anchor.diff:                    Child;
                 Error ->
                     Error
  -          end
  +          end,
       {reply, Res, State};
   handle_call(_Request, _From, State) ->
       Reply = ok,
  
positive.code:     gen_server:call(Pid, {message, Name, Id, MessageString, Timeout}, 
                      Timeout).
  
  cast(Pid, Id, MessageString) ->
      gen_server:cast(Pid, {message, Name, Id, MessageString}).
  
  
  
negative.code: 
  %% API
  -export([start_link/0, register/2, unregister/1, worker/0, 
           call/3, call/5, cast/4]).
  
  %% gen_server callbacks
  -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  