AdditiveExpr

# File lib/rexml/parsers/xpathparser.rb, line 426
      def AdditiveExpr path, parsed
        n = []
        rest = MultiplicativeExpr( path, n )
        if rest != path
          while rest =~ /^\s*(\+| -)\s*/
            if $1[0] == ++
              n = [ :plus, n, [] ]
            else
              n = [ :minus, n, [] ]
            end
            rest = MultiplicativeExpr( $', n[-1] )
          end
        end
        if parsed.size == 0 and n.size != 0
          parsed.replace(n)
        elsif n.size > 0
          parsed << n
        end
        rest
      end