std::chrono::month_weekday:: ok

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chrono I/O
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C-style date and time
std::chrono::month_weekday
constexpr bool ok ( ) const noexcept ;
(since C++20)

Checks if the contained month and weekday_indexed objects are valid.

Return value

month ( ) . ok ( ) && weekday_indexed ( ) . ok ( )

Example

Run this code 
#include <cassert>
#include <chrono>
 
int main()
{
    auto mwdi{std::chrono::March/std::chrono::Friday[1]};
    assert(mwdi.ok());
 
    mwdi = {std::chrono::month(17)/std::chrono::Friday[1]}; 
    assert(not mwdi.ok());
 
    mwdi = {std::chrono::March/std::chrono::Friday[-4]}; 
    assert(not mwdi.ok());
}
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