From: shyouhei@... Date: 2020-04-10T14:42:18+00:00 Subject: [ruby-core:97802] [Ruby master Feature#16428] Add Array#uniq?, Enumerable#uniq? Issue #16428 has been updated by shyouhei (Shyouhei Urabe). kyanagi (Kouhei Yanagita) wrote in #note-5: > I was developing mobile games, and I met these situations: > > A card deck can't have duplicate characters. > i.e. `deck.cards.map(&:character_id).uniq.size == deck.cards.size` > -> `deck.cards.map(&:character_id).uniq?` or `deck.cards.uniq?(&:character_id)` So you just want to test? Why doesn't `deck.cards.map(...).uniq!`'s return value work? > When players compose items, each of them should be different. > i.e. `materials.map(&:item_id).uniq.size == materials.size` > -> `materials.map(&:item_id).uniq?` or `materials.uniq?(&:item_id)` So you just want to test? Don't you want to show the duplicated materials to the players? Does `uniq?` help then? > Another situation: > > I developed a registration form for relay runners. > A request body is like this: > ``` > # Missing sections are allowed. You can send them later. > [ > { section: 1, name: 'aaa' }, > { section: 3, name: 'bbb' }, > { section: 5, name: 'ccc' }, > ] > ``` > In this case, duplication of `section` is not allowed. > `runners.map(&:section).uniq.size == runners.size` > -> `runners.map(&:section).uniq?` or `runners.uniq?(&:section)` So you just want to test? Don't you want to render error message about what is the duplicated section? Does `uniq?` help then? > I think `uniq?` is easier to write and read than `x.uniq.size == x.size` > for expression of no duplication. It's even faster. My main question is: it isn't faster when you render error messages. How do you use it? > This check is also found in Ruby's repository (bundler): > https://github.com/ruby/ruby/blob/master/spec/bundler/support/matchers.rb#L84 Honestlt I don't understand what this matcher is trying to achieve. ---------------------------------------- Feature #16428: Add Array#uniq?, Enumerable#uniq? https://bugs.ruby-lang.org/issues/16428#change-85018 * Author: kyanagi (Kouhei Yanagita) * Status: Feedback * Priority: Normal ---------------------------------------- I propose Array#uniq?. I often need to check if an array have duplicate elements. This method returns true if no duplicates are found in self, otherwise returns false. If a block is given, it will use the return value of the block for comparison. This is equivalent to `array.uniq.size == array.size`, but faster. ``` % ~/tmp/r/bin/ruby -rbenchmark/ips -e 'a = Array.new(100) { rand(1000) }; Benchmark.ips { |x| x.report("uniq") { a.uniq.size == a.size }; x.report("uniq?") { a.uniq? } }' Warming up -------------------------------------- uniq 25.765k i/100ms uniq? 76.544k i/100ms Calculating ------------------------------------- uniq 278.144k (� 4.1%) i/s - 1.391M in 5.010858s uniq? 981.868k (� 5.1%) i/s - 4.975M in 5.081611s ``` I think the name `uniq?` is natural because Array already has `uniq`. patch: https://github.com/ruby/ruby/pull/2762 -- https://bugs.ruby-lang.org/ Unsubscribe: