Question

In c++ Is it OK to include same namespace twice?
compiler wont give any error but still will it affect in anyway

Thanks,

EDIT:
I meant

using namespace std;

// . . STUFF
using namespace std;

Answer 1

It depends what you mean by ‘include’. Saying:

using namespace std;    
...    
using namespace std:

is OK. But saying:

namespace X {
   ...
namespace X {

would create a nested namespace called X::X, which is probably not what you wanted.