Implement `hh_mm_ss` from P1466R3

[mclow.lists]

Summary

This is another piece in the ongoing <chrono> saga.
Implement the class hh_mm_ss.

[ldionne]

libcxx/include/chrono

2757

It seems like this shouldn't be reimplemented inside this class, instead we should put this at namespace scope if we don't already have something like that.

2765

Same comment as above regarding duplication.

2766

Indentation looks funny (here and elsewhere). Is it just Phab acting up?

[mclow.lists]

libcxx/include/chrono

2757

I put it in the class so it wouldn't be polluting the enclosing namespace. If it's generally useful, we can promote it.

2766

I think this is just phab. It might be that I've got a tab in here.

[mclow.lists]

More tests, also removed a couple tabs.

[mclow.lists]

The __pow10 and __width routines are only called at compile-time; no run-time code at all.
We have a "power of 10" table in charconv, but I don't think that coupling <chrono> and <charconv> is worth the benefit of removing this small routine.

libcxx/include/chrono

2766

It was some tabs.

[ldionne]

In D65365#1616172, @mclow.lists wrote:

We have a "power of 10" table in charconv, but I don't think that coupling <chrono> and <charconv> is worth the benefit of removing this small routine.

We've discussed that offline, however I want to say it here for posterity. The fact that we have monolithic headers in libc++ sometimes leads us to duplicate code (like here). If instead we had finer grained headers, we could reuse code without fear of adding coupling between unrelated headers.

I was told there was a fear that adding header files would increase compile-times, however I haven't personally seen that claim substantiated. Also, having finer grained headers means that we might be able to pull in less code when we include something.

libcxx/include/chrono

617

When do you plan do update the feature-test macro __cpp_lib_chrono?

2757

I'd like it to be promoted so it can be tested on its own.

libcxx/test/std/utilities/time/time.hms/time.hms.members/hours.pass.cpp

17

Can you add a comment in the other related test files saying there's a correspondence table in this file? Something like:

// See the table in hours.pass.cpp for correspondence between the magic values used below

libcxx/test/std/utilities/time/time.hms/time.hms.nonmembers/nothing.to.do.pass.cpp

12

What is this testing?

[mclow.lists]

libcxx/include/chrono

617

When I get the rest of the calendaring stuff implemented.

libcxx/test/std/utilities/time/time.hms/time.hms.members/hours.pass.cpp

17

I can do that.

libcxx/test/std/utilities/time/time.hms/time.hms.nonmembers/nothing.to.do.pass.cpp

12

Nothing. Due to historical reasons; we try not to have folders with no tests.
Probably not needed anymore, but easy to put in.

[mclow.lists]

libcxx/include/chrono

2757

But it's not used anywhere else; nor really do I think it will be.
Its already tested in precision_type.pass.cpp (indirectly)

[ldionne]

LGTM with my requested changes.

[mclow.lists]

Committed as revision 368299

libcxx/include/chrono

 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;
+// 26.9, class template hh_mm_ss
+template <class Duration>
+class hh_mm_ss
+{
+    bool            is_neg; // exposition only
+    chrono::hours   h;      // exposition only
+    chrono::minutes m;      // exposition only
+    chrono::seconds s;      // exposition only
+    precision       ss;     // exposition only
+
+public:
+    static unsigned constexpr fractional_width = see below;
+    using precision                            = see below;
+
+    constexpr hh_mm_ss() noexcept : hh_mm_ss{Duration::zero()} {}
+    constexpr explicit hh_mm_ss(Duration d) noexcept;
+
+    constexpr bool is_negative() const noexcept;
+    constexpr chrono::hours hours() const noexcept;
+    constexpr chrono::minutes minutes() const noexcept;
+    constexpr chrono::seconds seconds() const noexcept;
+    constexpr precision subseconds() const noexcept;
+
+    constexpr explicit operator  precision()   const noexcept;
+    constexpr          precision to_duration() const noexcept;
+};
+
+template <class charT, class traits, class Duration>
+  basic_ostream<charT, traits>&
+    operator<<(basic_ostream<charT, traits>& os, hh_mm_ss<Duration> const& hms);
+
+// 26.10, 12/24 hour functions
+constexpr bool is_am(hours const& h) noexcept;
+constexpr bool is_pm(hours const& h) noexcept;
+constexpr hours make12(const hours& h) noexcept;
+constexpr hours make24(const hours& h, bool is_pm) noexcept;
 
