// -*- C++ -*-
//===---------------------------- chrono ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_CHRONO
#define _LIBCPP_CHRONO

/*
    chrono synopsis

namespace std
{
namespace chrono
{

template <class ToDuration, class Rep, class Period>
constexpr
ToDuration
duration_cast(const duration<Rep, Period>& fd);

template <class Rep> struct treat_as_floating_point : is_floating_point<Rep> {};

template <class Rep> inline constexpr bool treat_as_floating_point_v
    = treat_as_floating_point<Rep>::value;                       // C++17

template <class Rep>
struct duration_values
{
public:
    static constexpr Rep zero();
    static constexpr Rep max();
    static constexpr Rep min();
};

// duration

template <class Rep, class Period = ratio<1>>
class duration
{
    static_assert(!__is_duration<Rep>::value, "A duration representation can not be a duration");
    static_assert(__is_ratio<Period>::value, "Second template parameter of duration must be a std::ratio");
    static_assert(Period::num > 0, "duration period must be positive");
public:
    typedef Rep rep;
    typedef typename _Period::type period;

    constexpr duration() = default;
    template <class Rep2>
        constexpr explicit duration(const Rep2& r,
            typename enable_if
            <
               is_convertible<Rep2, rep>::value &&
               (treat_as_floating_point<rep>::value ||
               !treat_as_floating_point<rep>::value && !treat_as_floating_point<Rep2>::value)
            >::type* = 0);

    // conversions
    template <class Rep2, class Period2>
        constexpr duration(const duration<Rep2, Period2>& d,
            typename enable_if
            <
                treat_as_floating_point<rep>::value ||
                ratio_divide<Period2, period>::type::den == 1
            >::type* = 0);

    // observer

    constexpr rep count() const;

    // arithmetic

    constexpr common_type<duration>::type  operator+() const;
    constexpr common_type<duration>::type  operator-() const;
    constexpr duration& operator++();
    constexpr duration  operator++(int);
    constexpr duration& operator--();
    constexpr duration  operator--(int);

    constexpr duration& operator+=(const duration& d);
    constexpr duration& operator-=(const duration& d);

    duration& operator*=(const rep& rhs);
    duration& operator/=(const rep& rhs);

    // special values

    static constexpr duration zero();
    static constexpr duration min();
    static constexpr duration max();
};

typedef duration<long long,         nano> nanoseconds;
typedef duration<long long,        micro> microseconds;
typedef duration<long long,        milli> milliseconds;
typedef duration<long long              > seconds;
typedef duration<     long, ratio<  60> > minutes;
typedef duration<     long, ratio<3600> > hours;

template <class Clock, class Duration = typename Clock::duration>
class time_point
{
public:
    typedef Clock                     clock;
    typedef Duration                  duration;
    typedef typename duration::rep    rep;
    typedef typename duration::period period;
private:
    duration d_;  // exposition only

public:
    time_point();  // has value "epoch" // constexpr in C++14
    explicit time_point(const duration& d);  // same as time_point() + d // constexpr in C++14

    // conversions
    template <class Duration2>
       time_point(const time_point<clock, Duration2>& t); // constexpr in C++14

    // observer

    duration time_since_epoch() const; // constexpr in C++14

    // arithmetic

    time_point& operator+=(const duration& d);
    time_point& operator-=(const duration& d);

    // special values

    static constexpr time_point min();
    static constexpr time_point max();
};

} // chrono

// common_type traits
template <class Rep1, class Period1, class Rep2, class Period2>
  struct common_type<chrono::duration<Rep1, Period1>, chrono::duration<Rep2, Period2>>;

template <class Clock, class Duration1, class Duration2>
  struct common_type<chrono::time_point<Clock, Duration1>, chrono::time_point<Clock, Duration2>>;

namespace chrono {


template<class T> struct is_clock;  // C++20
template<class T> inline constexpr bool is_clock_v = is_clock<T>::value;   // C++20


// duration arithmetic
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type
  operator+(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type
  operator-(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator*(const duration<Rep1, Period>& d, const Rep2& s);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator*(const Rep1& s, const duration<Rep2, Period>& d);
template <class Rep1, class Period, class Rep2>
  constexpr
  duration<typename common_type<Rep1, Rep2>::type, Period>
  operator/(const duration<Rep1, Period>& d, const Rep2& s);
template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr
  typename common_type<Rep1, Rep2>::type
  operator/(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);

// duration comparisons
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator==(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator!=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator< (const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator<=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator> (const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
   bool operator>=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);

// duration_cast
template <class ToDuration, class Rep, class Period>
  ToDuration duration_cast(const duration<Rep, Period>& d);

template <class ToDuration, class Rep, class Period>
    constexpr ToDuration floor(const duration<Rep, Period>& d);    // C++17
template <class ToDuration, class Rep, class Period>
    constexpr ToDuration ceil(const duration<Rep, Period>& d);     // C++17
template <class ToDuration, class Rep, class Period>
    constexpr ToDuration round(const duration<Rep, Period>& d);    // C++17

// duration I/O is elsewhere

// time_point arithmetic (all constexpr in C++14)
template <class Clock, class Duration1, class Rep2, class Period2>
  time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
  operator+(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Rep1, class Period1, class Clock, class Duration2>
  time_point<Clock, typename common_type<duration<Rep1, Period1>, Duration2>::type>
  operator+(const duration<Rep1, Period1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Rep2, class Period2>
  time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
  operator-(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
template <class Clock, class Duration1, class Duration2>
  typename common_type<Duration1, Duration2>::type
  operator-(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);

