[func.wrap.ref.ctor] (original) (raw)

22 General utilities library [utilities]

22.10 Function objects [function.objects]

22.10.17 Polymorphic function wrappers [func.wrap]

22.10.17.6 Non-owning wrapper [func.wrap.ref]

22.10.17.6.3 Constructors and assignment operators [func.wrap.ref.ctor]

template<class... T> static constexpr bool _is-invocable-using_ = _see below_;

If noex is true,is-invocable-using<T...> is equal to:is_nothrow_invocable_r_v<R, T..., ArgTypes...>

Otherwise, is-invocable-using<T...> is equal to:is_invocable_r_v<R, T..., ArgTypes...>

template<class F> function_ref(F* f) noexcept;

Constraints:

• is_function_v<F> is true, and
• is-invocable-using<F> is true.

Preconditions: f is not a null pointer.

Effects: Initializes_bound-entity_ with f, and_thunk-ptr_ with the address of a function thunk_such that_thunk(bound-entity, call-args...)is expression-equivalent ([defns.expression.equivalent]) toinvoke_r<R>(f, call-args...).

template<class F> constexpr function_ref(F&& f) noexcept;

Let T be remove_reference_t<F>.

Constraints:

• remove_cvref_t<F> is not the same type as function_ref,
• is_member_pointer_v<T> is false, and
• is-invocable-using<cv T&> is true.

Effects: Initializes_bound-entity_ with addressof(f), and_thunk-ptr_ with the address of a function thunk_such that_thunk(bound-entity, call-args...)is expression-equivalent ([defns.expression.equivalent]) toinvoke_r<R>(static_cast<cv T&>(f), call-args...).

template<auto f> constexpr function_ref(nontype_t<f>) noexcept;

Constraints: is-invocable-using<F> is true.

Mandates: If is_pointer_v<F> || is_member_pointer_v<F> is true, then f != nullptr is true.

Effects: Initializes_bound-entity_ with a pointer to an unspecified object or null pointer value, and_thunk-ptr_ with the address of a function thunk_such that_thunk(bound-entity, call-args...)is expression-equivalent ([defns.expression.equivalent]) toinvoke_r<R>(f, call-args...).

template<auto f, class U> constexpr function_ref(nontype_t<f>, U&& obj) noexcept;

Let T be remove_reference_t<U> andF be decltype(f).

Constraints:

• is_rvalue_reference_v<U&&> is false, and
• is-invocable-using<F, cv T&> is true.

Mandates: If is_pointer_v<F> || is_member_pointer_v<F> is true, then f != nullptr is true.

Effects: Initializes_bound-entity_ with addressof(obj), and_thunk-ptr_ with the address of a function thunk_such that_thunk(bound-entity, call-args...)is expression-equivalent ([defns.expression.equivalent]) toinvoke_r<R>(f, static_cast<cv T&>(obj), call-args...).

template<auto f, class T> constexpr function_ref(nontype_t<f>, cv T* obj) noexcept;

Constraints: is-invocable-using<F, cv T*> is true.

Mandates: If is_pointer_v<F> || is_member_pointer_v<F> is true, then f != nullptr is true.

Preconditions: If is_member_pointer_v<F> is true,obj is not a null pointer.

Effects: Initializes_bound-entity_ with obj, and_thunk-ptr_ with the address of a function thunk_such that_thunk(bound-entity, call-args...)is expression-equivalent ([defns.expression.equivalent]) toinvoke_r<R>(f, obj, call-args...).

template<class T> function_ref& operator=(T) = delete;

Constraints:

• T is not the same type as function_ref,
• is_pointer_v<T> is false, and
• T is not a specialization of nontype_t.