19 General utilities library [utilities]

19.8 Storage for any type [any]

19.8.3 Class any [any.class]

19.8.3.3 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 Cpp17CopyConstructible 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)....
Ensures: *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 Cpp17CopyConstructible 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)....
Ensures: *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.
Ensures: has_­value() is false.
void swap(any& rhs) noexcept;
Effects: Exchanges the states of *this and rhs.