You should only have to include <sstream>.
If you are writing oss.string(), then you can't possibly be using std::string.
(Where oss is your std::ostringstream).
But it is definitely str(), anyway.
On the subject of
using namespace
, IMO it's best to put it in limited scope, for example inside your main function (yes, you can do that
![Wink ;)](https://www.sfml-dev.org/forums/Smileys/default/wink.gif)
). Then it will only bring stuff in std into scope within main. Of course, sometimes it's easier to put it globally, but that is risky.
@Nexus Beat me to it ^^