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C++ Operator Precedence

From cppreference.com
< cpp‎ | language
 
 
 
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Operators
Assignment operators: a=b, a+=b, a-=b, a*=b, a/=b, a%=b, a&=b, a|=b, a^=b, a<<=b, a>>=
Increment and decrement: ++a, --a, a++, a--
Arithmetic operators: +a, -a, a+b, a-b, a*b, a/b, a%b, ~a, a&b, a|b, a^b, a<<b, a>>b
Logical operators: a||b, a&&b, !a
Comparison operators: a==b, a!=b, a<b, a>b, a<=b, a>=b
Member access operators: a[b], *a, &a, a->b, a.b, a->*b, a.*b
Other operators: a(...), a,b, (T)a, a?b:c
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Precedence and associativity
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The following table lists the precedence and associativity of C++ operators. Operators are listed top to bottom, in descending precedence.

Precedence Operator Description Associativity
1 :: Scope resolution Left-to-right
2 ++   -- Suffix/postfix increment and decrement
type() type{} Function-style cast
() Function call
[] Array subscripting
. Member access
-> Member access through pointer
3 ++   -- Prefix increment and decrement Right-to-left
+   - Unary plus and minus
!   ~ Logical NOT and bitwise NOT
(type) C-style explicit cast
* Indirection (dereference)
& Address-of
sizeof Size-of[note 1]
new, new[] Dynamic memory allocation
delete, delete[] Dynamic memory deallocation
4 .*   ->* Pointer to member Left-to-right
5 *   /   % Multiplication, division, and remainder
6 +   - Addition and subtraction
7 <<   >> Bitwise left shift and right shift
8 <   <= For relational operators < and ≤ respectively
>   >= For relational operators > and ≥ respectively
9 ==   != For relational operators = and ≠ respectively
10 & Bitwise AND
11 ^ Bitwise XOR (exclusive or)
12 | Bitwise OR (inclusive or)
13 && Logical AND
14 || Logical OR
15 ?: Ternary conditional[note 2] Right-to-left
throw throw 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 OR
16 , Comma Left-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 will be bound tighter (as if by parentheses) to its arguments than any operator that is listed on a row further below it. 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.

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.

[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.).

Relative precedence of the conditional and assignment operators differs between C and C++: in C, assignment is not allowed on the right hand side of a conditional operator, so e = a < d ? a++ : a = d cannot 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)).

[edit] See also

Common operators
assignment increment
decrement
arithmetic logical comparison member
access
other

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
(type) a
? :

Special operators

static_cast converts one type to another compatible type
dynamic_cast converts virtual base class to derived class
const_cast converts type to compatible type with different cv qualifiers
reinterpret_cast converts type to incompatible type
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)

C documentation for C operator precedence