From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: replace element in list Date: Thu, 22 Nov 2018 08:19:49 -0500 Message-ID: References: <2087821187f90948d25d93c7ea475e66@openmail.cc> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1542892729 1959 195.159.176.226 (22 Nov 2018 13:18:49 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 22 Nov 2018 13:18:49 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Nov 22 14:18:45 2018 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gPosW-0000IG-Ao for geh-help-gnu-emacs@m.gmane.org; Thu, 22 Nov 2018 14:18:44 +0100 Original-Received: from localhost ([::1]:46554 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gPouX-0001Od-IR for geh-help-gnu-emacs@m.gmane.org; Thu, 22 Nov 2018 08:20:49 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:46620) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gPotk-0001NA-NP for help-gnu-emacs@gnu.org; Thu, 22 Nov 2018 08:20:01 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gPoth-0005A1-Ku for help-gnu-emacs@gnu.org; Thu, 22 Nov 2018 08:20:00 -0500 Original-Received: from [195.159.176.226] (port=33100 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gPoth-00059J-C3 for help-gnu-emacs@gnu.org; Thu, 22 Nov 2018 08:19:57 -0500 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1gPorY-0007ZH-87 for help-gnu-emacs@gnu.org; Thu, 22 Nov 2018 14:17:44 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 13 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:VT6nvYaW/EGCvlz4kPobl++oxxw= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 195.159.176.226 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.21 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 Original-Sender: "help-gnu-emacs" Xref: news.gmane.org gmane.emacs.help:118730 Archived-At: > I want to share and know if there is a better way (more efficient or > clearer) to replace something within a list (I don't know LISP). My suggestion is to not do it: - if you do it by modifying the list in place, it means you're using nasty side-effects, which are better avoided when possible (especially with lists). - if you want to do it without side-effects, your operation will inevitably be algorithmically inefficient because a list is not designed for that. -- Stefan