Can a class share a namespace's name?

Question

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?

Possible duplicate of [Using a class in a namespace with the same name?](http://stackoverflow.com/questions/1539333/using-a-class-in-a-namespace-with-the-same-name) — jww, May 05 '17 at 18:11

Ozair Kafray · Answer 1 · 2017-11-20T05:29:50.580

19

"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.

edited Nov 20 '17 at 05:29

answered May 02 '11 at 11:52

Ozair Kafray

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No, that question is about using the same name in *different* namespaces. – Mike Seymour May 02 '11 at 12:03
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@Mike: I think that Ozair has answered the second question of the OP. – quamrana May 02 '11 at 12:06
@quamrana: Yes, I did answer the second part of the question. – Ozair Kafray May 02 '11 at 13:23
7

OK. To clarify this answer: anything can have the same name as anything else if they are in different namespaces; a class cannot have the same name as a namespace if they are both in the same namespace. – Mike Seymour May 02 '11 at 13:26

score 19 · Accepted Answer · answered May 02 '11 at 11:58

19

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

answered May 02 '11 at 11:58

quamrana

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The compiler can't just check to see if I'm calling something in the `Bar` namespace or the `Bar` class? – Maxpm May 02 '11 at 12:09
6

@Maxpm: The compiler has to disambiguate `Bar` first before it checks inside. If you call `Foo::Bar::SomeFunction();`, then should the compiler say 'OK' or should it say 'Error' - class Bar has no member? – quamrana May 02 '11 at 12:13

score 3 · Answer 3 · answered Oct 04 '18 at 03:42

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.

Can a class share a namespace's name?

3 Answers3

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