c++ 运算符优先级

原文地址：http://en.cppreference.com/w/cpp/language/operator_precedence

C++ Operator Precedence

The following table lists the precedence and associativity of C++ operators. Operators are listed top to bottom, in descending precedence.

PrecedenceOperatorDescriptionAssociativity1::Scope resolutionLeft-to-right2++   --Suffix/postfix increment and decrementtype()   type{}Functional cast()Function call[]Subscript.   ->Member access3++   --Prefix increment and decrementRight-to-left+   -Unary plus and minus!   ~Logical NOT and bitwise NOT(type)C-style cast*Indirection (dereference)&Address-ofsizeofSize-of^{[note 1]}new   new[]Dynamic memory allocationdelete   delete[]Dynamic memory deallocation4.*   ->*Pointer-to-memberLeft-to-right5*   /   %Multiplication, division, and remainder6+   -Addition and subtraction7<<   >>Bitwise left shift and right shift8<   <=For relational operators < and ≤ respectively>   >=For relational operators > and ≥ respectively9==   !=For relational operators = and ≠ respectively10&Bitwise AND11^Bitwise XOR (exclusive or)12|Bitwise OR (inclusive or)13&&Logical AND14||Logical OR15?:Ternary conditional^{[note 2]}Right-to-leftthrowthrow operator=Direct assignment (provided by default for C++ classes)+=   -=Compound assignment by sum and difference*=   /=   %=Compound assignment by product, quotient, and remainder<<=   >>=Compound assignment by bitwise left shift and right shift&=   ^=   |=Compound assignment by bitwise AND, XOR, and OR16,CommaLeft-to-right

1. ↑ The operand of sizeof can't be a C-style type cast: the expression sizeof (int) * p is unambiguously interpreted as (sizeof(int)) * p, but not sizeof((int)*p).
2. ↑ The expression in the middle of the conditional operator (between ? and :) is parsed as if parenthesized: its precedence relative to ?: is ignored.

When parsing an expression, an operator which is listed on some row of the table above with a precedence will be bound tighter (as if by parentheses) to its arguments than any operator that is listed on a row further below it with a lower precedence. For example, the expressions std::cout << a & b and *p++ are parsed as (std::cout << a) & b and *(p++), and not as std::cout << (a & b) or (*p)++.

Operators that have the same precedence are bound to their arguments in the direction of their associativity. For example, the expression a = b = c is parsed as a = (b = c), and not as (a = b) = c because of right-to-left associativity of assignment, but a + b - c is parsed (a + b) - c and not a + (b - c) because of left-to-right associativity of addition and subtraction.

Associativity specification is redundant for unary operators and is only shown for completeness: unary prefix operators always associate right-to-left (delete ++*p is delete(++(*p))) and unary postfix operators always associate left-to-right (a[1][2]++ is ((a[1])[2])++). Note that the associativity is meaningful for member access operators, even though they are grouped with unary postfix operators: a.b++ is parsed (a.b)++ and not a.(b++))

Operator precedence is unaffected by operator overloading.

Notes

Precedence and associativity are compile-time concepts and are independent from order of evaluation, which is a runtime concept.

The standard itself doesn't specify precedence levels. They are derived from the grammar.

const_cast, static_cast, dynamic_cast, reinterpret_cast, typeid, sizeof..., noexcept and alignof are not included since they are never ambiguous.

Some of the operators have alternate spellings (e.g., and for &&, or for ||, not for !, etc.).

Relative precedence of the ternary conditional and assignment operators differs between C and C++: in C, assignment is not allowed on the right-hand side of a ternary conditional operator, so e = a < d ? a++ : a = dcannot be parsed. Many C compilers use a modified grammar where ?: has higher precedence than =, which parses that as e = ( ((a < d) ? (a++) : a) = d ) (which then fails to compile because ?: is never lvalue in C and =requires lvalue on the left). In C++, ?: and = have equal precedence and group right-to-left, so that e = a < d ? a++ : a = d parses as e = ((a < d) ? (a++) : (a = d)).

See also

Common operatorsassignmentincrement
decrementarithmeticlogicalcomparisonmember
accessother

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

++a
--a
a++
a--

+a
-a
a + b
a - b
a * b
a / b
a % b
~a
a & b
a | b
a ^ b
a << b
a >> b

!a
a && b
a || b

a == b
a != b
a < b
a > b
a <= b
a >= b

a[b]
*a
&a
a->b
a.b
a->*b
a.*b

a(...)
a, b
? :

Special operators

static_cast converts one type to another related type 
dynamic_cast converts within inheritance hierarchies 
const_cast adds or removes cv qualifiers
reinterpret_cast converts type to unrelated type
C-style cast converts one type to another by a mix of static_cast, const_cast, and reinterpret_cast 
new allocates memory
delete deallocates memory
sizeof queries the size of a type
sizeof... queries the size of a parameter pack (since C++11)
typeid queries the type information of a type
noexcept checks if an expression can throw an exception (since C++11)
alignof queries alignment requirements of a type (since C++11)