From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Jean Louis Newsgroups: gmane.emacs.help Subject: Re: Appending lists Date: Wed, 16 Jun 2021 12:13:21 +0300 Message-ID: References: <4tl1yvylvg1fxx5eefjs9mnk.1623688568572@email.android.com> <87o8c8l32h.fsf@posteo.net> <87zgvs2bup.fsf@zoho.eu> <87y2bby1kr.fsf@zoho.eu> <20210615091834.GB24886@tuxteam.de> <87im2ewr3k.fsf@zoho.eu> <20210616072819.GB17919@tuxteam.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="6903"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/2.0.7+183 (3d24855) (2021-05-28) Cc: help-gnu-emacs@gnu.org To: tomas@tuxteam.de Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Wed Jun 16 11:15:24 2021 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1ltRdr-0001TH-6T for geh-help-gnu-emacs@m.gmane-mx.org; Wed, 16 Jun 2021 11:15:23 +0200 Original-Received: from localhost ([::1]:58056 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ltRdq-0006wn-4C for geh-help-gnu-emacs@m.gmane-mx.org; Wed, 16 Jun 2021 05:15:22 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:41300) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ltRck-0006sT-Nk for help-gnu-emacs@gnu.org; Wed, 16 Jun 2021 05:14:14 -0400 Original-Received: from stw1.rcdrun.com ([217.170.207.13]:45201) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ltRci-0004qQ-QO for help-gnu-emacs@gnu.org; Wed, 16 Jun 2021 05:14:14 -0400 Original-Received: from localhost ([::ffff:197.157.0.23]) (AUTH: PLAIN admin, TLS: TLS1.3,256bits,ECDHE_RSA_AES_256_GCM_SHA384) by stw1.rcdrun.com with ESMTPSA id 0000000000076067.0000000060C9C0E1.00001758; Wed, 16 Jun 2021 02:14:09 -0700 Mail-Followup-To: tomas@tuxteam.de, help-gnu-emacs@gnu.org Content-Disposition: inline In-Reply-To: <20210616072819.GB17919@tuxteam.de> Received-SPF: pass client-ip=217.170.207.13; envelope-from=bugs@gnu.support; helo=stw1.rcdrun.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_SORBS_WEB=1.5, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.23 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-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:130893 Archived-At: * tomas@tuxteam.de [2021-06-16 10:29]: > On Wed, Jun 16, 2021 at 03:11:43AM +0200, Emanuel Berg via Users list for the GNU Emacs text editor wrote: > > tomas wrote: > > > > > (setq thing (copy-sequence '(one two three four five six))) > > > (setq thang (cddr thing)) > > > > > > thang => (three four five six) > > > > > > (nreverse thing) => (six five four three two one) > > > > > > thing => (one) > > > > > > thang => (three two one) > > > ; now this is what I was after. Who the heck "changed my > > > ; variable!?" Who is General Failure and why is he reading > > > ; my disk? > > > > Well, let's see, `nreverse' has updated the data without > > setting the variables to whatever desired values they should > > take > > It can't. It's a function. > > Doing (foo x y) will *never* change "the variable x" -- unless > foo is a macro/special form. (setq list-1 '(1 2 3)) (setq list-2 '(A B)) (nconc list-1 list-2) ⇒ (1 2 3 A B) list-1 ⇒ (1 2 3 A B) nconc is a built-in function in ‘C source code’. So it obviously changes the variable `list-1' from (1 2 3) to (1 2 3 A B) -- how do you explain that? So far I know from Common Lisp those functions starting with "n" are common with side effects. (nreverse list-1) ⇒ (B A 3 2 1) list-1 ⇒ (1) ⁈⁈⁈⁈⁈⁈⁈⁈⁈⁈⁈ -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/