Issue #15590 has been updated by dpepper (Daniel Pepper). I stumbled upon this thread during my own quest to find duplicates in an array. Here's a PR to create `Array#duplicates?`. If that gains any traction, maybe we could follow with `Array#duplicates` to return the actual list of duplicate elements, which seems of interest to this group. https://github.com/ruby/ruby/pull/14805 ---------------------------------------- Feature #15590: Add dups to Array to find duplicates https://bugs.ruby-lang.org/issues/15590#change-114825 * Author: xdmx (Eric Bloom) * Status: Open ---------------------------------------- Many times I find myself debugging data and the need of finding duplicated values inside of an Array. Based on the amount of data it could be a simple `array.detect { |value| array.count(value) > 1 }` or a more performant way like ```ruby def dups_for(array) duplicated_values = [] tmp = {} array.each do |value| duplicated_values << value if tmp[value] tmp[value] = true end duplicated_values end ``` It would be awesome if there was a way directly from the core language to call `dups` (or another name, as it could be too similar to the current `dup`) on an array in order to get all the duplicated values. I'd love to create a PR for this, but my C level is non-existent 😞 -- https://bugs.ruby-lang.org/