#!/usr/bin/env ruby

class Array
	def combinations n
		result = Array.new
		if n > 0
			(0 .. self.length - n).each do |i|
				combs = self[i + 1 .. -1].combinations(n - 1)
				combs = [[]] if combs.empty?
				combs.collect {|comb| [self[i]] + comb}.each {|x| result << x}
			end
		end
		return result
	end
end