Issue #16155 has been updated by connorshea (Connor Shea). shevegen (Robert A. Heiler) wrote: > You could consider adding this to the upcoming developer meeting: > > https://bugs.ruby-lang.org/issues/16152 > > And ask matz whether he would be fine with the functionality > itself; or, more importantly, the name for the method > (#intersection) since the functionality already exists. Thanks, I will :) After thinking about the proposal a bit more, one other thing I wanted to ask was about whether we should allow multiple arrays to be passed as arguments. `Array#difference` and `Array#union` both allow this, so it might make sense to have `Array#intersection` also take multiple arguments. For example: ```ruby # intersection with multiple arguments. [ 'a', 'b', 'b', 'z' ].intersection([ 'a', 'b', 'c' ], [ 'b' ]) #=> [ 'b' ] ``` Should we keep `intersection` as a simple alias for `&` or have it allow multiple arrays, to match the `difference` and `union` methods? ---------------------------------------- Feature #16155: Add an Array#intersection method https://bugs.ruby-lang.org/issues/16155#change-81487 * Author: connorshea (Connor Shea) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- `Array#union` and `Array#difference` were added in Ruby 2.6 ([see this bug](https://bugs.ruby-lang.org/issues/14097)), but an equivalent for `&` (intersection) was not. I'd like to propose `Array#intersection`. This would essentially just be a more readable alias for `Array#&`, in the same way that `Array#|` and `Array#-` have `Array#union` and `Array#difference`. I think it'd make sense for Ruby to have a more readable name for this method :) Current syntax: ``` ruby [ 1, 1, 3, 5 ] & [ 3, 2, 1 ] #=> [ 1, 3 ] [ 'a', 'b', 'b', 'z' ] & [ 'a', 'b', 'c' ] #=> [ 'a', 'b' ] ``` What I'd like to see added: ```ruby [ 1, 1, 3, 5 ].intersection([ 3, 2, 1 ]) #=> [ 1, 3 ] [ 'a', 'b', 'b', 'z' ].intersection([ 'a', 'b', 'c' ]) #=> [ 'a', 'b' ] ``` mame asks about `intersection` [in this comment](https://bugs.ruby-lang.org/issues/14097#note-26) on the `union`/`difference` bug, but as far as I can tell it was never addressed. [`Set#intersection`](http://ruby-doc.org/stdlib-2.6.2/libdoc/set/rdoc/Set.html#method-i-intersection) already exists and is an alias for `Set#&`, so there's precedent for such a method to exist. Thanks for Ruby, I enjoy using it a lot! :) Related links: - [PR for `union`](https://github.com/ruby/ruby/pull/1747) - [PR for `difference`](https://github.com/ruby/ruby/pull/1758) - [Bug for adding `union` and `difference` methods](https://bugs.ruby-lang.org/issues/14097) -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>