From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Dmitry Gutov Newsgroups: gmane.emacs.bugs Subject: bug#40671: [DOC] modify literal objects Date: Fri, 24 Apr 2020 19:46:38 +0300 Message-ID: <93463227-33a8-85a0-fd19-8b29b75997f3@yandex.ru> References: <83tv1finob.fsf@gnu.org> <1E9E4C19-37C2-4E24-91B7-8101F9CFBF35@acm.org> <527dc4b5-3176-38b5-f2c1-1483ffc814a1@cs.ucla.edu> <87k12b6sv2.fsf@web.de> <2225099d-16e1-645d-0342-a054da53363f@cs.ucla.edu> <87a7376nv9.fsf@web.de> <99d7a8f9-7732-e1e3-414e-aabbea4433ac@cs.ucla.edu> <87o8rnasfk.fsf@web.de> <9e6c138d-cb9f-6075-34df-a8d1d931343b@cs.ucla.edu> <871rofxbz9.fsf@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="24354"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 Cc: Michael Heerdegen , ke.vigouroux@laposte.net, eggert@cs.ucla.edu, 40671@debbugs.gnu.org To: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= , Richard Stallman Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Apr 24 18:47:13 2020 Return-path: Envelope-to: geb-bug-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 1jS1Tt-0006FQ-S5 for geb-bug-gnu-emacs@m.gmane-mx.org; 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Fri, 24 Apr 2020 09:46:41 -0700 (PDT) Original-Received: from [192.168.0.2] ([66.205.73.129]) by smtp.googlemail.com with ESMTPSA id i129sm3781799wmi.20.2020.04.24.09.46.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Apr 2020 09:46:41 -0700 (PDT) In-Reply-To: Content-Language: en-US X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-Received-From: 209.51.188.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:178944 Archived-At: On 24.04.2020 19:39, Mattias Engdegård wrote: > That is an interesting point. What is the difference between CANNOT and SHOULD NOT, operationally? To the user, nothing; there is no gain from disobeying our advice. The difference is at runtime, obviously. And the problem is using the words in a way that differs from other programming languages, for instance. > It's useful to have the option to add strong checks, so that (setcar '(1 . 2) 3) throws an error. Then, what used to be SHOULD NOT turns into CANNOT, but the attentive user has no reason to change behaviour. *If* we do that, we could call them constants. But I imagine we never will, for backward compatibility reasons. Emacs core itself modifies these "constants" at runtime in quite a few places, I'm sure.