From mboxrd@z Thu Jan 1 00:00:00 1970 Path: main.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: replacing a certain element in a list with another Date: Tue, 30 Sep 2003 15:47:01 GMT Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Message-ID: References: <3F79A1AA.5040008@yahoo.com> NNTP-Posting-Host: deer.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1064939022 8744 80.91.224.253 (30 Sep 2003 16:23:42 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Tue, 30 Sep 2003 16:23:42 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue Sep 30 18:23:40 2003 Return-path: Original-Received: from monty-python.gnu.org ([199.232.76.173]) by deer.gmane.org with esmtp (Exim 3.35 #1 (Debian)) id 1A4NHo-00084I-00 for ; Tue, 30 Sep 2003 18:23:40 +0200 Original-Received: from localhost ([127.0.0.1] helo=monty-python.gnu.org) by monty-python.gnu.org with esmtp (Exim 4.22) id 1A4Mwq-0007rB-AA for geh-help-gnu-emacs@m.gmane.org; Tue, 30 Sep 2003 12:02:00 -0400 Original-Path: shelby.stanford.edu!newsfeed.stanford.edu!cyclone.bc.net!snoopy.risq.qc.ca!charlie.risq.qc.ca!53ab2750!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 12 User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50 Original-NNTP-Posting-Host: 132.204.24.42 Original-X-Complaints-To: abuse@umontreal.ca Original-X-Trace: charlie.risq.qc.ca 1064936821 132.204.24.42 (Tue, 30 Sep 2003 11:47:01 EDT) Original-NNTP-Posting-Date: Tue, 30 Sep 2003 11:47:01 EDT Original-Xref: shelby.stanford.edu gnu.emacs.help:116970 Original-To: help-gnu-emacs@gnu.org X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.2 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: main.gmane.org gmane.emacs.help:12895 X-Report-Spam: http://spam.gmane.org/gmane.emacs.help:12895 > Well, it depends on whether the OP wants to return a new list or to modify > the original list. That's exactly what was meant by "have good reasons to do it". Mixing the in-place-update style with the create-new-stuff style (aka imperative style vs functional style) is a common source of error because it generally makes the code more "subtle" (more difficult to understand). Since elisp usually copies things around, inplace-update operations such as nconc, nreverse, setcar, setcdr, delete, delq, ... should be used with caution. Stefan