anchor.diff:          {Pids, NewRemoteGroups} ->
               sync_groups(Scope, ScopeMon, MG, NewRemoteGroups, Tail);
           {OldPids, NewRemoteGroups} ->
  -            [{Group, AllOldPids, LocalPids}] = ets:lookup(Scope, Group),
  +            [{_Group, AllOldPids, LocalPids}] = ets:lookup(Scope, Group),
               %% should be really rare...
               AllNewPids = Pids ++ AllOldPids -- OldPids,
               true = ets:insert(Scope, {Group, AllNewPids, LocalPids}),
  
positive.code: leave_remote_update_ets(Scope, ScopeMon, MG, Pids, Groups) ->
      _ = [
          case ets:lookup(Scope, Group) of
              [{Group, All, Local}] ->
                  case All -- Pids of
                      [] when Local =:= [] ->
                          ets:delete(Scope, Group);
  
negative.code: leave_remote_update_ets(Scope, ScopeMon, MG, Pid, Groups) when is_pid(Pid) ->
      _ = [
          case ets:lookup(Scope, Group) of
              [{_Group, [Pid], []}] ->
                  ets:delete(Scope, Group),
                  notify_group(ScopeMon, MG, leave, Group, [Pid]);
              [{_Group, All, Local}] ->
                  ets:insert(Scope, {Group, lists:delete(Pid, All), Local}),
                  notify_group(ScopeMon, MG, leave, Group, [Pid]);
              [] ->
  