29 Time library [time]

29.6 Class template time_point [time.point]

29.6.1 General [time.point.general]

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namespace std::chrono { template<class Clock, class Duration = typename Clock::duration> class time_point { public: using clock = Clock; using duration = Duration; using rep = typename duration::rep; using period = typename duration::period; private: duration d_; // exposition only public: // [time.point.cons], construct constexpr time_point(); // has value epoch constexpr explicit time_point(const duration& d); // same as time_point() + d template<class Duration2> constexpr time_point(const time_point<clock, Duration2>& t); // [time.point.observer], observer constexpr duration time_since_epoch() const; // [time.point.arithmetic], arithmetic constexpr time_point& operator++(); constexpr time_point operator++(int); constexpr time_point& operator--(); constexpr time_point operator--(int); constexpr time_point& operator+=(const duration& d); constexpr time_point& operator-=(const duration& d); // [time.point.special], special values static constexpr time_point min() noexcept; static constexpr time_point max() noexcept; }; }
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If Duration is not a specialization of duration, the program is ill-formed.

29.6.2 Constructors [time.point.cons]

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constexpr time_point();
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Effects: Initializes d_ with duration​::​zero().
Such a time_point object represents the epoch.
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constexpr explicit time_point(const duration& d);
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Effects: Initializes d_ with d.
Such a time_point object represents the epoch + d.
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template<class Duration2> constexpr time_point(const time_point<clock, Duration2>& t);
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Constraints: is_convertible_v<Duration2, duration> is true.
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Effects: Initializes d_ with t.time_since_epoch().

29.6.3 Observer [time.point.observer]

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constexpr duration time_since_epoch() const;
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Returns: d_.

29.6.4 Arithmetic [time.point.arithmetic]

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constexpr time_point& operator++();
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Effects: Equivalent to: ++d_.
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Returns: *this.
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constexpr time_point operator++(int);
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Effects: Equivalent to: return time_point{d_++};
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constexpr time_point& operator--();
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Effects: Equivalent to: --d_.
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Returns: *this.
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constexpr time_point operator--(int);
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Effects: Equivalent to: return time_point{d_--};
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constexpr time_point& operator+=(const duration& d);
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Effects: Equivalent to: d_ += d.
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Returns: *this.
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constexpr time_point& operator-=(const duration& d);
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Effects: Equivalent to: d_ -= d.
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Returns: *this.

29.6.5 Special values [time.point.special]

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static constexpr time_point min() noexcept;
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Returns: time_point(duration​::​min()).
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static constexpr time_point max() noexcept;
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Returns: time_point(duration​::​max()).

29.6.6 Non-member arithmetic [time.point.nonmember]

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template<class Clock, class Duration1, class Rep2, class Period2> constexpr time_point<Clock, common_type_t<Duration1, duration<Rep2, Period2>>> operator+(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
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Returns: CT(lhs.time_since_epoch() + rhs), where CT is the type of the return value.
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template<class Rep1, class Period1, class Clock, class Duration2> constexpr time_point<Clock, common_type_t<duration<Rep1, Period1>, Duration2>> operator+(const duration<Rep1, Period1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: rhs + lhs.
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template<class Clock, class Duration1, class Rep2, class Period2> constexpr time_point<Clock, common_type_t<Duration1, duration<Rep2, Period2>>> operator-(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
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Returns: CT(lhs.time_since_epoch() - rhs), where CT is the type of the return value.
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template<class Clock, class Duration1, class Duration2> constexpr common_type_t<Duration1, Duration2> operator-(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: lhs.time_since_epoch() - rhs.time_since_epoch().

29.6.7 Comparisons [time.point.comparisons]

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template<class Clock, class Duration1, class Duration2> constexpr bool operator==(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: lhs.time_since_epoch() == rhs.time_since_epoch().
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template<class Clock, class Duration1, class Duration2> constexpr bool operator<(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: lhs.time_since_epoch() < rhs.time_since_epoch().
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template<class Clock, class Duration1, class Duration2> constexpr bool operator>(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: rhs < lhs.
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template<class Clock, class Duration1, class Duration2> constexpr bool operator<=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: !(rhs < lhs).
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template<class Clock, class Duration1, class Duration2> constexpr bool operator>=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: !(lhs < rhs).
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template<class Clock, class Duration1, three_way_comparable_with<Duration1> Duration2> constexpr auto operator<=>(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
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Returns: lhs.time_since_epoch() <=> rhs.time_since_epoch().

29.6.8 Conversions [time.point.cast]

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template<class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> time_point_cast(const time_point<Clock, Duration>& t);
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Constraints: ToDuration is a specialization of duration.
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Returns: time_point<Clock, ToDuration>(duration_cast<ToDuration>(t.time_since_epoch()))
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template<class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> floor(const time_point<Clock, Duration>& tp);
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Constraints: ToDuration is a specialization of duration.
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Returns: time_point<Clock, ToDuration>(floor<ToDuration>(tp.time_since_epoch())).
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template<class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> ceil(const time_point<Clock, Duration>& tp);
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Constraints: ToDuration is a specialization of duration.
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Returns: time_point<Clock, ToDuration>(ceil<ToDuration>(tp.time_since_epoch())).
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template<class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> round(const time_point<Clock, Duration>& tp);
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Constraints: ToDuration is a specialization of duration, and treat_as_floating_point_v<typename ToDuration​::​rep> is false.
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Returns: time_point<Clock, ToDuration>(round<ToDuration>(tp.time_since_epoch())).