std::move_only_function::move_only_function - cppreference.com (original) (raw)

move_only_function() noexcept;	(1)	(since C++23)
move_only_function( std::nullptr_t ) noexcept;	(2)	(since C++23)
move_only_function( move_only_function&& other ) noexcept;	(3)	(since C++23)
move_only_function( const move_only_function& ) = delete;	(4)	(since C++23)
template< class F > move_only_function( F&& f );	(5)	(since C++23)
template< class T, class... CArgs > explicit move_only_function( std::in_place_type_t<T>, CArgs&&... args );	(6)	(since C++23)
template< class T, class U, class... CArgs > explicit move_only_function( std::in_place_type_t<T>, std::initializer_list<U> il, CArgs&&... args );	(7)	(since C++23)

Creates a new std::move_only_function.

1,2) Default constructor and the constructor taking nullptr construct an empty std::move_only_function.

Move constructor constructs a std::move_only_function whose target is that of other. other is in a valid but unspecified state after move construction.
Copy constructor is deleted. std::move_only_function does not satisfy CopyConstructible.
Let VT be std::decay_t<F>. If f is a null function pointer, a null pointer to member value, or an empty std::move_only_function (may be any other specialization), then constructs an empty std::move_only_function. Otherwise, constructs a std::move_only_function whose target is of type VT and direct-non-list-initialized with std::forward<F>(f).

This overload participates in overload resolution only if VT is neither same as move_only_function nor a specialization of std::in_place_type_t, and /*is-callable-from*/<VT> (see below) is true.
The program is ill-formed if std::is_constructible_v<VT, F> is not true.

Let VT be std::decay_t<T>. Constructs a std::move_only_function whose target is of type VT and direct-non-list-initialized with std::forward<CArgs>(args)....

This overload participates in overload resolution only if both std::is_constructible_v<VT, CArgs...> and /*is-callable-from*/<VT> (see below) are true.
The program is ill-formed if VT is not the same type as T.

Let VT be std::decay_t<T>. Constructs a std::move_only_function whose target is of type VT and direct-non-list-initialized with il, std::forward<CArgs>(args)....

This overload participates in overload resolution only if both std::is_constructible_v<VT, std::initializer_list<U>&, CArgs...> and /*is-callable-from*/<VT> (see below) are true.
The program is ill-formed if VT is not the same type as T.

For constructors (5-7), the behavior is undefined if VT does not satisfy the Destructible requirements, or std::is_move_constructible_v<VT> is true but VT does not satisfy the MoveConstructible requirements.

The constant /*is-callable-from*/<VT> is dependent on cv, ref, and noex in the template parameter of std::move_only_function as below:

cv ref noexcept(noex)	/is-callable-from/<VT>
noexcept(false)	std::is_invocable_r_v<R, VT, Args...> && std::is_invocable_r_v<R, VT&, Args...>
noexcept(true)	std::is_nothrow_invocable_r_v<R, VT, Args...> && std::is_nothrow_invocable_r_v<R, VT&, Args...>
const noexcept(false)	std::is_invocable_r_v<R, const VT, Args...> && std::is_invocable_r_v<R, const VT&, Args...>
const noexcept(true)	std::is_nothrow_invocable_r_v<R, const VT, Args...> && std::is_nothrow_invocable_r_v<R, const VT&, Args...>
& noexcept(false)	std::is_invocable_r_v<R, VT&, Args...>
& noexcept(true)	std::is_nothrow_invocable_r_v<R, VT&, Args...>
const & noexcept(false)	std::is_invocable_r_v<R, const VT&, Args...>
const & noexcept(true)	std::is_nothrow_invocable_r_v<R, const VT&, Args...>
&& noexcept(false)	std::is_invocable_r_v<R, VT, Args...>
&& noexcept(true)	std::is_nothrow_invocable_r_v<R, VT, Args...>
const && noexcept(false)	std::is_invocable_r_v<R, const VT, Args...>
const && noexcept(true)	std::is_nothrow_invocable_r_v<R, const VT, Args...>

[edit] Parameters

other	-	another std::move_only_function to move from
f	-	a function or a Callable object to wrap
args	-	arguments to construct the target object
il	-	std::initializer_list to construct the target object

[edit] Exceptions

5-7) May throw std::bad_alloc on allocation failure or propagate the exception thrown by the initialization of the target. No exception is thrown if VT is a function pointer type or a specialization of std::reference_wrapper.

[edit] Example

[edit] See also

| | constructs a new std::function instance (public member function of std::function<R(Args...)>) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | constructs a new std::copyable_function object (public member function of std::copyable_function) [edit] |