In article <1993Apr11.140408.25891@ucc.su.OZ.AU> maxtal@physics.su.OZ.AU (John Max Skaller) writes:
> There is a separate proposal for namespace management.
>
> namespace X { f(); }
> using namespace X;
> int i=f();
>
> namespace X { g(); }
> int j=g(); // OK!
>
> namespace Y { k(); }
> int l=Y::k();
>
> namespace {
>  int w; // 'static' not needed!
> };


Can we use multiple namespaces simultaneously?  And is there another
command after "using" to indicate "no longer using" that namespace?

Can we nest the "using"s?  For example,
   using namespace X;
      int i=f(); // Searches X for f;
      using namespace G;
  int j=f(); // Searches G, then X, for f.
      no longer using namespace G;
   no longer using namespace X;

Or maybe the "using"s are nested by the blocks containing them?
   {using namespace X;
      int i=f(); // Searches X for f;
      {using namespace G;
  int j=f(); // Searches G, then X, for f.
      } // no longer using namespace G
   } // no longer using namespace X

And which definition takes precedence when the name is found in both
a namespace and an enclosing block?

In article <ercC5C1rL.5sr@netcom.com> erc@netcom.com (Eric Smith) writes:
>
>Can we use multiple namespaces simultaneously?  And is there another
>command after "using" to indicate "no longer using" that namespace?
>
>Or maybe the "using"s are nested by the blocks containing them?
>   {using namespace X;
>      int i=f(); // Searches X for f;
>      {using namespace G;
>  int j=f(); // Searches G, then X, for f.
>      } // no longer using namespace G
>   } // no longer using namespace X
>
>And which definition takes precedence when the name is found in both
>a namespace and an enclosing block?

The second is the right usage, the namespace takes effect from the
point of the "using" declaration until it goes out of scope.  If a
locally declared name collides with a name in namespace being "used"
in that scope, I believe the local one will always win.

For example:

namespace X {
    int x;
};

main()
{
  {
    using namespace X;
    int x=42;
    cout << x << endl;   // prints local x
  }
  {
    int x=42;
    using namespace X;
    cout << x << endl;   // still prints local x
  }
}

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Andrew "Fuz" Lih               Columbia University
lih@cs.columbia.edu        CRF Tech Staff
"Never let schooling interfere with your education"