anchor.diff:  -export([start_link/0]).
   -export([start/0]).
   -export([stop/0]).
  +-export([dirs/0]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code: %%--------------------------------------------------------------------
  handle_call(stop, _From, State) ->
      {stop, normal, ok, State};
  handle_call(_Request, _From, State) ->
      {reply, {error,bad_call}, State}.
  
  %%--------------------------------------------------------------------
  
negative.code: 
  stop() ->
      gen_server:call(?SERVER, stop).
  
  dirs() ->
      gen_server:call(?SERVER, dirs).
  
  %%%===================================================================
  %%% gen_server callbacks
  