std::chrono::is_am, std::chrono::is_pm, std::chrono::make12, std::chrono::make24
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Defined in header
<chrono>
constexpr bool is_am( const std::chrono::hours & h ) noexcept;
(1)
(since C++20)
constexpr bool is_pm( const std::chrono::hours & h ) noexcept;
(2)
(since C++20)
constexpr std::chrono::hours make12( const std::chrono::hours & h ) noexcept;
(3)
(since C++20)
constexpr std::chrono::hours make24( const std::chrono::hours & h,
bool is_pm ) noexcept;
(4)
(since C++20)
bool is_pm ) noexcept;
These functions aid in translating between a 12-hour format time of day, and a 24-hour format time of day.
1) Detects whether the 24-hour format time is a.m. (ante meridiem, before midday).
2) Detects whether the 24-hour format time is p.m. (post meridiem, after midday).
3) Returns the 12-hour equivalent of a 24-hour format time.
4) Returns the 24-hour equivalent of a 12-hour format time h, where is_pm determines whether the time is p.m.
[edit] Parameters
h
-
12-hour or 24-hour format time to detect
is_pm
-
whether the 12-hour format time is p.m.
[edit] Return value
1) 0h <= h && h <= 11h
2) 12h <= h && h <= 23h
3) If h is in range
[0h, 23h], returns the 12-hour equivalent in range [1h, 12h]. Otherwise, the return value is unspecified.4) If h is in range
[1h, 12h], returns the 24-hour equivalent in range [0h, 11h] if is_pm is false, or in range [12h, 23h] otherwise. Otherwise, the return value is unspecified.[edit] Example
Run this code
#include <chrono> #include <iomanip> #include <iostream> #include <utility> int main() { using namespace std::chrono; static_assert( is_am(10h) && is_am(11h) && !is_am(12h) && !is_am(23h) && !is_pm(10h) && !is_pm(11h) && is_pm(12h) && is_pm(23h) ); std::cout << "make12():\n"; for (const hours hh : {0h, 1h, 11h, 12h, 13h, 23h}) { const hours am{make12(hh)}; std::cout << std::setw (2) << hh.count() << "h == " << std::setw (2) << am.count() << (is_am(hh) ? "h a.m.\n" : "h p.m.\n"); } std::cout << "\nmake24():\n"; using p = std::pair <hours, bool>; for (const auto& [hh, pm] : {p{1h, 0}, p{12h, 0}, p{1h, 1}, p{12h, 1}}) { std::cout << std::setw (2) << hh.count() << (pm ? "h p.m." : "h a.m.") << " == " << std::setw (2) << make24(hh, pm).count() << "h\n"; } }
Output:
make12(): 0h == 12h a.m. 1h == 1h a.m. 11h == 11h a.m. 12h == 12h p.m. 13h == 1h p.m. 23h == 11h p.m. make24(): 1h a.m. == 1h 12h a.m. == 0h 1h p.m. == 13h 12h p.m. == 12h