std::chrono::operator+, std::chrono::operator- (std::chrono::year)

 

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std::chrono::year

成员函数

year::year

year::operator++year::operator--

year::operator+=year::operator-=

year::operator+year::operator-

year::is_leap

year::operator int

year::ok

year::min

year::max

非成员函数

operator==operator<=>

operator+operator-

operator<<

from_stream

辅助类

formatter<std::chrono::year>

 

定义于头文件 <chrono>
constexpr std::chrono::year operator+(const std::chrono::year& y,                                       const std::chrono::years& ys) noexcept;	(1)	(C++20 起)
constexpr std::chrono::year operator+(const std::chrono::years& ys,                                       const std::chrono::year& y) noexcept;	(2)	(C++20 起)
constexpr std::chrono::year operator-(const std::chrono::year& y,                                       const std::chrono::years& ys) noexcept;	(3)	(C++20 起)
constexpr std::chrono::years operator-(const std::chrono::year& y1,                                        const std::chrono::year& y2) noexcept;	(4)	(C++20 起)

1-2) 对 y 加 ys.count() 年。

3) 从 y 减去 ys.count() 年。

4) 返回 y1 与 y2 间按年计算的差。

返回值

1-2) std::chrono::year(int(y) + ys.count())

3) std::chrono::year(int(y) - ys.count())

4) std::chrono::years(int(y1) - int(y2))

注解

若 (1-3) 产生的年份值在范围 [-32767,32767] 外，则实际存储值未指定。

二个 year 值相减的结果是 std::chrono::years 类型时长。此时长单位表示格里高利年的平均长度，而结果与运算数所表示的具体年中的日数无关。例如 2018y - 2017y 的结果是 std::chrono::years(1) ，它表示 365.2425 日，而非 365 日。

示例

运行此代码

#include <iostream>
#include <chrono>
 
int main()
{
 
    std::chrono::year y {2020};
 
    y = y + std::chrono::years(12);
    if (y == std::chrono::year(2032)) {
        std::cout << "Years added correctly" << "\n";
    } else {
        std::cout << "Years not added correctly" << "\n";
    }
 
    y = y - std::chrono::years(33);
    if (y == std::chrono::year(1999)) {
        std::cout << "Years subtracted correctly" << "\n";
    } else {
        std::cout << "Years not subtracted correctly" << "\n";
    }
 
    std::chrono::years ys = std::chrono::year(2025) - std::chrono::year(2020);
    if (ys == std::chrono::years(5)) {
        std::cout << "Years subtracted correctly" << "\n";
    } else {
        std::cout << "Years not subtracted correctly" << "\n";
    }
 
}

输出：

Years added correctly
Years subtracted correctly
Years subtracted correctly

返回值

operator++operator++(int)operator--operator--(int)	自增或自减 month (std::chrono::month 的公开成员函数)
operator+=operator-=	加或减月数 (std::chrono::month 的公开成员函数)