// time_point comparisons (all constexpr in C++14)
template <class Clock, class Duration1, class Duration2>
   bool operator==(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator!=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator< (const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator<=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator> (const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
template <class Clock, class Duration1, class Duration2>
   bool operator>=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);

// time_point_cast (constexpr in C++14)

template <class ToDuration, class Clock, class Duration>
  time_point<Clock, ToDuration> time_point_cast(const time_point<Clock, Duration>& t);

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    floor(const time_point<Clock, Duration>& tp);                  // C++17

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    ceil(const time_point<Clock, Duration>& tp);                   // C++17

template <class ToDuration, class Clock, class Duration>
    constexpr time_point<Clock, ToDuration>
    round(const time_point<Clock, Duration>& tp);                  // C++17

template <class Rep, class Period>
    constexpr duration<Rep, Period> abs(duration<Rep, Period> d);  // C++17

// Clocks

class system_clock
{
public:
    typedef microseconds                     duration;
    typedef duration::rep                    rep;
    typedef duration::period                 period;
    typedef chrono::time_point<system_clock> time_point;
    static const bool is_steady =            false; // constexpr in C++14

    static time_point now() noexcept;
    static time_t     to_time_t  (const time_point& __t) noexcept;
    static time_point from_time_t(time_t __t) noexcept;
};

template <class Duration>
  using sys_time  = time_point<system_clock, Duration>; // C++20
using sys_seconds = sys_time<seconds>;                  // C++20
using sys_days    = sys_time<days>;                     // C++20

class utc_clock;                                        // C++20

template <class Duration>
  using utc_time  = time_point<utc_clock, Duration>;    // C++20
using utc_seconds = utc_time<seconds>;                  // C++20

class tai_clock;                                        // C++20

template <class Duration>
  using tai_time  = time_point<tai_clock, Duration>;    // C++20
using tai_seconds = tai_time<seconds>;                  // C++20

class file_clock;                                       // C++20

template<class Duration>
  using file_time = time_point<file_clock, Duration>;   // C++20

class steady_clock
{
public:
    typedef nanoseconds                                   duration;
    typedef duration::rep                                 rep;
    typedef duration::period                              period;
    typedef chrono::time_point<steady_clock, duration>    time_point;
    static const bool is_steady =                         true; // constexpr in C++14

    static time_point now() noexcept;
};

typedef steady_clock high_resolution_clock;

// 25.7.8, local time           // C++20
struct local_t {};
template<class Duration>
  using local_time  = time_point<local_t, Duration>;
using local_seconds = local_time<seconds>;
using local_days    = local_time<days>;

// 25.7.9, time_point conversions template<class DestClock, class SourceClock>    // C++20
struct clock_time_conversion;

template<class DestClock, class SourceClock, class Duration>
  auto clock_cast(const time_point<SourceClock, Duration>& t);
  
// 25.8.2, class last_spec    // C++20
struct last_spec;

// 25.8.3, class day          // C++20

class day;
constexpr bool operator==(const day& x, const day& y) noexcept;
constexpr bool operator!=(const day& x, const day& y) noexcept;
constexpr bool operator< (const day& x, const day& y) noexcept;
constexpr bool operator> (const day& x, const day& y) noexcept;
constexpr bool operator<=(const day& x, const day& y) noexcept;
constexpr bool operator>=(const day& x, const day& y) noexcept;
constexpr day  operator+(const day&  x, const days& y) noexcept;
constexpr day  operator+(const days& x, const day&  y) noexcept;
constexpr day  operator-(const day&  x, const days& y) noexcept;
constexpr days operator-(const day&  x, const day&  y) noexcept;

// 25.8.4, class month    // C++20
class month;
constexpr bool operator==(const month& x, const month& y) noexcept;
constexpr bool operator!=(const month& x, const month& y) noexcept;
constexpr bool operator< (const month& x, const month& y) noexcept;
constexpr bool operator> (const month& x, const month& y) noexcept;
constexpr bool operator<=(const month& x, const month& y) noexcept;
constexpr bool operator>=(const month& x, const month& y) noexcept;
constexpr month  operator+(const month&  x, const months& y) noexcept;
constexpr month  operator+(const months& x,  const month& y) noexcept;
constexpr month  operator-(const month&  x, const months& y) noexcept;
constexpr months operator-(const month&  x,  const month& y) noexcept;

// 25.8.5, class year    // C++20
class year;
constexpr bool operator==(const year& x, const year& y) noexcept;
constexpr bool operator!=(const year& x, const year& y) noexcept;
constexpr bool operator< (const year& x, const year& y) noexcept;
constexpr bool operator> (const year& x, const year& y) noexcept;
constexpr bool operator<=(const year& x, const year& y) noexcept;
constexpr bool operator>=(const year& x, const year& y) noexcept;
constexpr year  operator+(const year&  x, const years& y) noexcept;
constexpr year  operator+(const years& x, const year&  y) noexcept;
constexpr year  operator-(const year&  x, const years& y) noexcept;
constexpr years operator-(const year&  x, const year&  y) noexcept;

// 25.8.6, class weekday    // C++20
class weekday;

constexpr bool operator==(const weekday& x, const weekday& y) noexcept;
constexpr bool operator!=(const weekday& x, const weekday& y) noexcept;
constexpr weekday operator+(const weekday& x, const days&    y) noexcept;
constexpr weekday operator+(const days&    x, const weekday& y) noexcept;
constexpr weekday operator-(const weekday& x, const days&    y) noexcept;
constexpr days    operator-(const weekday& x, const weekday& y) noexcept;

// 25.8.7, class weekday_indexed    // C++20

class weekday_indexed;
constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept;
constexpr bool operator!=(const weekday_indexed& x, const weekday_indexed& y) noexcept;

