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-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_PASS shortcircuit=no autolearn=ham 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 7498C211B4 for ; Thu, 10 Jan 2019 08:04:36 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 808261215C2; Thu, 10 Jan 2019 17:04:33 +0900 (JST) Received: from o1678916x28.outbound-mail.sendgrid.net (o1678916x28.outbound-mail.sendgrid.net [167.89.16.28]) by neon.ruby-lang.org (Postfix) with ESMTPS id 8141D121495 for ; Thu, 10 Jan 2019 17:04:31 +0900 (JST) Received: by filter0181p3mdw1.sendgrid.net with SMTP id filter0181p3mdw1-19202-5C36FC8D-13 2019-01-10 08:04:29.19108306 +0000 UTC m=+201503.455187681 Received: from herokuapp.com (ec2-54-166-164-231.compute-1.amazonaws.com [54.166.164.231]) by ismtpd0036p1mdw1.sendgrid.net (SG) with ESMTP id MO1ya2hZQ8mtAYGn8rAKUA Thu, 10 Jan 2019 08:04:29.156 +0000 (UTC) Date: Thu, 10 Jan 2019 08:04:30 +0000 (UTC) From: matz@ruby-lang.org To: ruby-core@ruby-lang.org Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 66412 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 15477 X-Redmine-Issue-Author: robb X-Redmine-Sender: matz 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: ync6xU2WACa70kv/Ymy4QrNMhiuLXJG8OTL2vJD1yS7RtWdQcWsi3nSUBO38JNLEp/jnlAsCkMMXh4 UR2+1gb86b4IhLzftp+MGcYxd8VExIauEtWtuuTrMi0ax2neBg5shtGVMSKTM6GHqqSJS4LfB+y7/K 1lD5aaueV56U/ceDH1Ves6LkBDf/7Sg0H76MLW12nlSQqLlZ9vCOFBzDLw== X-ML-Name: ruby-core X-Mail-Count: 90978 Subject: [ruby-core:90978] [Ruby trunk Feature#15477] Proc#arity returns -1 for composed lambda Procs of known arguments 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 #15477 has been updated by matz (Yukihiro Matsumoto). Yes, please. Matz. ---------------------------------------- Feature #15477: Proc#arity returns -1 for composed lambda Procs of known arguments https://bugs.ruby-lang.org/issues/15477#change-76191 * Author: robb (Robb Shecter) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- ``` f = -> x { x + 2 } g = -> x { x * 2 } h = f << g f.arity # => 1 g.arity # => 1 h.arity # => -1 THIS SHOULD BE 1 because h "knows" that it takes exactly 1 argument: h.call # => ArgumentError (given 0, expected 1) ``` Lambda Procs which are composed using `<<` seem to partially lose knowledge of their arity. I don't know if this affects other procs, or the `>>` operator as well. The Proc#arity docs state that -1 is returned only when a variable or unknown number of arguments are expected by the Proc. But here, that's not the case. -- https://bugs.ruby-lang.org/