From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=AWL,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY shortcircuit=no autolearn=no autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id 48D361F9FC for ; Sat, 20 Mar 2021 06:35:55 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id B2EB3120A1C; Sat, 20 Mar 2021 15:34:56 +0900 (JST) Received: from xtrwkhkc.outbound-mail.sendgrid.net (xtrwkhkc.outbound-mail.sendgrid.net [167.89.16.28]) by neon.ruby-lang.org (Postfix) with ESMTPS id 5C703120A1D for ; Sat, 20 Mar 2021 15:34:54 +0900 (JST) Received: by filterdrecv-p3iad2-7b664dbcb7-6wr4z with SMTP id filterdrecv-p3iad2-7b664dbcb7-6wr4z-19-605597C5-1F 2021-03-20 06:35:49.474154857 +0000 UTC m=+127812.414983042 Received: from herokuapp.com (unknown) by geopod-ismtpd-canary-0 (SG) with ESMTP id ZYRrfMYFSBuXufhF5WNL0w for ; Sat, 20 Mar 2021 06:35:49.428 +0000 (UTC) Date: Sat, 20 Mar 2021 06:35:49 +0000 (UTC) From: nagachika00@gmail.com Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 78985 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Bug X-Redmine-Issue-Id: 17218 X-Redmine-Issue-Author: rorymolinari X-Redmine-Issue-Assignee: mrkn X-Redmine-Sender: nagachika X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?O2wxg26uOO6cft6GjkEp=2FGevTnH9lR=2FEdG60AX3F8=2FCidnpqjaFkqcsVwQB7Kh?= =?us-ascii?Q?C=2FOxNWSVtuAC+73=2F2F9BOCod1ZLYh4MPqOXMmwf?= =?us-ascii?Q?JgqKBJDtAWJ3SFi8pO5DFWk7RHIqXCVDQRweRjU?= =?us-ascii?Q?z0RFtdetjmtxsuSAhRtM5Aa9qcRyLEZsDhRBF9z?= =?us-ascii?Q?G2QmwIuUp2ASswqUV74ftbmu=2FKDT1rMLBWpva4D?= =?us-ascii?Q?eBsRvb3EcP60cHAGw=3D?= To: ruby-core@ruby-lang.org X-Entity-ID: b/2+PoftWZ6GuOu3b0IycA== X-ML-Name: ruby-core X-Mail-Count: 102950 Subject: [ruby-core:102950] [Ruby master Bug#17218] Range#step sometimes behaves unexpectedly with Rational endpoints and increment X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #17218 has been updated by nagachika (Tomoyuki Chikanaga). Backport changed from 2.5: DONTNEED, 2.6: REQUIRED, 2.7: REQUIRED to 2.5: DONTNEED, 2.6: REQUIRED, 2.7: DONE ruby_2_7 82bce422ba9e131e62b528854dea69a6e8cc0c04 merged revision(s) 254bed302752a401b5fcc3b6c65a9c93711d91d6,fad3023e94c45e7f03478732f7641b6f39ba9d12,3156fb0f2c3ebf8229f392c8502c08fe165ab181. ---------------------------------------- Bug #17218: Range#step sometimes behaves unexpectedly with Rational endpoints and increment https://bugs.ruby-lang.org/issues/17218#change-91015 * Author: rorymolinari (Rory Molinari) * Status: Closed * Priority: Normal * Assignee: mrkn (Kenta Murata) * ruby -v: ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-darwin19] * Backport: 2.5: DONTNEED, 2.6: REQUIRED, 2.7: DONE ---------------------------------------- I am using the latest stable version. The same behavior exists in 2.6.6. ``` 11:28:25 $ ruby -v ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-darwin19] ``` When creating an `Enumerator::ArithmeticSequence` with Rational endpoints and increment, sometimes inconsistent behavior results due to floating-point approximation in `#last`. ``` ruby x = Rational(10997, 10000) y = Rational(11, 10) s = Rational(1, 10000) puts "#{[x, y, s].map(&:to_f)}" # -> [1.0997, 1.1, 0.0001] # intention: this contains exactly the precise Rational representations of 1.0997, 1.0998, 1.0999, 1.1 arith_seq = (x..y).step(s) puts arith_seq.class # -> Enumerator::ArithmeticSequence # Things look OK puts arith_seq.first # -> 10997/10000 puts arith_seq.end # -> 11/10 puts arith_seq.step # -> 1/10000 # But the array that we get from #to_a is missing the last element, (11/10) puts arith_seq.to_a.to_s # -> [(10997/10000), (5499/5000), (10999/10000)] # This is apparently due to the value of #last puts arith_seq.last # -> 1.0999999999999999 # The object itself is confused puts arith_seq.size # -> 4 puts arith_seq.to_a.size # -> 3 ``` The issue is in the `Enumerator::ArithmeticSequence` instance we get when we call `Range#step` without a block. The `Range#step` method passes the right things when it gets a block. ``` ruby block_vals = [] (x..y).step(s) { |v| block_vals << v } puts block_vals.to_s # -> [(10997/10000), (5499/5000), (10999/10000), (11/10)] ``` I would expect `arith_seq.last` to be the exact value `Rational(11, 10)`. After all, `arith_seq` was created from a `Range` with `Rational` endpoints and given a rational step size. -- https://bugs.ruby-lang.org/