// 25.8.8, class weekday_last    // C++20
class weekday_last;

constexpr bool operator==(const weekday_last& x, const weekday_last& y) noexcept;
constexpr bool operator!=(const weekday_last& x, const weekday_last& y) noexcept;

// 25.8.9, class month_day    // C++20
class month_day;

constexpr bool operator==(const month_day& x, const month_day& y) noexcept;
constexpr bool operator!=(const month_day& x, const month_day& y) noexcept;
constexpr bool operator< (const month_day& x, const month_day& y) noexcept;
constexpr bool operator> (const month_day& x, const month_day& y) noexcept;
constexpr bool operator<=(const month_day& x, const month_day& y) noexcept;
constexpr bool operator>=(const month_day& x, const month_day& y) noexcept;


// 25.8.10, class month_day_last    // C++20
class month_day_last;

constexpr bool operator==(const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator!=(const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator< (const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator> (const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator<=(const month_day_last& x, const month_day_last& y) noexcept;
constexpr bool operator>=(const month_day_last& x, const month_day_last& y) noexcept;

// 25.8.11, class month_weekday    // C++20
class month_weekday;

constexpr bool operator==(const month_weekday& x, const month_weekday& y) noexcept;
constexpr bool operator!=(const month_weekday& x, const month_weekday& y) noexcept;

// 25.8.12, class month_weekday_last    // C++20
class month_weekday_last;

constexpr bool operator==(const month_weekday_last& x, const month_weekday_last& y) noexcept;
constexpr bool operator!=(const month_weekday_last& x, const month_weekday_last& y) noexcept;


// 25.8.13, class year_month    // C++20
class year_month;

constexpr bool operator==(const year_month& x, const year_month& y) noexcept;
constexpr bool operator!=(const year_month& x, const year_month& y) noexcept;
constexpr bool operator< (const year_month& x, const year_month& y) noexcept;
constexpr bool operator> (const year_month& x, const year_month& y) noexcept;
constexpr bool operator<=(const year_month& x, const year_month& y) noexcept;
constexpr bool operator>=(const year_month& x, const year_month& y) noexcept;

constexpr year_month operator+(const year_month& ym, const months& dm) noexcept;
constexpr year_month operator+(const months& dm, const year_month& ym) noexcept;
constexpr year_month operator-(const year_month& ym, const months& dm) noexcept;
constexpr months operator-(const year_month& x, const year_month& y) noexcept;
constexpr year_month operator+(const year_month& ym, const years& dy) noexcept;
constexpr year_month operator+(const years& dy, const year_month& ym) noexcept;
constexpr year_month operator-(const year_month& ym, const years& dy) noexcept;

// 25.8.14, class year_month_day class    // C++20
year_month_day;

constexpr bool operator==(const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator!=(const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator< (const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator> (const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator<=(const year_month_day& x, const year_month_day& y) noexcept;
constexpr bool operator>=(const year_month_day& x, const year_month_day& y) noexcept;

constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept;
constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept;
constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept;


// 25.8.15, class year_month_day_last    // C++20
class year_month_day_last;

constexpr bool operator==(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator!=(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator< (const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator> (const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator<=(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;
constexpr bool operator>=(const year_month_day_last& x,
                          const year_month_day_last& y) noexcept;

constexpr year_month_day_last
  operator+(const year_month_day_last& ymdl, const months& dm) noexcept;
constexpr year_month_day_last
  operator+(const months& dm, const year_month_day_last& ymdl) noexcept;
constexpr year_month_day_last
  operator+(const year_month_day_last& ymdl, const years& dy) noexcept;
constexpr year_month_day_last
  operator+(const years& dy, const year_month_day_last& ymdl) noexcept;
constexpr year_month_day_last
  operator-(const year_month_day_last& ymdl, const months& dm) noexcept;
constexpr year_month_day_last
  operator-(const year_month_day_last& ymdl, const years& dy) noexcept;

// 25.8.16, class year_month_weekday    // C++20
class year_month_weekday;

constexpr bool operator==(const year_month_weekday& x,
                          const year_month_weekday& y) noexcept;
constexpr bool operator!=(const year_month_weekday& x,
                          const year_month_weekday& y) noexcept;

constexpr year_month_weekday
  operator+(const year_month_weekday& ymwd, const months& dm) noexcept;
constexpr year_month_weekday
  operator+(const months& dm, const year_month_weekday& ymwd) noexcept;
constexpr year_month_weekday
  operator+(const year_month_weekday& ymwd, const years& dy) noexcept;
constexpr year_month_weekday
  operator+(const years& dy, const year_month_weekday& ymwd) noexcept;
constexpr year_month_weekday
  operator-(const year_month_weekday& ymwd, const months& dm) noexcept;
constexpr year_month_weekday
  operator-(const year_month_weekday& ymwd, const years& dy) noexcept;

// 25.8.17, class year_month_weekday_last    // C++20
class year_month_weekday_last;

constexpr bool operator==(const year_month_weekday_last& x,
                          const year_month_weekday_last& y) noexcept;
constexpr bool operator!=(const year_month_weekday_last& x,
                          const year_month_weekday_last& y) noexcept;
constexpr year_month_weekday_last
  operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
constexpr year_month_weekday_last
  operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
constexpr year_month_weekday_last
  operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
constexpr year_month_weekday_last
  operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
constexpr year_month_weekday_last
  operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
constexpr year_month_weekday_last
  operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
  
