Can I include iostream header file into custom namespace? [closed]

Question

namespace A
{
   #include <iostream>
};

int main(){
 A::std::cout << "\nSample";
 return 0;
}

Answer 1

You could write:

#include <vector> // for additional sample
#include <iostream>
namespace A
{
  namespace std = std; // that's ok according to Standard C++ 7.3.2/3
};

// the following code works
int main(){
 A::std::cout << "\nSample"; // works fine !!!
 A::std::vector<int> ints;
 sort( ints.begin(), ints.end() );  // works also because of Koenig lookup

 std::cout << "\nSample";  // but this one works also
 return 0;
}

Thit approach is called namespace aliasing. Real purpose for that feature showed in the following sample:

namespace Company_with_very_long_name { /* ... */ }
namespace CWVLN = Company_with_very_long_name;

// another sample from real life
namespace fs = boost::filesystem;
void f()
{
  fs::create_directory( "foobar" );   // use alias for long namespace name
}