tmp/tmpara_611s/{from.md → to.md}
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| 1 |
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##### Class template `function_ref` <a id="func.wrap.ref.class">[[func.wrap.ref.class]]</a>
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``` cpp
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namespace std {
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template<class R, class... ArgTypes>
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class function_ref<R(ArgTypes...) cv noexcept(noex)> {
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public:
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// [func.wrap.ref.ctor], constructors and assignment operators
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template<class F> function_ref(F*) noexcept;
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template<class F> constexpr function_ref(F&&) noexcept;
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template<auto f> constexpr function_ref(nontype_t<f>) noexcept;
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template<auto f, class U> constexpr function_ref(nontype_t<f>, U&&) noexcept;
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template<auto f, class T> constexpr function_ref(nontype_t<f>, cv T*) noexcept;
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constexpr function_ref(const function_ref&) noexcept = default;
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constexpr function_ref& operator=(const function_ref&) noexcept = default;
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template<class T> function_ref& operator=(T) = delete;
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// [func.wrap.ref.inv], invocation
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R operator()(ArgTypes...) const noexcept(noex);
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private:
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template<class... T>
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static constexpr bool is-invocable-using = see belownc; // exposition only
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R (*thunk-ptr)(BoundEntityType, ArgTypes&&...) noexcept(noex); // exposition only
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BoundEntityType bound-entity; // exposition only
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};
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// [func.wrap.ref.deduct], deduction guides
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template<class F>
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function_ref(F*) -> function_ref<F>;
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template<auto f>
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function_ref(nontype_t<f>) -> function_ref<see below>;
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template<auto f, class T>
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function_ref(nontype_t<f>, T&&) -> function_ref<see below>;
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}
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```
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An object of class `function_ref<R(Args...) cv noexcept(noex)>` stores a
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pointer to function *`thunk-ptr`* and an object *`bound-entity`*. The
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object *`bound-entity`* has an unspecified trivially copyable type
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*`BoundEntityType`*, that models `copyable` and is capable of storing a
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pointer to object value or a pointer to function value. The type of
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*`thunk-ptr`* is `R(*)(BoundEntityType, Args&&...) noexcept(noex)`.
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Each specialization of `function_ref` is a trivially copyable type
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[[term.trivially.copyable.type]] that models `copyable`.
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Within subclause [[func.wrap.ref]], `call-args` is an argument pack
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with elements such that
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``` cpp
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decltype((call-args))...
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```
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denote `ArgTypes&&...` respectively.
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