From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Emanuel Berg via Users list for the GNU Emacs text editor Newsgroups: gmane.emacs.help Subject: Re: Appending to a list Date: Mon, 14 Dec 2020 05:50:47 +0100 Message-ID: <873609vvmg.fsf@zoho.eu> References: <877dpljtwg.fsf@fastmail.fm> <87sg89v1f7.fsf@telefonica.net> <87mtyhxovn.fsf@zoho.eu> <871rftxlwl.fsf@zoho.eu> <87czzdyqra.fsf@web.de> Reply-To: Emanuel Berg 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="21969"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:ZPaAjxgSUiQLWsATwBZoMfSv0DA= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Mon Dec 14 05:51:21 2020 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 1kofpR-0005cQ-OQ for geh-help-gnu-emacs@m.gmane-mx.org; Mon, 14 Dec 2020 05:51:21 +0100 Original-Received: from localhost ([::1]:36142 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kofpQ-0004OA-Rq for geh-help-gnu-emacs@m.gmane-mx.org; Sun, 13 Dec 2020 23:51:20 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:38412) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kofp4-0004O4-PE for help-gnu-emacs@gnu.org; Sun, 13 Dec 2020 23:50:58 -0500 Original-Received: from static.214.254.202.116.clients.your-server.de ([116.202.254.214]:39986 helo=ciao.gmane.io) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kofp3-000490-2v for help-gnu-emacs@gnu.org; Sun, 13 Dec 2020 23:50:58 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1kofoz-00056n-3n for help-gnu-emacs@gnu.org; Mon, 14 Dec 2020 05:50:53 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Mail-Copies-To: never Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=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:126351 Archived-At: steve-humphreys wrote: > I thought I could push element by element. You can, you can push whatever, if that data structure makes it more involved solve it for onee pilot case, then write a small `defun', put it there, and ever after just pass the single element to that. > I got inspiration from some discussions here that push is > more efficient and wanted to have a go. Yes, I do use push to > make the larger list. Have not thought about defvar before. > I have read that "setq" does not introduce a variable, but > I would need some explanation about that. It works with `setq' only without `defvar' the byte-compiler, which should always be used BTW, without it the byte-compiler will complain. Comment-out the defvars in this (require 'cl-lib) (defvar bird-list-all) (defvar bird-list-1) (defvar bird-list-2) (setq bird-list-all '()) (setq bird-list-1 '("Western jackdaw" "European goldfinch")) (setq bird-list-2 '("rook")) (cl-pushnew bird-list-1 bird-list-all) ; (("Western jackdaw" "European goldfinch")) (cl-pushnew bird-list-2 bird-list-all) ; (("rook") ("Western jackdaw" "European goldfinch")) and the byte-compiler will say geh.el: In toplevel form: geh.el:193:7: Warning: assignment to free variable ‘bird-list-all’ geh.el:195:7: Warning: assignment to free variable ‘bird-list-1’ geh.el:196:7: Warning: assignment to free variable ‘bird-list-2’ geh.el:198:13: Warning: reference to free variable ‘bird-list-1’ geh.el:198:25: Warning: reference to free variable ‘bird-list-all’ geh.el:199:13: Warning: reference to free variable ‘bird-list-2’ In more ambitious projects, like a package, e.g. [1], defvar should be used also to make available documentation, both in the code and for the on-line help which in practice is the same thing - Emacs is self-documenting, remember? Heh, not really, right? But still, do it. Anyway, don't rely too much on variables, defvar or no defvar. Better to rely on defuns and use `let' and `let*' there. IMO! [1] https://dataswamp.org/~incal/emacs-init/buc.el -- underground experts united http://user.it.uu.se/~embe8573 https://dataswamp.org/~incal