[func.wrap.move.ctor]
22 General utilities library [utilities]
22.10 Function objects [function.objects]
22.10.17 Polymorphic function wrappers [func.wrap]
22.10.17.4 Move-only wrapper [func.wrap.move]
22.10.17.4.3 Constructors, assignments, and destructor [func.wrap.move.ctor]
template<class VT>
static constexpr bool is-callable-from = see below;
If noex is true, is-callable-from<VT> is equal to: is_nothrow_invocable_r_v<R, VT cv ref, ArgTypes...> && is_nothrow_invocable_r_v<R, VT inv-quals, ArgTypes...>
Otherwise, is-callable-from<VT> is equal to: is_invocable_r_v<R, VT cv ref, ArgTypes...> && is_invocable_r_v<R, VT inv-quals, ArgTypes...>
move_only_function() noexcept;
move_only_function(nullptr_t) noexcept;
Postconditions: *this has no target object.
move_only_function(move_only_function&& f) noexcept;
Postconditions: The target object of *this is the target object f had before construction, and f is in a valid state with an unspecified value.
template<class F> move_only_function(F&& f);
Constraints:
- remove_cvref_t<F> is not the same type as move_only_function, and
- remove_cvref_t<F> is not a specialization of in_place_type_t, and
- is-callable-from<VT> is true.
Mandates: is_constructible_v<VT, F> is true.
Postconditions: *this has no target object if any of the following hold:
- f is a null function pointer value,
- f is a null member pointer value, or
- remove_cvref_t<F> is a specialization of the move_only_function or copyable_function class template, and f has no target object.
Otherwise, *this has a target object of type VT direct-non-list-initialized with std::forward<F>(f).
Throws: Any exception thrown by the initialization of the target object.
May throw bad_alloc unless VT is a function pointer or a specialization of reference_wrapper.
template<class T, class... Args>
explicit move_only_function(in_place_type_t<T>, Args&&... args);
Constraints:
- is_constructible_v<VT, Args...> is true, and
- is-callable-from<VT> is true.
Mandates: VT is the same type as T.
Postconditions: *this has a target object of type VT direct-non-list-initialized with std::forward<Args>(args)....
Throws: Any exception thrown by the initialization of the target object.
May throw bad_alloc unless VT is a function pointer or a specialization of reference_wrapper.
template<class T, class U, class... Args>
explicit move_only_function(in_place_type_t<T>, initializer_list<U> ilist, Args&&... args);
Constraints:
- is_constructible_v<VT, initializer_list<U>&, Args...> is true, and
- is-callable-from<VT> is true.
Mandates: VT is the same type as T.
Postconditions: *this has a target object of type VT direct-non-list-initialized with ilist, std::forward<Args>(args)....
Throws: Any exception thrown by the initialization of the target object.
May throw bad_alloc unless VT is a function pointer or a specialization of reference_wrapper.
move_only_function& operator=(move_only_function&& f);
Effects: Equivalent to: move_only_function(std::move(f)).swap(*this);
move_only_function& operator=(nullptr_t) noexcept;
Effects: Destroys the target object of *this, if any.
template<class F> move_only_function& operator=(F&& f);
Effects: Equivalent to: move_only_function(std::forward<F>(f)).swap(*this);
Effects: Destroys the target object of *this, if any.