20 General utilities library [utilities]

20.14 Function objects [function.objects]

20.14.4 Function template invoke [func.invoke]

template<class F, class... Args> constexpr invoke_result_t<F, Args...> invoke(F&& f, Args&&... args) noexcept(is_nothrow_invocable_v<F, Args...>);
Returns: INVOKE(std​::​forward<F>(f), std​::​forward<Args>(args)...).