title: What's the purpose of: "using namespace"?
body: <p>There are convincing  arguments <a href="https://stackoverflow.com/questions/1452721/">against</a> <code>using namespace std</code>, so why was it introduced into the language at all? Doesn't <code>using namespace</code> defeat the purpose of namespaces? Why would I ever want to write <code>using namespace</code>? Is there any problem I am not aware of that is solved elegantly by <code>using namespace</code>, maybe in the lines of the <code>using std::swap</code> idiom or something like that?</p>