erlang第三天总结

1.cmd进入某个盘，比如F盘

直接f:

-module(fac1).

%% ====================================================================
%% API functions
%% ====================================================================
-export([main/1]).

%% ====================================================================
%% Internal functions
%% ====================================================================

main([A]) ->
   I = list_to_integer(atom_to_list(A)),
   F = fac(I),
   io:format("factorial ~w = ~w~n", [I, F]),
   init:stop().

fac(0) -> 1;
fac(N) -> N*fac(N-1).

这里因为-s fac1 main 25这种方式，参数是[25]

3.windows下启动escript脚本

脚本代码如下:

#!/usr/bin/env escript
main([A]) ->
   I = list_to_integer(A),
   F = fac(I),
   io:format("factorial ~w = ~w~n",[I, F]).

fac(0) -> 1;

fac(N) -> N*fac(N-1).

在cmd进入代码目录，执行escript.exe factorial 25 (25是参数)

4. spawn的两种创建方式

Pid = spawn(Mod, Func, Args)

Pid = spawn(Fun)

5.超时值为0的接收

-module(area_server1).
-export([loop/0, rpc/2, test/0]).

rpc(Pid, Request) ->
   Pid ! {self(), Request},
   receive
       Response ->
           Response
   end.

loop() ->
   receive
       {From, {rectangle, Width, Ht}} ->
           io:format("rectangle is ~p~n",[Width * Ht]);
       {From, {circle, R}} ->
           io:format("circle is ~p~n",[R * R])
   after 0 ->
       receive
           Any ->
               io:format("hello")
       end
   end.

test() ->
   Pid = spawn(area_server1, loop, []),
   Pid ! {self,apple},
   % Pid ! {self(),{rectangle, 10, 8}},
   Pid ! {self(),banana},
   ok.

这里超时是指消息发送到邮箱后才开始计时，比如说after 0，消息到达邮箱后，会先执行receive，如果不匹配，再执行after 0.若是after 1000,消息到达邮箱后，判断1秒内是否匹配receive里面语句，如果不匹配，1秒后执行after 1000里面的语句

5.普通进程可以通过执行process_flag(trap_exit， true)变成系统进程

6.节点是一个独立的Erlang系统，包含一个自带地址空间和进程组的完整虚拟机。

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