How do you properly use namespaces in C++?

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Namespaces are packages essentially. They can be used like this:

namespace MyNamespace
{
  class MyClass
  {
  };
}

Then in code:

MyNamespace::MyClass* pClass = new MyNamespace::MyClass();

Or, if you want to always use a specific namespace, you can do this:

using namespace MyNamespace;

MyClass* pClass = new MyClass();

Edit: Following what bernhardrusch has said, I tend not to use the “using namespace x” syntax at all, I usually explicitly specify the namespace when instantiating my objects (i.e. the first example I showed).

And as you asked below, you can use as many namespaces as you like.

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