anchor.diff:  
   map(_, {_, _, 0, _, _, nil} = BTree) ->
       erlang:error({empty_tree, BTree});
  -map(Function, {SubtreeNoMin, KeyNoMax, NumberKeyValues, SortFunction, State, Tree}) when is_function(Function, 2) ->
  -    {SubtreeNoMin, KeyNoMax, NumberKeyValues, SortFunction, State, map_tree(Function, State, Tree)}.
  +map(Function, {SubtreeNoMin, KeyNoMax, SizeKeyValues, SortFunction, State, Tree}) when is_function(Function, 2) ->
  +    {SubtreeNoMin, KeyNoMax, SizeKeyValues, SortFunction, State, map_tree(Function, State, Tree)}.
   
   -spec map_key_values(map_function(), key_values(), key_values()) -> key_values().
   
  
positive.code: 
  -spec size_key_values(b_tree()) -> non_neg_integer().
  
  size_key_values({_, _, NumberKeyValues, _, _, _}) ->
      NumberKeyValues.
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  
negative.code: -spec size_nodes_tree(tree(), state(), {non_neg_integer(), non_neg_integer()}) -> {non_neg_integer(), non_neg_integer()}.
  
  % Leaf node.
  size_nodes_tree({_, 0, _, []}, _, {SizeTotal, SizeLeaves}) ->
      {SizeTotal + 1, SizeLeaves + 1};
  size_nodes_tree({_, _, _, Subtrees}, State, {SizeTotal, SizeLeaves}) ->
      size_nodes_subtrees(Subtrees, State, {SizeTotal + 1, SizeLeaves}).
  
  -spec size_nodes_subtrees(subtrees(), state(), {non_neg_integer(), non_neg_integer()}) -> {non_neg_integer(), non_neg_integer()}.
  
  size_nodes_subtrees([], _, {SizeTotal, SizeLeaves}) ->
      {SizeTotal, SizeLeaves};
  size_nodes_subtrees([Tree | Tail], nil, {SizeTotal, SizeLeaves}) ->
      size_nodes_subtrees(Tail, nil, size_nodes_tree(Tree, nil, {SizeTotal, SizeLeaves}));
  size_nodes_subtrees([{KeyNo, SubtreeNo, KeyValues, SubtreesKey} | Tail], {StateTarget, _, _, LookupFunction} = State, {SizeTotal, SizeLeaves}) ->
      size_nodes_subtrees(Tail, State, size_nodes_tree({KeyNo, SubtreeNo, KeyValues, LookupFunction(StateTarget, lookup, SubtreesKey)}, State, {SizeTotal, SizeLeaves})).
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  