C++ 中的命名空间和运算符重载

Namespaces and Operator Overloading in C++(C++ 中的命名空间和运算符重载)

问题描述

在特定命名空间中编写库时，为该命名空间中的类提供重载运算符通常很方便.似乎(至少在 g++ 中)重载的运算符可以在库的命名空间中实现:

When authoring a library in a particular namespace, it's often convenient to provide overloaded operators for the classes in that namespace. It seems (at least with g++) that the overloaded operators can be implemented either in the library's namespace:

namespace Lib {
class A {
};

A operator+(const A&, const A&);
} // namespace Lib

或全局命名空间

namespace Lib {
class A {
};
} // namespace Lib

Lib::A operator+(const Lib::A&, const Lib::A&);

根据我的测试，它们似乎都运行良好.这两个选项之间有什么实际区别吗?哪种方法更好?

From my testing, they both seem to work fine. Is there any practical difference between these two options? Is either approach better?

推荐答案

你应该在库命名空间中定义它们.编译器无论如何都会通过参数相关查找找到它们.

You should define them in the library namespace. The compiler will find them anyway through argument dependant lookup.

无需污染全局命名空间.

No need to pollute the global namespace.

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