-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;

 inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
 inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
 
+
+template <class _Duration>
+class hh_mm_ss
+{
+private:
+  static_assert(__is_duration<_Duration>::value, "template parameter of hh_mm_ss must be a std::chrono::duration");
+    using __CommonType = common_type_t<_Duration, chrono::seconds>;
+
+    static constexpr uint64_t __pow10(unsigned __exp)
+    {
+        uint64_t __ret = 1;
+        for (unsigned __i = 0; __i < __exp; ++__i)
+            __ret *= 10U;
+    return __ret;
+    }
+
+    static constexpr unsigned __width(uint64_t __n, uint64_t __d = 10, unsigned __w = 0)
+        {
+        if (__n >= 2 && __d != 0 && __w < 19)
+            return 1 + __width(__n, __d % __n * 10, __w+1);
+        return 0;
+        }
+
+public:
+    static unsigned constexpr fractional_width = __width(__CommonType::period::den) < 19 ?
+                                                 __width(__CommonType::period::den) : 6u;
+    using precision = duration<typename __CommonType::rep, ratio<1, __pow10(fractional_width)>>;
+
+    constexpr hh_mm_ss() noexcept : hh_mm_ss{_Duration::zero()} {}
+
+    constexpr explicit hh_mm_ss(_Duration __d) noexcept :
+        __is_neg(__d < _Duration(0)),
+        __h(duration_cast<chrono::hours>  (abs(__d))),
+        __m(duration_cast<chrono::minutes>(abs(__d) - hours())),
+        __s(duration_cast<chrono::seconds>(abs(__d) - hours() - minutes())),
+        __f(duration_cast<precision>      (abs(__d) - hours() - minutes() - seconds()))
+        {}
+
+    constexpr bool is_negative()        const noexcept { return __is_neg; }
+    constexpr chrono::hours hours()     const noexcept { return __h; }
+    constexpr chrono::minutes minutes() const noexcept { return __m; }
+    constexpr chrono::seconds seconds() const noexcept { return __s; }
+    constexpr precision subseconds()    const noexcept { return __f; }
+
+    constexpr precision to_duration() const noexcept
+    {
+        auto __dur = __h + __m + __s + __f;
+        return __is_neg ? -__dur : __dur;
+    }
+
+    constexpr explicit operator precision() const noexcept { return to_duration(); }
+
+private:
+    bool            __is_neg;
+    chrono::hours   __h;
+    chrono::minutes __m;
+    chrono::seconds __s;
+    precision       __f;
+};
+
+constexpr bool is_am(const hours& __h) noexcept { return __h >= hours( 0) && __h < hours(12); }
+constexpr bool is_pm(const hours& __h) noexcept { return __h >= hours(12) && __h < hours(24); }
+
+constexpr hours make12(const hours& __h) noexcept
+{
+    if      (__h == hours( 0)) return hours(12);
+    else if (__h <= hours(12)) return __h;
+    else                       return __h - hours(12);
+}
+
+constexpr hours make24(const hours& __h, bool __is_pm) noexcept
+{
+    if (__is_pm)
+        return __h == hours(12) ? __h : __h + hours(12);
+    else
+        return __h == hours(12) ? hours(0) : __h;
+}
+
 #endif // _LIBCPP_STD_VER > 17
 } // chrono
 

