7 Expressions [expr]

7.1 Preamble [expr.pre]

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[expr] defines the syntax, order of evaluation, and meaning of expressions.57
An expression is a sequence of operators and operands that specifies a computation.
An expression can result in a value and can cause side effects.
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2
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Operators can be overloaded, that is, given meaning when applied to expressions of class type or enumeration type.
Uses of overloaded operators are transformed into function calls as described in [over.oper].
Overloaded operators obey the rules for syntax and evaluation order specified in [expr.compound], but the requirements of operand type and value category are replaced by the rules for function call.
Relations between operators, such as ++a meaning a+=1, are not guaranteed for overloaded operators.
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Subclause [expr.compound] defines the effects of operators when applied to types for which they have not been overloaded.
Operator overloading shall not modify the rules for the built-in operators, that is, for operators applied to types for which they are defined by this Standard.
However, these built-in operators participate in overload resolution, and as part of that process user-defined conversions will be considered where necessary to convert the operands to types appropriate for the built-in operator.
If a built-in operator is selected, such conversions will be applied to the operands before the operation is considered further according to the rules in subclause [expr.compound]; see [over.match.oper], [over.built].
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If during the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined.
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Treatment of division by zero, forming a remainder using a zero divisor, and all floating-point exceptions vary among machines, and is sometimes adjustable by a library function.
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The values of the floating operands and the results of floating expressions may be represented in greater precision and range than that required by the type; the types are not changed thereby.58
57)
The precedence of operators is not directly specified, but it can be derived from the syntax.
58)
The cast and assignment operators must still perform their specific conversions as described in [expr.cast], [expr.static.cast] and [expr.ass].