anchor.diff:  
   -record(trace_state, {
             actors                        :: [pid() | channel_actor()],
  -          clock_map        = dict:new() :: clock_map(),
  +          clock_map        = empty_map():: clock_map(),
             done             = []         :: [event()],
             enabled          = []         :: [pid() | channel_actor()],
             index                         :: index(),
  
positive.code: -type clock_map()           :: dict().
  -type message_event_queue() :: queue().
  -else.
  -type clock_map()           :: dict:dict(pid(), vector_clock()).
  -type message_event_queue() :: queue:queue(#message_event{}).
  -endif.
  
  
negative.code:   {[], UntimedLate};
  split_trace([#trace_state{clock_map = ClockMap} = State|RevEarlier] = RevEarly,
              UntimedLate) ->
    case is_empty_map(ClockMap) of
      true  -> split_trace(RevEarlier, [State|UntimedLate]);
      false -> {RevEarly, UntimedLate}
    end.
  