anchor.diff:                                        {Max, AccIn}
                                 end
                         end, {MaxNum, []}, DB),
  +    %% see HINT in foldl/3
       lists:foldl(Fun, Acc, Data).
   
  -%% @doc Is equivalent to ets:foldr(Fun, Acc0, DB).
  +%% @doc makes a foldr over the whole dataset.
  +%%      Returns a potentially larger-than-memory dataset. Use with care.
   -spec foldr(DB::db(), Fun::fun((entry(), AccIn::A) -> AccOut::A), Acc0::A) -> Acc1::A.
   foldr({DB, _FileName}, Fun, Acc) ->
       Data = toke_drv:fold(fun(_Key, Entry, AccIn) ->
                                    [?OUT(Entry) | AccIn]
                            end, [], DB),
  +    %% see HINT in foldl/3
       lists:foldr(Fun, Acc, Data).
   
  -%% @doc Is equivalent to foldr(DB, Fun, Acc0, Interval, get_load(DB)).
  +%% @equiv foldr(DB, Fun, Acc0, Interval, get_load(DB))
  +%% @doc   Returns a potentially larger-than-memory dataset. Use with care.
   -spec foldr(DB::db(), Fun::fun((entry(), AccIn::A) -> AccOut::A), Acc0::A,
                                  Interval::db_backend_beh:interval()) -> Acc1::A.
   foldr({DB, _FileName}, Fun, Acc, Interval) ->
  
positive.code:     toke_drv:delete(DB, ?IN(Key)),
      State.
  
  %% @doc Returns the name of the DB specified in new/1.
  -spec get_name(DB::db()) -> nonempty_string().
  get_name({_DB, FileName}) ->
      FileName.
  
negative.code:                                  end
                           end, [], DB),
      CutData = lists:sublist(Data, MaxNum),
      %% see HINT in foldl/3
      lists:foldr(Fun, Acc, CutData).
  
  is_in({element, Key}, OtherKey) -> Key =:= OtherKey;
  