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std::expected<T,E>::emplace

From cppreference.com
< cpp‎ | utility‎ | expected
 
 
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T is not cv void
template< class... Args >
constexpr T& emplace( Args&&... args ) noexcept;
(1) (since C++23)
template< class U, class... Args >
constexpr T& emplace( std::initializer_list<U> il, Args&&... args ) noexcept;
(2) (since C++23)
T is cv void
constexpr void emplace() noexcept;
(3) (since C++23)

Constructs an expected value in-place. After the call, has_value() returns true.

1) Destroys the contained value, then initializes the expected value contained in *this as if by direct-initializing an object of type T from the arguments std::forward<Args>(args)....
This overload participates in overload resolution only if std::is_nothrow_constructible_v<T, Args...> is true.
2) Destroys the contained value, then initializes the expected value contained in *this as if by direct-initializing an object of type T from the arguments il and std::forward<Args>(args)....
This overload participates in overload resolution only if std::is_nothrow_constructible_v<T, std::initializer_list<U>&, Args...> is true.
3) If *this contains an unexpected value, destroys that value.

Contents

[edit] Parameters

args - the arguments to pass to the constructor
il - the initializer list to pass to the constructor

[edit] Return value

1,2) A reference to the new contained value.
3) (none)

[edit] Notes

If the construction of T is potentially-throwing, this function is not defined. In this case, it is the responsibility of the user to create a temporary object and move or copy it.

[edit] Example

[edit] See also

assigns contents
(public member function) [edit]