anchor.diff:  %% @doc Incs and returns the current Serial
   handle_call(get_serial, _From,
               State=#state{serial_number=SerialNumber}) ->
  -  NextSerial = SerialNumber + 1,
  -  {reply, NextSerial, State#state{serial_number=NextSerial}};
  +  {reply, SerialNumber, State};
   
   handle_call({subscribe, WPid, Topics}, _From,
               State=#state{pid_to_topics=PidToTopics,
  
positive.code:                          per_topic_message_queue=CurrentMQueueMap}) ->
    %% Compute the Next Serial Number
    NextSerial = CurrentSerialNumber + 1,
  
    %% The minimum information to know how to: rm things from the message queue
    %% and to know if the client serial is too old to retroact properly
  
negative.code:     empty ->
        AggList;
      {value, MessagePack = {_Message, _Topics, Serial}} ->
        if (Serial =< MinSerial) ->
            % MinSerial is the serial of the latest message that we don't need.
            % Thus, here, we've reached the first message in this per-topic
            % queue that we don't need. Return what we have.
            AggList;
          true ->
            % Haven't reached the first message we don't need yet, keep collecting
            get_messages_above_limit(Rest, MinSerial, [MessagePack | AggList])
        end
    end.
  