std::chrono::weekday::operator+=, std::chrono::weekday::operator-=

 

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日历
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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chrono I/O
parse (C++20)
C 样式日期和时间

 

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)

 

constexpr std::chrono::weekday& operator+=( const std::chrono::days& d ) noexcept;	(1)	(自 C++20 起)
constexpr std::chrono::weekday& operator-=( const std::chrono::days& d ) noexcept;	(2)	(自 C++20 起)

从星期值中添加或减去 d.count()，将结果模 7 减少为范围内的整数 [0, 6]。

1) 执行 *this = *this + d;.

2) 执行 *this = *this - d;.

返回值

修改后此 weekday 的引用。

备注

在调用这些函数之一后，如果操作期间没有发生溢出，则 ok() 始终为真。

示例

运行此代码

#include <chrono>
#include <iostream>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::chrono::weekday wd{5}; // Friday is 5
    wd += std::chrono::days(2);
    std::cout << (wd == std::chrono::weekday(0)) << ' '
              << (wd == std::chrono::Sunday) << ' ';
 
    wd -= std::chrono::days(3);
    std::cout << (wd == std::chrono::weekday(4)) << ' '
              << (wd == std::chrono::Thursday) << ' ';
 
    wd = std::chrono::Wednesday;
    wd += std::chrono::days{8}; // ((3 += 8 == 11) % 7) == 4;
    std::cout << (wd == std::chrono::Thursday) << ' ';
 
    wd -= (std::chrono::Sunday - std::chrono::Tuesday); // -= -2
    // (4 -= -2) == 6
    std::cout << (wd == std::chrono::Saturday) << '\n';
}

输出

true true true true true true

参见

operator++operator++(int)operator--operator--(int)	递增或递减星期 (公有成员函数)
operator+operator- (C++20)	对 weekday 进行算术运算 (函数)