std::chrono::operator/ (日历)

 

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C 风格日期和时间

 

定义于头文件 <chrono>
year_month
constexpr auto operator/(const std::chrono::year& y,                          const std::chrono::month& m) noexcept     -> std::chrono::year_month;	(1)	(C++20 起)
constexpr auto operator/(const std::chrono::year& y, int m) noexcept     -> std::chrono::year_month;	(2)	(C++20 起)
month_day
constexpr auto operator/(const std::chrono::month& m,                          const std::chrono::day& d) noexcept     -> std::chrono::month_day;	(3)	(C++20 起)
constexpr auto operator/(const std::chrono::month& m, int d) noexcept     -> std::chrono::month_day;	(4)	(C++20 起)
constexpr auto operator/(int m, const std::chrono::day& d) noexcept     -> std::chrono::month_day;	(5)	(C++20 起)
constexpr auto operator/(const std::chrono::day& d,                          const std::chrono::month& m) noexcept    -> std::chrono::month_day;	(6)	(C++20 起)
constexpr auto operator/(const std::chrono::day& d, int m) noexcept     -> std::chrono::month_day;	(7)	(C++20 起)
month_day_last
constexpr auto operator/(const std::chrono::month& m,                          std::chrono::last_spec) noexcept     -> std::chrono::month_day_last;	(8)	(C++20 起)
constexpr auto operator/(int m, std::chrono::last_spec) noexcept     -> std::chrono::month_day_last;	(9)	(C++20 起)
constexpr auto operator/(std::chrono::last_spec,                          const std::chrono::month& m) noexcept     -> std::chrono::month_day_last;	(10)	(C++20 起)
constexpr auto operator/(std::chrono::last_spec, int m) noexcept     -> std::chrono::month_day_last;	(11)	(C++20 起)
month_weekday
constexpr auto operator/(const std::chrono::month& m,                          const std::chrono::weekday_indexed& wdi) noexcept     -> std::chrono::month_weekday;	(12)	(C++20 起)
constexpr auto operator/(int m, const std::chrono::weekday_indexed& wdi) noexcept     -> std::chrono::month_weekday;	(13)	(C++20 起)
constexpr auto operator/(const std::chrono::weekday_indexed& wdi,                          const std::chrono::month& m) noexcept     -> std::chrono::month_weekday;	(14)	(C++20 起)
constexpr auto operator/(const std::chrono::weekday_indexed& wdi, int m) noexcept     -> std::chrono::month_weekday;	(15)	(C++20 起)
month_weekday_last
constexpr auto operator/(const std::chrono::month& m,                          const std::chrono::weekday_last& wdl) noexcept     -> std::chrono::month_weekday_last;	(16)	(C++20 起)
constexpr auto operator/(int m, const std::chrono::weekday_last& wdl) noexcept     -> std::chrono::month_weekday_last;	(17)	(C++20 起)
constexpr auto operator/(const std::chrono::weekday_last& wdl,                          const std::chrono::month& m) noexcept     -> std::chrono::month_weekday_last;	(18)	(C++20 起)
constexpr auto operator/(const std::chrono::weekday_last& wdl, int m) noexcept     -> std::chrono::month_weekday_last;	(19)	(C++20 起)
year_month_day
constexpr auto operator/(const std::chrono::year_month& ym,                          const std::chrono::day& d) noexcept     -> std::chrono::year_month_day;	(20)	(C++20 起)
constexpr auto operator/(const std::chrono::year_month& ym, int d) noexcept     -> std::chrono::year_month_day;	(21)	(C++20 起)
constexpr auto operator/(const std::chrono::year& y,                          const std::chrono::month_day& md) noexcept     -> std::chrono::year_month_day;	(22)	(C++20 起)
constexpr auto operator/(int y, const std::chrono::month_day& md) noexcept     -> std::chrono::year_month_day;	(23)	(C++20 起)
constexpr auto operator/(const std::chrono::month_day& md,                          const std::chrono::year& y) noexcept     -> std::chrono::year_month_day;	(24)	(C++20 起)
constexpr auto operator/(const std::chrono::month_day& md, int y) noexcept     -> std::chrono::year_month_day;	(25)	(C++20 起)
year_month_day_last
constexpr auto operator/(const std::chrono::year_month& ym,                          std::chrono::last_spec) noexcept     -> std::chrono::year_month_day_last;	(26)	(C++20 起)
constexpr auto operator/(const std::chrono::year& y,                          const std::chrono::month_day_last& mdl) noexcept     -> std::chrono::year_month_day_last;	(27)	(C++20 起)
constexpr auto operator/(int y, const std::chrono::month_day_last& mdl) noexcept     -> std::chrono::year_month_day_last;	(28)	(C++20 起)
constexpr auto operator/(const std::chrono::month_day_last& mdl,                          const std::chrono::year& y) noexcept     -> std::chrono::year_month_day_last;	(29)	(C++20 起)
constexpr auto operator/(const std::chrono::month_day_last& mdl, int y) noexcept     -> std::chrono::year_month_day_last;	(30)	(C++20 起)
year_month_weekday
constexpr auto operator/(const std::chrono::year_month& ym,                          const std::chrono::weekday_indexed& wdi) noexcept     -> std::chrono::year_month_weekday;	(31)	(C++20 起)
constexpr auto operator/(const std::chrono::year& y,                          const std::chrono::month_weekday& mwd) noexcept     -> std::chrono::year_month_weekday;	(32)	(C++20 起)
constexpr auto operator/(int y, const std::chrono::month_weekday& mwd) noexcept     -> std::chrono::year_month_weekday;	(33)	(C++20 起)
constexpr auto operator/(const std::chrono::month_weekday& mwd,                          const std::chrono::year& y) noexcept     -> std::chrono::year_month_weekday;	(34)	(C++20 起)
constexpr auto operator/(const std::chrono::month_weekday& mwd, int y) noexcept     -> std::chrono::year_month_weekday;	(35)	(C++20 起)
year_month_weekday_last
constexpr auto operator/(const std::chrono::year_month& ym,                          const std::chrono::weekday_last& wdl) noexcept     -> std::chrono::year_month_weekday_last;	(36)	(C++20 起)
constexpr auto operator/(const std::chrono::year& y,                          const std::chrono::month_weekday_last& mwdl) noexcept     -> std::chrono::year_month_weekday_last;	(37)	(C++20 起)
constexpr auto operator/(int y, const std::chrono::month_weekday_last& mwdl) noexcept     -> std::chrono::year_month_weekday_last;	(38)	(C++20 起)
constexpr auto operator/(const std::chrono::month_weekday_last& mwdl,                          const std::chrono::year& y) noexcept     -> std::chrono::year_month_weekday_last;	(39)	(C++20 起)
constexpr auto operator/(const std::chrono::month_weekday_last& mwdl, int y) noexcept     -> std::chrono::year_month_weekday_last;	(40)	(C++20 起)

