rickhull/gist:5667367

## gistfile1.txt
def foo(a)
  ret = []
  1.upto(a.size) { |i| ret << a.combination(i).to_a }
  ret
end

foo([1,2,3])
#=> [[[1], [2], [3]], [[1, 2], [1, 3], [2, 3]], [[1, 2, 3]]]
	def foo(a)
	ret = []
	1.upto(a.size) { \|i\| ret << a.combination(i).to_a }
	ret
	end

	foo([1,2,3])
	#=> [[[1], [2], [3]], [[1, 2], [1, 3], [2, 3]], [[1, 2, 3]]]