anchor.diff:  -export([start_link/4,
            start/4,
            notify/2,
  +         shutdown/1,
            behaviour_info/1]).
   
   %% gen_server callbacks
  
positive.code:             {stop, {error,[{reason, Reason}, {stacktrace, erlang:get_stacktrace()}]}}
      end.
  
  handle_call(_Request, _From, State) ->
      Reply = ok,
      {reply, Reply, State}.
  
negative.code:            Args,
             Opts) ->
      gen_server:start(ServerName, ?MODULE, {ElipsBehavior, Args}, Opts).
  
  shutdown(ServerRef) ->
      ok=gen_server:call(ServerRef, shutdown).
  
  
  notify(ServerRef, Event) ->
  