派生类和基类运算符重载

class Parent{
private:
    int a, b;
public:
    Parent(int x, int y){
        a = x;
        b = y;
    }
    
   friend ostream& operator<<(ostream &os, Parent &p){
        os << "a: "<<p.a<<" b: "<<p.b;
       return os;
    }
};
//子类也重载了 >> 操作符，希望调用父类的成员函数
class Child: public Parent{
private:
    int c;
public:
    Child(int x, int y, int z):Parent(x, y)
    {
        c = z;
    }
    

    friend ostream& operator<<(ostream &os, Child &c){
    	// ****** //
        return os;
    }
};

这一段应该怎么写，如何分离出父类这部分。因为基类和派生类重载了同一个函数，无法在子类中直接调用，否则会无限循环调用自身。
解决办法是，重用尽量都在成员函数中实现，友元函数就不要想重用了。

class Parent{
private:
    int a, b;
public:
    Parent(int x, int y){
        a = x;
        b = y;
    }
    
    ostream & disc(ostream& os){
        os << "a: "<<a<<" b: "<<b;
        return os;
    }
    
   friend ostream& operator<<(ostream &os, Parent &p){
		p.disc(os);
       return os;
    }
};


class Child: public Parent{
private:
    int c;
public:
    Child(int x, int y, int z):Parent(x, y)
    {
        c = z;
    }
    
    void disc(ostream &os){
        Parent::disc(os);
        cout<<" c: "<<c;
    }
    
    friend ostream& operator<<(ostream &os, Child &co){
        co.disc(os);
        cout << co.c;
        return os;
    }
};