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std::chrono:: operator/ (calendar)

From cppreference.net
C++
Date and time library
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
(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 <span class="kw262

这些 operator / 重载为创建 公历溯推日历 日期提供了常规语法。

创建完整日期时，以下三种顺序均可接受：

  • 年/月/日 ,
  • 月/日/年 ,
  • 日/月/年 .

在每种情况下 day 可替换为以下选项之一：

  • std::chrono::last ，表示该月的最后一天；
  • weekday [ i ] ，表示该月的第 i th 个 weekday ；
  • weekday [ std::chrono::last ] ，表示该月的最后一个 weekday 。

当普通整数的含义通过其他操作数的类型可以明确时，该整数可以被接受： 2005y / 4 / 5 是允许的，但 5 / April / 2005 则不允许。

部分日期类型（ year_month 、 month_day 等）可通过在三种顺序中不应用第二个 operator / 来创建。

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 <chrono>
using namespace std::chrono;
constexpr auto ym{2021y/8};
static_assert(ym == year_month(year(2021), August));
constexpr auto md{9/15d};
static_assert(md == month_day(September, day(15)));
constexpr auto mdl{October/last};
static_assert(mdl == month_day_last(month(10)));
constexpr auto mw{11/Monday[3]};
static_assert(mw == month_weekday(November, Monday[3]));
constexpr auto mwdl{December/Sunday[last]};
static_assert(mwdl == month_weekday_last(month(12), weekday_last(Sunday)));
// 这个星球及其他地方实际使用的三种年月日顺序：
constexpr auto ymd{year(2021)/January/day(23)};
static_assert(ymd == month{1}/23/2021);
static_assert(ymd == day{23}/1/2021);
static_assert(ymd == year_month_day(2021y, month(January), 23d));
int main() {}