libcxx/test/std/utilities/time/time.hms/hhmmss.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration> class hh_mm_ss;
+//   If Duration is not an instance of duration, the program is ill-formed.
+
+#include <chrono>
+#include <string>
+#include <cassert>
+#include "test_macros.h"
+
+struct A {};
+
+int main(int, char**)
+{
+    std::chrono::hh_mm_ss<void> h0;        // expected-error-re@chrono:* {{static_assert failed {{.*}} "template parameter of hh_mm_ss must be a std::chrono::duration"}}
+    std::chrono::hh_mm_ss<int> h1;         // expected-error-re@chrono:* {{static_assert failed {{.*}} "template parameter of hh_mm_ss must be a std::chrono::duration"}}
+    std::chrono::hh_mm_ss<std::string> h2; // expected-error-re@chrono:* {{static_assert failed {{.*}} "template parameter of hh_mm_ss must be a std::chrono::duration"}}
+    std::chrono::hh_mm_ss<A> h3;           // expected-error-re@chrono:* {{static_assert failed {{.*}} "template parameter of hh_mm_ss must be a std::chrono::duration"}}
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/hours.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// 
+// constexpr chrono::hours hours() const noexcept;
+   
+// Test values
+// duration     hours   minutes seconds fractional
+// 5000s            1       23      20      0
+// 5000 minutes     83      20      0       0
+// 123456789ms      34      17      36      789ms
+// 123456789us      0       2       3       456789us
+// 123456789ns      0       0       0       123456789ns
+// 1000mfn          2       20      9       0.6 (6000/10000)
+// 10000mfn         3       21      36      0
+
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration>
+constexpr long check_hours(Duration d)
+{
+    using HMS = std::chrono::hh_mm_ss<Duration>;
+    ASSERT_SAME_TYPE(std::chrono::hours, decltype(std::declval<HMS>().hours()));
+    ASSERT_NOEXCEPT(                              std::declval<HMS>().hours());
+    return HMS(d).hours().count();
+}
+
+int main(int, char**)
+{
+    using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+    
+    static_assert( check_hours(std::chrono::minutes( 1)) == 0, "");
+    static_assert( check_hours(std::chrono::minutes(-1)) == 0, "");
+    
+    assert( check_hours(std::chrono::seconds( 5000)) == 1);
+    assert( check_hours(std::chrono::seconds(-5000)) == 1);
+    assert( check_hours(std::chrono::minutes( 5000)) == 83);
+    assert( check_hours(std::chrono::minutes(-5000)) == 83);
+    assert( check_hours(std::chrono::hours( 11))     == 11);
+    assert( check_hours(std::chrono::hours(-11))     == 11);
+
+    assert( check_hours(std::chrono::milliseconds( 123456789LL)) == 34);
+    assert( check_hours(std::chrono::milliseconds(-123456789LL)) == 34);
+    assert( check_hours(std::chrono::microseconds( 123456789LL)) ==  0);
+    assert( check_hours(std::chrono::microseconds(-123456789LL)) ==  0);
+    assert( check_hours(std::chrono::nanoseconds( 123456789LL))  ==  0);
+    assert( check_hours(std::chrono::nanoseconds(-123456789LL))  ==  0);
+
+    assert( check_hours(microfortnights(  1000)) == 0);
+    assert( check_hours(microfortnights( -1000)) == 0);
+    assert( check_hours(microfortnights( 10000)) == 3);
+    assert( check_hours(microfortnights(-10000)) == 3);
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/is_negative.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// 
+// constexpr bool is_negative() const noexcept;
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration>
+constexpr bool check_neg(Duration d)
+{
+  ASSERT_SAME_TYPE(bool, decltype(std::declval<std::chrono::hh_mm_ss<Duration>>().is_negative()));
+  ASSERT_NOEXCEPT(                std::declval<std::chrono::hh_mm_ss<Duration>>().is_negative());
+  return std::chrono::hh_mm_ss<Duration>(d).is_negative();
+}
+
+int main(int, char**)
+{
+  using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+  
+  static_assert(!check_neg(std::chrono::minutes( 1)), "");
+  static_assert( check_neg(std::chrono::minutes(-1)), "");
+  
+  assert(!check_neg(std::chrono::seconds( 5000)));
+  assert( check_neg(std::chrono::seconds(-5000)));
+  assert(!check_neg(std::chrono::minutes( 5000)));
+  assert( check_neg(std::chrono::minutes(-5000)));
+  assert(!check_neg(std::chrono::hours( 11)));
+  assert( check_neg(std::chrono::hours(-11)));
+
+  assert(!check_neg(std::chrono::milliseconds( 123456789LL)));
+  assert( check_neg(std::chrono::milliseconds(-123456789LL)));
+  assert(!check_neg(std::chrono::microseconds( 123456789LL)));
+  assert( check_neg(std::chrono::microseconds(-123456789LL)));
