levenshtein_distance

# File railties/lib/rails/generators.rb, line 282
      def self.levenshtein_distance str1, str2
        s = str1
        t = str2
        n = s.length
        m = t.length

        return m if (0 == n)
        return n if (0 == m)

        d = (0..m).to_a
        x = nil

        # avoid duplicating an enumerable object in the loop
        str2_codepoint_enumerable = str2.each_codepoint

        str1.each_codepoint.with_index do |char1, i|
          e = i+1

          str2_codepoint_enumerable.with_index do |char2, j|
            cost = (char1 == char2) ? 0 : 1
            x = [
                 d[j+1] + 1, # insertion
                 e + 1,      # deletion
                 d[j] + cost # substitution
                ].min
            d[j] = e
            e = x
          end

          d[m] = x
        end

        x
      end