Operators Associativity
() [] -> . left to right
! ~ ++ -- + - * (type) sizeof 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
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。
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（单目运算符出外，！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 « typeid(var).name(); cout « 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 |