+  assert(!check_neg(std::chrono::nanoseconds( 123456789LL)));
+  assert( check_neg(std::chrono::nanoseconds(-123456789LL)));
+
+  assert(!check_neg(microfortnights( 10000)));
+  assert( check_neg(microfortnights(-10000)));
+
+  return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/minutes.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// 
+// constexpr chrono::minutes minutes() const noexcept;
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration>
+constexpr long check_minutes(Duration d)
+{
+    using HMS = std::chrono::hh_mm_ss<Duration>;
+    ASSERT_SAME_TYPE(std::chrono::minutes, decltype(std::declval<HMS>().minutes()));
+    ASSERT_NOEXCEPT(                                std::declval<HMS>().minutes());
+    return HMS(d).minutes().count();
+}
+
+int main(int, char**)
+{
+    using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+    
+    static_assert( check_minutes(std::chrono::minutes( 1)) == 1, "");
+    static_assert( check_minutes(std::chrono::minutes(-1)) == 1, "");
+    
+    assert( check_minutes(std::chrono::seconds( 5000)) == 23);
+    assert( check_minutes(std::chrono::seconds(-5000)) == 23);
+    assert( check_minutes(std::chrono::minutes( 5000)) == 20);
+    assert( check_minutes(std::chrono::minutes(-5000)) == 20);
+    assert( check_minutes(std::chrono::hours( 11))     == 0);
+    assert( check_minutes(std::chrono::hours(-11))     == 0);
+
+    assert( check_minutes(std::chrono::milliseconds( 123456789LL)) == 17);
+    assert( check_minutes(std::chrono::milliseconds(-123456789LL)) == 17);
+    assert( check_minutes(std::chrono::microseconds( 123456789LL)) == 2);
+    assert( check_minutes(std::chrono::microseconds(-123456789LL)) == 2);
+    assert( check_minutes(std::chrono::nanoseconds( 123456789LL))  == 0);
+    assert( check_minutes(std::chrono::nanoseconds(-123456789LL))  == 0);
+
+    assert( check_minutes(microfortnights(  1000)) == 20);
+    assert( check_minutes(microfortnights( -1000)) == 20);
+    assert( check_minutes(microfortnights( 10000)) == 21);
+    assert( check_minutes(microfortnights(-10000)) == 21);
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/precision.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// {
+// public:
+//     static unsigned constexpr fractional_width = see below;
+//     using precision                            = see below;
+//
+//   precision is duration<common_type_t<Duration::rep, seconds::rep>, 
+//                                 ratio<1, 10^^fractional_width>>
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr unsigned long long powers[] = {
+  1ULL,
+  10ULL,
+  100ULL,
+  1000ULL,
+  10000ULL,
+  100000ULL,
+  1000000ULL,
+  10000000ULL,
+  100000000ULL,
+  1000000000ULL,
+  10000000000ULL,
+  100000000000ULL,
+  1000000000000ULL,
+  10000000000000ULL,
+  100000000000000ULL,
+  1000000000000000ULL,
+  10000000000000000ULL,
+  100000000000000000ULL,
+  1000000000000000000ULL,
+  10000000000000000000ULL
+  };
+  
+template <typename Duration, unsigned width>
+constexpr bool check_precision()
+{
+  using HMS = std::chrono::hh_mm_ss<Duration>;
+  using CT  = std::common_type_t<typename Duration::rep, std::chrono::seconds::rep>;
+  using Pre = std::chrono::duration<CT, std::ratio<1, powers[width]>>;
+  return std::is_same_v<typename HMS::precision, Pre>;
+}
+
+int main(int, char**)
+{
+  using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+
+  static_assert( check_precision<std::chrono::hours,                               0>(), "");
+  static_assert( check_precision<std::chrono::minutes,                             0>(), "");
+  static_assert( check_precision<std::chrono::seconds,                             0>(), "");
+  static_assert( check_precision<std::chrono::milliseconds,                        3>(), "");
+  static_assert( check_precision<std::chrono::microseconds,                        6>(), "");
+  static_assert( check_precision<std::chrono::nanoseconds,                         9>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   2>>, 1>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   3>>, 6>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   4>>, 2>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   5>>, 1>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   6>>, 6>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   7>>, 6>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   8>>, 3>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   9>>, 6>(), "");
+  static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,  10>>, 1>(), "");
