forward declaration of namespace

Question

namespace CounterNameSpace {
    int upperbound;
    int lowerbound;
    using namespace NS;//Error
}
namespace NS {
int i;
}
// ...
namespace NS {
int j;
}

In the above case it shows an error . error C2871: 'NS' : a namespace with this name does not exist I know if i define NS before counternamespace problem will be solved . But just want to know whether any thing like forward declaration of namespace exist in c++ or not .So that the above problem will be resolved without defining NS before counternamespace . please help .

Answer 1

Nothing says a namespace needs all of its contents right away:

namespace NS {}
namespace CounterNameSpace {
    int upperbound;
    int lowerbound;
    using namespace NS;
}
namespace NS {
int i;
}

However, this might not do what you want. You still won't be able to use any of the types in that namespace until you've declared them.