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: `append' vs. `nconc' (was: Re: Error: Setting the shell in sh-mode via a local variable does not work) Date: Wed, 30 Dec 2015 16:41:51 +0100 Message-ID: <87a8osrlj4.fsf_-_@debian.uxu> References: <568164D8.6050700@ojkastl.de> <87io3iyr7t.fsf@debian.uxu> <87si2kezg1.fsf@mithlond.arda> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1451490145 4595 80.91.229.3 (30 Dec 2015 15:42:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 30 Dec 2015 15:42:25 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Wed Dec 30 16:42:16 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 1aEItB-0005B1-NC for geh-help-gnu-emacs@m.gmane.org; Wed, 30 Dec 2015 16:42:13 +0100 Original-Received: from localhost ([::1]:52833 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEItB-0006Wl-54 for geh-help-gnu-emacs@m.gmane.org; Wed, 30 Dec 2015 10:42:13 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:53215) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEIt1-0006We-9E for help-gnu-emacs@gnu.org; Wed, 30 Dec 2015 10:42:04 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aEIsx-0008LV-5v for help-gnu-emacs@gnu.org; Wed, 30 Dec 2015 10:42:03 -0500 Original-Received: from plane.gmane.org ([80.91.229.3]:48909) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEIsw-0008LR-VX for help-gnu-emacs@gnu.org; Wed, 30 Dec 2015 10:41:59 -0500 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aEIsv-0004w1-1V for help-gnu-emacs@gnu.org; Wed, 30 Dec 2015 16:41:57 +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 ; Wed, 30 Dec 2015 16:41:57 +0100 Original-Received: from embe8573 by nl106-137-56.student.uu.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 30 Dec 2015 16:41:57 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Original-Lines: 30 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:swB/iz3orDCnpHVjCmuqgPgfGzY= 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:108525 Archived-At: Teemu Likonen writes: > There you create a list MODES and then APPEND copies > the whole list and joins it to AUTO-MODE-ALIST. > The original list is discarded. No problem, it's > just a configuration code. But in some other > situation it might be good idea to construct the > list only once and use NCONC which only traverses > the lists through and modifies last conses to join > it to the next list: > > (let ((modes (list '(a . b) ;; ... ))) (setq > auto-mode-alist (nconc modes auto-mode-alist))) So what you are saying, if `append' is replaced by `nconc', the same thing happens, only one less list has to be created? I have several appends in my source, is there a rule-of-thumb when to use `append' and when to use `nconc'? > The PROGN is redundant because LAMBDA has an implicit > PROGN OK, cool. -- underground experts united http://user.it.uu.se/~embe8573