C++ Operator Precedence
The following table lists the precedence and associativity of C++ operators. Operators are listed top to bottom, in descending precedence. a, b and c are operands.
| Precedence | Operator | Description | Associativity |
|---|---|---|---|
| 1 | a::b | Scope resolution | Left-to-right → |
| 2 | a++ a-- | Suffix/postfix increment and decrement | |
type(a) type{a} | Functional cast | ||
| a() | Function call | ||
| a[] | Subscript | ||
| a.b a->b | Member access | ||
| 3 | ++a --a | Prefix increment and decrement | Right-to-left ← |
| +a -a | Unary plus and minus | ||
| !a ~a | Logical NOT and bitwise NOT | ||
(type)a | C-style cast | ||
| *a | Indirection (dereference) | ||
| &a | Address-of | ||
sizeof | Size-of[note 1] | ||
| co_await | await-expression(C++20) | ||
new – new[] | Dynamic memory allocation | ||
delete – delete[] | Dynamic memory deallocation | ||
| 4 | a.*b a->*b | Pointer-to-member | Left-to-right → |
| 5 | a * b a / b a % b | Multiplication, division, and remainder | |
| 6 | a + b a - b | Addition and subtraction | |
| 7 | a << b a >> b | Bitwise left shift and right shift | |
| 8 | a <=> b | Three-way comparison operator(since C++20) | |
| 9 | a < b a <= b a > b a >= b | For relational operators< and <= and > and >= respectively | |
| 10 | a == b a != b | For equality operators= and != respectively | |
| 11 | a & b | Bitwise AND | |
| 12 | a ^ b | Bitwise XOR (exclusive or) | |
| 13 | a | b | Bitwise OR (inclusive or) | |
| 14 | a && b | Logical AND | |
| 15 | a || b | Logical OR | |
| 16 | a ? b : c | Ternary conditional[note 2] | Right-to-left ← |
throw | throw operator | ||
| co_yield | yield-expression(C++20) | ||
| a = b | Direct assignment (provided by default for C++ classes) | ||
| a += b a -= b | Compound assignment by sum and difference | ||
| a *= b a /= b a %= b | Compound assignment by product, quotient, and remainder | ||
| a <<= b a >>= b | Compound assignment by bitwise left shift and right shift | ||
| a &= b a ^= b a |= b | Compound assignment by bitwise AND, XOR, and OR | ||
| 17 | a, b | Comma | Left-to-right → |
- ↑The operand of sizeof cannot be a C-style type cast: the expression sizeof (int)* p is unambiguously interpreted as (sizeof(int))* p, but not sizeof((int)*p).
- ↑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. For example, std::cout<< a ? b : c; parses as (std::cout<< a)? b : c; because the precedence of arithmetic left shift is higher than the conditional operator.
[edit]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.).
In C, the ternary conditional operator has higher precedence than assignment operators. Therefore, the expression e = a < d ? a++: a = d, which is parsed in C++ as e =((a < d)?(a++):(a = d)), will fail to compile in C due to grammatical or semantic constraints in C. See the corresponding C page for details.
[edit]See also
| Common operators | ||||||
|---|---|---|---|---|---|---|
| assignment | increment decrement | arithmetic | logical | comparison | member access | other |
a = b | ++a | +a | !a | a == b | a[...] | function call a(...) |
| comma a, b | ||||||
| conditional a ? b : c | ||||||
| Special operators | ||||||
static_cast converts one type to another related type | ||||||
C documentation for C operator precedence |