// 25.8.18, civil calendar conventional syntax operators    // C++20
constexpr year_month
  operator/(const year& y, const month& m) noexcept;
constexpr year_month
  operator/(const year& y, int m) noexcept;
constexpr month_day
  operator/(const month& m, const day& d) noexcept;
constexpr month_day
  operator/(const month& m, int d) noexcept;
constexpr month_day
  operator/(int m, const day& d) noexcept;
constexpr month_day
  operator/(const day& d, const month& m) noexcept;
constexpr month_day
  operator/(const day& d, int m) noexcept;
constexpr month_day_last
  operator/(const month& m, last_spec) noexcept;
constexpr month_day_last
  operator/(int m, last_spec) noexcept;
constexpr month_day_last
  operator/(last_spec, const month& m) noexcept;
constexpr month_day_last
  operator/(last_spec, int m) noexcept;
constexpr month_weekday
  operator/(const month& m, const weekday_indexed& wdi) noexcept;
constexpr month_weekday
  operator/(int m, const weekday_indexed& wdi) noexcept;
constexpr month_weekday
  operator/(const weekday_indexed& wdi, const month& m) noexcept;
constexpr month_weekday
  operator/(const weekday_indexed& wdi, int m) noexcept;
constexpr month_weekday_last
  operator/(const month& m, const weekday_last& wdl) noexcept;
constexpr month_weekday_last
  operator/(int m, const weekday_last& wdl) noexcept;
constexpr month_weekday_last
  operator/(const weekday_last& wdl, const month& m) noexcept;
constexpr month_weekday_last
  operator/(const weekday_last& wdl, int m) noexcept;
constexpr year_month_day
  operator/(const year_month& ym, const day& d) noexcept;
constexpr year_month_day
  operator/(const year_month& ym, int d) noexcept;
constexpr year_month_day
  operator/(const year& y, const month_day& md) noexcept;
constexpr year_month_day
  operator/(int y, const month_day& md) noexcept;
constexpr year_month_day
  operator/(const month_day& md, const year& y) noexcept;
constexpr year_month_day
  operator/(const month_day& md, int y) noexcept;
constexpr year_month_day_last
  operator/(const year_month& ym, last_spec) noexcept;
constexpr year_month_day_last
  operator/(const year& y, const month_day_last& mdl) noexcept;
constexpr year_month_day_last
  operator/(int y, const month_day_last& mdl) noexcept;
constexpr year_month_day_last
  operator/(const month_day_last& mdl, const year& y) noexcept;
constexpr year_month_day_last
  operator/(const month_day_last& mdl, int y) noexcept;
constexpr year_month_weekday
  operator/(const year_month& ym, const weekday_indexed& wdi) noexcept;
constexpr year_month_weekday
  operator/(const year& y, const month_weekday& mwd) noexcept;
constexpr year_month_weekday
  operator/(int y, const month_weekday& mwd) noexcept;
constexpr year_month_weekday
  operator/(const month_weekday& mwd, const year& y) noexcept;
constexpr year_month_weekday
  operator/(const month_weekday& mwd, int y) noexcept;
constexpr year_month_weekday_last
  operator/(const year_month& ym, const weekday_last& wdl) noexcept;
constexpr year_month_weekday_last
  operator/(const year& y, const month_weekday_last& mwdl) noexcept;
constexpr year_month_weekday_last
  operator/(int y, const month_weekday_last& mwdl) noexcept;
constexpr year_month_weekday_last
  operator/(const month_weekday_last& mwdl, const year& y) noexcept;
constexpr year_month_weekday_last
  operator/(const month_weekday_last& mwdl, int y) noexcept;  

// 25.9, class template time_of_day    // C++20
template<class Duration> class time_of_day;

template<> class time_of_day<hours>;
template<> class time_of_day<minutes>;
template<> class time_of_day<seconds>;
template<class Rep, class Period> class time_of_day<duration<Rep, Period>>;

// 25.10.2, time zone database     // C++20
struct tzdb;
class tzdb_list;

// 25.10.2.3, time zone database access    // C++20
const tzdb& get_tzdb();
tzdb_list& get_tzdb_list();
const time_zone* locate_zone(string_view tz_name);
const time_zone* current_zone();

// 25.10.2.4, remote time zone database support    // C++20
const tzdb& reload_tzdb();
string remote_version();

// 25.10.3, exception classes    // C++20
class nonexistent_local_time;
class ambiguous_local_time;

// 25.10.4, information classes    // C++20
struct sys_info;
struct local_info;
    
// 25.10.5, class time_zone    // C++20
enum class choose {earliest, latest};
class time_zone;
bool operator==(const time_zone& x, const time_zone& y) noexcept;
bool operator!=(const time_zone& x, const time_zone& y) noexcept;
bool operator<(const time_zone& x, const time_zone& y) noexcept;
bool operator>(const time_zone& x, const time_zone& y) noexcept;
bool operator<=(const time_zone& x, const time_zone& y) noexcept;
bool operator>=(const time_zone& x, const time_zone& y) noexcept;
  
// 25.10.6, class template zoned_traits    // C++20
template<class T> struct zoned_traits;

// 25.10.7, class template zoned_time    // C++20
template<class Duration, class TimeZonePtr = const time_zone*> class zoned_time;
using zoned_seconds = zoned_time<seconds>;

template<class Duration1, class Duration2, class TimeZonePtr>
  bool operator==(const zoned_time<Duration1, TimeZonePtr>& x,
                  const zoned_time<Duration2, TimeZonePtr>& y);
template<class Duration1, class Duration2, class TimeZonePtr>
  bool operator!=(const zoned_time<Duration1, TimeZonePtr>& x,
                  const zoned_time<Duration2, TimeZonePtr>& y);

