Virtual friend functions for a base class?

Question

I\'m in the proccess of learning the language and this is a noob doubt.

Is it possible to use a virtual friend function? I don\'t know if it\'s possible, I didn\'t

Answer 1

Nope, friend virtual functions doesn't make sense at all.

friend functions are such, that are not methods (a.k.a. member functions) and have the right to access private/protected members of a class.

virtual functions can only be member functions. You can't have virtual non-member function.

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You can make the operator<< take a reference to a base class and then call some virtual member function. This way, you can make the operator<< "almost virtual" :)

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For example

class A
{
public:
    virtual void f() const { std::cout << "base"; }
};
class B: public A
{
public:
    virtual void f() const { std::cout << "derived"; }
};

std::ostream& operator<<(std::ostream& os, const A& a )
{
     a.f();
     return os;
}

int main()
{
    B b;
    std::cout << b << std::endl;

    return 0;
}

will print derived.