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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY 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 760FE1F5AE for ; Sat, 27 Jun 2020 14:28:51 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 78FF1120AC3; Sat, 27 Jun 2020 23:28:21 +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 7A2A51209FC for ; Sat, 27 Jun 2020 23:28:18 +0900 (JST) Received: by filterdrecv-p3iad2-5b55dcd864-5dqzw with SMTP id filterdrecv-p3iad2-5b55dcd864-5dqzw-19-5EF75797-5C 2020-06-27 14:28:39.732758933 +0000 UTC m=+76752.607523796 Received: from herokuapp.com (unknown) by ismtpd0068p1mdw1.sendgrid.net (SG) with ESMTP id 6_WuV6gvTv6H2K1DGHIuAQ for ; Sat, 27 Jun 2020 14:28:39.617 +0000 (UTC) Date: Sat, 27 Jun 2020 14:28:39 +0000 (UTC) From: brooke@alchemists.io Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 74772 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Feature X-Redmine-Issue-Id: 16986 X-Redmine-Issue-Author: ko1 X-Redmine-Issue-Assignee: matz X-Redmine-Sender: bkuhlmann 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?wZSUyHTOofNLkMRGKt5UdbskXzNRrWSJJ8pQ2aWchtNKQME9UFpW9uzlu6fa2R?= =?us-ascii?Q?lqp96FS54qgBhcqtBWmsmh90uAGys=2FS1893vsQl?= =?us-ascii?Q?5wGWdHeCdK43Nk2WPCimPnHyXuksrbNgyAleTpb?= =?us-ascii?Q?Id9sWRWrCVRqL8Iqsj5M4HSBG91DIkPD1kD88IT?= =?us-ascii?Q?hMmubo+LLt5jJgw+1FZsGnEUVpjotc0S+3OWlMs?= =?us-ascii?Q?uGvCh7vcLjvRD7Yb4=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 98982 Subject: [ruby-core:98982] [Ruby master Feature#16986] Anonymous Struct literal 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 #16986 has been updated by bkuhlmann (Brooke Kuhlmann). I like the idea of being able to quickly create an anonymous Struct but am concerned about the use of `$` for the syntax since that hinders readability and causes confusion due to `$` generally denoting a *global variable*. Why not allow structs to have similar behavior to existing objects in Ruby like hashes, arrays, etc in order to remain *consistent*? Example: ``` ruby # Kernel.Hash Hash a: 1, b: 2 # => {a: 1, b: 2} # Hash.[] Hash[a: 1, b: 2] # => {a: 1, b: 2} # Kernel.Array Array 1 # => [1] # Array.[] Array[1] => [1] ``` With the suggestion above, we could implement the same for Structs too. Example: ``` ruby # Kernel.Struct Struct a: 1, b: 2 # => # # Struct.[] Struct[a: 1, b: 2] # => # ``` ---------------------------------------- Feature #16986: Anonymous Struct literal https://bugs.ruby-lang.org/issues/16986#change-86362 * Author: ko1 (Koichi Sasada) * Status: Open * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) ---------------------------------------- # Abstract How about to introduce anonymous Struct literal such as `${a: 1, b: 2}`? It is almost same as `Struct.new(:a, :b).new(1, 2)`. # Proposal ## Background In many cases, people use hash objects to represents a set of values such as `person = {name: "ko1", country: 'Japan'}` and accesses it with `person[:name]` and so on. It is not easy to write (3 letters `[:]`!), and easy to introduce misspelling (`person[:nama]` doesn't raise an error). If we make a `Struct` objects such as `Person = Struct.new(:name, :age)` and `person = Person.new('ko1', 'Japan')`, we can access it with `person.name` naturally. However making new `Struct` is a cost of coding. Some cases we don't want to name (such as `Person`). Using `OpenStruct` (`person = OpenStruct.new(name: "ko1", country: "Japan")`), we can access it with `person.name`, but we can extend the fields and the performance is not good. Of course, we can define the class `Person` and attr_readers. But several lines we need. To summaries the issues: * Easy to Write * Don't need to declare the class * Accessible with `person.name` format * Limited fields * Better performance ## Idea Introduce new syntax to make an anonymous Struct literal such as: `${ a: 1, b: 2 }`. Similar to Hash syntax (with labels), but `$` prefix to recognize. Anonymous structs which has same member with same order share the class. ```ruby s1 = ${a: 1, b: 2, c: 3} s2 = ${a: 1, b: 2, c: 3} assert s1 == s2 s3 = ${a: 1, c: 3, b: 2} s4 = ${d: 4} assert_equal false, s1 == s3 assert_equal false, s1 == s4 ``` ## Note Unlike Hash literal syntax, this proposal only allows `label: expr` notation. No `${**h}` syntax. This is because if we allow to splat a Hash, it can be a vulnerability by splatting outer-input Hash. Thanks for this spec, we can specify the anonymous Struct class at compile time. We don't need to find or create Struct classes at runtime. ## Implementatation https://github.com/ruby/ruby/pull/3259 # Discussion ## Notation Matz said he thought about `{|a: 1, b: 2 |}` syntax. ## Performance Surprisingly, Hash is fast and Struct is slow. ```ruby Benchmark.driver do |r| r.prelude <<~PRELUDE st = Struct.new(:a, :b).new(1, 2) hs = {a: 1, b: 2} class C attr_reader :a, :b def initialize() = (@a = 1; @b = 2) end ob = C.new PRELUDE r.report "ob.a" r.report "hs[:a]" r.report "st.a" end __END__ Warming up -------------------------------------- ob.a 38.100M i/s - 38.142M times in 1.001101s (26.25ns/i, 76clocks/i) hs[:a] 37.845M i/s - 38.037M times in 1.005051s (26.42ns/i, 76clocks/i) st.a 33.348M i/s - 33.612M times in 1.007904s (29.99ns/i, 87clocks/i) Calculating ------------------------------------- ob.a 87.917M i/s - 114.300M times in 1.300085s (11.37ns/i, 33clocks/i) hs[:a] 85.504M i/s - 113.536M times in 1.327850s (11.70ns/i, 33clocks/i) st.a 61.337M i/s - 100.045M times in 1.631064s (16.30ns/i, 47clocks/i) Comparison: ob.a: 87917391.4 i/s hs[:a]: 85503703.6 i/s - 1.03x slower st.a: 61337463.3 i/s - 1.43x slower ``` I believe we can speed up `Struct` similar to ivar accesses, so we can improve the performance. BTW, OpenStruct (os.a) is slow. ``` Comparison: hs[:a]: 92835317.7 i/s ob.a: 85865849.5 i/s - 1.08x slower st.a: 53480417.5 i/s - 1.74x slower os.a: 12541267.7 i/s - 7.40x slower ``` For memory consumption, `Struct` is more lightweight because we don't need to keep key names. ## Naming If we name the anonymous class, the same member literals share the name. ```ruby s1 = ${a:1} s2 = ${a:2} p [s1, s2] #=> [#, #] A = s1.class p [s1, s2] #=> [#, #] ``` Maybe it is not good behavior. -- https://bugs.ruby-lang.org/