向名称空间别名添加定义

Question

Is it possible to add something to a namespace alias? Or how can I achieve the following:

using KdTree = ExternalLibrary::Special::KdTree;

namespace KdTree{
    class MySpezial {};
};

That does not work, but the following works:

using KdTree = ExternalLibrary::Special::KdTree;

namespace ExternalLibrary{ namespace Special { namespace KdTree{
    class MySpezial {};
}}};

Is the first method just prohibited by the standart?

Answer 1

The first example is currently not allowed and probably won't be in C++1Z either, but note that a recent proposal is allowing

namespace ExternalLibrary::Special::KdTree {
    class MySpezial {};
}

This is already implemented in Clang .