From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Drew Adams Newsgroups: gmane.emacs.devel Subject: RE: 7 logical-xor implementations in source tree Date: Wed, 31 Jul 2019 15:03:02 -0700 (PDT) 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> <7n36iny4yq.fsf@ecube.ecubist.org> <7nftmmkz83.fsf@ecube.ecubist.org> <87y30e6j5b.fsf@web.de> <4de86e2c-18ab-4cf1-9a70-e43310234ad0@default> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="11477"; mail-complaints-to="usenet@blaine.gmane.org" Cc: emacs-devel@gnu.org To: Michael Heerdegen , Barry Fishman Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Aug 01 00:03:33 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 1hswh3-0002qw-Kt for ged-emacs-devel@m.gmane.org; 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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:239069 Archived-At: > Is it hard to understand (eq (not a) (not b))? Well, someone off list pointed out that that is (not (xor a b)); it is not (xor a b). Yes, of course. I thought it'd be enough to speak to the general thing under discussion, for which opposite-value names such as "equiv", "iff", and `<=3D>' were proposed. But to be more pedantic/correct, is it hard to=20 understand (not (eq (not a) (not b)))? Or if you prefer, (eq (not a) (not (not b)))? Is lack of an `xor' (or an `equiv') operator a problem in practice? How often have you felt the need for it, really? Why do you think Emacs Lisp, which was by design=20 smaller than Common Lisp, needs such a function, but Common Lisp does not? What's the special need we have for this?