# File lib/mail/parsers/rfc2822_obsolete.rb, line 232
    def _nt_obs_phrase
      start_index = index
      if node_cache[:obs_phrase].has_key?(index)
        cached = node_cache[:obs_phrase][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      s0, i0 = [], index
      loop do
        i1 = index
        r2 = _nt_word
        if r2
          r1 = r2
        else
          if has_terminal?(".", false, index)
            r3 = instantiate_node(SyntaxNode,input, index...(index + 1))
            @index += 1
          else
            terminal_parse_failure(".")
            r3 = nil
          end
          if r3
            r1 = r3
          else
            if has_terminal?("@", false, index)
              r4 = instantiate_node(SyntaxNode,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure("@")
              r4 = nil
            end
            if r4
              r1 = r4
            else
              @index = i1
              r1 = nil
            end
          end
        end
        if r1
          s0 << r1
        else
          break
        end
      end
      if s0.empty?
        @index = i0
        r0 = nil
      else
        r0 = instantiate_node(SyntaxNode,input, i0...index, s0)
      end

      node_cache[:obs_phrase][start_index] = r0

      r0
    end