cppdraft_translate/cppdraft/func/wrap/ref/ctor.md

[func.wrap.ref.ctor]

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]

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template<class... T> static constexpr bool is-invocable-using = see below;

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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...>

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

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Constraints:

• (2.1)

is_function_v is true, and

• (2.2)

is-invocable-using is true.

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Preconditions: f is not a null pointer.

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Effects: Initializesbound-entity with f, andthunk-ptr with the address of a function thunk such thatthunk(bound-entity, call-args...) is expression-equivalent ([defns.expression.equivalent]) toinvoke_r(f, call-args...).

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

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Let T be remove_reference_t.

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Constraints:

• (6.1)

remove_cvref_t is not the same type as function_ref,

• (6.2)

is_member_pointer_v is false, and

• (6.3)

is-invocable-using<cv T&> is true.

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Effects: Initializesbound-entity with addressof(f), andthunk-ptr with the address of a function thunk such thatthunk(bound-entity, call-args...) is expression-equivalent ([defns.expression.equivalent]) toinvoke_r(static_cast<cv T&>(f), call-args...).

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

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Let F be decltype(f).

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Constraints: is-invocable-using is true.

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

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Effects: Initializesbound-entity with a pointer to an unspecified object or null pointer value, andthunk-ptr with the address of a function thunk such thatthunk(bound-entity, call-args...) is expression-equivalent ([defns.expression.equivalent]) toinvoke_r(f, call-args...).

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

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Let T be remove_reference_t andF be decltype(f).

13

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Constraints:

• (13.1)

is_rvalue_reference_v<U&&> is false, and

• (13.2)

is-invocable-using<F, cv T&> is true.

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

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Effects: Initializesbound-entity with addressof(obj), andthunk-ptr with the address of a function thunk such thatthunk(bound-entity, call-args...) is expression-equivalent ([defns.expression.equivalent]) toinvoke_r(f, static_cast<cv T&>(obj), call-args...).

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

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Let F be decltype(f).

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

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

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

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Effects: Initializesbound-entity with obj, andthunk-ptr with the address of a function thunk such thatthunk(bound-entity, call-args...) is expression-equivalent ([defns.expression.equivalent]) toinvoke_r(f, obj, call-args...).

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

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Constraints:

• (21.1)

T is not the same type as function_ref,

• (21.2)

is_pointer_v is false, and

• (21.3)

T is not a specialization of nontype_t.