// 25.10.8, leap second support    // C++20
class leap;

bool operator==(const leap& x, const leap& y);
bool operator!=(const leap& x, const leap& y);
bool operator< (const leap& x, const leap& y);
bool operator> (const leap& x, const leap& y);
bool operator<=(const leap& x, const leap& y);
bool operator>=(const leap& x, const leap& y);
template<class Duration>
  bool operator==(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator==(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator!=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator!=(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator< (const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator< (const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator> (const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator> (const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator<=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator<=(const sys_time<Duration>& x, const leap& y);
template<class Duration>
  bool operator>=(const leap& x, const sys_time<Duration>& y);
template<class Duration>
  bool operator>=(const sys_time<Duration>& x, const leap& y);

// 25.10.9, class link    // C++20
class link;
bool operator==(const link& x, const link& y);
bool operator!=(const link& x, const link& y);
bool operator< (const link& x, const link& y);
bool operator> (const link& x, const link& y);
bool operator<=(const link& x, const link& y);
bool operator>=(const link& x, const link& y);

// 25.11, formatting    // C++20
template<class charT, class Streamable>
  basic_string<charT>
    format(const charT* fmt, const Streamable& s);

template<class charT, class Streamable>
  basic_string<charT>
    format(const locale& loc, const charT* fmt, const Streamable& s);

template<class charT, class traits, class Alloc, class Streamable>
  basic_string<charT, traits, Alloc>
    format(const basic_string<charT, traits, Alloc>& fmt, const Streamable& s);

template<class charT, class traits, class Alloc, class Streamable>
  basic_string<charT, traits, Alloc>
    format(const locale& loc, const basic_string<charT, traits, Alloc>& fmt,
           const Streamable& s);             

// 25.12, parsing    // C++20
template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          basic_string<charT, traits, Alloc>& abbrev);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          minutes& offset);

template<class charT, class traits, class Alloc, class Parsable>
unspecified
    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
          basic_string<charT, traits, Alloc>& abbrev, minutes& offset);

inline constexpr last_spec								last{};       // C++20
inline constexpr chrono::weekday                        Sunday{0};    // C++20
inline constexpr chrono::weekday                        Monday{1};    // C++20
inline constexpr chrono::weekday                        Tuesday{2};   // C++20
inline constexpr chrono::weekday                        Wednesday{3}; // C++20
inline constexpr chrono::weekday                        Thursday{4};  // C++20
inline constexpr chrono::weekday                        Friday{5};    // C++20
inline constexpr chrono::weekday                        Saturday{6};  // C++20

inline constexpr chrono::month                          January{1};   // C++20
inline constexpr chrono::month                          February{2};  // C++20
inline constexpr chrono::month                          March{3};     // C++20
inline constexpr chrono::month                          April{4};     // C++20
inline constexpr chrono::month                          May{5};       // C++20
inline constexpr chrono::month                          June{6};      // C++20
inline constexpr chrono::month                          July{7};      // C++20
inline constexpr chrono::month                          August{8};    // C++20
inline constexpr chrono::month                          September{9}; // C++20
inline constexpr chrono::month                          October{10};  // C++20
inline constexpr chrono::month                          November{11}; // C++20
inline constexpr chrono::month                          December{12}; // C++20
}  // chrono

inline namespace literals {
  inline namespace chrono_literals {
constexpr chrono::hours                                 operator ""h(unsigned long long); // C++14
constexpr chrono::duration<unspecified , ratio<3600,1>> operator ""h(long double); // C++14
constexpr chrono::minutes                               operator ""min(unsigned long long); // C++14
constexpr chrono::duration<unspecified , ratio<60,1>>   operator ""min(long double); // C++14
constexpr chrono::seconds                               operator ""s(unsigned long long); // C++14
constexpr chrono::duration<unspecified >                operator ""s(long double); // C++14
constexpr chrono::milliseconds                          operator ""ms(unsigned long long); // C++14
constexpr chrono::duration<unspecified , milli>         operator ""ms(long double); // C++14
constexpr chrono::microseconds                          operator ""us(unsigned long long); // C++14
constexpr chrono::duration<unspecified , micro>         operator ""us(long double); // C++14
constexpr chrono::nanoseconds                           operator ""ns(unsigned long long); // C++14
constexpr chrono::duration<unspecified , nano>          operator ""ns(long double); // C++14
constexpr chrono::day                                   operator ""d(unsigned long long d) noexcept; // C++20
constexpr chrono::year                                  operator ""y(unsigned long long y) noexcept; // C++20
}  // chrono_literals
}  // literals

}  // std
*/

#include <__config>
#include <ctime>
#include <type_traits>
#include <ratio>
#include <limits>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


_LIBCPP_BEGIN_NAMESPACE_STD

namespace chrono
{

template <class _Rep, class _Period = ratio<1> > class _LIBCPP_TEMPLATE_VIS duration;

template <class _Tp>
struct __is_duration : false_type {};

template <class _Rep, class _Period>
struct __is_duration<duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<const duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<volatile duration<_Rep, _Period> > : true_type  {};

template <class _Rep, class _Period>
struct __is_duration<const volatile duration<_Rep, _Period> > : true_type  {};

} // chrono

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
struct _LIBCPP_TEMPLATE_VIS common_type<chrono::duration<_Rep1, _Period1>,
                                         chrono::duration<_Rep2, _Period2> >
{
    typedef chrono::duration<typename common_type<_Rep1, _Rep2>::type,
                             typename __ratio_gcd<_Period1, _Period2>::type> type;
};

namespace chrono {

// duration_cast

template <class _FromDuration, class _ToDuration,
          class _Period = typename ratio_divide<typename _FromDuration::period, typename _ToDuration::period>::type,
          bool = _Period::num == 1,
          bool = _Period::den == 1>
struct __duration_cast;

