# std::chrono::operator==,<=>(std::chrono::year)

< cpp‎ | chrono‎ | year

定义于头文件 `<chrono>` |  |
constexpr bool operator==( const std::chrono::year& x, const std::chrono::year& y ) noexcept; | (1) | (C++20 起)
constexpr std::strong_ordering operator<=>( const std::chrono::year& x, const std::chrono::year& y ) noexcept; | (2) | (C++20 起)

比较二个 std::chrono::year `x` 与 `y` 。

`<`、 `<=`、 `>`、 `>=` 及 `!=` 运算符分别从 `operator<=>` 与 `operator==` 合成。

### 返回值

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

### 示例

    #include <iostream>
    #include <chrono>

    int main()
    {
        using namespace std::chrono;

        constexpr year y1{2020};
        constexpr year y2{2021};

        if (y1 == y2) {
            std::cout << "y1 and y2 are equal\n";
        } else {
            std::cout << "y1 and y2 are not equal\n";
        }

        static_assert(
            (2020y < 2023y) && (2020y == 2020y) && (2020y <= 2023y) &&
            (2023y > 2020y) && (2023y != 2020y) && (2023y >= 2020y)
        );
    }

输出：

    y1 and y2 are not equal