Can a class share a namespace's name?

问题

Is the following C++ code valid?

namespace Foo
{
    class Bar
    {
        // Class code here.
    };
}

namespace Foo
{
    namespace Bar
    {
        void SomeFunction();
        {
            // Function code here.
        }
    }
 }

In other words, can there be a namespace with the same name as a class?

回答1:

You cannot have the arrangement you have in your question because there is no way to disambiguate Bar.

My compiler says:

error C2757: 'Bar' : a symbol with this name already exists and therefore this name cannot be used as a namespace name

回答2:

"can there be a namespace with the same name as a class?"

No, If they are in the same namespace, as in your case.

Otherwise, yes. Anything can have the same name as anything else if they are in different namespaces. See this stackoverflow thread as reference.

回答3:

No, but you can have SomeFunction be a static member of the Bar class.

namespace Foo
{
    class Bar
    {
        // Class code here.
        static void SomeFunction()
        {
            // Function code here.
        }
    };
}

The result is not 100% equivalent to what you want (because of ADL) but the qualified names are what you expect.

来源：https://stackoverflow.com/questions/5856759/can-a-class-share-a-namespaces-name