anchor.diff:                  true ->
                       foldr_element(F, F((Key ++ [Offset + I]) ++ Node, Value, A),
                           I - 1, Offset, Key, Data)
  +            end
  +    end.
  +
  +%%-------------------------------------------------------------------------
  +%% @doc
  +%% ===Call a function for each element.===
  +%% Traverses in alphabetical order.
  +%% @end
  +%%-------------------------------------------------------------------------
  +
  +foreach(F, Node) when is_function(F, 2) ->
  +    foreach(F, [], Node).
  +
  +foreach(F, Key, {I0, I1, Data}) ->
  +    foreach_element(F, 1, I1 - I0 + 2, I0 - 1, Key, Data).
  +
  +foreach_element(_, N, N, _, _, _) ->
  +    ok;
  +
  +foreach_element(F, I, N, Offset, Key, Data) ->
  +    {Node, Value} = erlang:element(I, Data),
  +    if
  +        is_list(Node) == false ->
  +            if
  +                Value == error ->
  +                    foreach(F, Key ++ [Offset + I], Node),
  +                    foreach_element(F, I + 1, N, Offset, Key, Data);
  +                true ->
  +                    NewKey = Key ++ [Offset + I],
  +                    F(NewKey, Value),
  +                    foreach(F, NewKey, Node),
  +                    foreach_element(F, I + 1, N, Offset, Key, Data)
  +            end;
  +        true ->
  +            if
  +                Value == error ->
  +                    foreach_element(F, I + 1, N, Offset, Key, Data);
  +                true ->
  +                    F((Key ++ [Offset + I]) ++ Node, Value),
  +                    foreach_element(F, I + 1, N, Offset, Key, Data)
               end
       end.
   
  
positive.code: %%-------------------------------------------------------------------------
  %% @doc
  %% ===Fold a function over the trie.===
  %% @end
  %%-------------------------------------------------------------------------
  
  
negative.code:     false = trie:is_key("aaaa", RootNode4),
      ok.
  
  %%%------------------------------------------------------------------------
  %%% Private functions
  %%%------------------------------------------------------------------------
  