levenshtein_distance

# File lib/bundler/similarity_detector.rb, line 32
    def levenshtein_distance(this, that, ins = 2, del = 2, sub = 1)
      # ins, del, sub are weighted costs
      return nil if this.nil?
      return nil if that.nil?
      dm = [] # distance matrix

      # Initialize first row values
      dm[0] = (0..this.length).collect {|i| i * ins }
      fill = [0] * (this.length - 1)

      # Initialize first column values
      (1..that.length).each do |i|
        dm[i] = [i * del, fill.flatten]
      end

      # populate matrix
      (1..that.length).each do |i|
        (1..this.length).each do |j|
          # critical comparison
          dm[i][j] = [
            dm[i - 1][j - 1] + (this[j - 1] == that[i - 1] ? 0 : sub),
            dm[i][j - 1] + ins,
            dm[i - 1][j] + del
          ].min
        end
      end

      # The last value in matrix is the Levenshtein distance between the strings
      dm[that.length][this.length]
    end