From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Drew Adams" Newsgroups: gmane.emacs.bugs Subject: bug#12314: 24.2.50; `add-to-history': use `setq' with `delete' Date: Sat, 8 Sep 2012 09:42:59 -0700 Message-ID: <8E40573C868D4B339513A16A02588F5E@us.oracle.com> 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> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1347122629 2283 80.91.229.3 (8 Sep 2012 16:43:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 8 Sep 2012 16:43:49 +0000 (UTC) Cc: 12314@debbugs.gnu.org, cyd@gnu.org To: "'Eli Zaretskii'" Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sat Sep 08 18:43:51 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 1TAO8H-0004cV-Jd for geb-bug-gnu-emacs@m.gmane.org; Sat, 08 Sep 2012 18:43:45 +0200 Original-Received: from localhost ([::1]:52424 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TAO8E-0001WW-AP for geb-bug-gnu-emacs@m.gmane.org; Sat, 08 Sep 2012 12:43:42 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:46764) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TAO8B-0001WF-0k for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 12:43:39 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TAO8A-0006J3-3u for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 12:43:38 -0400 Original-Received: from debbugs.gnu.org ([140.186.70.43]:39316) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TAO8A-0006Iz-0p for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 12:43:38 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.72) (envelope-from ) id 1TAO8X-0007OU-N7 for bug-gnu-emacs@gnu.org; Sat, 08 Sep 2012 12:44:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: "Drew Adams" Original-Sender: debbugs-submit-bounces@debbugs.gnu.org Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 08 Sep 2012 16:44:01 +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=B12314.134712262028388 (code B ref 12314); Sat, 08 Sep 2012 16:44:01 +0000 Original-Received: (at 12314) by debbugs.gnu.org; 8 Sep 2012 16:43:40 +0000 Original-Received: from localhost ([127.0.0.1]:48862 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.72) (envelope-from ) id 1TAO8B-0007Np-SQ for submit@debbugs.gnu.org; Sat, 08 Sep 2012 12:43:40 -0400 Original-Received: from acsinet15.oracle.com ([141.146.126.227]:16795) by debbugs.gnu.org with esmtp (Exim 4.72) (envelope-from ) id 1TAO88-0007Nh-H1 for 12314@debbugs.gnu.org; Sat, 08 Sep 2012 12:43:37 -0400 Original-Received: from ucsinet22.oracle.com (ucsinet22.oracle.com [156.151.31.94]) by acsinet15.oracle.com (Sentrion-MTA-4.2.2/Sentrion-MTA-4.2.2) with ESMTP id q88Gh98A028646 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Sat, 8 Sep 2012 16:43:10 GMT Original-Received: from acsmt358.oracle.com (acsmt358.oracle.com [141.146.40.158]) by ucsinet22.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id q88Gh8AE026944 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 8 Sep 2012 16:43:09 GMT Original-Received: from abhmt107.oracle.com (abhmt107.oracle.com [141.146.116.59]) by acsmt358.oracle.com (8.12.11.20060308/8.12.11) with ESMTP id q88Gh8RL025554; Sat, 8 Sep 2012 11:43:08 -0500 Original-Received: from dradamslap1 (/71.202.147.44) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sat, 08 Sep 2012 09:43:08 -0700 X-Mailer: Microsoft Office Outlook 11 In-Reply-To: <83a9x0mq5e.fsf@gnu.org> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 Thread-Index: Ac2N34+YUBThbqvUTEmQwPgrQrQIjAAAIAlg X-Source-IP: ucsinet22.oracle.com [156.151.31.94] 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:63958 Archived-At: > 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. These operations are not concerned with any variables, period - they act only on list structure. 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. It all depends on what you want/need. (This is a bit like using pointers. A variable points to a particular cons cell. Modifying one or more cons cells in a chain might or might not change that particular cons cell or cells that its cdr points to. The variable continues to point to the same cons cell, but that cell might not still reflect the "list" that you expect it to reflect.)