const std::chrono::duration<Rep, std::ratio<Num, Denom>>& d) {
return boost::chrono::duration<Rep, boost::ratio<Num, Denom>>(d.count());
}
const std::chrono::duration<Rep, std::ratio<Num, Denom>>& d) {
return boost::chrono::duration<Rep, boost::ratio<Num, Denom>>(d.count());
}