相关疑难解决方法(0)

在"erlang编程"一书中,在这个堆栈溢出问题中,我看到我们可以使用以下命令为邮箱中的erlang消息提供不同的优先级:

我尝试用这段代码实现类似的东西:

-module(mytest).
-export([start/0, test/0]).

start() ->
    register(?MODULE, spawn(fun() -> do_receive() end)).

do_receive() ->
    receive
        {high_p, Message} ->
            io:format("High priority: ~p~n", [Message]),
            do_receive()
    after 0 ->
            receive
                {low_p, Message} ->
                    io:format("Low priority: ~p~n", [Message]),
                    do_receive()
            end
    end.

test() ->
    mytest ! {high_p, msg1},
    mytest ! {low_p, msg2},
    mytest ! {high_p, msg3}.

但结果是:

1> mytest:start().
true
2> mytest:test(). 
Low priority: msg2
{high_p,msg3}
High priority: msg1
High priority: msg3

这似乎不对,所以我将代码更改为:

do_receive() ->
    receive
        {high_p, Message} ->
            io:format("High priority: ~p~n", [Message]), …