anchor.diff:          _ when Args >= 0, Args =< 255 -> {Args, true}
       end.
   
  -validate_output_to(Opts) ->
  -  OutputTo = proplists:get_value(output, Opts, undefined),
  -  case OutputTo of
  -    P when is_pid(OutputTo) -> P;
  -    _ -> group_leader()
  -  end.
  +validate_io_server(Opts) ->
  +  proplists:get_value(io_server, Opts, group_leader()).
   
   %%%%%%%%%%%%%%%%%%%%%%%%
   %%% TRACE FORMATTING %%%
  
positive.code: calls({Mod, Fun, Args}, Max, Opts, FormatterFun) ->
      calls([{Mod,Fun,Args}], Max, Opts, FormatterFun);
  calls(TSpecs = [_|_], {Max, Time}, Opts, FormatterFun) ->
      OutputTo = validate_output_to (Opts),
      Pid = setup(rate_tracer, [Max, Time], FormatterFun, OutputTo),
      trace_calls(TSpecs, Pid, Opts);
  calls(TSpecs = [_|_], Max, Opts, FormatterFun) ->
      OutputTo = validate_output_to (Opts),
      Pid = setup(count_tracer, [Max], FormatterFun, OutputTo),
      trace_calls(TSpecs, Pid, Opts).
  
  %%%%%%%%%%%%%%%%%%%%%%%
  
negative.code:     end.
  
  %% @private Formats traces to be output
  formatter(Tracer, Parent, Ref, FormatterFun, IOServer) ->
      process_flag(trap_exit, true),
      link(Tracer),
      Parent ! {Ref, linked},
      formatter(Tracer, IOServer, FormatterFun).
  
  formatter(Tracer, Leader, FormatterFun) ->
      receive
  