From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Pascal J. Bourguignon" Newsgroups: gmane.emacs.help Subject: Re: `append' vs. `nconc' Date: Thu, 31 Dec 2015 04:45:26 +0100 Organization: Informatimago Message-ID: <877fjve0x5.fsf@kuiper.lan.informatimago.com> References: <568164D8.6050700@ojkastl.de> <87io3iyr7t.fsf@debian.uxu> <87si2kezg1.fsf@mithlond.arda> <87a8osrlj4.fsf_-_@debian.uxu> <87lh8bgafa.fsf@mithlond.arda> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: ger.gmane.org 1451533820 30665 80.91.229.3 (31 Dec 2015 03:50:20 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 31 Dec 2015 03:50:20 +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 04:50:19 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 1aEUFm-000170-Ia for geh-help-gnu-emacs@m.gmane.org; Thu, 31 Dec 2015 04:50:18 +0100 Original-Received: from localhost ([::1]:54558 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aEUFl-0004hg-SJ for geh-help-gnu-emacs@m.gmane.org; Wed, 30 Dec 2015 22:50:17 -0500 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 28 Original-X-Trace: individual.net ybRurLLlMwntKIKuUNu0LQIlUe0MtDy2PPzZqHObfYng9ZrXiE Cancel-Lock: sha1:MzEwOGYxMDA3OGQ3MTVhODM2ZGZkMzNiNDdhNWM3Y2E5OTlmMWJmYw== sha1:H+yDcvcHQnUuRcnmKPfdxxxIFaw= Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:216251 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:108541 Archived-At: Emanuel Berg writes: > OK, so for example this: > > (setq completion-ignored-extensions > (append completion-ignored-extensions '(".bcf" ".run.xml")) ) > > Is better as: > > (nconc completion-ignored-extensions (list ".bcf" ".run.xml")) > > ? No. You should never use nconc only for effect (just like delete, etc). Always re-assign the modified list: (setf completion-ignored-extensions (nconc completion-ignored-extensions (list ".bcf" ".run.xml"))) otherwise it will break when the place is bound to nil. (nil is a symbol and cannot be mutated into a cons cell!). -- __Pascal Bourguignon__ http://www.informatimago.com/ “The factory of the future will have only two employees, a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment.” -- Carl Bass CEO Autodesk