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=-3.1 required=3.0 tests=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 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 F13CE1F463 for ; Mon, 9 Sep 2019 19:10:49 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 34240120A22; Tue, 10 Sep 2019 04:10:37 +0900 (JST) Received: from o1678948x4.outbound-mail.sendgrid.net (o1678948x4.outbound-mail.sendgrid.net [167.89.48.4]) by neon.ruby-lang.org (Postfix) with ESMTPS id 2FD931208A5 for ; Tue, 10 Sep 2019 04:10:35 +0900 (JST) Received: by filter0060p3iad2.sendgrid.net with SMTP id filter0060p3iad2-23768-5D76A3AC-12 2019-09-09 19:10:36.265185155 +0000 UTC m=+8407.810538479 Received: from herokuapp.com (unknown [3.86.63.147]) by ismtpd0050p1iad1.sendgrid.net (SG) with ESMTP id Mh1mvwLQRkWmZrCHtK0-Nw for ; Mon, 09 Sep 2019 19:10:36.218 +0000 (UTC) Date: Mon, 09 Sep 2019 19:10:36 +0000 (UTC) From: connor.james.shea@gmail.com Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 70425 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 16155 X-Redmine-Issue-Author: connorshea X-Redmine-Sender: connorshea 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?k9U0VZ8qL0tMw+MOJrdh7mB2Rz9nL9Df2yQthLiTTZzuVP3WeuqyruGrB4y28Z?= =?us-ascii?Q?5p2O=2FnoJd5oEB+WYsPtNDVnzgNitDky29F1ymeZ?= =?us-ascii?Q?lYhwg9KDILhCg5nWNJiiBXqTHC8pk1V+0Oacueh?= =?us-ascii?Q?b3LEGA7tB5PBUsudUGOIp8TW2zOA27Ad7BM+dTe?= =?us-ascii?Q?yWPSX3cMpqLA5w1E0ts7yIrQ89uNLWhaTsA=3D=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 94871 Subject: [ruby-core:94871] [Ruby master Feature#16155] Add an Array#intersection method 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 #16155 has been updated by connorshea (Connor Shea). shevegen (Robert A. Heiler) wrote: > You could consider adding this to the upcoming developer meeting: > > https://bugs.ruby-lang.org/issues/16152 > > And ask matz whether he would be fine with the functionality > itself; or, more importantly, the name for the method > (#intersection) since the functionality already exists. Thanks, I will :) After thinking about the proposal a bit more, one other thing I wanted to ask was about whether we should allow multiple arrays to be passed as arguments. `Array#difference` and `Array#union` both allow this, so it might make sense to have `Array#intersection` also take multiple arguments. For example: ```ruby # intersection with multiple arguments. [ 'a', 'b', 'b', 'z' ].intersection([ 'a', 'b', 'c' ], [ 'b' ]) #=> [ 'b' ] ``` Should we keep `intersection` as a simple alias for `&` or have it allow multiple arrays, to match the `difference` and `union` methods? ---------------------------------------- Feature #16155: Add an Array#intersection method https://bugs.ruby-lang.org/issues/16155#change-81487 * Author: connorshea (Connor Shea) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- `Array#union` and `Array#difference` were added in Ruby 2.6 ([see this bug](https://bugs.ruby-lang.org/issues/14097)), but an equivalent for `&` (intersection) was not. I'd like to propose `Array#intersection`. This would essentially just be a more readable alias for `Array#&`, in the same way that `Array#|` and `Array#-` have `Array#union` and `Array#difference`. I think it'd make sense for Ruby to have a more readable name for this method :) Current syntax: ``` ruby [ 1, 1, 3, 5 ] & [ 3, 2, 1 ] #=> [ 1, 3 ] [ 'a', 'b', 'b', 'z' ] & [ 'a', 'b', 'c' ] #=> [ 'a', 'b' ] ``` What I'd like to see added: ```ruby [ 1, 1, 3, 5 ].intersection([ 3, 2, 1 ]) #=> [ 1, 3 ] [ 'a', 'b', 'b', 'z' ].intersection([ 'a', 'b', 'c' ]) #=> [ 'a', 'b' ] ``` mame asks about `intersection` [in this comment](https://bugs.ruby-lang.org/issues/14097#note-26) on the `union`/`difference` bug, but as far as I can tell it was never addressed. [`Set#intersection`](http://ruby-doc.org/stdlib-2.6.2/libdoc/set/rdoc/Set.html#method-i-intersection) already exists and is an alias for `Set#&`, so there's precedent for such a method to exist. Thanks for Ruby, I enjoy using it a lot! :) Related links: - [PR for `union`](https://github.com/ruby/ruby/pull/1747) - [PR for `difference`](https://github.com/ruby/ruby/pull/1758) - [Bug for adding `union` and `difference` methods](https://bugs.ruby-lang.org/issues/14097) -- https://bugs.ruby-lang.org/