anchor.diff:  
   loop({Next, Messages} = State) ->
       receive
  -	{send_message, Message} ->
  +	{send_message, Message, _from} ->
   	    Next ! {new_message, {Message, self()}},
   	    loop(State);
   	{new_message, {Message, Node}} when Node == self() ->
  
positive.code: 		    ok;
  	    	Pid when is_pid(Pid) ->
  		    Next ! quit
  	    end
      end.
  
  set_next(Node, Next) ->
      Node ! {set_next, Next}.
  
  send_messages(M, Node, Message) ->
      send_message(M, 0, Node, Message).
  
negative.code: send_message(M, M, _Node, _Message) ->
      {ok, noreply};
  send_message(M, I, Node, Message) ->
      Node ! {send_message, Message, self()},
      send_message(M, I + 1, Node, Message).
  