14.2.1 Operator precedence and associativity

王朝other·作者佚名  2006-01-10
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When an expression contains multiple operators, the precedence of the

operators controls the order in which

the individual operators are evaluated. [Note: For example, the expression

x + y * z is evaluated as

x + (y * z) because the * operator has higher precedence than the binary +

operator. end note] The

precedence of an operator is established by the definition of its

associated grammar production. [Note: For

example, an additive-expression consists of a sequence of

multiplicative-expressions separated by + or -

operators, thus giving the + and - operators lower precedence than the *,

/, and % operators. end note]

The following table summarizes all operators in order of precedence from

highest to lowest:

Section Category Operators

14.5 Primary x.y f(x) a[x] x++ x-- new typeof checked unchecked

14.6 Unary + - ! ~ ++x --x (T)x

14.7 Multiplicative * / %

14.7 Additive + -

14.8 Shift << >>

14.9 Relational and type-testing < > <= >= is as

14.9 Equality == !=

14.10 Logical AND &

14.10 Logical XOR ^

14.10 Logical OR |

14.11 Conditional AND &&

14.11 Conditional OR ||

14.12 Conditional ?:

14.13 Assignment = *= /= %= += -= <<= >>= &= ^= |=

When an operand occurs between two operators with the same precedence, the

associativity of the operators

controls the order in which the operations are performed:

?Except for the assignment operators, all binary operators are

left-associative, meaning that operations

are performed from left to right. [Example: For example, x + y + z is

evaluated as (x + y) + z.

end example]

?The assignment operators and the conditional operator (?:) are

right-associative, meaning that

operations are performed from right to left. [Example: For example, x = y =

z is evaluated as

x = (y = z). end example]

Precedence and associativity can be controlled using parentheses. [Example:

For example, x + y * z first

multiplies y by z and then adds the result to x, but (x + y) * z first adds

x and y and then multiplies the

result by z. end example]

 
 
 
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