anchor.diff:  %% ====================================================================
   %% API functions
   %% ====================================================================
  --export([new_volume/0, new_volume/1, new_volume/2]).
  +-export([new_volume/0, new_volume/1, new_volume/2, 
  +         to_node_id/1, to_node_id/2]).
   
   
   -ifdef(TEST).
   %% export the private functions for testing only.
  --export([normalize/2, to_node_id/1, to_node_id/2, to_node_id/3,
  +-export([normalize/2, to_node_id/3,
            to_node_list/1, box_to_volume/2, filter_full_area/1,common_prefix/2,
            is_equal/2, first_node/1, rest_nodes/1, append_node/2,
            xval/1, yval/1, zval/1, is_all_ones/1, is_all_zeroes/1,
  
positive.code: new_volume(P1 = {_X1, _Y1, _Z1}, P2 = {_X2, _Y2, _Z2}) ->
      new_volume(to_node_id(P1, ?DEFAULT_MAX_DEPTH),
                 to_node_id(P2, ?DEFAULT_MAX_DEPTH)).
  
  
  %% ====================================================================
  
negative.code:     throw(unsupported_point_type_combination).
  
  
  %% to_node_id/3
  %% --------------------------------------------------------------------
  %% @private
  