array_rotate.rb

class Array
  def rotate(number_of_times = 1)
    returning(self) do
      number_of_times.times { unshift(pop) }
    end
  end
end

# why would you use this?
#
# an array representing the hours in the day, in sequence up to the last hour:
#
#   hours_in_day = (0..23).to_a
#   hours_up_to_last = hours_in_day.rotate(24 - Time.now.hour)
#
#   # assuming its currently 6:30pm
#   # => [18, 19, 20, 21, 22, 23, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]