# File lib/diff/lcs.rb, line 215
    def LCS(seq1, seq2, &block) #:yields seq1[ii] for each matched:
      matches = Diff::LCS.__lcs(seq1, seq2)
      ret = []
      matches.each_with_index do |ee, ii|
        unless matches[ii].nil?
          if block_given?
            ret << (yield seq1[ii])
          else
            ret << seq1[ii]
          end
        end
      end
      ret
    end