From: Stefan Walk <stefan.walk@...>
Date: 2005-12-24T09:32:51+09:00
Subject: Re: Translate from Python to Ruby

Non-recursive version:
I'm sure you can translate this for sets...

class Array
   def powset
     ret = []
     0.upto(2**size - 1) do |n|
       ret << []
       0.upto(size - 1) do |i|
         ret.last << self[i] if (n & (1 << i)) != 0
       end
     end
     ret
   end
end

p [].powset
p [1].powset
p [1,2].powset
p [1,2,3].powset
[[]]
[[], [1]]
[[], [1], [2], [1, 2]]
[[], [1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3]]