From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Andy Moreton Newsgroups: gmane.emacs.devel Subject: Re: 7 logical-xor implementations in source tree Date: Tue, 30 Jul 2019 12:28:53 +0100 Message-ID: References: <87tvbd9a8p.fsf@oremacs.com> <87pnm14u95.fsf@tcd.ie> <87sgqvoz5c.fsf@tcd.ie> <87d0hz2e11.fsf@tcd.ie> <5B633129-B795-4BFA-AE81-FE9FD0A24CE9@acm.org> <0edfffbb-6f5a-a6b2-334a-9000e8f2eb3e@gmail.com> <20190728080417.GA5072@ACM> <875znm3q19.fsf@mbork.pl> <20190730093651.GA5427@ACM> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="163572"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2.90 (windows-nt) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Jul 30 13:29:14 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hsQJc-000gS6-7k for ged-emacs-devel@m.gmane.org; Tue, 30 Jul 2019 13:29:12 +0200 Original-Received: from localhost ([::1]:59866 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQJa-0001jx-UM for ged-emacs-devel@m.gmane.org; Tue, 30 Jul 2019 07:29:11 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:52823) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQJW-0001jr-9I for emacs-devel@gnu.org; Tue, 30 Jul 2019 07:29:07 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hsQJV-00007o-CY for emacs-devel@gnu.org; Tue, 30 Jul 2019 07:29:06 -0400 Original-Received: from 195-159-176-226.customer.powertech.no ([195.159.176.226]:55286 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hsQJV-00007X-3t for emacs-devel@gnu.org; Tue, 30 Jul 2019 07:29:05 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.89) (envelope-from ) id 1hsQJQ-000gE9-VK for emacs-devel@gnu.org; Tue, 30 Jul 2019 13:29:00 +0200 X-Injected-Via-Gmane: http://gmane.org/ Cancel-Lock: sha1:su16NixcmhiFxJxKZ4n0Glhm7VU= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 195.159.176.226 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:239022 Archived-At: On Tue 30 Jul 2019, Philippe Schnoebelen wrote: > On 2019/07/30 11:36, Alan Mackenzie wrote: >> Less importantly, I don't like iff being used in this way. I'm not sure >> why. > > Pros: (1) short (like and & xor) > >         (2) exactly what we mean when writing assertions in code > >            e.g.      (cl-assert (iff (listp arg) (listp res))) > >             e.g.     (should (iff  (= b (max a b))   (<= a b)  )) > > Cons: (1) name not known outside of mathematicians; > >           (2) is an acronym > >           (3) is not purely boolean, has order of evaluation, allows > side-effects (like and & or) > > --Philippe Please do not add `iff' as a symbol under any circumstance. Short names must be universally understood by readers of the code with a wide range of expertise and experience. A short name must also be needed due to frequent use in typical code. This usage meets neither test. AndyM