gistfile1.hrl

-module(counter_with_retry).
-compile(export_all).


start_counter() ->
	Pid = spawn(?MODULE, counter_loop, [0]),
	register(counter, Pid).

counter_loop(N) ->
	receive 
		{get, Pid} -> 
			Pid ! {value, N},
			counter_loop(N);

		{set, Pid, N, New} ->
			Pid ! ok,
			counter_loop(New);

		{set, Pid, _Something, _New} ->
			Pid ! fail,
			counter_loop(N);

		value -> io:format("Value = ~w~n", [N])
	end.

counter_locked(Pid, N) ->
	receive 
		{inc, Pid} -> counter_locked(Pid, N+1);
		{unlock, Pid} -> counter_loop(N)
	end.

proc() ->
	Pid = self(),
	counter ! {get, Pid},
	receive
		{value, N} ->
			counter ! {set, Pid, N, N + 1},
			receive fail -> proc();	% retry
				ok -> wait_death()
			end
	end.
			
wait_death() ->
	receive
		{halt, Parent} -> Parent ! {halted, self()}
	end.


sync([]) -> ok;
sync([Pid|Pids]) ->
	Pid ! {halt, self()},
	receive 
		{halted, Pid} -> sync(Pids)
	end.

run() ->
	start_counter(),
	N = lists:seq(1, 10000),
	Pids = lists:map(fun(_) -> spawn(?MODULE, proc, []) end, N),
	sync(Pids),
	counter ! value,
	ok.