erlang 符号相关基本语法

http://blog.csdn.net/anghlq/article/details/6803332

ErLang语法约定：

大写字母开头的名字（比如Address），表示一个变量，包括参数、局部变量等；

小写字母开头的单词（比如ok），表示一个常量，叫做atom（原子的意思），包括常量名、函数名、模块名等。

ErLang的注释用%开头。ErLang用下划线“_”表示任意变量，类似于Java的switch语法里面的default选项。

参数中没使用到的变量用下杠和首字母大写，如_Sample

比较符

op	Description
==	equal to
/=	not equal to
=<	less than or equal to
<	less than
>=	greater than or equal to
>	greater than
=:=	exactly equal to
=/=	exactly not equal to

1> 1==1.0.
true
2> 1=:=1.0.
false

运算符

op	Description	Argument type
+	unary +	number
-	unary -	number
+		number
-		number
*		number
/	floating point division	number
bnot	unary bitwise not	integer
div	integer division	integer
rem	integer remainder of X/Y	integer
band	bitwise and	integer
bor	bitwise or	integer
bxor	arithmetic bitwise xor	integer
bsl	arithmetic bitshift left	integer
bsr	bitshift right	integer

7> 2#10 band 2#01.
0
8> 2#10 bor 2#01.
3

Boolean表达式

op	Description
not	unary logical not
and	logical and
or	logical or
xor	logical xor

短路表达式

Expr1 orelse Expr2
Expr1 andalso Expr2

case A >= -1.0 andalso math:sqrt(A+1) > B of

列表表达式

++
--

1> [1,2,3]++[4,5].
[1,2,3,4,5]
2> [1,2,3,2,1,2]--[2,1,2].
[3,1,2]

二进制表达式

<<>>
<<E1,...,En>>

Ei = Value |
Value:Size |
Value/TypeSpecifierList |
Value:Size/TypeSpecifierList

TypeSpecifierList

Type= integer | float | binary | bytes |bitstring | bits | utf8 | utf16 | utf32

Signedness= signed | unsigned

Endianness= big | little | nativeUnit= unit:IntegerLiteral

11> <<G,H/bitstring>> = <<1,17,42:12>>.
<<1,17,1,10:4>>
12> H.
<<17,1,10:4>>
13> <<1024/utf8>>.
<<208,128>>

赋值时注意增加空格 B=<<1>> 会变成语法错误，因为跟比较符号=<冲突、、
<<"--\r\n", Data/binary>>,

strchr(Bin, C, I) ->
case Bin of
<<_X:I/binary>> ->
0;
<<_X:I/binary, C, _Rest/binary>> ->
I+1;
_ ->
strchr(Bin, C, I+1)
end.

parse_boolean(Value) ->
case Value of
true -> true;
false -> false;
<<"true">> -> true;
<<"false">> -> false;
<<"1">> -> true;
<<"0">> -> false;
1 -> true;
0 -> false
end.

<<N1:32/integer, N2:32/float>> = Bin.
<< PointID:32/unsigned-little-integer, Value:32/little-float>> = Bin.
case Packet of
<<Len:16, PayLoad:Len/binary, 16#ef>> ->
{body, PayLoad};
_ ->
{error, invalid_packet}
end.
case Info of
<<"get ",Str1/bitstring>>->
io:format("case0:~s~n", [binary_to_list(Str1)]);
<<1:1,Str1/bitstring>>->
io:format("case1:~s~n", [Str1])
end.