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: [External] : Set the default-directory dynamically according to the buffer-file-name. Date: Fri, 01 Oct 2021 09:09:35 +0200 Message-ID: <87zgrtgr0w.fsf@zoho.eu> References: 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="12879"; 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:aQE7v83DWPZL2yoUX+s2aqXyZNg= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Fri Oct 01 09:21:56 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 1mWCrk-0003AU-JG for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 01 Oct 2021 09:21:56 +0200 Original-Received: from localhost ([::1]:41510 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mWCrj-0003BL-9i for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 01 Oct 2021 03:21:55 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:36210) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mWCg2-0007MD-Pj for help-gnu-emacs@gnu.org; Fri, 01 Oct 2021 03:09:50 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:35932) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mWCg1-0002zo-5i for help-gnu-emacs@gnu.org; Fri, 01 Oct 2021 03:09:50 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1mWCfw-0008nY-RY for help-gnu-emacs@gnu.org; Fri, 01 Oct 2021 09:09:44 +0200 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:133472 Archived-At: Hongyi Zhao wrote: >> (if (not WHATEVER) >> (message "PROBLEM NOTIFICATION") >> (DO-STUFF)) >> >> If you want to stop everything and be sure the >> message is seen, you might want to raise an error: >> >> (unless WHATEVER (error "PROBLEM")) ; End it all >> (DO-STUFF) > > Do you mean this is a good practice for usage scenarios in > production environments? Well, yes, but also in every other environment where your aspiration is to write good, idiomatic Lisp. He is showing the syntax and how it is put together for two scenarios. But the more tricky question is another, namely when should one use the first one (i.e., `message' the situation, then branch out) and when is the situation in fact an `error', much like division by zero? (/ 1337 0) ; Arithmetic error -- underground experts united https://dataswamp.org/~incal