Erlang, register/2: exception error bad argument -

i want write program creates 2 processes. first print number , send second process , on. have problem in start function.

-module(zad).  -export([start/0, one/0, two/0]).  one() ->     receive         {go1, n} ->             io:format("1 ~w~n", [n]),             2 ! {go2, n+1},             one();         {go2, 50} ->             io:format("end ~w~n", [n+1]),             2 ! finished     end.  two() ->     receive         finished ->             io:format("two finished~n", []);         {go2, n} ->             io:format("2 ~w~n", [n]),             1 ! {go1, n+1 },             two()     end.  start() ->      register(two, spawn(zad, two, [])),     register(one, spawn(zad, one, [])),     1 ! {go1, 0}. 

here's error

** exception error: bad argument  in function  register/2     called register(two,<0.146.0>)  in call zad:start/0 (zad.erl, line 29) 

does mean cant register 2 processes in start? wrong code?

update weird. after changed

{go2, 50} -> io:format("end ~w~n", [n+1]), 

to

{go2, 50} -> io:format("end ~w~n", [50]), 

error disappeared. it's strange because problem in one(), error in register(two)

you can register 2 processes in start/0. means values passing register/2 wrong. documentation(http://erlang.org/doc/man/erlang.html#register-2):

failures:

• badarg if pidorport not existing local process or port.
• badarg if regname in use.
• badarg if process or port registered (already has name). badarg if regname atom undefined.

likely has happened process died before register/2 called (see first failure in list above).