From: "Simon Kröger" <SimonKroeger@...>
Date: 2005-12-24T09:55:43+09:00
Subject: Re: Translate from Python to Ruby

Sorry, i couldn't resist:

class Array
   def powset
     (0...(2**size)).map do |n|
       (0...size).reject{|i|n[i].zero?}.map{|i|at(i)}
     end
   end
end

cheers

Simon

Stefan Walk wrote:

> 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]]
> 
>