std::chrono::weekday::weekday

 

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day (C++20) month (C++20) year (C++20) weekday (C++20) operator/ (C++20) year_month_day (C++20)	year_month_day_last (C++20) year_month_weekday (C++20) year_month_weekday_last (C++20)   weekday_indexed (C++20) weekday_last (C++20) month_day (C++20)	month_day_last (C++20) month_weekday (C++20) month_weekday_last (C++20) year_month (C++20) last_speclast (C++20)(C++20)
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std::chrono::weekday

成员函数

weekday::weekday

weekday::operator++weekday::operator--

weekday::operator+=weekday::operator-=

weekday::c_encodingweekday::iso_encoding

weekday::ok

weekday::operator[]

非成员函数

operator==

operator+operator-

operator<<

from_stream

辅助类

formatter<std::chrono::weekday>

formatter<std::chrono::hash> (C++26)

 

weekday() = default;	(1)	(C++20 起)
constexpr explicit weekday( unsigned wd ) noexcept;	(2)	(C++20 起)
constexpr weekday( const std::chrono::sys_days& sd ) noexcept;	(3)	(C++20 起)
constexpr explicit weekday( const std::chrono::local_days& ld ) noexcept;	(4)	(C++20 起)

构造 weekday 对象。

1) 默认构造函数保留星期之日值未初始化。

2) 构造保有星期之日值 wd 的 weekday 对象。若 wd == 7，则保有的值为 ​0​。若 wd > 255，则保有的值未指定。

3) 构造表示 sd 所对应星期之日的 weekday。此构造函数定义从 std::chrono::sys_days 到 weekday 的隐式转换。

4) 构造表示 ld 所对应星期之日的 weekday，如同用 weekday(std::chrono::sys_days(ld.time_since_epoch()))。

参数

wd	-	星期之日值
sd	-	系统日期对象
ld	-	本地日期对象

示例

运行此代码

#include <chrono>
#include <iomanip>
#include <iostream>
 
int main()
{
    constexpr std::chrono::weekday friday{5}; // 使用重载 (2)
    static_assert(friday == std::chrono::Friday);
 
    for (int y{2020}; y <= 2024; ++y)
    {
        const std::chrono::year cur_year{y};
        for (int cur_month{1}; cur_month != 13; ++cur_month)
        {
            const std::chrono::year_month_day ymd{cur_year/cur_month/13};
            const std::chrono::weekday cur_weekday{std::chrono::sys_days(ymd)}; // (3)
            if (cur_weekday == friday)
                std::cout << ymd << " is " << friday << '\n';
        }
    }
}

输出：

2020-03-13 is Fri
2020-11-13 is Fri
2021-08-13 is Fri
2022-05-13 is Fri
2023-01-13 is Fri
2023-10-13 is Fri
2024-09-13 is Fri
2024-12-13 is Fri