hamming.rb

module Hamming
  def compute_hamming_distance string_1, string_2
    raise ArgumentError unless strings_like_length? string_1, string_2
    string_1.chars.zip(string_2.chars).count { |x, y| x != y }
  end
  
  def strings_like_length? a, b
    a.length == b.length
  end
end

class MyMathyClass
  extend Hamming
end

MyMathyClass.new.compute_hamming_distance "abc", "abcde"