From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: Functions with multiple optional arguments Date: Mon, 17 Oct 2022 06:18:56 +0200 Message-ID: <87sfjn2ibz.fsf@dataswamp.org> References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="25311"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:JlUlOoFkcYCg1Uz2hhcpD1/97JU= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Mon Oct 17 20:57:02 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 1okVIM-0006Je-OT for geh-help-gnu-emacs@m.gmane-mx.org; Mon, 17 Oct 2022 20:57:02 +0200 Original-Received: from localhost ([::1]:35898 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1okVIL-0000YC-9N for geh-help-gnu-emacs@m.gmane-mx.org; Mon, 17 Oct 2022 14:57:01 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:60982) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1okHbk-00051R-AX for help-gnu-emacs@gnu.org; Mon, 17 Oct 2022 00:20:09 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:47226) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1okHbh-0006NZ-SC for help-gnu-emacs@gnu.org; Mon, 17 Oct 2022 00:20:08 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1okHbe-0003WF-M1 for help-gnu-emacs@gnu.org; Mon, 17 Oct 2022 06:20:02 +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-Mailman-Approved-At: Mon, 17 Oct 2022 14:54:47 -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:140084 Archived-At: Jean Louis wrote: >> Have been writing a function that has two optional >> arguments. It is turning out to be a difficult task in >> situations when one in missing an argument. Anybody has >> experience about this, as I have not seen much code with >> multiple optional arguments. > > If argument is optional but required by your function, I use > this method: > > (defun my-fun (&optional title description) > (let ((title (or title "Best Movie")) > (description (or description "Description"))) > (message "%s: %s" title description))) > > (my-fun) Yes, and to set 'description' (and not 'title') you'd do (my-fun nil "Poor movie IMO") CL has another way, more practical probably, to assign default values to optional arguments and that can be used in Elisp as well with `cl-defun' ... -- underground experts united https://dataswamp.org/~incal