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, true, true>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        return _ToDuration(static_cast<typename _ToDuration::rep>(__fd.count()));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, true, false>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) / static_cast<_Ct>(_Period::den)));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, false, true>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) * static_cast<_Ct>(_Period::num)));
    }
};

template <class _FromDuration, class _ToDuration, class _Period>
struct __duration_cast<_FromDuration, _ToDuration, _Period, false, false>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    _ToDuration operator()(const _FromDuration& __fd) const
    {
        typedef typename common_type<typename _ToDuration::rep, typename _FromDuration::rep, intmax_t>::type _Ct;
        return _ToDuration(static_cast<typename _ToDuration::rep>(
                           static_cast<_Ct>(__fd.count()) * static_cast<_Ct>(_Period::num)
                                                          / static_cast<_Ct>(_Period::den)));
    }
};

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
duration_cast(const duration<_Rep, _Period>& __fd)
{
    return __duration_cast<duration<_Rep, _Period>, _ToDuration>()(__fd);
}

template <class _Rep>
struct _LIBCPP_TEMPLATE_VIS treat_as_floating_point : is_floating_point<_Rep> {};

#if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
template <class _Rep>
_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool treat_as_floating_point_v
    = treat_as_floating_point<_Rep>::value;
#endif

template <class _Rep>
struct _LIBCPP_TEMPLATE_VIS duration_values
{
public:
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep zero() {return _Rep(0);}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep max()  {return numeric_limits<_Rep>::max();}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep min()  {return numeric_limits<_Rep>::lowest();}
};

#if _LIBCPP_STD_VER > 14
template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
floor(const duration<_Rep, _Period>& __d)
{
    _ToDuration __t = duration_cast<_ToDuration>(__d);
    if (__t > __d)
        __t = __t - _ToDuration{1};
    return __t;
}

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
ceil(const duration<_Rep, _Period>& __d)
{
    _ToDuration __t = duration_cast<_ToDuration>(__d);
    if (__t < __d)
        __t = __t + _ToDuration{1};
    return __t;
}

template <class _ToDuration, class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    _ToDuration
>::type
round(const duration<_Rep, _Period>& __d)
{
    _ToDuration __lower = floor<_ToDuration>(__d);
    _ToDuration __upper = __lower + _ToDuration{1};
    auto __lowerDiff = __d - __lower;
    auto __upperDiff = __upper - __d;
    if (__lowerDiff < __upperDiff)
        return __lower;
    if (__lowerDiff > __upperDiff)
        return __upper;
    return __lower.count() & 1 ? __upper : __lower;
}
#endif

// duration

template <class _Rep, class _Period>
class _LIBCPP_TEMPLATE_VIS duration
{
    static_assert(!__is_duration<_Rep>::value, "A duration representation can not be a duration");
    static_assert(__is_ratio<_Period>::value, "Second template parameter of duration must be a std::ratio");
    static_assert(_Period::num > 0, "duration period must be positive");

    template <class _R1, class _R2>
    struct __no_overflow
    {
    private:
        static const intmax_t __gcd_n1_n2 = __static_gcd<_R1::num, _R2::num>::value;
        static const intmax_t __gcd_d1_d2 = __static_gcd<_R1::den, _R2::den>::value;
        static const intmax_t __n1 = _R1::num / __gcd_n1_n2;
        static const intmax_t __d1 = _R1::den / __gcd_d1_d2;
        static const intmax_t __n2 = _R2::num / __gcd_n1_n2;
        static const intmax_t __d2 = _R2::den / __gcd_d1_d2;
        static const intmax_t max = -((intmax_t(1) << (sizeof(intmax_t) * CHAR_BIT - 1)) + 1);

        template <intmax_t _Xp, intmax_t _Yp, bool __overflow>
        struct __mul    // __overflow == false
        {
            static const intmax_t value = _Xp * _Yp;
        };

        template <intmax_t _Xp, intmax_t _Yp>
        struct __mul<_Xp, _Yp, true>
        {
            static const intmax_t value = 1;
        };

    public:
        static const bool value = (__n1 <= max / __d2) && (__n2 <= max / __d1);
        typedef ratio<__mul<__n1, __d2, !value>::value,
                      __mul<__n2, __d1, !value>::value> type;
    };
    
public:
    typedef _Rep rep;
    typedef typename _Period::type period;
private:
    rep __rep_;
public:

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
#ifndef _LIBCPP_CXX03_LANG
        duration() = default;
#else
        duration() {}
#endif

    template <class _Rep2>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
        explicit duration(const _Rep2& __r,
            typename enable_if
            <
               is_convertible<_Rep2, rep>::value &&
               (treat_as_floating_point<rep>::value ||
               !treat_as_floating_point<_Rep2>::value)
            >::type* = 0)
                : __rep_(__r) {}

    // conversions
    template <class _Rep2, class _Period2>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
        duration(const duration<_Rep2, _Period2>& __d,
            typename enable_if
            <
                __no_overflow<_Period2, period>::value && (
                treat_as_floating_point<rep>::value ||
                (__no_overflow<_Period2, period>::type::den == 1 &&
                 !treat_as_floating_point<_Rep2>::value))
            >::type* = 0)
                : __rep_(_VSTD::chrono::duration_cast<duration>(__d).count()) {}

    // observer

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR rep count() const {return __rep_;}

    // arithmetic

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator+() const {return typename common_type<duration>::type(*this);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator-() const {return typename common_type<duration>::type(-__rep_);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator++()      {++__rep_; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator++(int)   {return duration(__rep_++);}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator--()      {--__rep_; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator--(int)   {return duration(__rep_--);}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator+=(const duration& __d) {__rep_ += __d.count(); return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator-=(const duration& __d) {__rep_ -= __d.count(); return *this;}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator*=(const rep& rhs) {__rep_ *= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator/=(const rep& rhs) {__rep_ /= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const rep& rhs) {__rep_ %= rhs; return *this;}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const duration& rhs) {__rep_ %= rhs.count(); return *this;}