这些 operator/ 为创建格里高利历日期提供约定语法。

对于创建完整日期，任何下列三种顺序都可接受：

• year/month/day
• month/day/year
• day/month/year

每种情况中，能以下列之一替换 day ：

• std::chrono::last ，对于月的最后一日；
• weekday[i] ，对于月的第 i 个 weekday ；
• weekday[std::chrono::last] ，对于该月的最后一个 weekday 。

若单纯的整数的含义相对于其他运算数的类型无歧义，则可接受它：允许 2005y/4/5 ，但不允许 5/April/2005 。

能够不以三种顺序之一应用第二个 operator/ 创建部分日期类型（ year_month 、 month_day 等）。

返回值

1) std::chrono::year_month(y, m)

2) std::chrono::year_month(y, std::chrono::month(m))

3,6) std::chrono::month_day(m, d)

4) std::chrono::month_day(m, std::chrono::day(d))

5,7) std::chrono::month_day(std::chrono::month(m), d)

8,10) std::chrono::month_day_last(m)

9,11) std::chrono::month_day_last(std::chrono::month(m))

12,14) std::chrono::month_weekday(m, wdi)

13,15) std::chrono::month_weekday(std::chrono::month(m), wdi)

16,18) std::chrono::month_weekday_last(m, wdl)

17,19) std::chrono::month_weekday_last(std::chrono::month(m), wdl)

20) std::chrono::year_month_day(ym.year(), ym.month(), d)

21) std::chrono::year_month_day(ym.year(), ym.month(), std::chrono::day(d))

22,24) std::chrono::year_month_day(y, md.month(), md.day())

23,25) std::chrono::year_month_day(std::chrono::year(y), md.month(), md.day())

26) std::chrono::year_month_day_last(ym.year(), std::chrono::month_day_last(ym.month()))

27,29) std::chrono::year_month_day_last(y, mdl)

28,30) std::chrono::year_month_day_last(std::chrono::year(y), mdl)

31) std::chrono::year_month_weekday(ym.year(), ym.month(), wdi)

32,34) std::chrono::year_month_weekday(y, mwd.month(), mwd.weekday_indexed())

33,35) std::chrono::year_month_weekday(std::chrono::year(y), mwd.month(), mwd.weekday_indexed())

36) std::chrono::year_month_weekday_last(ym.year(), ym.month(), wdl)

37,39) std::chrono::year_month_weekday_last(y, mwdl.month(), mwdl.weekday_last())

38,40) std::chrono::year_month_weekday_last(std::chrono::year(y), mwdl.month(), mwdl.weekday_last())

示例

运行此代码

#include <iostream>
#include <chrono>
using namespace std::chrono;
 
int main()
{
    std::cout << std::boolalpha;
 
    // 标准提供 2021y 作为 std::chrono::year(2021) 的备选
    // 标准提供 15d 作为 std::chrono::day(15) 的备选
 
    constexpr auto ym {year(2021)/8};
    std::cout << (ym == year_month(year(2021), August)) << ' ';
 
    constexpr auto md {9/day(15)};
    std::cout << (md == month_day(September, day(15))) << ' ';
 
    constexpr auto mdl {October/last};
    std::cout << (mdl == month_day_last(month(10))) << ' ';
 
    constexpr auto mw {11/Monday[3]};
    std::cout << (mw == month_weekday(November, Monday[3])) << ' ';
 
    constexpr auto mwdl {December/Sunday[last]};
    std::cout << (mwdl == month_weekday_last(month(12), weekday_last(Sunday))) << ' ';
 
    constexpr auto ymd {year(2021)/January/day(23)};
    std::cout << (ymd == year_month_day(2021y, month(January), 23d)) << '\n';
}

输出：

true true true true true true