From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: `append' vs. `nconc' Date: Thu, 31 Dec 2015 08:13:41 +0100 Message-ID: <87si2jqee2.fsf@debian.uxu> References: <568164D8.6050700@ojkastl.de> <87io3iyr7t.fsf@debian.uxu> <87si2kezg1.fsf@mithlond.arda> <87a8osrlj4.fsf_-_@debian.uxu> <87lh8bgafa.fsf@mithlond.arda> <87r3i3ch63.fsf@kuiper.lan.informatimago.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1451546056 28280 80.91.229.3 (31 Dec 2015 07:14:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 31 Dec 2015 07:14:16 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Dec 31 08:14:06 2015 Return-path: Envelope-to: geh-help-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 1aEXQz-0004Iw-61 for geh-help-gnu-emacs@m.gmane.org; Thu, 31 Dec 2015 08:14:05 +0100 Original-Received: from localhost ([::1]:54891 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEXQy-0003Pt-8c for geh-help-gnu-emacs@m.gmane.org; Thu, 31 Dec 2015 02:14:04 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:59752) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEXQn-0003PY-TX for help-gnu-emacs@gnu.org; Thu, 31 Dec 2015 02:13:54 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aEXQk-0002AX-Nd for help-gnu-emacs@gnu.org; Thu, 31 Dec 2015 02:13:53 -0500 Original-Received: from plane.gmane.org ([80.91.229.3]:53495) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEXQk-0002AR-HB for help-gnu-emacs@gnu.org; Thu, 31 Dec 2015 02:13:50 -0500 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aEXQj-00045x-96 for help-gnu-emacs@gnu.org; Thu, 31 Dec 2015 08:13:49 +0100 Original-Received: from nl106-137-56.student.uu.se ([130.243.137.56]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Dec 2015 08:13:49 +0100 Original-Received: from embe8573 by nl106-137-56.student.uu.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Dec 2015 08:13:49 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Original-Lines: 25 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: nl106-137-56.student.uu.se Mail-Copies-To: never User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) Cancel-Lock: sha1:4JtExwcPmpjBbL3gYZgJWGDE3oY= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 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-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:108546 Archived-At: "Pascal J. Bourguignon" writes: > You must remember the literal/immutable status of > each item at each level. > > Since you are incapable of remembering it, you > should assume that the whole input data is immutable > and write purely functional code (ie. use append, > not nconc) in general. OK, so you use `nconc' when you yourself create the lists by hand and thus know they are not empty, all the while using `list' and not ', and when done you assign the result to a variable associated with a list INSTEAD of using `nconc' directly because that variable can hold the empty list, i.e. nil, which `nconc' contrary to `append' cannot handle. And you do this to save time! Now I got it right! -- underground experts united http://user.it.uu.se/~embe8573