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std::chrono:: operator==,<=> (std::chrono::day)

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< cpp ‎ | chrono ‎ | day
C++
Date and time library
std::chrono::day
定义于头文件 <chrono>
constexpr bool operator == ( const std:: chrono :: day & x,
const std:: chrono :: day & y ) noexcept ;
(1) (C++20 起)
constexpr std:: strong_ordering operator <=> ( const std:: chrono :: day & x,
const std:: chrono :: day & y ) noexcept ;
(2) (C++20 起)

比较两个 std::chrono::day x 和 y 。

< 、 <= 、 > 、 >= 和 != 运算符分别由 operator <=> 和 operator == 自动合成。

返回值

1) unsigned ( x ) == unsigned ( y )
2) unsigned ( x ) <=> unsigned ( y )

示例

运行此代码 
#include <chrono>
#include <iostream>
int main()
{
    constexpr std::chrono::day x{13}, y{31};
    static_assert(x != y);
    if constexpr (constexpr auto res = x <=> y; res < 0)
        std::cout << "x is less than y\n";
    else if constexpr (res > 0)
        std::cout << "x is greater than y\n";
    else
        std::cout << "x and y are equal\n";
    using namespace std::literals::chrono_literals;
    static_assert
    (
        (6d < 9d) && (6d == 6d) && (6d <= 9d) &&
        (9d > 6d) && (9d != 6d) && (9d >= 6d)
    );
}

输出： 

x is less than y