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=-3.9 required=3.0 tests=AWL,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 ABDC11F4B4 for ; Tue, 29 Sep 2020 15:57:07 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 0FF11120A94; Wed, 30 Sep 2020 00:56:30 +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 841F0120A87 for ; Wed, 30 Sep 2020 00:56:27 +0900 (JST) Received: by filterdrecv-p3mdw1-5dd6bc5999-zstxr with SMTP id filterdrecv-p3mdw1-5dd6bc5999-zstxr-19-5F73594C-20 2020-09-29 15:57:00.381595196 +0000 UTC m=+669503.300025002 Received: from herokuapp.com (unknown) by geopod-ismtpd-6-0 (SG) with ESMTP id ANdWu8pdTPS3bVCre1W4vQ for ; Tue, 29 Sep 2020 15:57:00.285 +0000 (UTC) Date: Tue, 29 Sep 2020 15:57:00 +0000 (UTC) From: marcandre-ruby-core@marc-andre.ca Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 76059 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: marcandre 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?6=2FIMxCQLDposcQf5wmbDAtfaKduBAO0bKyhL3BGZtMQ5q7K2TvpbN6A7JIyt9E?= =?us-ascii?Q?aOgCteYEPcDD0AujU5UaSg4EWgdwoeC2aeS+8Vk?= =?us-ascii?Q?5KqYom25vg7rQIWc9fRmAidGh4zXlLI7evdT9em?= =?us-ascii?Q?YPIV9qEpPn0njjdCG=2FCO=2Foo0ar+2WkilMBzk3=2F0?= =?us-ascii?Q?76WBJnvar+ZoeinwCOlN2SCujz6VXQwZ8RbtNB9?= =?us-ascii?Q?X3hI77t4mwI8XpSmdD0KUoiAKpCkSCkc5WddXj?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 100218 Subject: [ruby-core:100218] [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 marcandre (Marc-Andre Lafortune). esquinas (Enrique Esquinas) wrote in #note-46: > Here `calculationOn3D` expects the `point` variable to implement the 3D interface and be accessed like `point.x`,`point.y`,`point.z` so it just works. > > In Ruby we currently have the option to `Struct.new(:x, :y, :z).new(12, 34, 56)` or use `OpenStruct.new({ x: 12, y: 34, z; 56 })` which we have to require and has other problems already addressed at the top by @Ko1 I don't find this example convincing at all. In Ruby, we would have an actual class `Point3D` with specialized `+`, `-`, as well as extra methods, and there's no way to know which of these `calculationOn3D` would use (now or in the future). There's also no gain in passing `%struct{...}` instead of `Point3D.new(...)`. I wish someone would point out a few examples in a popular gem or a Rails app say where this would be useful and actually improve actual code. ---------------------------------------- Feature #16986: Anonymous Struct literal https://bugs.ruby-lang.org/issues/16986#change-87807 * Author: ko1 (Koichi Sasada) * Status: Open * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) ---------------------------------------- # Abstract How about introducing anonymous Struct literal such as `${a: 1, b: 2}`? It is almost the same as `Struct.new(:a, :b).new(1, 2)`. # Proposal ## Background In many cases, people use hash objects to represent a set of values such as `person = {name: "ko1", country: 'Japan'}` and access its values through `person[:name]` and so on. It is not easy to write (three characters `[:]`!), and it easily introduces misspelling (`person[:nama]` doesn't raise an error). If we make a `Struct` object by doing `Person = Struct.new(:name, :age)` and `person = Person.new('ko1', 'Japan')`, we can access its values through `person.name` naturally. However, it costs coding. And in some cases, we don't want to name the class (such as `Person`). Using `OpenStruct` (`person = OpenStruct.new(name: "ko1", country: "Japan")`), we can access it through `person.name`, but we can extend the fields unintentionally, and the performance is not good. Of course, we can define a class `Person` with attr_readers. But it takes several lines. To summarize the needs: * Easy to write * Doesn't require declaring the class * Accessible through `person.name` format * Limited fields * Better performance ## Idea Introduce new literal syntax for an anonymous Struct such as: `${ a: 1, b: 2 }`. Similar to Hash syntax (with labels), but with `$` prefix to distinguish. Anonymous structs which have the same member in the same order share their 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 to this spec, we can specify anonymous Struct classes 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` similarly 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 the key names. ## Naming If we name an anonymous class, literals with the same members share the name. ```ruby s1 = ${a:1} s2 = ${a:2} p [s1, s2] #=> [#, #] A = s1.class p [s1, s2] #=> [#, #] ``` Maybe that is not a good behavior. -- https://bugs.ruby-lang.org/