lvalue การใช้

• The subscripting specification can be used as a lvalue within an expression.
• Unlike strings, a slice using a range cannot be a lvalue.
• Stroustrup observed that the reference-dropping semantics offered by the typeof operator provided by the lvalue-ness of the expression was deemed too confusing.
• Due to the nature of the wording of rvalue references, and to some modification to the wording for lvalue references ( regular references ), rvalue references allow developers to provide perfect function forwarding.
• This is legal C99 and above because the stored value of an object may be accessed through an lvalue of aggregate or union type that includes one of the aforementioned types among its members ( including, recursively, a member of a subaggregate or contained union ).
• :As for your first question, it's true that + + i yields an rvalue ( which is just a value ) and not an lvalue ( which is a modifiable variable-like thing ) in C . But that's not really relevant here.
• When a class or individual attribute is declared with the is rw modifier ( short for " read / write " ), the auto-accessor can be passed a new value to set the attribute to, or it can be directly assigned to as an lvalue ( as in the example ).
• Such a compiled expression may be used as a VALUE, i . e . the right side of an assignment ( rvalue ), but more interestingly, such a compiled expression may be used to resolve the left side ( lvalue ) of an assignment, i . e . PRIVATE, or PUBLIC variables, or a database FIELD.
• Just like std : : make _ pair for std : : pair, there exists std : : make _ tuple to automatically create std : : tuple s using type deduction and auto helps to declare such a tuple . std : : tie creates tuples of lvalue references to help unpack tuples . std : : ignore also helps here.