Keyword using namespace in C++

Question

是否有逻辑上的原因，即在using namespace的关键字之后，我们不能在using namespace拥有一个名为myfunction的函数， myfunction在命名空间之外没有另一个名为myfunction函数（具有相同的原型），但是我们可以将其用于变量（ myvariable in命名空间和myvariable之外的myvariable ）？

Answer 1

Of course you can have a function with the same name and signature in different namespaces -- that's part of the reason namespaces exist. The only consideration is that if you want to call it you will have to qualify its name.

namespace Foo {
    void func();
}

namespace Bar {
    void func();
}

using namespace Foo;
using namespace Bar;

func(); // does not compile -- which func()?

Foo::func(); // ok
Bar::func(); // ok