namespace std { template <class T> class reference_wrapper { public : // types using type = T; // construct/copy/destroy reference_wrapper(T&) noexcept; reference_wrapper(T&&) = delete; // do not bind to temporary objects reference_wrapper(const reference_wrapper& x) noexcept; // assignment reference_wrapper& operator=(const reference_wrapper& x) noexcept; // access operator T& () const noexcept; T& get() const noexcept; // invocation template <class... ArgTypes> invoke_result_t<T&, ArgTypes...> operator() (ArgTypes&&...) const; }; template<class T> reference_wrapper(reference_wrapper<T>) -> reference_wrapper<T>; }
reference_wrapper<T> is a CopyConstructible and CopyAssignable wrapper around a reference to an object or function of type T.
reference_wrapper(T& t) noexcept;
reference_wrapper(const reference_wrapper& x) noexcept;
reference_wrapper& operator=(const reference_wrapper& x) noexcept;
operator T& () const noexcept;
T& get() const noexcept;
template <class... ArgTypes>
invoke_result_t<T&, ArgTypes...>
operator()(ArgTypes&&... args) const;
Returns: INVOKE(get(), std::forward<ArgTypes>(args)...). ([func.require])
template <class T> reference_wrapper<T> ref(T& t) noexcept;
template <class T> reference_wrapper<T> ref(reference_wrapper<T> t) noexcept;
template <class T> reference_wrapper<const T> cref(const T& t) noexcept;
template <class T> reference_wrapper<const T> cref(reference_wrapper<T> t) noexcept;