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: Is there a way of setting a variable only when it exists? Date: Mon, 14 Mar 2022 14:48:10 +0100 Message-ID: <878rtcir1h.fsf@zoho.eu> References: <87lexdul8e.fsf@mbork.pl> Reply-To: Emanuel Berg Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="22309"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:dI/7Q77DaaEtErzpxcXHJBhZ/3c= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Mar 15 04:16:00 2022 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 1nTxfE-0005df-Bt for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 15 Mar 2022 04:16:00 +0100 Original-Received: from localhost ([::1]:43752 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nTxfC-0008VQ-Nh for geh-help-gnu-emacs@m.gmane-mx.org; Mon, 14 Mar 2022 23:15:58 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:46026) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTl3d-0004j2-7S for help-gnu-emacs@gnu.org; Mon, 14 Mar 2022 09:48:21 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:52496) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTl3a-0003YK-8s for help-gnu-emacs@gnu.org; Mon, 14 Mar 2022 09:48:20 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1nTl3Y-00099g-IH for help-gnu-emacs@gnu.org; Mon, 14 Mar 2022 14:48:16 +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, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Mon, 14 Mar 2022 23:14:43 -0400 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 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:136553 Archived-At: Stefan Monnier via Users list for the GNU Emacs text editor wrote: >> I assume it would be fairly easy to code such a macro >> (using `boundp'), but maybe it exists already? > > AFAIK it doesn't exist yet. The reason for it is that it is > not often useful. Typically there are two cases: > > - If the var exist, you want to set it and if not you have > no fallback. In that case, it is typically harmless to set > the var even when it doesn't exist, so the code just uses > `setq` without bothering to test `boundp`. > > - If the var exist you want to set it, and if it doesn't you > want to do something else. In that case, the something > else tends to depend on the specifics so (if (boundp 'foo) > (setq foo ..) ...) is about s good as it gets. If it exists set it with `setq'. If it doesn't exist, create and set it ... with `setq'? -- underground experts united https://dataswamp.org/~incal