Deriving an abstract class from concrete class

Question

Let\'s say we have a concrete class Apple. (Apple objects can be instantiated.) Now, someone comes and derives an abstract class Peach from Apple. It\'

Answer 1

a bit unusual, but if you had some other subclass of the base class and the subclasses of the abstract class had enough common stuff to justify the existance of the abstract class like:

class Concrete
{
public:
    virtual void eat() {}
};
class Sub::public Concrete { // some concrete subclass
    virtual void eat() {}
};
class Abstract:public Concrete // abstract subclass
{
public:
    virtual void eat()=0;
    // and some stuff common to Sub1 and Sub2
};
class Sub1:public Abstract {
    void eat() {}
};
class Sub2:public Abstract {
    void eat() {}
};
int main() {
    Concrete *sub1=new Sub1(),*sub2=new Sub2();
    sub1->eat();
    sub2->eat();
    return 0;
}