# File lib/core/facets/enumerable/probability.rb, line 9
  def probability
    probs = Hash.new(0.0)
    size = 0.0
    each do | e |
      probs[e] += 1.0
      size += 1.0
    end
    probs.keys.each{ |e| probs[e] /= size }
    probs
  end