+  static_assert( check_precision<microfortnights,                                  4>(), "");
+
+  return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/seconds.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// 
+// constexpr chrono::seconds seconds() const noexcept;
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration>
+constexpr long check_seconds(Duration d)
+{
+    using HMS = std::chrono::hh_mm_ss<Duration>;
+    ASSERT_SAME_TYPE(std::chrono::seconds, decltype(std::declval<HMS>().seconds()));
+    ASSERT_NOEXCEPT(                                std::declval<HMS>().seconds());
+    return HMS(d).seconds().count();
+}
+
+int main(int, char**)
+{
+    using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+    
+    static_assert( check_seconds(std::chrono::seconds( 1)) == 1, "");
+    static_assert( check_seconds(std::chrono::seconds(-1)) == 1, "");
+    
+    assert( check_seconds(std::chrono::seconds( 5000)) == 20);
+    assert( check_seconds(std::chrono::seconds(-5000)) == 20);
+    assert( check_seconds(std::chrono::minutes( 5000)) == 0);
+    assert( check_seconds(std::chrono::minutes(-5000)) == 0);
+    assert( check_seconds(std::chrono::hours( 11))     == 0);
+    assert( check_seconds(std::chrono::hours(-11))     == 0);
+
+    assert( check_seconds(std::chrono::milliseconds( 123456789LL)) == 36);
+    assert( check_seconds(std::chrono::milliseconds(-123456789LL)) == 36);
+    assert( check_seconds(std::chrono::microseconds( 123456789LL)) == 3);
+    assert( check_seconds(std::chrono::microseconds(-123456789LL)) == 3);
+    assert( check_seconds(std::chrono::nanoseconds( 123456789LL))  == 0);
+    assert( check_seconds(std::chrono::nanoseconds(-123456789LL))  == 0);
+
+    assert( check_seconds(microfortnights(  1000)) ==  9);
+    assert( check_seconds(microfortnights( -1000)) ==  9);
+    assert( check_seconds(microfortnights( 10000)) == 36);
+    assert( check_seconds(microfortnights(-10000)) == 36);
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/subseconds.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// 
+// constexpr precision subseconds() const noexcept;
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration>
+constexpr long check_subseconds(Duration d)
+{
+    using HMS = std::chrono::hh_mm_ss<Duration>;
+    ASSERT_SAME_TYPE(typename HMS::precision, decltype(std::declval<HMS>().subseconds()));
+    ASSERT_NOEXCEPT(                                   std::declval<HMS>().subseconds());
+    return HMS(d).subseconds().count();
+}
+
+int main(int, char**)
+{
+    using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+    
+    static_assert( check_subseconds(std::chrono::seconds( 1)) == 0, "");
+    static_assert( check_subseconds(std::chrono::seconds(-1)) == 0, "");
+    
+    assert( check_subseconds(std::chrono::seconds( 5000)) == 0);
+    assert( check_subseconds(std::chrono::seconds(-5000)) == 0);
+    assert( check_subseconds(std::chrono::minutes( 5000)) == 0);
+    assert( check_subseconds(std::chrono::minutes(-5000)) == 0);
+    assert( check_subseconds(std::chrono::hours( 11))     == 0);
+    assert( check_subseconds(std::chrono::hours(-11))     == 0);
+
+    assert( check_subseconds(std::chrono::milliseconds( 123456789LL)) == 789);
+    assert( check_subseconds(std::chrono::milliseconds(-123456789LL)) == 789);
+    assert( check_subseconds(std::chrono::microseconds( 123456789LL)) == 456789LL);
+    assert( check_subseconds(std::chrono::microseconds(-123456789LL)) == 456789LL);
+    assert( check_subseconds(std::chrono::nanoseconds( 123456789LL))  == 123456789LL);
+    assert( check_subseconds(std::chrono::nanoseconds(-123456789LL))  == 123456789LL);
+
+    assert( check_subseconds(microfortnights(  1000)) == 6000);
+    assert( check_subseconds(microfortnights( -1000)) == 6000);
+    assert( check_subseconds(microfortnights( 10000)) == 0);
+    assert( check_subseconds(microfortnights(-10000)) == 0);
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.members/width.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// {
+// public:
+//     static unsigned constexpr fractional_width = see below;
+//     using precision                            = see below;
+//
+//  fractional_width is the number of fractional decimal digits represented by precision. 
+//  fractional_width has the value of the smallest possible integer in the range [0, 18] 
+//    such that precision will exactly represent all values of Duration. 
+//  If no such value of fractional_width exists, then fractional_width is 6.
