anchor.diff:  -type instr()      :: term().
   -type transition() :: {concuerror_lid:lid(), instr(), list()}.
   -type clock_map()  :: dict(). %% dict(concuerror_lid:lid(), clock_vector()).
  -%% -type clock_vector() :: dict(). %% dict(concuerror_lid:lid(), s_i()).
  +%% -type clock_vector() :: orddict(). %% dict(concuerror_lid:lid(), s_i()).
   
   select_one_shallow_except_with_fix(DeepList, Exceptions) ->
       select_one_shallow_except_with_fix(DeepList, Exceptions, []).
  
positive.code: add_all_backtracks_trace({Lid, _, _} = Transition, Trace, PreBound, Flavor) ->
      [#trace_state{i = I} = Top|
       [#trace_state{clock_map = ClockMap}|_] = PTrace] = Trace,
      ClockVector = dict:store(Lid, I, lookup_clock(Lid, ClockMap)),
      add_all_backtracks_trace(Transition, Lid, ClockVector, PreBound,
                               Flavor, PTrace, [Top]).
  
  
negative.code: lookup_clock(P, ClockMap) ->
      case dict:find(P, ClockMap) of
          {ok, Clock} -> Clock;
          error -> orddict:new()
      end.
  
  lookup_clock_value(P, CV) ->
      case orddict:find(P, CV) of
          {ok, Value} -> Value;
          error -> 0
      end.
  