From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#40671: [DOC] modify literal objects Date: Fri, 24 Apr 2020 18:39:29 +0200 Message-ID: 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 (Mac OS X Mail 12.4 \(3445.104.14\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="123347"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Michael Heerdegen , ke.vigouroux@laposte.net, eggert@cs.ucla.edu, 40671@debbugs.gnu.org To: Richard Stallman Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Apr 24 18:40:11 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 1jS1N5-000VxV-4w for geb-bug-gnu-emacs@m.gmane-mx.org; 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Fri, 24 Apr 2020 12:39:53 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1587746373; bh=WiOXY+XarX7wQ62iKxR98YDnCrSTW2fgFGSDd8iyCMM=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=nTNe9VtkNSYEuWnp/V7x8jMAIkhOepYI7Oe48kzbrL/s8rLRQVyivpYkutTWVsa5/ NStw1i0vHgHeVP6po1jp9X4uzhWJV8NhkBxdTDSlyPldDAwcDBTPREbeq8cLvbkkWP VpV7dL4PopsDuhnAocu4bAOaSs+ReblRuttdFWgU= Feedback-ID: mattiase@acm.or Original-Received: from stanniol.lan (c-4e4ae655.032-75-73746f71.bbcust.telenor.se [85.230.74.78]) (authenticated bits=0) by mail268c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 03OGdUsW026397; Fri, 24 Apr 2020 16:39:31 +0000 In-Reply-To: X-Mailer: Apple Mail (2.3445.104.14) X-CTCH-RefID: str=0001.0A782F19.5EA31645.005B, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-CSC: 0 X-CHA: v=2.3 cv=BZ+mLYl2 c=1 sm=1 tr=0 a=klNLuyVZdLUgl+K5Uafb2A==:117 a=klNLuyVZdLUgl+K5Uafb2A==:17 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=mDV3o1hIAAAA:8 a=GuW4MMiu9jjuFNPyENIA:9 a=CjuIK1q_8ugA:10 a=_FVE-zBwftR9WsbkzFJk:22 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:178942 Archived-At: 24 apr. 2020 kl. 04.36 skrev Richard Stallman : > It seems strange to use the terms "constant" and "mutable" to describe > whether modifying its contents is something you had better avoid. > I think people will find that terminology confusing. Normally > "mutable" means that you CAN change it, not that it is OK to change = it. 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. Implementation-wise, it's whether there are = strong checks or not. (For example, in C you should not read from = already freed memory, but there is no mechanism actually preventing you = from doing so.) 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. Of course the real world is messy and people sometimes have code that = breaks the rules but still seem to work. There would need to be a = transition period, and a switch to run in a permissive mode.