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std::chrono::weekday_indexed:: ok

From cppreference.net
C++
Date and time library
std::chrono::weekday_indexed
constexpr bool ok ( ) const noexcept ;
(自 C++20 起)

检查星期对象和存储在 * this 中的索引是否均有效。

返回值

当 weekday ( ) . ok ( ) == true 且 index() 处于范围 [ 1 , 5 ] 内时返回 true ，否则返回 false 。

示例

运行此代码 
#include <chrono>
#include <iostream>
int main()
{
    std::cout << std::boolalpha;
    std::chrono::weekday_indexed wdi{std::chrono::Tuesday[2]};
    std::cout << (wdi.ok()) << ' ';
    wdi = {std::chrono::weekday(42)[2]}; 
    std::cout << (wdi.ok()) << ' ';
    wdi = {std::chrono::Tuesday[-4]}; 
    std::cout << (wdi.ok()) << '\n';
}

输出： 

true false false