37     class interval_t : public clock_type::duration {
40         interval_t() : clock_type::duration(clock_type::duration::zero()) {}  in interval_t()  function
43         explicit interval_t( double sec )  in interval_t()  function
52         friend interval_t operator-( const tick_count& t1, const tick_count& t0 );
55         friend interval_t operator+( const interval_t& i, const interval_t& j ) {
56             return interval_t(std::chrono::operator+(i, j));
60         friend interval_t operator-( const interval_t& i, const interval_t& j ) {
61             return interval_t(std::chrono::operator-(i, j));
65         explicit interval_t( clock_type::duration value_ ) : clock_type::duration(value_) {}  in interval_t()  function
76     friend interval_t operator-( const tick_count& t1, const tick_count& t0 ) {
77         return tick_count::interval_t(t1.my_time_point - t0.my_time_point);
82         return static_cast<double>(interval_t::period::num) / interval_t::period::den;  in resolution()