enumerable.rb

module Enumerable
  def normalize
    magnitude = Math.sqrt(reduce(:+))
    return self if magnitude.nan?
    map { |x| x.to_f / magnitude }
  end

  def similarity(arr)
    return 0.0 if arr.count != count
    similarity = Math.sqrt(zip(arr).map { |d| d.first * d.second }.reduce(:+))
    similarity.nan? ? 0.0 : similarity
  end

  def score
    score = Math.sqrt(map { |d| d * d }.reduce(:+))
    score.nan? ? 0.0 : score
  end
end