From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Jean Louis Newsgroups: gmane.emacs.help Subject: (*) -> 1 Date: Tue, 17 Jan 2023 08:46:14 +0300 Message-ID: References: <87r0vuidjc.fsf@eder.anydns.info> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="2908"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/2.2.9+54 (af2080d) (2022-11-21) Cc: Andreas Eder , Anders Munch , "help-gnu-emacs@gnu.org" To: Eduardo Ochs Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Jan 17 16:06:45 2023 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1pHnXw-0000Ux-4E for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 17 Jan 2023 16:06:44 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pHnXZ-00087L-Kg; Tue, 17 Jan 2023 10:06:21 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pHnXV-00080y-08 for help-gnu-emacs@gnu.org; Tue, 17 Jan 2023 10:06:17 -0500 Original-Received: from stw1.rcdrun.com ([217.170.207.13]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pHnXS-0000zJ-Hu for help-gnu-emacs@gnu.org; Tue, 17 Jan 2023 10:06:16 -0500 Original-Received: from localhost ([::ffff:102.85.233.9]) (AUTH: PLAIN admin, TLS: TLS1.3,256bits,ECDHE_RSA_AES_256_GCM_SHA384) by stw1.rcdrun.com with ESMTPSA id 00000000000561BA.0000000063C6B967.00000F81; Tue, 17 Jan 2023 08:06:14 -0700 Mail-Followup-To: Eduardo Ochs , Andreas Eder , Anders Munch , "help-gnu-emacs@gnu.org" Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=217.170.207.13; envelope-from=bugs@gnu.support; helo=stw1.rcdrun.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_06_12=1.543, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.help:142307 Archived-At: * Eduardo Ochs [2023-01-17 05:39]: > a few months ago I had to prepare some figures to explain to my > students what should be the "neutral elements" for some operations... > The main idea is that we want all these expressions to yield the same > result, including the two last ones, that are weird, > > (+ (+ 2 2) (+ 2 2 2 2 2)) > (+ (+ 2 2 2) (+ 2 2 2 2)) > (+ (+ 2 2 2 2) (+ 2 2 2)) > (+ (+ 2 2 2 2 2) (+ 2 2)) > (+ (+ 2 2 2 2 2 2) (+ 2)) > (+ (+ 2 2 2 2 2 2 2) (+)) That still does not make sense to me. I translate that to ordinary notation: (2 + 2) + (2 + 2 + 2 + 2 + 2) (2 + 2 + 2) + (2 + 2 + 2 + 2) (2 + 2 + 2 + 2) + (2 + 2 + 2) (2 + 2 + 2 + 2 + 2) + (2 + 2) (2 + 2 + 2 + 2 + 2 + 2) + 2 (2 + 2 + 2 + 2 + 2 + 2 + 2) + -- this is impossible situation as summand is missing because "14 + " lacks summand. There must be some number first. People speak how Lisp follows mathematical conventions, but obviously it follows some, but not all. Convention in multiplication is that there must be two numbers, that is not followed, something else is followed. The reason behind is what? > and my real objective was to convince them that we had very good > reasons to decide that the result of (or) should be false the result > of (and) should be true, and then extend these ideas to "for all" and > "exists". I wish I could see that good reason. Just by placing (+) and expecting it to yield something is not clear that it is good reason. I expect it then also here, but it does not work: (/ (/ 2 2) (/)) So the above alone can't explain my why is it that Lisp uses identities. -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/