Interleaves another array into the current one, returns a new array

interleave.rb

class Array
  def interleave(other)
    arr = []
    size.times { |i| arr << self[i]; arr << other[i] unless i + 1 > other.size }
    left = other[size - 1 .. -1]
    arr += left if left
    arr
  end
end