DouKaku?

require 'pseudohash' # http://www.notwork.org/~gotoken/ruby/p/pseudohash/

xs = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9]

h = PseudoHash.new
xs.each{|i|
  h[i, true] = nil
}
xs_out = h.map{|k, v| k}

p xs_out