ADT and pure virtual functions help

// Listing 14.10
// Deriving ADTs from other ADTs

Code:

---

#include <iostream>
using namespace std;

enum COLOR { Red, Green, Blue, Yellow, White, Black, Brown } ;

class Animal        // common base to both Mammal and Fish
{
public:
        Animal(int);
        virtual ~Animal() { cout << "Animal destructor...\n"; }
        virtual int GetAge() const { return itsAge; }
        virtual void SetAge(int age) { itsAge = age; }
        virtual void Sleep() const = 0;
        virtual void Eat() const = 0;
        virtual void Reproduce() const = 0;
        virtual void Move() const = 0;
        virtual void Speak() const = 0;
private:
        int itsAge;
};

Animal::Animal(int age):
itsAge(age)
{
        cout << "Animal constructor...\n";
}

class Mammal : public Animal
{
public:
        Mammal(int age):Animal(age)
                { cout << "Mammal constructor...\n";}
        virtual ~Mammal() { cout << "Mammal destructor...\n";}
        virtual void Reproduce() const
                { cout << "Mammal reproduction depicted...\n"; }
};

class Fish : public Animal
{
public:
        Fish(int age):Animal(age)
                { cout << "Fish constructor...\n";}
        virtual ~Fish() {cout << "Fish destructor...\n";  }
        virtual void Sleep() const { cout << "fish snoring...\n"; }
        virtual void Eat() const { cout << "fish feeding...\n"; }
        virtual void Reproduce() const
                { cout << "fish laying eggs...\n"; }
        virtual void Move() const
                { cout << "fish swimming...\n";  }
        virtual void Speak() const { }
};

class Horse : public Mammal
{
public:
        Horse(int age, COLOR color ):
        Mammal(age), itsColor(color)
                { cout << "Horse constructor...\n"; }
        virtual ~Horse() { cout << "Horse destructor...\n"; }
        virtual void Speak()const { cout << "Whinny!... \n"; }
        virtual COLOR GetItsColor() const { return itsColor; }
        virtual void Sleep() const
                { cout << "Horse snoring...\n"; }
        virtual void Eat() const { cout << "Horse feeding...\n"; }
        virtual void Move() const { cout << "Horse running...\n";}

protected:
        COLOR itsColor;
};

class Dog : public Mammal
{
public:
        Dog(int age, COLOR color ):
        Mammal(age), itsColor(color)
                { cout << "Dog constructor...\n"; }
        virtual ~Dog() { cout << "Dog destructor...\n"; }
        virtual void Speak()const { cout << "Whoof!... \n"; }
        virtual void Sleep() const { cout << "Dog snoring...\n"; }
        virtual void Eat() const { cout << "Dog eating...\n"; }
        virtual void Move() const  { cout << "Dog running...\n"; }
        virtual void Reproduce() const
                { cout << "Dogs reproducing...\n"; }

protected:
        COLOR itsColor;
};

int main()
{
        Animal *pAnimal=0;
        int choice;
        bool fQuit = false;

        while (1)
        {
                cout << "(1)Dog (2)Horse (3)Fish (0)Quit: ";
                cin >> choice;

                switch (choice)
                {
                case 1: pAnimal = new Dog(5,Brown);
                                break;
                case 2: pAnimal = new Horse(4,Black);
                                break;
                case 3: pAnimal = new Fish (5);
                                break;
                default: fQuit = true;
                                break;
                }
                if (fQuit)
                        break;

                pAnimal->Speak();
                pAnimal->Eat();
                pAnimal->Reproduce();
                pAnimal->Move();
                pAnimal->Sleep();
                delete pAnimal;
                cout << "\n";
        }
        return 0;
}

---

/*######################################*/

I have a question, because even though Mammal doesn't have a lot of method defined, I want to know if it still has this methods
virtual int GetAge() const { return itsAge; }
virtual void SetAge(int age) { itsAge = age; }
virtual void Sleep() const = 0;
virtual void Eat() const = 0;
virtual void Move() const = 0;
virtual void Speak() const = 0;

because it derives from Animal and therefore making it and ADT, so in turn you cannot make an instance of it? Is this right? If not please explain.

anybody...........

Three ...'s is sufficient, more than three .'s looks stupid.

That doesn't answer my question brian...............don't you have anything better to do than to just ****ing criticize people?

second and last bump for this thread........"bump"

The ones that are written functionname()=0 means that they can only be used by an inheritted class and that inheritted class will modify the function.


[edit]Sorry, I didn't really read ur question. Why don't u try creating an instance of an animal and see what happens. I think that you should be able to create an instance of animal but will not be able to call the function. Not sure though cause I never really tried.[edit]