TITLE: "entering and leaving" namespaces

(Newsgroups: comp.lang.c++.moderated, 15 Oct 96)

PROBLEM: olczyk@interaccess.com (Thaddeus L. Olczyk)

By now most C++ programmers know that
to use a namespace you use the statement

using namespace mynamespace.

But is there a way to stop using a namespace?
Something like

!using namespace mynamespace.


RESPONSE: clamage@taumet.Eng.Sun.COM (Steve Clamage)

You don't "enter" a namespace with
	using namespace mynamespace;
You enter a namespace with
	namespace mynamespace {
and you leave it with
	}

The using-directive makes the declarations in the namespace visible
without qualifiers in the current scope. To make qualification required
again, you exit the current scope. Example:

	{
		using namespace mynamespace;
		// members of mynamespace can be used without qualifiers
		...
	}
	//  members of mynamespace require qualifiers
	...

C++ does not provide a mechanism for "undeclaring" a name in the
same scope where it was declared.