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: Fri, 01 Jan 2016 19:31:58 +0100 Message-ID: <87y4c9rw0x.fsf@debian.uxu> References: <568164D8.6050700@ojkastl.de> <87io3iyr7t.fsf@debian.uxu> <87si2kezg1.fsf@mithlond.arda> <87a8osrlj4.fsf_-_@debian.uxu> <87lh8bgafa.fsf@mithlond.arda> <87io3fdqfm.fsf@mithlond.arda> <87mvsqv52v.fsf@debian.uxu> <87wprucrlz.fsf@mithlond.arda> <87lh89tovl.fsf@debian.uxu> <87r3i1fldz.fsf@mithlond.arda> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1451673415 10821 80.91.229.3 (1 Jan 2016 18:36:55 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 1 Jan 2016 18:36:55 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Jan 01 19:36:45 2016 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 1aF4ZB-0001MP-0z for geh-help-gnu-emacs@m.gmane.org; Fri, 01 Jan 2016 19:36:45 +0100 Original-Received: from localhost ([::1]:36482 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aF4ZA-00010M-EU for geh-help-gnu-emacs@m.gmane.org; Fri, 01 Jan 2016 13:36:44 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:41195) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aF4XN-0000uJ-Td for help-gnu-emacs@gnu.org; Fri, 01 Jan 2016 13:36:33 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aF4Uh-0004ZT-2k for help-gnu-emacs@gnu.org; Fri, 01 Jan 2016 13:34:53 -0500 Original-Received: from plane.gmane.org ([80.91.229.3]:60932) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aF4Ug-0004Z9-RH for help-gnu-emacs@gnu.org; Fri, 01 Jan 2016 13:32:06 -0500 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aF4Ud-0005Cc-O9 for help-gnu-emacs@gnu.org; Fri, 01 Jan 2016 19:32:03 +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 ; Fri, 01 Jan 2016 19:32:03 +0100 Original-Received: from embe8573 by nl106-137-56.student.uu.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 01 Jan 2016 19:32:03 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Original-Lines: 42 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:IY7RGM4l2rRDkknaz817yBhbmes= 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:108572 Archived-At: Teemu Likonen writes: >> OK, then what functions, other than `nconc', are >> mutators (or, how do you now)? > > A manual or the specification says it. > Such operation is called "destructive". A function is destructive if it changes its arguments. I suppose it is even more destructive if it changes things that aren't even passed to the function. What I can tell this definition is straightforward so it is rather a question of knowing what functions are like that. For example, the help for `nconc' says: (nconc &rest LISTS) Concatenate any number of lists by altering them. Only the last argument is not altered, and need not be a list. And `append': (append &rest SEQUENCES) Concatenate all the arguments and make the result a list. The result is a list whose elements are the elements of all the arguments. Each argument may be a list, vector or string. The last argument is not copied, just used as the tail of the new list. You need to be attentive but if you are, sure, it is there. -- underground experts united http://user.it.uu.se/~embe8573