FAQ #1. Why using namespace arbitrary_name; is a bad practice

namespace is a great feature introduced in C++. It allows us to:

  • Make modular projects.
  • Put your functions in categories.
  • Write more readable and self-explaining code.
  • Write more trustable code by means of specifying which function belongs to what library.

It becomes more critical when it comes to the Standard Library of C++ that is enclosed in the namspace std. By writing using namespace std; in your global scope, this exposes huge amount of functions from the library to be used without the namespace. So What?!

  • What if you have created a function having the same name of one of the thousands functions from std?

    • Names collision,
    • Compiler get confused,
    • Your team members get angry.

  • You will never know every function inside the std so you avoid using a reserved name, and it is pointless to know every function and name inside the std.

Possible Solution

If you are using (for example) std::cout extensively inside a function. What you can do is specifying a particular member (or members) that you are going to use:

// Some function that prints a lot of text in the terminal
void printArrayStatistics( int *array , int size )
{
    using std::cout;

    for( int i = 0 ; i < size ; ++i )
    {
        cout << array[0];
    }

    cout << mean( arr , size ) << std::endl;

    // More and more printing
    // And more.
}

Again, if you insist to expose some name-space:

  • Specify particular members from the name-space, For example:

    • DO using std::cout;.
    • DO NOT using namespace std;.

  • Do it inside a local scope, not in the global scope.