std::chrono::year_month_day_last::operator sys_days, std::chrono::year_month_day_last::operator local_days

 

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C 样式日期和时间

 

std::chrono::year_month_day_last

成员函数

year_month_day_last::year_month_day_last

year_month_day_last::operator+=year_month_day_last::operator-=

year_month_day_last::yearyear_month_day_last::monthyear_month_day_last::dayyear_month_day_last::month_day_last

year_month_day_last::operator sys_daysyear_month_day_last::operator local_days

year_month_day_last::ok

非成员函数

operator==operator<=>

operator+operator-

operator<<

辅助类

formatter<std::chrono::year_month_day_last>

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

 

constexpr operator std::chrono::sys_days() const noexcept;	(1)	(自 C++20 起)
constexpr explicit operator std::chrono::local_days() const noexcept;	(2)	(自 C++20 起)

将 *this 转换为一个 std::chrono::time_point，它代表与该 year_month_day_last 相同的日期。这等同于从 year()、month() 和 day() 组成一个 year_month_day，并将该 year_month_day 转换为目标类型。

1) 等同于 std::chrono::sys_days(year()/month()/day()).

2) 等同于 std::chrono::local_days(year()/month()/day()).

示例

运行此代码

#include <array>
#include <chrono>
#include <iostream>
#include <string_view>
using namespace std::chrono;
using namespace std::literals;
 
int main()
{
    constexpr std::chrono::year y{2023y};
    constexpr std::array quarters{"1st"sv, "2nd"sv, "3rd"sv, "4th"sv};
    constexpr auto mq{12 / 4}; // months per quarter        
 
    std::cout << "In year " << static_cast<int>(y) << '\n';
    for (auto q = 1; q < 5; ++q)
    {
        const auto ls = y / std::chrono::month(q * mq) / Sunday[last];
        const auto ld = y / std::chrono::month(q * mq) / last;
        // subtract last Sunday from last day for day of week
        const auto index = (sys_days(ld) - sys_days(ls)).count();
        std::cout << "The " << quarters[q - 1] << " quarter ends on a "  
                  << std::chrono::weekday(index) << '\n';
    }
}

输出

In year 2023
The 1st quarter ends on a Fri
The 2nd quarter ends on a Fri
The 3rd quarter ends on a Sat
The 4th quarter ends on a Sun

另请参阅

operator sys_daysoperator local_days

转换为 std::chrono::time_point (std::chrono::year_month_day 的公共成员函数)