> If you really want, you’re free to add “using namespace std”
You're free to, but I discourage the habit. It's more verbose to add the namespace:: prefix to symbols, but it sure does make it easier on the devs that have to work with the code later.
Oh, I’m completely with you on this and always prefix my namespaces. Occasionally I will alias long namespaces to short ones, but I never pull identifiers into the global scope and I really dislike when I see code online that does “using namespace” (unless it’s tightly scoped, at least). I’ve been prefixing std:: for years and won’t stop now, I like knowing where an identifier is coming from, which is extra important when you have multiple types of similar containers that you use for different performance characteristics (eg abseil, folly, immer versions of containers vs std containers)
Leave un-namespaced identifiers to those that are declared in the current file and namespace everything else. If you really want, you’re free to add “using namespace std” or otherwise alias the namespace, but keeping standard library functions out of the global namespace as a default is a good thing! (In any language, not just C++)