I was looking for a way to create combinations of things in Ruby and I found an article by Uncle Bob detailing his attempt at writing a combination generator in Ruby. I modified it slightly to use an array of items, instead of simple indexes. require 'pp' def choose(n, k) return [[]] if n.nil? || n.empty? && k == 0 return [] if n.nil? || n.empty? && k > 0 return [[]] if n.size > 0 && k == 0 c2 = n.clone c2.pop new_element = n.clone.pop choose(c2, k) + append_all(choose(c2, k-1), new_element) end def append_all(lists, element) lists.map { |l| l << element } end all = [:a, :b, :c, :d] pp choose(all,3) The above code prints out: [[:a, :b, :c], [:a, :b, :d], [:a, :c, :d], [:b, :c, :d]] If you don't want these types of combinations, there is a Ruby library for calculating Permutations which will give you all the different permutations, or orderings, of a set of things.