学习笔记--C++

1.C语言运算符优先级

运算符按照优先级大小由上向下排列，在同一行的运算符具有相同优先级。第二行是所有的一元运算符。
 

运算符	解释	结合方式
() [] -> .	括号（函数等），数组，两种结构成员访问	由左向右
! ~ ++ -- + -  * & (类型) sizeof	否定，按位否定，增量，减量，正负号， 间接，取地址，类型转换，求大小	由右向左
* / %	乘，除，取模	由左向右
+ -	加，减	由左向右
<< >>	左移，右移	由左向右
< <= >= >	小于，小于等于，大于等于，大于	由左向右
== !=	等于，不等于	由左向右
&	按位与	由左向右
^	按位异或	由左向右
|	按位或	由左向右
&&	逻辑与	由左向右
||	逻辑或	由左向右
? :	条件	由右向左
= += -= *= /=  &= ^= |= <<= >>=	各种赋值	由右向左
,	逗号（顺序）	由左向右

 

2.C++运算符优先级

Precedence	Operator	Description	Example	Associativity
1	() [] -> . :: ++ --	Grouping operator Array access Member access from a pointer Member access from an object Scoping operator Post-increment Post-decrement	(a + b) / 4; array[4] = 2; ptr->age = 34; obj.age = 34; Class::age = 2; for( i = 0; i < 10; i++ ) ... for( i = 10; i > 0; i-- ) ...	left to right
2	! ~ ++ -- - + * & (type) sizeof	Logical negation Bitwise complement Pre-increment Pre-decrement Unary minus Unary plus Dereference Address of Cast to a given type Return size in bytes	if( !done ) ... flags = ~flags; for( i = 0; i < 10; ++i ) ... for( i = 10; i > 0; --i ) ... int i = -1; int i = +1; data = *ptr; address = &obj; int i = (int) floatNum; int size = sizeof(floatNum);	right to left
3	->* .*	Member pointer selector Member pointer selector	ptr->*var = 24; obj.*var = 24;	left to right
4	* / %	Multiplication Division Modulus	int i = 2 * 4; float f = 10 / 3; int rem = 4 % 3;	left to right
5	+ -	Addition Subtraction	int i = 2 + 3; int i = 5 - 1;	left to right
6	<< >>	Bitwise shift left Bitwise shift right	int flags = 33 << 1; int flags = 33 >> 1;	left to right
7	< <= > >=	Comparison less-than Comparison less-than-or-equal-to Comparison greater-than Comparison geater-than-or-equal-to	if( i < 42 ) ... if( i <= 42 ) ... if( i > 42 ) ... if( i >= 42 ) ...	left to right
8	== !=	Comparison equal-to Comparison not-equal-to	if( i == 42 ) ... if( i != 42 ) ...	left to right
9	&	Bitwise AND	flags = flags & 42;	left to right
10	^	Bitwise exclusive OR	flags = flags ^ 42;	left to right
11	|	Bitwise inclusive (normal) OR	flags = flags | 42;	left to right
12	&&	Logical AND	if( conditionA && conditionB ) ...	left to right
13	||	Logical OR	if( conditionA || conditionB ) ...	left to right
14	? :	Ternary conditional (if-then-else)	int i = (a > b) ? a : b;	right to left
15	= += -= *= /= %= &= ^= |= <<= >>=	Assignment operator Increment and assign Decrement and assign Multiply and assign Divide and assign Modulo and assign Bitwise AND and assign Bitwise exclusive OR and assign Bitwise inclusive (normal) OR and assign Bitwise shift left and assign Bitwise shift right and assign	int a = b; a += 3; b -= 4; a *= 5; a /= 2; a %= 3; flags &= new_flags; flags ^= new_flags; flags |= new_flags; flags <<= 2; flags >>= 2;	right to left
16	,	Sequential uation operator	for( i = 0, j = 0; i < 10; i++, j++ ) ...	left to right

例如：C++中

1）y=*px++ 相当于y=*(px++) (++优先级高)

2）&ptr->a等于&(ptr->a)而不是等于(&ptr)->a

3）逻辑运算符的优先级： ！(非) >   &&(与)   >   ||(或)

4）关系运算符优先级

      <     <=       >       >=                       ==    !=

       优先级相同（高）            优先级相同（低）

5)  条件运算符优级高于赋值运算符，低于逻辑运算符   x=a>b?a:b;

6）有10种复合运算符：+=, -=, *=, /=, %=,<<=,>>=,&=,^=,|=

#include <iostream>

using namespace std;

int main()
{
const char *cp="hello";
cout<<cp<<" "<<++cp<<endl;
getchar();
return 0;

}

输出为 ello  ello

因为++运算符优先级高,先算++cp,再执行cout语句.