    // special values

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration zero() {return duration(duration_values<rep>::zero());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration min()  {return duration(duration_values<rep>::min());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR duration max()  {return duration(duration_values<rep>::max());}
};

typedef duration<long long,         nano> nanoseconds;
typedef duration<long long,        micro> microseconds;
typedef duration<long long,        milli> milliseconds;
typedef duration<long long              > seconds;
typedef duration<     long, ratio<  60> > minutes;
typedef duration<     long, ratio<3600> > hours;

// Duration ==

template <class _LhsDuration, class _RhsDuration>
struct __duration_eq
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const
        {
            typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
            return _Ct(__lhs).count() == _Ct(__rhs).count();
        }
};

template <class _LhsDuration>
struct __duration_eq<_LhsDuration, _LhsDuration>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const
        {return __lhs.count() == __rhs.count();}
};

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator==(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __duration_eq<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
}

// Duration !=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator!=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__lhs == __rhs);
}

// Duration <

template <class _LhsDuration, class _RhsDuration>
struct __duration_lt
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const
        {
            typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
            return _Ct(__lhs).count() < _Ct(__rhs).count();
        }
};

template <class _LhsDuration>
struct __duration_lt<_LhsDuration, _LhsDuration>
{
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const
        {return __lhs.count() < __rhs.count();}
};

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator< (const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __duration_lt<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
}

// Duration >

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator> (const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return __rhs < __lhs;
}

// Duration <=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator<=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__rhs < __lhs);
}

// Duration >=

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
bool
operator>=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    return !(__lhs < __rhs);
}

// Duration +

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator+(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(_Cd(__lhs).count() + _Cd(__rhs).count());
}

// Duration -

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator-(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(_Cd(__lhs).count() - _Cd(__rhs).count());
}

// Duration *

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    is_convertible<_Rep2, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() * static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename enable_if
<
    is_convertible<_Rep1, typename common_type<_Rep1, _Rep2>::type>::value,
    duration<typename common_type<_Rep1, _Rep2>::type, _Period>
>::type
operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d)
{
    return __d * __s;
}

// Duration /

template <class _Duration, class _Rep, bool = __is_duration<_Rep>::value>
struct __duration_divide_result
{
};

template <class _Duration, class _Rep2,
    bool = is_convertible<_Rep2,
                          typename common_type<typename _Duration::rep, _Rep2>::type>::value>
struct __duration_divide_imp
{
};

template <class _Rep1, class _Period, class _Rep2>
struct __duration_divide_imp<duration<_Rep1, _Period>, _Rep2, true>
{
    typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period> type;
};

template <class _Rep1, class _Period, class _Rep2>
struct __duration_divide_result<duration<_Rep1, _Period>, _Rep2, false>
    : __duration_divide_imp<duration<_Rep1, _Period>, _Rep2>
{
};

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename __duration_divide_result<duration<_Rep1, _Period>, _Rep2>::type
operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() / static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<_Rep1, _Rep2>::type
operator/(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Ct;
    return _Ct(__lhs).count() / _Ct(__rhs).count();
}

// Duration %

template <class _Rep1, class _Period, class _Rep2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename __duration_divide_result<duration<_Rep1, _Period>, _Rep2>::type
operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef duration<_Cr, _Period> _Cd;
    return _Cd(_Cd(__d).count() % static_cast<_Cr>(__s));
}

template <class _Rep1, class _Period1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type
operator%(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef typename common_type<_Rep1, _Rep2>::type _Cr;
    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Cd;
    return _Cd(static_cast<_Cr>(_Cd(__lhs).count()) % static_cast<_Cr>(_Cd(__rhs).count()));
}

//////////////////////////////////////////////////////////
///////////////////// time_point /////////////////////////
//////////////////////////////////////////////////////////

template <class _Clock, class _Duration = typename _Clock::duration>
class _LIBCPP_TEMPLATE_VIS time_point
{
    static_assert(__is_duration<_Duration>::value,
                  "Second template parameter of time_point must be a std::chrono::duration");
public:
    typedef _Clock                    clock;
    typedef _Duration                 duration;
    typedef typename duration::rep    rep;
    typedef typename duration::period period;
private:
    duration __d_;

public:
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 time_point() : __d_(duration::zero()) {}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 explicit time_point(const duration& __d) : __d_(__d) {}

    // conversions
    template <class _Duration2>
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    time_point(const time_point<clock, _Duration2>& t,
        typename enable_if
        <
            is_convertible<_Duration2, duration>::value
        >::type* = 0)
            : __d_(t.time_since_epoch()) {}

    // observer

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 duration time_since_epoch() const {return __d_;}

    // arithmetic

    _LIBCPP_INLINE_VISIBILITY time_point& operator+=(const duration& __d) {__d_ += __d; return *this;}
    _LIBCPP_INLINE_VISIBILITY time_point& operator-=(const duration& __d) {__d_ -= __d; return *this;}

    // special values

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR time_point min() {return time_point(duration::min());}
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR time_point max() {return time_point(duration::max());}
};

} // chrono

template <class _Clock, class _Duration1, class _Duration2>
struct _LIBCPP_TEMPLATE_VIS common_type<chrono::time_point<_Clock, _Duration1>,
                                         chrono::time_point<_Clock, _Duration2> >
{
    typedef chrono::time_point<_Clock, typename common_type<_Duration1, _Duration2>::type> type;
};

namespace chrono {

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, _ToDuration>
time_point_cast(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>(_VSTD::chrono::duration_cast<_ToDuration>(__t.time_since_epoch()));
}

