From: Sam Kong <sam.s.kong@...>
Date: 2005-12-24T07:52:50+09:00
Subject: Translate from Python to Ruby

Hi!

I am trying to get a powerset (all subsets) of a set.
I couldn't find a code in Ruby, but I found a code in Python.
I'm trying to convert it to Ruby but it's not done easily.

def powset(seq):
    if seq:
        head, tail = seq[:1], seq[1:]
        for smaller in powset(tail):
            yield smaller
            yield head + smaller
    else:
        yield []

1. Can somebody translate the Python code into Ruby?
(I have difficulty in understanding the yield part)

2. Actually I want to add a method to Set class.
How can I change the function into a method which won't take any
parameter.
(Can a method be recursive if it doesn't take a parameter?
Maybe not.
Do I need a helper private method?)
example:
  s = Set[1,2,3]
  ps = s.powerset #returns a set of powerset of s

Thanks.

Sam