C++ Primer 学习笔记（3）——表达式

C++提供了一元操作符和二元操作符，另外还有三元操作符（三目操作符cond?expr1:exprl2）。

算术运算符

一元正号（+）返回操作数本身，对操作数不做任何修改。

逻辑运算符

存在短路求值。

优先级表如下：

PrecedenceOperatorDescriptionExampleAssociativity1

()
[]
->
.
::
++
--

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 right2

!
~
++
--
-
+
*
&
(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 left3

->*
.*

Member pointer selector
Member pointer selector

ptr->*var = 24;
obj.*var = 24;

left to right4

*
/
%

Multiplication
Division
Modulus

int i = 2 * 4;
float f = 10 / 3;
int rem = 4 % 3;

left to right5

+
-

Addition
Subtraction

int i = 2 + 3;
int i = 5 - 1;

left to right6

<<
>>

Bitwise shift left
Bitwise shift right

int flags = 33 << 1;
int flags = 33 >> 1;

left to right7

<
<=
>
>=

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 right8

==
!=

Comparison equal-to
Comparison not-equal-to

if( i == 42 ) ...
if( i != 42 ) ...

left to right9&Bitwise ANDflags = flags & 42;left to right10^Bitwise exclusive ORflags = flags ^ 42;left to right11|Bitwise inclusive (normal) ORflags = flags | 42;left to right12&&Logical ANDif( conditionA && conditionB ) ...left to right13||Logical ORint i = (a > b) ? a : bleft to right14? :Ternary conditional (if-then-else)if( conditionA || conditionB ) ...right to left15

=
+=
-=
*=
/=
%=
&=
^=
|=
<<=
>>=

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 left16,Sequential evaluation operatorfor( i = 0, j = 0; i < 10; i++, j++ ) ...left to right