anchor.diff:          end,
       F(State#state.left),
       F(State#state.right),
  -    {reply, ok, State}.
  +    {stop, normal, ok, State}.
   
   %%--------------------------------------------------------------------
   %% @private
  
positive.code: %% Adds data to the tree.
  add(Data) ->
      gen_server:call(?SERVER, {add, Data}).
  
  addNValues(0) ->
      ok;
  
negative.code: -behaviour(gen_server).
  
  %% API
  -export([start_link/0, walk/0, add/1, quit/0, addNValues/1, addValues/1, testforn/1]).
  
  %% gen_server callbacks
  -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  