ruby_array_permutations.rb

# http://facets.rubyforge.org/doc/api/core/classes/Array.html#M000145

require 'rubygems'
require 'facets'

class Array
  def permutations(min = 0, max = size + 1)
    variations = []
    (min..max).each do |permutation_size|
      permutation(permutation_size) do |permutation|
        variations << permutation
      end
    end
    variations
  end
end

puts [1, 2, 3].permutations.inspect
# => [[], [1], [2], [3], [1, 2], [2, 1], [1, 3], [3, 1], [2, 3], [3, 2], 
#    [1, 2, 3], [2, 1, 3], [2, 3, 1], [1, 3, 2], [3, 1, 2], [3, 2, 1]]