# File lib/mail/parsers/content_type.rb, line 163
    def _nt_discrete_type
      start_index = index
      if node_cache[:discrete_type].has_key?(index)
        cached = node_cache[:discrete_type][index]
        @index = cached.interval.end if cached
        return cached
      end

      i0 = index
      if has_terminal?("text", false, index)
        r1 = instantiate_node(SyntaxNode,input, index...(index + 4))
        @index += 4
      else
        terminal_parse_failure("text")
        r1 = nil
      end
      if r1
        r0 = r1
      else
        if has_terminal?("image", false, index)
          r2 = instantiate_node(SyntaxNode,input, index...(index + 5))
          @index += 5
        else
          terminal_parse_failure("image")
          r2 = nil
        end
        if r2
          r0 = r2
        else
          if has_terminal?("audio", false, index)
            r3 = instantiate_node(SyntaxNode,input, index...(index + 5))
            @index += 5
          else
            terminal_parse_failure("audio")
            r3 = nil
          end
          if r3
            r0 = r3
          else
            if has_terminal?("video", false, index)
              r4 = instantiate_node(SyntaxNode,input, index...(index + 5))
              @index += 5
            else
              terminal_parse_failure("video")
              r4 = nil
            end
            if r4
              r0 = r4
            else
              if has_terminal?("application", false, index)
                r5 = instantiate_node(SyntaxNode,input, index...(index + 11))
                @index += 11
              else
                terminal_parse_failure("application")
                r5 = nil
              end
              if r5
                r0 = r5
              else
                r6 = _nt_extension_token
                if r6
                  r0 = r6
                else
                  @index = i0
                  r0 = nil
                end
              end
            end
          end
        end
      end

      node_cache[:discrete_type][start_index] = r0

      r0
    end