Add cartesian to Enumerable


module Enumerable
  def cartesian(other)
    inject([]) { |res, x| other.inject(res) { |res, y| res << [x,y] } }
  end
end

1.	get Enumerable involved
2.	Sorting an Array by Frequency of Appearance
3.	Building a Histogram
4.	Call each a number of times
5.	randomly each
6.	Writing Block Methods that Classify or Collect
7.	Implementing Enumerable - Write One Method, Get 22 Free
8.	Enumerable.instance_methods.sort
9.	Sort on two arrays

Add cartesian to Enumerable : Enumerable « Collections « Ruby