Given a set S, generates the power set P(S) by using a mapping of the elements in S to binary strings

pset.rb

def pset(set)
  bins = (0...(2 ** set.length)).map { |x| ("%0#{set.length}d" % x.to_s(2)).split('').map(&:to_i) }
  bins.map do |a|
    a.map.with_index.map { |v, i| v > 0 ? set[i] : nil }.compact
  end
end