std::experimental::propagate_const<T>:: propagate_const

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C++
Experimental
Library fundamentals v2
std::experimental::propagate_const
constexpr propagate_const ( ) = default ;
(1) (library fundamentals TS v2)
constexpr propagate_const ( propagate_const && p ) = default ;
(2) (library fundamentals TS v2)
template < class U >
/* see below */ constexpr propagate_const ( propagate_const < U > && pu ) ;
(3) (library fundamentals TS v2)
template < class U >
/* see below */ constexpr propagate_const ( U && u ) ;
(4) (library fundamentals TS v2)
propagate_const ( const propagate_const & ) = delete ;
(5) (library fundamentals TS v2)

Let t_ designate the private data member that is the wrapped pointer-like object.

1) Constructs a propagate_const , default-initializing this - > t_ .
2) Explicitly defaulted move constructor that move constructs this - > t_ from p. t_ .
3) Initializes this - > t_ as if by direct-non-list-initialization from the expression std :: move ( pu. t_ ) .
This constructor does not participate in overload resolution unless std:: is_constructible < T, U > :: value is true , and is explicit if and only if std:: is_convertible < U, T > :: value is false .
4) Initializes this - > t_ as if by direct-non-list-initialization with the expression std:: forward < U > ( u ) .
This constructor does not participate in overload resolution unless std:: is_constructible < T, U > :: value is true and std:: decay_t < U > is not a specialization of propagate_const . This constructor is explicit if and only if std:: is_convertible < U, T > :: value is false .
5) Copy constructor is explicitly deleted. propagate_const is non-copyable.

Parameters

p - another propagate_const object to move from
pu - another propagate_const object of a different specialization to move from
u - another object to initialize the contained pointer with

Notes

In Library Fundamental TS v2 (based on C++14), (4) and (5) are typically implemented in explicit /non- explicit overload pairs. Since Library Fundamental TS v3 (based on C++20), they can be implemented in conditional explicit specifiers.

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