+
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Duration, unsigned width>
+constexpr bool check_width()
+{
+  using HMS = std::chrono::hh_mm_ss<Duration>;
+  return HMS::fractional_width == width;
+}
+
+int main(int, char**)
+{
+  using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+
+  static_assert( check_width<std::chrono::hours,                               0>(), "");
+  static_assert( check_width<std::chrono::minutes,                             0>(), "");
+  static_assert( check_width<std::chrono::seconds,                             0>(), "");
+  static_assert( check_width<std::chrono::milliseconds,                        3>(), "");
+  static_assert( check_width<std::chrono::microseconds,                        6>(), "");
+  static_assert( check_width<std::chrono::nanoseconds,                         9>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   2>>, 1>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   3>>, 6>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   4>>, 2>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   5>>, 1>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   6>>, 6>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   7>>, 6>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   8>>, 3>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,   9>>, 6>(), "");
+  static_assert( check_width<std::chrono::duration<int, std::ratio<  1,  10>>, 1>(), "");
+  static_assert( check_width<microfortnights,                                  4>(), "");
+
+  return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.hms.nonmembers/nothing.to.do.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// template <class Duration> class hh_mm_ss;
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.12/is_am.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// constexpr bool is_am(const hours& h) noexcept;
+//   Returns: 0h <= h && h <= 11h.
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+  using hours = std::chrono::hours;
+  ASSERT_SAME_TYPE(bool, decltype(std::chrono::is_am(std::declval<hours>())));
+  ASSERT_NOEXCEPT(        std::chrono::is_am(std::declval<hours>()));
+
+  static_assert( std::chrono::is_am(hours( 0)), "");
+  static_assert( std::chrono::is_am(hours(11)), "");
+  static_assert(!std::chrono::is_am(hours(12)), "");
+  static_assert(!std::chrono::is_am(hours(23)), "");
+  
+  for (int i = 0; i < 12; ++i)
+    assert( std::chrono::is_am(hours(i)));
+  for (int i = 12; i < 24; ++i)
+    assert(!std::chrono::is_am(hours(i)));
+
+  return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.12/is_pm.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// constexpr bool is_pm(const hours& h) noexcept;
+//   Returns: 12h <= h && h <= 23
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    using hours = std::chrono::hours;
+    ASSERT_SAME_TYPE(bool, decltype(std::chrono::is_pm(std::declval<hours>())));
+    ASSERT_NOEXCEPT(                std::chrono::is_pm(std::declval<hours>()));
+
+    static_assert(!std::chrono::is_pm(hours( 0)), "");
+    static_assert(!std::chrono::is_pm(hours(11)), "");
+    static_assert( std::chrono::is_pm(hours(12)), "");
+    static_assert( std::chrono::is_pm(hours(23)), "");
+    
+    for (int i = 0; i < 12; ++i)
+        assert(!std::chrono::is_pm(hours(i)));
+    for (int i = 12; i < 24; ++i)
+        assert( std::chrono::is_pm(hours(i)));
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.12/make12.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// constexpr hours make12(const hours& h) noexcept;
+//   Returns: The 12-hour equivalent of h in the range [1h, 12h].
+//     If h is not in the range [0h, 23h], the value returned is unspecified.
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    using hours = std::chrono::hours;
+    ASSERT_SAME_TYPE(hours, decltype(std::chrono::make12(std::declval<hours>())));
+    ASSERT_NOEXCEPT(                 std::chrono::make12(std::declval<hours>()));
+
+    static_assert( std::chrono::make12(hours( 0)) == hours(12), "");
+    static_assert( std::chrono::make12(hours(11)) == hours(11), "");
+    static_assert( std::chrono::make12(hours(12)) == hours(12), "");
+    static_assert( std::chrono::make12(hours(23)) == hours(11), "");
+    
+    assert( std::chrono::make12(hours(0)) == hours(12));
+    for (int i = 1; i < 13; ++i)
+        assert( std::chrono::make12(hours(i)) == hours(i));
+    for (int i = 13; i < 24; ++i)
+        assert( std::chrono::make12(hours(i)) == hours(i-12));
+
+    return 0;
+}

