anchor.diff:      ?f_debug("------------\nExplore ~p\n------------\n",
                [TraceTop#trace_state.i + 1]),
       case ordsets:subtract(Backtrack, Done) of
  -	[] ->
  +        [] ->
               ?f_debug("Backtrack set explored\n",[]),
               none;
           [SelectedLid|_RestLids] ->
  
positive.code:         {done, Ret} -> Ret;
          {cont, NewArg} -> dynamic_loop_acc(Fun, NewArg)
      end.
      
  update_lid_enabled(Lid, {_, Next, _}, Pollable, Enabled, Blocked) ->
      {NewEnabled, NewBlocked} =
          case is_enabled(Next) of
  
negative.code:                     true -> replay_trace(MightNeedReplayState);
                      false -> MightNeedReplayState
                  end,
              Instruction = dict:fetch(SelectedLid, TraceTop#trace_state.nexts),
              NewDone = ordsets:add_element(SelectedLid, Done),
              NewTraceTop = TraceTop#trace_state{done = NewDone},
              NewState = State#dpor_state{trace = [NewTraceTop|RestTrace]},
              {ok, Instruction, NewState}
      end.
  
  replay_trace(#dpor_state{proc_before = ProcBefore,
  