[Thorrez]

std::integral was added in C++20 , so this example will only work in C++20. Weird that the author used this example.

https://en.cppreference.com/w/cpp/concepts/integral

[mmebane]

In this case, I think it's a typo, and should be std::is_integral:

https://en.cppreference.com/w/cpp/types/is_integral