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: Testing whether a list contains at least one non-nil element Date: Wed, 26 Oct 2022 21:56:30 +0300 Message-ID: References: <87r0yw85la.fsf@dataswamp.org> 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="13920"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/2.2.7+37 (a90f69b) (2022-09-02) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Thu Oct 27 05:04:39 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 1ontCA-0003Nb-Lf for geh-help-gnu-emacs@m.gmane-mx.org; Thu, 27 Oct 2022 05:04:38 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ont8s-0007zZ-FA; Wed, 26 Oct 2022 23:01:14 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ont8n-0007n4-Nx for help-gnu-emacs@gnu.org; Wed, 26 Oct 2022 23:01:09 -0400 Original-Received: from stw1.rcdrun.com ([217.170.207.13]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ont8m-00057e-1U for help-gnu-emacs@gnu.org; Wed, 26 Oct 2022 23:01:09 -0400 Original-Received: from localhost ([::ffff:102.82.225.124]) (AUTH: PLAIN admin, TLS: TLS1.3,256bits,ECDHE_RSA_AES_256_GCM_SHA384) by stw1.rcdrun.com with ESMTPSA id 0000000000081D92.000000006359F472.00006110; Wed, 26 Oct 2022 20:01:05 -0700 Mail-Followup-To: help-gnu-emacs@gnu.org Content-Disposition: inline In-Reply-To: <87r0yw85la.fsf@dataswamp.org> 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, DATE_IN_PAST_06_12=1.543, 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: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: "help-gnu-emacs" Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.help:140416 Archived-At: * Emanuel Berg [2022-10-26 15:55]: > Jean Louis wrote: > > >> I would like to test whether a list contains at least one > >> non-nil element? If I do that, then I would be able to > >> continue a loop where a non-nil element would mean that > >> a match was found. > > > > Here is the test for non nil element: > > > > (elt (delq nil (list nil nil)) 0) ⇒ nil > > > > (elt (delq nil (list nil 1)) 0) ⇒ 1 > > Interesting question ... > > (cl-position-if (lambda (e) e) '(nil nil)) ; nil > (cl-position-if (lambda (e) e) '(nil 1)) ; 1 While `remq' is more suitable as not destructive one: (elt (remq nil (list nil nil)) 0) ⇒ nil (elt (remq nil (list nil "any")) 0) ⇒ "any" cl- is Common Lisp prefix to conform those people who are used to Common Lisp. Those functions are bloated. (defun list-has-non-nil-p (list) "Test if list has non nil element." (elt (remq nil list) 0)) (list-has-non-nil-p '(1 2 3)) ⇒ 1 (list-has-non-nil-p '(nil nil nil)) ⇒ nil -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/