#if _LIBCPP_STD_VER > 14
template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
floor(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{floor<_ToDuration>(__t.time_since_epoch())};
}

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
ceil(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{ceil<_ToDuration>(__t.time_since_epoch())};
}

template <class _ToDuration, class _Clock, class _Duration>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    __is_duration<_ToDuration>::value,
    time_point<_Clock, _ToDuration>
>::type
round(const time_point<_Clock, _Duration>& __t)
{
    return time_point<_Clock, _ToDuration>{round<_ToDuration>(__t.time_since_epoch())};
}

template <class _Rep, class _Period>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
    numeric_limits<_Rep>::is_signed,
    duration<_Rep, _Period>
>::type
abs(duration<_Rep, _Period> __d)
{
    return __d >= __d.zero() ? __d : -__d;
}
#endif

// time_point ==

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator==(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() == __rhs.time_since_epoch();
}

// time_point !=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator!=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__lhs == __rhs);
}

// time_point <

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() < __rhs.time_since_epoch();
}

// time_point >

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __rhs < __lhs;
}

// time_point <=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__rhs < __lhs);
}

// time_point >=

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>=(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return !(__lhs < __rhs);
}

// time_point operator+(time_point x, duration y);

template <class _Clock, class _Duration1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type>
operator+(const time_point<_Clock, _Duration1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type> _Tr;
    return _Tr (__lhs.time_since_epoch() + __rhs);
}

// time_point operator+(duration x, time_point y);

template <class _Rep1, class _Period1, class _Clock, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<duration<_Rep1, _Period1>, _Duration2>::type>
operator+(const duration<_Rep1, _Period1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __rhs + __lhs;
}

// time_point operator-(time_point x, duration y);

template <class _Clock, class _Duration1, class _Rep2, class _Period2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type>
operator-(const time_point<_Clock, _Duration1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
{
    typedef time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type> _Ret;
    return _Ret(__lhs.time_since_epoch() -__rhs);
}

// duration operator-(time_point x, time_point y);

template <class _Clock, class _Duration1, class _Duration2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
typename common_type<_Duration1, _Duration2>::type
operator-(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock, _Duration2>& __rhs)
{
    return __lhs.time_since_epoch() - __rhs.time_since_epoch();
}

//////////////////////////////////////////////////////////
/////////////////////// clocks ///////////////////////////
//////////////////////////////////////////////////////////

class _LIBCPP_TYPE_VIS system_clock
{
public:
    typedef microseconds                     duration;
    typedef duration::rep                    rep;
    typedef duration::period                 period;
    typedef chrono::time_point<system_clock> time_point;
    static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;

    static time_point now() _NOEXCEPT;
    static time_t     to_time_t  (const time_point& __t) _NOEXCEPT;
    static time_point from_time_t(time_t __t) _NOEXCEPT;
};

#ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK
class _LIBCPP_TYPE_VIS steady_clock
{
public:
    typedef nanoseconds                                   duration;
    typedef duration::rep                                 rep;
    typedef duration::period                              period;
    typedef chrono::time_point<steady_clock, duration>    time_point;
    static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = true;

    static time_point now() _NOEXCEPT;
};

typedef steady_clock high_resolution_clock;
#else
typedef system_clock high_resolution_clock;
#endif

} // chrono

#if _LIBCPP_STD_VER > 11
// Suffixes for duration literals [time.duration.literals]
inline namespace literals
{ 
  inline namespace chrono_literals
  {

    constexpr chrono::hours operator""h(unsigned long long __h)
    {
        return chrono::hours(static_cast<chrono::hours::rep>(__h));
    }

    constexpr chrono::duration<long double, ratio<3600,1>> operator""h(long double __h)
    {
        return chrono::duration<long double, ratio<3600,1>>(__h);
    }


    constexpr chrono::minutes operator""min(unsigned long long __m)
    {
        return chrono::minutes(static_cast<chrono::minutes::rep>(__m));
    }

    constexpr chrono::duration<long double, ratio<60,1>> operator""min(long double __m)
    {
        return chrono::duration<long double, ratio<60,1>> (__m);
    }


    constexpr chrono::seconds operator""s(unsigned long long __s)
    {
        return chrono::seconds(static_cast<chrono::seconds::rep>(__s));
    }

    constexpr chrono::duration<long double> operator""s(long double __s)
    {
        return chrono::duration<long double> (__s);
    }


    constexpr chrono::milliseconds operator""ms(unsigned long long __ms)
    {
        return chrono::milliseconds(static_cast<chrono::milliseconds::rep>(__ms));
    }

    constexpr chrono::duration<long double, milli> operator""ms(long double __ms)
    {
        return chrono::duration<long double, milli>(__ms);
    }


    constexpr chrono::microseconds operator""us(unsigned long long __us)
    {
        return chrono::microseconds(static_cast<chrono::microseconds::rep>(__us));
    }

    constexpr chrono::duration<long double, micro> operator""us(long double __us)
    {
        return chrono::duration<long double, micro> (__us);
    }
    

    constexpr chrono::nanoseconds operator""ns(unsigned long long __ns)
    {
        return chrono::nanoseconds(static_cast<chrono::nanoseconds::rep>(__ns));
    }

    constexpr chrono::duration<long double, nano> operator""ns(long double __ns)
    {
        return chrono::duration<long double, nano> (__ns);
    }

}}

namespace chrono { // hoist the literals into namespace std::chrono
   using namespace literals::chrono_literals;
}

#endif

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif  // _LIBCPP_CHRONO