Quick Sort program in ruby

quick_sort.rb

# quick_sort.rb
#
# $ ruby quick_sort.rb
# [1, 2, 3, 4, 5, 6, 7, 8]

def quicksort(array)
  return array if array.length <= 1
  pivot_index = (array.length / 2).to_i
  pivot_value = array[pivot_index]
  array.delete_at(pivot_index)
  lesser = []
  greater = []
  array.each do |x|
    if x <= pivot_value
      lesser << x
    else
      greater << x
    end
  end
  return quicksort(lesser) + [pivot_value] + quicksort(greater)
end

array = [6,5,3,1,8,7,2,4]
sorted = quicksort(array)
print sorted