Namespaces and Operator Overloading in C++

c++ operator-overloading namespaces
jonner picture jonner · Oct 5, 2008 · Viewed 18.5k times · Source

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

or the global namespace

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

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

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

Answer

David Pierre picture David Pierre · Oct 5, 2008

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

No need to pollute the global namespace.

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