From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Original-To: poffice@blade.nagaokaut.ac.jp Delivered-To: poffice@blade.nagaokaut.ac.jp Received: from kankan.nagaokaut.ac.jp (kankan.nagaokaut.ac.jp [133.44.2.24]) by blade.nagaokaut.ac.jp (Postfix) with ESMTP id 171A719C003C for ; Mon, 9 Nov 2015 20:55:33 +0900 (JST) Received: from voscc.nagaokaut.ac.jp (voscc.nagaokaut.ac.jp [133.44.1.100]) by kankan.nagaokaut.ac.jp (Postfix) with ESMTP id F2B5DB5D8C3 for ; Mon, 9 Nov 2015 21:25:00 +0900 (JST) Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by voscc.nagaokaut.ac.jp (Postfix) with ESMTP id 6FF4D18CC7AF for ; Mon, 9 Nov 2015 21:25:01 +0900 (JST) Received: from [221.186.184.76] (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 30320120461; Mon, 9 Nov 2015 21:25:00 +0900 (JST) X-Original-To: ruby-core@ruby-lang.org Delivered-To: ruby-core@ruby-lang.org Received: from o10.shared.sendgrid.net (o10.shared.sendgrid.net [173.193.132.135]) by neon.ruby-lang.org (Postfix) with ESMTPS id 1017912043F for ; Mon, 9 Nov 2015 21:24:55 +0900 (JST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sendgrid.me; h=from:to:references:subject:mime-version:content-type:content-transfer-encoding:list-id; s=smtpapi; bh=8GkczLfrD0h/QmLj7Q8jhVhHNik=; b=DDGZhippCJYmm5efCO 5MvbczAOpfLA4Tq2+snsD6rmErTzbESju2DUWSQxVUnf4C3hSn/swS2AiB71rvQ1 G4xW+rJDpmZXjaAggHACwb/ZJHiRgjz95P7kmWy1LUmveRgu1OAEvrfGUaVhlEc/ rwxBo9FVh6ZHqvRxo8LVCBxD4= Received: by filter-332.sjc1.sendgrid.net with SMTP id filter-332.3203.5640909237 2015-11-09 12:24:50.65316405 +0000 UTC Received: from herokuapp.com (ec2-54-82-2-136.compute-1.amazonaws.com [54.82.2.136]) by ismtpd0004p1iad1.sendgrid.net (SG) with ESMTP id HccmXsi9RnmXI2TdvvoCpA for ; Mon, 09 Nov 2015 12:24:50.548 +0000 (UTC) Date: Mon, 09 Nov 2015 12:24:50 +0000 From: mame@ruby-lang.org To: ruby-core@ruby-lang.org Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Redmine-MailingListIntegration-Message-Ids: 46057 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 11665 X-Redmine-Issue-Author: keithrbennett X-Redmine-Sender: mame 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/Ymy4QrNMhiuLXJG8OTL2vJD1yS5OefjNaj0yuTV585u/pBk3+eirfeTevvPgZ9 GIdW1aJAcKyLAX3DkoRNuXKD1LeKfKZptCuqm8JYz+uE+ZdOdhgO5cNUH1mgcWBPnjl1mKReo4AJxh E3M9RtmWCHW2d0U= X-ML-Name: ruby-core X-Mail-Count: 71415 Subject: [ruby-core:71415] [Ruby trunk - Feature #11665] Support nested functions for better code organization 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: , Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #11665 has been updated by Yusuke Endoh. > But at least, the current behavior of nested method definition is useless I'd like to show some cases where the current behavior is actually useful. I'm not against the change, though. ~~~ def warn_foo warn "foo def warn_foo end end 3.times do |i| p i warn_foo #=> warn only once end ~~~ ~~~ def enable_log def log(s) puts s end end def disable_log def log(s) end end enable_log log("foo") disable_log log("bar") enable_log log("baz") ~~~ -- Yusuke Endoh ---------------------------------------- Feature #11665: Support nested functions for better code organization https://bugs.ruby-lang.org/issues/11665#change-54784 * Author: Keith Bennett * Status: Open * Priority: Normal * Assignee: ---------------------------------------- The wisdom of using local variables has been internalized in all of us from the beginning of our software careers. If we need a variable referring to data that is used only in a single method, we create a local variable for it. Yet if it is logic to which we need to refer, we make it an instance method instead. In my opinion, this is inconsistent and unfortunate. The result is a bloated set of instance methods that the reader must wade through to mentally parse the class. The fact that some of these methods are used only by one other method is never communicated by the code; the reader has to discover that for him/herself. The number of possible interactions among the instance methods is one of many measures of our software's complexity. The number of possible instance method interactions is (method_count * (method_count) - 1). Using this formula, a class with 10 methods will have a complexity of 90. If 4 of those methods are used by only 1 other method, and we could move them inside those methods, the complexity would plummet to 30 (6 * (6 - 1)), a third of the original amount! While it is possible to extract subsets of these methods into new smaller classes, this is not always practical, especially in the case of methods called only by the constructor. Fortunately, we do have lambdas in Ruby, so I will sometimes create lambdas inside methods for this purpose. However, lambdas are not as isolated as methods, in that they can access and modify local variables previously defined outside their scope. Furthermore, the lambdas can be passed elsewhere in the program and modify those locals from afar! So using methods would be cleaner and safer. Another weakness of using lambdas for this purpose is that, unlike methods that are created at interpret time, lambdas are objects created at runtime -- so if a method creating 2 lambdas is called a million times in a loop, you'll need to create and garbage collect another 2 million objects. (This can be circumvented by defining the lambdas as class constants or assigning them to instance variables, but then they might as well be instance methods.) I realize that implementing this feature would be a substantial undertaking and may not be feasible at this time. That said, I think it would be useful to discuss this now so we might benefit from its implementation someday. * * * * (Much of this content is communicated in my talk on Ruby lambdas; slide show is at https://speakerdeck.com/keithrbennett/ruby-lambdas-functional-conf-bangalore-oct-2014 and YouTube video of the presentation at FunctionalConf in Bangalore at https://www.youtube.com/watch?v=hyRgf6Qc5pw.) Also, this post is also posted as a blog article at http://www.bbs-software.com/blog/2015/11/07/the-case-for-nested-methods-in-ruby/. -- https://bugs.ruby-lang.org/