From: gotoken@... Date: 2021-08-14T06:12:51+00:00 Subject: [ruby-core:104917] [Ruby master Feature#16428] Add Array#uniq?, Enumerable#uniq? Issue #16428 has been updated by gotoken (Kentaro Goto). Recently I read similar topic again elsewhere. They pointed * in most cases we have something to do on each duplicate element if any duplicate detected, e.g., reporting all duplicate elements as an error message * `uniq?` looks slightly odd because we don't have `sort?` or `clear?` (uniq etymology: Perl funtion uniq. Originally Version 3 Unix command uniq.) Though they make sense to me, but sometimes, in the case of back-of-the-envelope calculations, I just want to write code that just checks the array for duplicate elements, for example, to check whether a particular csv column meets a unique constraint from the irb console as Keith gave as an example. So instead, I suggest a set of three methods * `#repeated` returns a new Array containing repeated elements. This may be what we need. * `#repeated?` returns `true` if there is a repeated element. This may be faster than `! array.duplicate.empty?` because can return `true` immediately when a repetition is detected. * `#no_repeated?` returns the same to nagation of `#duplicate?`. This is what we want intuitively. And functionally identical to Kouhei's `uniq?`. Here I chose word *repeated* instead of *duplicate* so as not to confuse it with the meaning of `dup`. ---------------------------------------- Feature #16428: Add Array#uniq?, Enumerable#uniq? https://bugs.ruby-lang.org/issues/16428#change-93281 * 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: