30 Time library [time]

30.7 Clocks [time.clock]

30.7.10 time_point conversions [time.clock.cast]

30.7.10.4 Conversions between system_clock and other clocks [time.clock.cast.sys]

template<class SourceClock> struct clock_time_conversion<system_clock, SourceClock> { template<class Duration> auto operator()(const time_point<SourceClock, Duration>& t) const -> decltype(SourceClock::to_sys(t)); };

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template<class Duration>
  auto operator()(const time_point<SourceClock, Duration>& t) const
    -> decltype(SourceClock::to_sys(t));

Constraints: SourceClock::to_sys(t) is well-formed.

Mandates: SourceClock::to_sys(t) returns a sys_time<Duration2> for some type Duration2 ([time.point.general]).

Returns: SourceClock::to_sys(t).

template<class DestClock> struct clock_time_conversion<DestClock, system_clock> { template<class Duration> auto operator()(const sys_time<Duration>& t) const -> decltype(DestClock::from_sys(t)); };

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template<class Duration>
  auto operator()(const sys_time<Duration>& t) const
    -> decltype(DestClock::from_sys(t));

Constraints: DestClock::from_sys(t) is well-formed.

Mandates: DestClock::from_sys(t) returns a time_point<DestClock, Duration2> for some type Duration2 ([time.point.general]).

Returns: DestClock::from_sys(t).