neon Absentius Newsgroups: gmane.emacs.help Subject: Re: Non-commutative symbolic multiplication in Calc Date: Tue, 6 Sep 2005 17:07:19 +0000 Message-ID: <20050906170719.GA12694@SDF.LONESTAR.ORG> References: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1126026772 20155 80.91.229.2 (6 Sep 2005 17:12:52 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Tue, 6 Sep 2005 17:12:52 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue Sep 06 19:12:43 2005 Return-path: Original-Received: from lists.gnu.org ([199.232.76.165]) by ciao.gmane.org with esmtp (Exim 4.43) id 1ECgxR-00050l-V0 for geh-help-gnu-emacs@m.gmane.org; Tue, 06 Sep 2005 19:10:06 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ECh1x-0007op-0u for geh-help-gnu-emacs@m.gmane.org; Tue, 06 Sep 2005 13:14:45 -0400 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1ECh12-0007LG-6I for help-gnu-emacs@gnu.org; Tue, 06 Sep 2005 13:13:48 -0400 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1ECh0x-0007JV-Pu for help-gnu-emacs@gnu.org; Tue, 06 Sep 2005 13:13:44 -0400 Original-Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ECh0x-0007Ho-Ho for help-gnu-emacs@gnu.org; Tue, 06 Sep 2005 13:13:43 -0400 Original-Received: from [192.94.73.21] (helo=sdf.lonestar.org) by monty-python.gnu.org with esmtp (Exim 4.34) id 1ECgz1-00035k-Hy for help-gnu-emacs@gnu.org; Tue, 06 Sep 2005 13:11:43 -0400 Original-Received: from sdf.lonestar.org (IDENT:absent@otaku.freeshell.org [192.94.73.2]) by sdf.lonestar.org (8.13.1/8.12.10) with ESMTP id j86H7JOH000045 for ; Tue, 6 Sep 2005 17:07:19 GMT Original-Received: (from absent@localhost) by sdf.lonestar.org (8.13.1/8.12.8/Submit) id j86H7Jf2000574 for help-gnu-emacs@gnu.org; Tue, 6 Sep 2005 17:07:19 GMT Original-To: help-gnu-emacs@gnu.org Mail-Followup-To: Neon Absentius , help-gnu-emacs@gnu.org Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i 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:29258 Archived-At: On Tue, Sep 06, 2005 at 04:09:36PM +0200, Roland Winkler wrote: > Neon Absentius writes: > > > Sorry if this is not the right list for this question. > > > > Is there a way to suspend some of the automatic simplifications that > > calc performs? In particular I am interested in suspending the > > assumption that multiplication is commutative. This would allow for > > symbolic calculations with entities that are not necessarily numbers > > or elements of some vector space. > > It's a pretty tricky issue to get useful results when doing > analytical calculations with noncommuting variables. It seems to me that is tricky to get useful results when doing any calculations! In any case I am mostly interested in algebraic rather than analytic results. > I doubt that you will get what you want when you just remove the > assumption that multiplication is commutative. Depends on what do you mean by "just" by "remove" and by "assumption". When I say "suspend the assumption" I mean (obviously) to also suspend its consequences, for example there should be a "left" and a "right" division. It depends also on what I want, which (at the moment of writing at least) is rather modest, I will be happy if I am able to work on a free group (or a tensor algebra) and define relations as rewrite rules. Ideally the multiplication should not be assumed commutative (or the variables invertible) unless explicitly declared so. > > Roland -- Most precious among the relics remaining of Peter's skeleton in the Vatican are 29 fragments of one of his skulls. (St. Peter's other skull is preserved in a reliquary at the Cathedral of St. John Lateran.) -- Frank R. Zindler, "Of Bones and Boners"