Question

C++ Programming Lab Exercise 09 Inheritance. Friend Functions, and Polymorphism (virtual functions) 4.a) Run the following code and observe the output. #include <iostream> #include <string> using namespace std; class Vehicle public: void print() { cout << "Print: I am a vehicle. \n"; } void display() { cout << "Display: I am a vehicle. \n"; } }; class Car: public Vehicle { public: void print() { cout << "Print: I am a car.\n"; } void display() { cout << "Display: I am a car. \n"; } }; int main() Vehicle *v; Car c; V = &c; c.print(); c.display(); v->print(); v->display(); return 0; } Next, change the public member function print() in class Vehicle to virtual using the following statement: virtual void print() { cout << "print: I am a vehicle. \n"; } Observe the output and explain the difference between the outputs of virtual function and non-virtual function. Explain the difference in the outputs.

4.a)
4.b>
4.c)

Answer 1

#include <iostream>
#include <string>
using namespace std;

class Vehicle{
   public:
       void print(){
           cout << "Print: I am a vehicle.\n";
       }
   void display(){
           cout << "Display: I am a vehicle.\n";
       }
};

class Car: public Vehicle{
   public:
       void print(){
           cout << "Print: I am a car.\n";
       }
   void display(){
           cout << "Display: I am a car.\n";
       }
};

int main(){
   Vehicle *v;
   Car c;
   v = &c;
   c.print(); //C is object of car so will print Car
   c.display();//C is object of car so will display Car
   v->print(); //v is pointer to car object, it will print vehicle, as superclass will be called [since virtual is not used]
   v->display(); //v is pointer to car object, it will print vehicle, as superclass will be called [since virtual is not used]
   return 0;
}

----output----------
Print: I am a car.
Display: I am a car.
Print: I am a vehicle.
Display: I am a vehicle.
----------------------------------------------------

---------------Change using Virtual----------------------------------
#include <iostream>
#include <string>
using namespace std;

class Vehicle{
   public:
       virtual void print(){
           cout << "Print: I am a vehicle.\n";
       }
   void display(){
           cout << "Display: I am a vehicle.\n";
       }
};

class Car: public Vehicle{
   public:
       void print(){
           cout << "Print: I am a car.\n";
       }
   void display(){
           cout << "Display: I am a car.\n";
       }
};

int main(){
   Vehicle *v;
   Car c;
   v = &c;
   c.print(); //C is object of car so will print Car
   c.display(); //C is object of car so will print Car
   v->print(); //v is pointer to car object, it will print vehicle, as superclass will be called [since virtual is not used]
   v->display();//v is pointer to car object, it will print Car, as derivedclass will be called [since virtual is used]
   return 0;
}

--------output-------------
Print: I am a car.
Display: I am a car.
Print: I am a car.
Display: I am a vehicle.
---------------------------------------------------------------

#include <iostream>
#include <string>
using namespace std;

class Point{
   public:
   Point(int=0, int=0);
   void setPoint(int, int);
   int getX() const{return x;}
   int getY() const{return y;}
   void printPoint() ;
private:
   int x, y;
};

Point::Point(int x, int y){
   this->x = x;
   this->y = y;  
}

void Point::setPoint(int x , int y){
   this->x = x;
   this->y = y;      
}

void Point::printPoint() {
  
   cout << "(" << getX() << ", " << getY() << ")" ;
}

class Circle: public Point{
   public:
   void setRadius(int r = 1);
       int getRadius();
       double area();
       Circle(int=0, int=0, int =1);
   private:
       int radius;  
};

Circle::Circle(int x, int y , int r){
  
   setPoint(x, y); //indirectly calling Point member function
   if( r <= 0) {
       this->radius = 1;
   }
   else{
       this->radius = r;
   }
  
}

void Circle::setRadius(int r){
   if( r <= 0) {
       this->radius = 1;
   }
   else{
       this->radius = r;
   }
}

int Circle::getRadius(){
   return radius;
}

double Circle::area(){
   return 3.142 * radius * radius;
}

int main(){
  
   int x, y, r;
   cout << "Enter x: " ;
   cin >> x;
   cout << "Enter y: " ;
   cin >> y;
  
   cout << "Enter radius:";
   cin >> r;
  
   Circle c =Circle(x, y, r);
   cout << "Circle Center is " ;
   c.printPoint();
   cout << endl;
  
   cout << "Radius is "<< c.getRadius() << endl;
   cout << "Area is "<< c.area() << endl;
return 0;
  
}

---output--------------------------------
Enter x: 2
Enter y: 4
Enter radius:3
Circle Center is (2, 4)   
Radius is 3   
Area is 28.278
-----------------------------

-----------------code change as assigning Protected members
#include <iostream>
#include <string>
using namespace std;

class Point{
   public:
   Point(int=0, int=0);
   void setPoint(int, int);
   int getX() const{return x;}
   int getY() const{return y;}
   void printPoint() ;
Protected:
   int x, y;
};

Point::Point(int x, int y){
   this->x = x;
   this->y = y;  
}

void Point::setPoint(int x , int y){
   this->x = x;
   this->y = y;  
}

void Point::printPoint() {
  
   cout << "(" << getX() << ", " << getY() << ")" ;
}

class Circle: public Point{
   public:
   void setRadius(int r = 1);
       int getRadius();
       double area();
       Circle(int=0, int=0, int =1);
   private:
       int radius;  
};

Circle::Circle(int x, int y , int r){  
   this->x = x; //directly calling Point member fields
   this->y = y;
   if( r <= 0) {
       this->radius = 1;
   }
   else{
       this->radius = r;
   }
  
}

void Circle::setRadius(int r){
   if( r <= 0) {
       this->radius = 1;
   }
   else{
       this->radius = r;
   }
}

int Circle::getRadius(){
   return radius;
}

double Circle::area(){
   return 3.142 * radius * radius;
}

int main(){
  
   int x, y, r;
   cout << "Enter x: " ;
   cin >> x;
   cout << "Enter y: " ;
   cin >> y;
  
   cout << "Enter radius:";
   cin >> r;
  
   Circle c =Circle(x, y, r);
   cout << "Circle Center is " ;
   c.printPoint();
   cout << endl;
  
   cout << "Radius is "<< c.getRadius() << endl;
   cout << "Area is "<< c.area() << endl;
return 0;
  
}

-------output------------------------
Enter x: 2
Enter y: 4
Enter radius:3
Circle Center is (2, 4)   
Radius is 3   
Area is 28.278
---------------------