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std::move_only_function::move_only_function

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.
3) 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.
4) Copy constructor is deleted. std::move_only_function does not satisfy CopyConstructible.
5) 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 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.
6) 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.
7) 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...>

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

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.

Example

See also

constructs a new std::function instance
(public member function of std::function<R(Args...)>)

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