语言操作符

三个优先级

算术运算符

C++运算符优先级

C#中的优先级

语言操作符

c语言的操作符共有15个优先级，如下：

Operators Associativity

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运算符 结合性

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() [] -> . left to right

! ~ ++ -- + - * sizeof(type) right to left

* / % left to right

+ - left to right

<< >> left to right

< <= > >= left to right

== != left to right

& left to right

^ left to right

| left to right

&& left to right

|| left to right

?: right to left

= += -= *= /= %= &= ^= |= <<= >>= right to left

, left to right

三个优先级

优先级从上到下依次递减，最上面具有最高的优先级，逗号操作符具有最低的优先级。

所有的优先级中，只有三个优先级是从右至左结合的，它们是单目运算符、条件运算符、赋值运算符。其它的都是从左至右结合。

具有最高优先级的其实并不算是真正的运算符，它们算是一类特殊的操作。()是与函数相关，[]与数组相关，而－>及.是取结构成员。

其次是单目运算符，所有的单目运算符具有相同的优先级，因此在我认为的 真正的运算符中它们具有最高的优先级，又由于它们都是从右至左结合的，因此*p++与*(p++)等效是毫无疑问的。

算术运算符

接下来是算术运算符，*、/、%的优先级当然比+、－高了。

移位运算符紧随其后。

其次的关系运算符中，< <= > >=要比 == !=高一个级别，不大好理解。

所有的逻辑操作符都具有不同的优先级（单目运算符除外，！和~）

逻辑位操作符的"与"比"或"高，而"异或"则在它们之间。

跟在其后的&&比||高。

接下来的是条件运算符，赋值运算符及逗号运算符。

在C语言中，只有4个运算符规定了运算方向，它们是&&、| |、条件运算符及赋值运算符。

&&、| |都是先计算左边表达式的值，当左边表达式的值能确定整个表达式的值时，就不再计算右边表达式的值。如 a = 0 && b; &&运算符的左边位为0，则右边表达式b就不再判断。

在条件运算符中。如a?b:c；先判断a的值，再根据a的值对b或c之中的一个进行求值。

赋值表达式则规定先对右边的表达式求值，因此使 a = b = c = 6;成为可能。

C++运算符优先级

Operator 　Description 　Example 　Overloadable

Group 1 (no associativity)

::　Scope resolution operator　Class::age = 2;　NO

Group 2

()　Function call　isdigit('1')　YES

()　Member initalization 　c_tor(int x, int y) : _x(x), _y(y*10){};　YES

[]　Array access　array[4] = 2;　YES

->　Member access from a pointer　ptr->age = 34;　YES

.　Member access from an object　obj.age = 34;　NO

++　Post-increment　for( int i = 0; i < 10; i++ ) cout << i;　YES

--　Post-decrement　for( int i = 10; i > 0; i-- ) cout << i;　YES

const_cast　Special cast　const_cast<type_to>(type_from);　NO

dynamic_cast　Special cast　dynamic_cast<type_to>(type_from);　NO

static_cast　Special cast　static_cast<type_to>(type_from);　NO

reinterpret_cast　Special cast　reinterpret_cast<type_to>(type_from);　NO

typeid　Runtime type information　cout &laquo; typeid(var).name();
cout &laquo; typeid(type).name();　NO

Group 3 (right-to-left associativity)

!　Logical negation　if( !done ) …　YES

not　Alternate spelling for !

~　Bitwise complement　flags = ~flags;　YES

compl　Alternate spelling for ~

++　Pre-increment　for( i = 0; i < 10; ++i ) cout << i;　YES

--　Pre-decrement　for( i = 10; i > 0; --i ) cout << i;　YES

-　Unary minus　int i = -1;　YES

+　Unary plus　int i = +1;　YES

*　Dereference　int data = *intPtr;　YES

&　Address of　int *intPtr = &data;　YES

new　Dynamic memory allocation　long *pVar = new long;
MyClass *ptr = new MyClass(args);　YES

new []　Dynamic memory allocation of array　long *array = new long[n];　YES

delete　Deallocating the memory　delete pVar;　YES

delete []　Deallocating the memory of array　delete [] array;　YES

(type)　Cast to a given type　int i = (int) floatNum;　YES

sizeof　Return size of an object or type　int size = sizeof floatNum;
int size = sizeof(float);　NO

Group 4

->*　Member pointer selector　ptr->*var = 24;　YES

.*　Member object selector　obj.*var = 24;　NO

Group 5

*　Multiplication　int i = 2 * 4;　YES

/　Division　float f = 10.0 / 3.0;　YES

%　Modulus　int rem = 4 % 3;　YES

Group 6

+　Addition　int i = 2 + 3;　YES

-　Subtraction　int i = 5 - 1;　YES

Group 7

<<　Bitwise shift left　int flags = 33 << 1;　YES

>>　Bitwise shift right　int flags = 33 >> 1;　YES

Group 8

<　Comparison less-than　if( i < 42 ) …　YES

<=　Comparison less-than-or-equal-to　if( i <= 42 ) ...　YES

>　Comparison greater-than　if( i > 42 ) …　YES

>=　Comparison greater-than-or-equal-to　if( i >= 42 ) ...　YES

Group 9

==　Comparison equal-to　if( i == 42 ) ...　YES

eq　Alternate spelling for ==

!=　Comparison not-equal-to　if( i != 42 ) …　YES

not_eq　Alternate spelling for !=

Group 10

&　Bitwise AND　flags = flags & 42;　YES

bitand　Alternate spelling for &

Group 11

^　Bitwise exclusive OR (XOR)　flags = flags ^ 42;　YES

xor　Alternate spelling for ^

Group 12

|　Bitwise inclusive (normal) OR　flags = flags | 42;　YES

bitor　Alternate spelling for |

Group 13

&&　Logical AND　if( conditionA && conditionB ) …　YES

and　Alternate spelling for &&

Group 14

||　Logical OR　if( conditionA || conditionB ) ...　YES

or　Alternate spelling for ||

Group 15 (right-to-left associativity)

? :　Ternary conditional (if-then-else)　int i = (a > b) ? a : b;　NO

Group 16 (right-to-left associativity)

=　Assignment operator　int a = b;　YES

+=　Increment and assign　a += 3;　YES

-=　Decrement and assign　b -= 4;　YES

*=　Multiply and assign　a *= 5;　YES

/=　Divide and assign　a /= 2;　YES

%=　Modulo and assign　a %= 3;　YES

&=　Bitwise AND and assign　flags &= new_flags;　YES

and_eq　Alternate spelling for &=

^=　Bitwise exclusive or (XOR) and assign　flags ^= new_flags;　YES

xor_eq　Alternate spelling for ^=

|=　Bitwise normal OR and assign　flags |= new_flags;　YES

or_eq　Alternate spelling for |=

<<=　Bitwise shift left and assign　flags <<= 2;　YES

>>=　Bitwise shift right and assign　flags >>= 2;　YES

Group 17

throw　throw exception　throw EClass(“Message”);　NO

Group 18

,　Sequential evaluation operator　for( i = 0, j = 0; i < 10; i++, j++ ) …　YES

C#中的优先级

优先级　类别　运算符

1　基本　（x） x.y f(x) a[x] x++ x――new typeof sizeof checked unchecked

2　单目　+ － ！ ～ ++x ――x (T)x

3　乘法与除法　* / %

4　加法与减法　+ －

5　移位运算　<< >>

6　关系运算　﹤ > <= >= is

7　条件等　= = ! =

8　位逻辑与　&

9　位逻辑异或　^

10　位逻辑或　|

11　条件与　&&

12　条件或　‖

13　条件　?:

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