【erlang】Hello Erlang!

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hello_erlang_1

  • hello.erl
    • code 
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      -module(hello).
-export([print/0]).
print() -> 
io:format("World!~n").
    • 解析
      • -module
      • -export
      • [print/0] : 函數名稱 print , 參數 0 個
      • io:format : 格式化標準輸出函數，參考 io : Available control sequences:
        • ~n : Writes a new line.
  • test
    • 流程
      1. erl
      2. pwd().
      3. ls().
      4. c(hello). : hello 為 hello.erl 的檔案名稱, c() 為編譯此檔案 -> 會產生 hello.beam 的執行擋
      5. hello:print().
    • 基本
      • . : 每一句皆以此，作為一個斷句

hello_erlang_2

  • hello2.erl 
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    -module(hello2).
-compile(export_all).
square(N) -> N*N.
sum([]) -> 0;
sum([Num|Ns]) -> Num + sum(Ns).
sum_square([]) -> 0;
sum_square([Num|Ns]) -> square(Num) + sum_square(Ns).
  • test
    • hello2:square(2). : 4
    • hello2:sum([1,2,3,4,5]). : 15
    • ; : 代表 or
    • , : 代表 and

hello_erlang_3

  • hello3.erl 
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    solve(1) -> [1];
solve(N) when N rem 2 == 0 -> [N|solve(N div 2)];
solve(N) -> [N|solve(N*3+1)].
set(N) 	-> {ok, [H|T] = solve(N)}.

hello_erlang_4 : regular expressions

  • hello4.erl ``` -module(do). -compile(export_all).

multire([],_) -> nomatch; multire([RE|RegExps],String) -> case re:run(String,RE,[{capture,none}]) of match -> RE; nomatch -> multire(RegExps,String) end.

% 開頭為 Hello, 結尾有 world, 均符合 test(Foo) -> test2(multire([“^Hello”,”world$”,”^….$”],Foo),Foo).

test2(“^Hello”,Foo) -> io:format(“~p matched the hello pattern~n”,[Foo]); test2(“world$”,Foo) -> io:format(“~p matched the world pattern~n”,[Foo]); test2(“^….$”,Foo) -> io:format(“~p matched the four chars pattern~n”,[Foo]); test2(nomatch,Foo) -> io:format(“~p failed to match~n”,[Foo]).

-define (Email_pattern, “\b[a-zA-Z0-9.!#$%&’+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)\b”). -define (Mac_address_pattern, “^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$”).

checkPattern(Foo) -> checkPattern2(multire([[?Email_pattern], [?Mac_address_pattern]],Foo),Foo).

checkPattern2([?Email_pattern], Foo) -> io:format(“email format : ~p ~n”, [Foo]); checkPattern2([?Mac_address_pattern], Foo) -> io:format(“device format : ~p ~n”, [Foo]); checkPattern2(nomatch, Foo) -> io:format(“nomatch : ~p ~n”, [Foo]). ```