Nested Namespace In C++

Namespaces can be nested, which means that you can define one namespace inside another called a nested namespace, as shown below:

namespace namespace_name1 {
   // code declarations
   namespace namespace_name2 {
      // code declarations
   }
}

The following resolution operators can be used to access members of a nested namespace:

// to access members of namespace_name2
using namespace namespace_name1::namespace_name2;

// to access members of namespace:name1
using namespace namespace_name1;

Now, Let’s see how nested namespace work through an example:

#include <iostream>
using namespace std;

namespace Outer_nameSpace
{
    void func()
    {
        cout << "Outer NameSpace." << endl;
    }

    namespace Inner_nameSpace
    {
        void func()
        {
            cout << "Inner NameSpace." << endl;
        }
    }
}

using namespace Outer_nameSpace::Inner_nameSpace;

int main()
{

    //Outer_nameSpace::func();
    func();

    return 0;
}

Output:

Inner NameSpace.

For calling outer namespace then we declare

Outer_nameSpace::func();

It prints the outer namespace function func().

Outer NameSpace.

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