C Operator Precedence
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 | ++ --
|
Suffix/postfix increment and decrement | Left-to-right |
()
|
Function call | ||
[]
|
Array subscripting | ||
.
|
Structure and union member access | ||
->
|
Structure and union member access through pointer | ||
(type){list}
|
Compound literal(C99) | ||
| 2 | ++ --
|
Prefix increment and decrement | Right-to-left |
+ -
|
Unary plus and minus | ||
! ~
|
Logical NOT and bitwise NOT | ||
(type)
|
Type cast | ||
*
|
Indirection (dereference) | ||
&
|
Address-of | ||
sizeof
|
Size-of | ||
_Alignof
|
Alignment requirement(C11) | ||
| 3 | * / %
|
Multiplication, division, and remainder | Left-to-right |
| 4 | + -
|
Addition and subtraction | |
| 5 | << >>
|
Bitwise left shift and right shift | |
| 6 | < <=
|
For relational operators < and ≤ respectively | |
> >=
|
For relational operators > and ≥ respectively | ||
| 7 | == !=
|
For relational = and ≠ respectively | |
| 8 | &
|
Bitwise AND | |
| 9 | ^
|
Bitwise XOR (exclusive or) | |
| 10 | |
|
Bitwise OR (inclusive or) | |
| 11 | &&
|
Logical AND | |
| 12 | ||
|
Logical OR | |
| 13[note 1] | ?:
|
Ternary conditional[note 2] | Right-to-Left |
| 14 | =
|
Simple assignment | |
+= -=
|
Assignment by sum and difference | ||
*= /= %=
|
Assignment by product, quotient, and remainder | ||
<<= >>=
|
Assignment by bitwise left shift and right shift | ||
&= ^= |=
|
Assignment by bitwise AND, XOR, and OR | ||
| 15 | ,
|
Comma | Left-to-right |
- ↑ Fictional precedence level, see Notes below
-
↑ 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 expression *p++ is parsed as *(p++), and not as (*p)++.
Operators that are in the same cell (there may be several rows of operators listed in a cell) are evaluated with the same precedence, in the given direction. 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.
[edit] Notes
Precedence and associativity are independent from order of evaluation.
The C language standard doesn't specify operator precedence. It specifies the language grammar, and the precedence table is derived from it to simplify understanding. There is a part of the grammar that cannot be represented by a precedence table: assignment is never allowed to appear on the right hand side of a conditional operator, so e = a < d ? a++ : a = d is an expression that cannot be parsed, and therefore relative precedence of conditional and assignment operators cannot be described easily.
However, many C compilers use non-standard expression grammar where ?: is designated higher precedence than =, which parses that expression as e = ( ((a < d) ? (a++) : a) = d ), which then fails to compile due to semantic constraints: ?: is never lvalue and = requires a modifiable lvalue on the left. This is the table presented on this page.
Note that this is different in C++, where the conditional operator has the same precedence as assignment.
[edit] References
- C11 standard (ISO/IEC 9899:2011):
-
- A.2.1 Expressions
- C99 standard (ISO/IEC 9899:1999):
-
- A.2.1 Expressions
- C89/C90 standard (ISO/IEC 9899:1990):
-
- A.1.2.1 Expressions
[edit] See Also
Order of evaluation of operator arguments at run time.
| Common operators | ||||||
|---|---|---|---|---|---|---|
| assignment | increment decrement |
arithmetic | logical | comparison | member access |
other |
|
a = b |
++a |
+a |
!a |
a == b |
a[b] |
a(...) |
|
C++ documentation for C++ operator precedence
|