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std::experimental::optional::emplace(3) C++ Standard Libary std::experimental::optional::emplace(3)


std::experimental::optional::emplace - std::experimental::optional::emplace


template< class... Args > (library fundamentals TS)
void emplace( Args&&... args );
template< class U, class... Args >
void emplace( std::initializer_list<U> ilist, Args&&... (library fundamentals TS)
args );

Constructs the contained value in-place. If *this already contains a value before
the call, the contained value is destroyed by calling its destructor.

1) Initializes the contained value by direct-initializing (but not
direct-list-initializing) with std::forward<Args>(args)... as parameters.
2) Initializes the contained value by calling its constructor with ilist,
std::forward<Args>(args)... as parameters. This overload participates in overload
resolution only if std::is_constructible<T, std::initializer_list<U>&,
Args&&...>::value is true.


args... - the arguments to pass to the constructor
ilist - the initializer list to pass to the constructor

Type requirements

T must be constructible from Args...
T must be constructible from std::initializer_list and Args...

Return value



Any exception thrown by the selected constructor of T. If an exception is thrown,
*this does not contain a value after this call (the previously contained value, if
any, had been destroyed).

See also

operator= assigns contents
(public member function)