From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#12314: 24.2.50; `add-to-history': use `setq' with `delete' Date: Sun, 09 Sep 2012 00:21:57 +0300 Message-ID: <837gs4mcqy.fsf@gnu.org> References: <7602D24B74DE42CF9901322634B85CA2@us.oracle.com> <87sjas4mc2.fsf@gnu.org> <83ipbomv6e.fsf@gnu.org> <2C45207ADF0E46BC98AF1B486695F632@us.oracle.com> <83fw6smti6.fsf@gnu.org> <9A8F619FD7584123A6319BD089E444E4@us.oracle.com> <83bohgmrdv.fsf@gnu.org> <83a9x0mq5e.fsf@gnu.org> <8E40573C868D4B339513A16A02588F5E@us.oracle.com> Reply-To: Eli Zaretskii NNTP-Posting-Host: plane.gmane.org X-Trace: ger.gmane.org 1347139365 24351 80.91.229.3 (8 Sep 2012 21:22:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 8 Sep 2012 21:22:45 +0000 (UTC) Cc: 12314@debbugs.gnu.org, cyd@gnu.org To: Drew Adams Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sat Sep 08 23:22:47 2012 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TASUH-0005rg-Gu for geb-bug-gnu-emacs@m.gmane.org; Sat, 08 Sep 2012 23:22:45 +0200 Original-Received: from localhost ([::1]:43407 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TASUE-0006mW-7Z for geb-bug-gnu-emacs@m.gmane.org; Sat, 08 Sep 2012 17:22:42 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:55731) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TASUA-0006la-Qt for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 17:22:39 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TASU9-00063W-GX for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 17:22:38 -0400 Original-Received: from debbugs.gnu.org ([140.186.70.43]:39587) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TASU9-00063Q-Dt for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 17:22:37 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.72) (envelope-from ) id 1TASUY-0005LV-Cw for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 17:23:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: debbugs-submit-bounces@debbugs.gnu.org Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 08 Sep 2012 21:23:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 12314 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 12314-submit@debbugs.gnu.org id=B12314.134713935520515 (code B ref 12314); Sat, 08 Sep 2012 21:23:02 +0000 Original-Received: (at 12314) by debbugs.gnu.org; 8 Sep 2012 21:22:35 +0000 Original-Received: from localhost ([127.0.0.1]:49133 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.72) (envelope-from ) id 1TASU7-0005Kq-AX for submit@debbugs.gnu.org; Sat, 08 Sep 2012 17:22:35 -0400 Original-Received: from mtaout20.012.net.il ([80.179.55.166]:40334) by debbugs.gnu.org with esmtp (Exim 4.72) (envelope-from ) id 1TASU4-0005Kg-5S for 12314@debbugs.gnu.org; Sat, 08 Sep 2012 17:22:33 -0400 Original-Received: from conversion-daemon.a-mtaout20.012.net.il by a-mtaout20.012.net.il (HyperSendmail v2007.08) id <0MA100A00V8U8Z00@a-mtaout20.012.net.il> for 12314@debbugs.gnu.org; Sun, 09 Sep 2012 00:21:55 +0300 (IDT) Original-Received: from HOME-C4E4A596F7 ([87.69.4.28]) by a-mtaout20.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0MA100ABEVCI1W40@a-mtaout20.012.net.il>; Sun, 09 Sep 2012 00:21:55 +0300 (IDT) In-reply-to: <8E40573C868D4B339513A16A02588F5E@us.oracle.com> X-012-Sender: halo1@inter.net.il X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.13 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 2) X-Received-From: 140.186.70.43 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.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:63980 Archived-At: > From: "Drew Adams" > Cc: , <12314@debbugs.gnu.org> > Date: Sat, 8 Sep 2012 09:42:59 -0700 > > > Why is it even necessary to talk about destructive modifications, if > > we are to advise to assign the result anyway? > > Not sure I understand the question. It is because these operations can be > destructive of list structure that we advise that. If you need to forget about the old value and assign the new one returned by 'delete', why does it matter that the modification was destructive? That pertains to the old value that you need to toss anyway. > If you have variables that point to some list structure that you modify somehow, > then it is up to you to ensure that the variables point to what you want them to > point to after such modification. Variables that point to that list structure will point to something whose value is unpredictable, a.k.a. "garbage". It is enough to say that the old value is garbage and shouldn't be used, IMO. > It all depends on what you want/need. You can never want/need the old value, because you cannot predict what it will be.