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

From cppreference.com
 
 
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C-style date and time
 
 
Defined in header <chrono>
constexpr bool operator==( const std::chrono::year_month_day& x,
                           const std::chrono::year_month_day& y ) noexcept;
(1) (since C++20)
constexpr std::strong_ordering

    operator<=>( const std::chrono::year_month_day& x,

                 const std::chrono::year_month_day& y ) noexcept;
(2) (since C++20)

Compares the two year_month_day values x and y. This is a lexicographical comparison: the year() is compared first, then month(), then day().

The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.

[edit] Return value

1) x.year() == y.year() && x.month() == y.month() && x.day() == y.day()
2) If x.year() <=> y.year != 0, x.year() <=> y.year; otherwise if x.month() <=> y.month() != 0, x.month() <=> y.month(); otherwise x.day() <=> y.day()

[edit] Notes

If both x and y represent valid dates (x.ok() && y.ok() == true), the result of the lexicographical comparison is consistent with the calendar order.

[edit] Example

#include <iostream>
#include <chrono>
 
int main()
{
    constexpr auto ymd1 {std::chrono::day(1)/7/2021};
    constexpr auto ymd2 {std::chrono::year(2021)/7/1};
    std::cout << std::boolalpha << (ymd1 == ymd2) << '\n';
 
    static_assert(ymd1 <= ymd2);
}

Output:

true