gistfile1.txt

module Enumerable

  def permutations
    Enumerable::Enumerator.new(self, :each_permutation)
  end

  def each_permutation
    each do |item|
      others = select {|other| item != other}

      others.permutations.each do |other_permutation|
        yield [item] + other_permutation
      end

      yield [item]

    end
  end

end


puts [1,2].permutations.to_a.inspect

puts [1,2,3,4].permutations.to_a.length.inspect
puts [1,2,3,4].permutations.to_a.uniq.length.inspect

puts ["foo", "bar"].permutations.to_a.inspect