Daily bit(e) of C++ | std::views::keys, std::views::values
Daily bit(e) of C++ #131, The C++20 views for associative containers: std::views::keys and std::views::values.
The C++20 std::views::keys and std::views::values are specialized views that represent the views over the keys and values of associate containers.
Reminder: for std::set and std::unordered_set (and their multi-variants), the elements are keys, not values.
