Delete first instance of matching element from array

Question

Say I have the array [1,2,3,1,2,3] and I want to delete the first instance of (say) 2 from the array giving [1,3,1,2,3]. What\'s the e

Answer 1

li.delete_at(li.index(n) || li.length)

li[li.length] is out of range, so the || li.length handles the case where n isn't in the list.

irb(main):001:0> li = [1,2,3,1,2,3]
=> [1, 2, 3, 1, 2, 3]
irb(main):002:0> li.delete_at(li.index(2) || li.length)
=> 2
irb(main):003:0> li.delete_at(li.index(42) || li.length)
=> nil
irb(main):004:0> li
=> [1, 3, 1, 2, 3]

Answer 2

Maybe it should become part of stdlib:

class Array
  def delete_first item
    delete_at(index(item) || length)
  end
end

Answer 3

If || li.length is to avoid sending nil to li.delete_at (which would result in a TypeError), then a more readable version might look like this

li.delete_at li.index(42) unless li.index(42).nil?