23 General utilities library [utilities]

23.8 Storage for any type [any]

23.8.3 Class any [any.class]

23.8.3.3 Modifiers [any.modifiers]

template <class T, class... Args> decay_t<T>& emplace(Args&&... args);

Let VT be decay_t<T>.

Requires: VT shall satisfy the CopyConstructible requirements.

Effects: Calls reset(). Then initializes the contained value as if direct-non-list-initializing an object of type VT with the arguments std::forward<Args>(args)....

Postconditions: *this contains a value.

Returns: A reference to the new contained value.

Throws: Any exception thrown by the selected constructor of VT.

Remarks: If an exception is thrown during the call to VT's constructor, *this does not contain a value, and any previously contained value has been destroyed. This function shall not participate in overload resolution unless is_copy_constructible_v<VT> is true and is_constructible_v<VT, Args...> is true.

template <class T, class U, class... Args> decay_t<T>& emplace(initializer_list<U> il, Args&&... args);

Let VT be decay_t<T>.

Requires: VT shall satisfy the CopyConstructible requirements.

Effects: Calls reset(). Then initializes the contained value as if direct-non-list-initializing an object of type VT with the arguments il, std::forward<Args>(args)....

Postconditions: *this contains a value.

Returns: A reference to the new contained value.

Throws: Any exception thrown by the selected constructor of VT.

Remarks: If an exception is thrown during the call to VT's constructor, *this does not contain a value, and any previously contained value has been destroyed. The function shall not participate in overload resolution unless is_copy_constructible_v<VT> is true and is_constructible_v<VT, initializer_list<U>&, Args...> is true.

void reset() noexcept;

Effects: If has_value() is true, destroys the contained value.

Postconditions: has_value() is false.

void swap(any& rhs) noexcept;

Effects: Exchanges the states of *this and rhs.