19 General utilities library [utilities]

19.14 Function objects [function.objects]

19.14.5 Class template reference_­wrapper [refwrap]

19.14.5.4 Invocation [refwrap.invoke]

template<class... ArgTypes> invoke_result_t<T&, ArgTypes...> operator()(ArgTypes&&... args) const;
Returns: INVOKE(get(), std::forward<ArgTypes>(args)...).