anchor.diff:  stack() ->
     stack(self()).
   stack(P) ->
  -  [string:strip(e(2,(string:tokens(L,"(+)")))) || L<- bt(P), $0 =:= hd(L)].
  +  [string:strip(e(2,(string:tokens(L,"(+)")))) || L<- bt(P),$0 =:= hd(L)].
   bt(P) ->
     string:tokens(binary_to_list(e(2,(process_info(P,backtrace)))),"\n").
   
  
positive.code: t_3_test() ->
    Filename = "redbug.txt",
    Pid = spawn(fun()->receive P when is_pid(P)->P!ding;quit->ok end end),
    {_,_} = redbug:start(send,[{procs,Pid},{print_file, Filename}]),
    Pid ! self(),
    timer:sleep(100),
    redbug:stop(),
  
negative.code: t_4_test() ->
    Filename = "redbug.txt",
    Pid = spawn(fun()->receive P when is_pid(P)->P!ding;quit->ok end end),
    {_,_} = redbug:start('receive',[{procs,Pid},{print_file,Filename}]),
    Pid ! pling,
    timer:sleep(100),
    redbug:stop(),
  