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: Elisp string function question Date: Fri, 18 Jun 2021 15:28:05 +0300 Message-ID: References: <20210618121807.xsjdbv4ouqbv4uex.ref@Ergus> <20210618121807.xsjdbv4ouqbv4uex@Ergus> 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="14738"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/2.0.7+183 (3d24855) (2021-05-28) Cc: help-gnu-emacs@gnu.org To: Ergus Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Fri Jun 18 14:33:06 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 1luDgG-0003gE-V0 for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 18 Jun 2021 14:33:04 +0200 Original-Received: from localhost ([::1]:54910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1luDgF-0005as-V0 for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 18 Jun 2021 08:33:03 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:55800) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1luDfc-0005Yu-P5 for help-gnu-emacs@gnu.org; Fri, 18 Jun 2021 08:32:24 -0400 Original-Received: from stw1.rcdrun.com ([217.170.207.13]:37135) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1luDfX-0002WM-H1 for help-gnu-emacs@gnu.org; Fri, 18 Jun 2021 08:32:24 -0400 Original-Received: from localhost ([::ffff:197.157.0.23]) (AUTH: PLAIN admin, TLS: TLS1.3,256bits,ECDHE_RSA_AES_256_GCM_SHA384) by stw1.rcdrun.com with ESMTPSA id 0000000000076065.0000000060CC9230.000059FD; Fri, 18 Jun 2021 05:31:44 -0700 Mail-Followup-To: Ergus , help-gnu-emacs@gnu.org Content-Disposition: inline In-Reply-To: <20210618121807.xsjdbv4ouqbv4uex@Ergus> Received-SPF: pass client-ip=217.170.207.13; envelope-from=bugs@gnu.support; helo=stw1.rcdrun.com X-Spam_score_int: 29 X-Spam_score: 2.9 X-Spam_bar: ++ X-Spam_report: (2.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_SBL_CSS=3.335, RCVD_IN_SORBS_WEB=1.5, 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: 2.1.23 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:130974 Archived-At: * Ergus [2021-06-18 15:19]: > Hi: > > I just tried and this: > > (string-empty-p nil) > > returns nil. But nil is not an non-empty string. This forces to add some > extra checks when using this function. > > Is this intended? I got this too, and it is not for all cases suitable. (defun string-blank-if-nil (s) "Returns blank string for nil values" (if (null s) "" s)) I often use this one as `nil' I sometimes wish to convert to empty string. (string-blank-if-nil nil) ⇒ "" (string-blank-if-nil "1") ⇒ "1" Maybe that idea will help. (defun string-or-empty-string (i) "Returns empty string for nil" (let* ((type (type-of i))) (cond ((or (eql type 'integer) (eql type 'float)) (number-to-string i)) ((null i) "") ((eql type 'symbol) (prin1-to-string i)) ((eql type 'string) i)))) Or that anything should be converted: (string-or-empty-string nil) ⇒ "" (string-or-empty-string 1) ⇒ "1" (string-or-empty-string "ok") ⇒ "ok" Or better idea: (seq-empty-p nil) ⇒ t (seq-empty-p "") ⇒ t -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/