std::chrono::weekday_indexed

Defined in header `<chrono>`
class weekday_indexed;		(since C++20)

The class weekday_indexed combines a weekday, representing a day of the week in the proleptic Gregorian calendar, with a small index n in the range [1, 5]. It represents the first, second, third, fourth, or fifth weekday of some month.

weekday_indexed is a TriviallyCopyable StandardLayoutType.

Member functions

(constructor)	constructs a `weekday_indexed` (public member function)
weekday	access the stored `weekday` (public member function)
index	access the stored index (public member function)
ok	checks if the weekday and index are both valid (public member function)

Nonmember functions

operator== (C++20)	compares two `weekday_indexed` values (function)
operator<< (C++20)	outputs a `weekday_indexed` into a stream (function template)

Helper classes

std::formatter<std::chrono::weekday_indexed> (C++20)	formatting support for `weekday_indexed` (class template specialization)
std::hash<std::chrono::weekday_indexed> (C++26)	hash support for `std::chrono::weekday_indexed` (class template specialization)

Example

#include <chrono>
#include <iostream>

int main()
{
    using namespace std::chrono;
    
    constexpr weekday_indexed wi = Friday[2];
    
    // Indexed weekday can be used at any place where chrono::day can be used:
    constexpr year_month_weekday ymwd = 2021y / August / wi;
    static_assert(ymwd == August / wi / 2021y &&
                  ymwd == wi / August / 2021y);
    std::cout << ymwd << '\n';
    
    constexpr year_month_day ymd{ymwd}; // a conversion
    static_assert(ymd == 2021y / 8 / 13);
    std::cout << ymd << '\n';
}

Possible output:

2021/Aug/Fri[2]
2021-08-13

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