# File lib/rufus/treechecker.rb, line 223
      def clone
        rs = RuleSet.new
        rs.instance_variable_set(:@excluded_symbols, @excluded_symbols.dup)
        rs.instance_variable_set(:@accepted_patterns, @accepted_patterns.dup)
        rs.instance_variable_set(:@excluded_patterns, @excluded_patterns.dup)
        rs
      end