anchor.diff:  await_evaluator_finish(Evs, Fails) ->
       receive
           {'DOWN', _MRef, process, Pid, normal} ->
  -            case lists:keydelete(Pid, 1, Evs) of
  +            case lists:delete(Pid, Evs) of
                   Evs ->
                       p("unknown process ~p died (normal)", [Pid]),
                       await_evaluator_finish(Evs, Fails);
  
positive.code:                     await_evaluator_finish(NewEvs, Fails)
              end;
          {'DOWN', _MRef, process, Pid, Reason} ->
              case lists:keydelete(Pid, 1, Evs) of
                  Evs ->
                      p("unknown process ~p died: "
                          "~n   ~p", [Pid, Reason]),
  
negative.code:         fun((State :: evaluator_state()) -> {error, term()}).
  
  -type command() :: #{desc  := string(),
                       cmd   := command_fun()}.
  
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  