https://blogs.msdn.microsoft.com/oldnewthing/20180516-00/?p=98765 > These tricks may be obvious, but at least I'm going to write them down. >It is common to import an entire namespace into the global namespace. I'm not saying it's a good idea, but it is common. The most notorious example is to put >```using namespace std;``` >to import the std namespace into the global namespace.