libcxx/test/std/utilities/time/time.hms/time.12/make24.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// constexpr hours make24(const hours& h, bool is_pm) noexcept;
+//   Returns: If is_pm is false, returns the 24-hour equivalent of h in the range [0h, 11h], 
+//       assuming h represents an ante meridiem hour. 
+//     Else returns the 24-hour equivalent of h in the range [12h, 23h], 
+//       assuming h represents a post meridiem hour. 
+//     If h is not in the range [1h, 12h], the value returned is unspecified.
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    using hours = std::chrono::hours;
+    ASSERT_SAME_TYPE(hours, decltype(std::chrono::make24(std::declval<hours>(), false)));
+    ASSERT_NOEXCEPT(                 std::chrono::make24(std::declval<hours>(), false));
+
+    static_assert( std::chrono::make24(hours( 1), false) == hours( 1), "");
+    static_assert( std::chrono::make24(hours(11), false) == hours(11), "");
+    static_assert( std::chrono::make24(hours(12), false) == hours( 0), "");
+    static_assert( std::chrono::make24(hours( 1), true)  == hours(13), "");
+    static_assert( std::chrono::make24(hours(11), true)  == hours(23), "");
+    static_assert( std::chrono::make24(hours(12), true)  == hours(12), "");
+    
+    for (int i = 1; i < 11; ++i)
+    {
+        assert((std::chrono::make24(hours(i), false)) == hours(i));
+        assert((std::chrono::make24(hours(i), true))  == hours(12+i));
+    }
+    assert((std::chrono::make24(hours(12), false)) == hours( 0));
+    assert((std::chrono::make24(hours(12), true))  == hours(12));
+
+    return 0;
+}