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25 строки
2.8 KiB
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25 строки
2.8 KiB
XML
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<clause number="14.2.1" title="Operator precedence and associativity">
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<paragraph>When an expression contains multiple operators, the precedence of the operators controls the order in which the individual operators are evaluated. <note>[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]</note> The precedence of an operator is established by the definition of its associated grammar production. <note>[Note: For example, an <non_terminal where="14.7">additive-expression</non_terminal> consists of a sequence of <non_terminal where="14.7">multiplicative-expression</non_terminal>s separated by + or -operators, thus giving the + and -operators lower precedence than the *, /, and % operators. end note]</note> </paragraph>
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<paragraph>The following table summarizes all operators in order of precedence from highest to lowest: <table_line>Section Category Operators </table_line>
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<table_line>14.5 Primary x.y f(x) a[x] x++ x--new </table_line>
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<table_line>typeof checked unchecked </table_line>
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<table_line>14.6 Unary + -! ~ ++x --x (T)x </table_line>
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<table_line>14.7 Multiplicative * / % </table_line>
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<table_line>14.7 Additive + </table_line>
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<table_line>-14.8 Shift << >> </table_line>
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<table_line>14.9 Relational and </table_line>
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<table_line>type-testing </table_line>
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<table_line>< > <= >= is as </table_line>
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<table_line>14.9 Equality == != </table_line>
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<table_line>14.10 Logical AND & </table_line>
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<table_line>14.10 Logical XOR ^ </table_line>
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<table_line>14.10 Logical OR | </table_line>
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<table_line>14.11 Conditional AND && </table_line>
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<table_line>14.11 Conditional OR || </table_line>
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<table_line>14.12 Conditional ?: </table_line>
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<table_line>14.13 Assignment = *= /= %= += -= <<= >>= &= ^= |= </table_line>
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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: <list><list_item> Except for the assignment operators, all binary operators are left-associative, meaning that operations are performed from left to right. <example>[Example: For example, x + y + z is evaluated as (x + y) + z. end example]</example> </list_item><list_item> The assignment operators and the conditional operator (?:) are right-associative, meaning that operations are performed from right to left. <example>[Example: For example, x = y = z is evaluated as x = (y = z). end example]</example> </list_item></list></paragraph>
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<paragraph>Precedence and associativity can be controlled using parentheses. <example>[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]</example> </paragraph>
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</clause>
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