How do I define friends in global namespace within another C++ namespace?

Question

I\'d like to define a binary operator on in the global namespace. The operator works on a class that is defined in another namespace and the operator should get access to th

Answer 1

This compiles, I assume without testing that it also works. Note the use of parentheses:

namespace NAME {class A; }
NAME::A operator * (double lhs, const NAME::A& rhs);

namespace NAME
{
    class A {
        public:
            friend A (::operator *) (double lhs, const A& rhs);
        private:
            int private_var;
    };
}

NAME::A operator * (double lhs, const NAME::A& rhs)
{
    double x = rhs.private_var;
    return rhs;
}

int main() {}

As Alexander mentions, though, your question doesn't explain why the operator isn't in namespace NAME. Either way it can be called as 1.0 * some_A_instance. So you may be creating needless trouble for yourself.