运算符优先级与结合性详解
博客介绍了表达式中运算符优先级和结合性的相关知识。运算符优先级决定运算顺序，如乘法优先于加法。还给出了运算符优先级从高到低的表格。结合性方面，除赋值运算符外，二元运算符左结合，赋值和条件运算符右结合，且可通过括号控制运算顺序。
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]
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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