From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.help Subject: Re: What is 0.01 here not 0.01 here 0.009999999999999? Date: Fri, 02 Apr 2021 17:02:41 +0300 Message-ID: <837dlkg4xq.fsf@gnu.org> References: 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="18990"; mail-complaints-to="usenet@ciao.gmane.io" To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Fri Apr 02 16:03:20 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 1lSKON-0004ph-Ok for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 02 Apr 2021 16:03:19 +0200 Original-Received: from localhost ([::1]:32798 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lSKOM-0002eB-Pi for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 02 Apr 2021 10:03:18 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:55912) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSKO1-0002dr-Lu for help-gnu-emacs@gnu.org; Fri, 02 Apr 2021 10:02:57 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:60522) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lSKO1-0000FJ-EY for help-gnu-emacs@gnu.org; Fri, 02 Apr 2021 10:02:57 -0400 Original-Received: from 84.94.185.95.cable.012.net.il ([84.94.185.95]:4441 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1lSKNz-0006O7-UT for help-gnu-emacs@gnu.org; Fri, 02 Apr 2021 10:02:56 -0400 In-Reply-To: (message from Jean Louis on Fri, 02 Apr 2021 16:42:42 +0300) 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:128810 Archived-At: > Date: Fri, 02 Apr 2021 16:42:42 +0300 > From: Jean Louis > > I would like to get a number increased for 0.01: > > (defun rcd-vc-increase-decimal-revision-number (nn.nn) > (let* ((nn.nn (format "%s" nn.nn)) > (nn.nn (format "%.2f" (string-to-number nn.nn))) > (nn.nn (string-to-number nn.nn))) > (+ nn.nn 0.01))) > > But result is not what I want, as I want to get 10.13, though it is > tiny loss: > > (rcd-vc-increase-decimal-revision-number "10.12") → 10.129999999999999 Welcome to floating-point computations. 0.01 doesn't have an exact binary representation, which is why you get what you get. Suggested reading: https://www.itu.dk/~sestoft/bachelor/IEEE754_article.pdf