cross multiple arraies

gistfile1.rb

class Array
  def cross(array)
    product(array).map { |e| e.flatten }
  end
end

p [1,2].cross([3,4])
#=> [[1, 3], [1, 4], [2, 3], [2, 4]]
p [1,2].cross([3,4]).cross([5,6])
#=> [[1, 3, 5], [1, 3, 6], [1, 4, 5], [1, 4, 6], [2, 3, 5], [2, 3, 6], [2, 4, 5], [2, 4, 6]]