class Nokogiri::CSS::Parser

def _reduce_43(val, _values, result) 

def _reduce_43(val, _values, result)
                    # 5n, -5n, 10n-1
        n = val[1]
        if n[0, 2] == 'n-'
          val[1] = 'n'
          val << "-"
          # b is contained in n as n is the string "n-b"
          val << n[2, n.size]
          result = Node.new(:NTH, val)
        elsif n == 'n'
          val << "+"
          val << "0"
          result = Node.new(:NTH, val)
        else
          raise Racc::ParseError, "parse error on IDENT '#{val[1]}'"
        end

    result
end