erlang笔记2

1.两进程的消息传递

以下面程序为例：

-module(tut16).-export([start/0, ping/1, pong/0]).

ping(0) ->    pong ! finished,  %% finished 被发送给了”pong”(导致它像下面所说的那个被终止) 

    io:format("ping finished~n", []);

ping(N) ->    pong ! {ping, self()},  %%表示 self()返回当前自在运行的进程 ID，在这里是”ping”的进程 ID。    receive

        pong ->            io:format("Ping received pong~n", [])

    end,    ping(N - 1).

pong() ->    receive
        finished ->            io:format("Pong finished~n", []);
        {ping, Ping_PID} ->            io:format("Pong received ping~n", []),            Ping_PID ! pong,            pong()
end.
start() ->    register(pong, spawn(tut16, pong, [])), %% 进程名称注册     spawn(tut16, ping, [3]).
2> c(tut16).{ok, tut16}3> tut16:start().<0.38.0>Pong received pingPing received pongPong received pingPing received pongPong received pingPing received pongping finishedPong finished

总结：

1.Erlang内建函数spawn被用于建立一个新的进程:spawn(模块, 导出的函数, 参数列表) 

2.发送消息方法：Pid ! Message , 即，Message(任何东西)被发到给了标识为 Pid 的进程。

3.receive构造用于允许进程等待来自其它进程的消息。它的格式是: 

receive   pattern1 ->

       actions1;   pattern2 ->

       actions2;   ....

   patternN       actionsN

end. 

注意，在结尾没有”;”。