A class can be DERIVED from another class

NOTE : -

THIS CONTENT IS NOT ORIGINAL

26. A class can be DERIVED from another class

A class can be DERIVED from another class. The new class INHERITS the variables and methods of the BASE CLASS. Additional variables and/or methods can be added:

using namespace std;
#include 
#include 

class vector
{
public:

  double x;
  double y;

  vector (double a = 0, double b = 0)
  {
     x = a;
     y = b;
  }

  double module()
  {
     return sqrt (x*x + y*y);
  }

  double surface()
  {
      return x * y;
  }
};

class trivector: public vector    // trivector is derived from vector
{
public:
  double z;                      // added to x and y from vector

  trivector (double m=0, double n=0, double p=0): vector (m, n)
  {
     z = p;                      // Vector constructor will
  }                              // be called before trivector
                                 // constructor, with parameters
                                 // m and n.

  trivector (vector a)           // What to do if a vector is
  {                              // cast to a trivector
     x = a.x;
     y = a.y;
     z = 0;
  }

  double module ()               // define module() for trivector
  {
     return sqrt (x*x + y*y + z*z);
  }

  double volume ()
  {
      return this->surface() * z;         // or x * y * z
  }
};

int main ()
{
  vector a (4, 5);
  trivector b (1, 2, 3);

  cout << "a (4, 5)    b (1, 2, 3)    *r = b" << endl << endl;

  cout << "Surface of a: " << a.surface() << endl;
  cout << "Volume of b: " << b.volume() << endl;
  cout << "Surface of base of b: " << b.surface() << endl;

  cout << "Module of a: " << a.module() << endl;
  cout << "Module of b: " << b.module() << endl;
  cout << "Module of base of b: " << b.vector::module() << endl;

  trivector k;
  k = a;               // thanks to trivector(vector) definition
                       // copy of x and y,       k.z = 0
  vector j;
  j = b;               // copy of x and y.       b.z leaved out

  vector *r;
  r = &b;

  cout << "Surface of r: " <<>surface() << endl;
  cout << "Module of r: " <<>module() << endl;

  return 0;
}

Output

a (4, 5) b (1, 2, 3) *r = b Surface of a: 20 Volume of b: 6 Surface of base of b: 2 Module of a: 6.40312 Module of b: 3.74166 Module of base of b: 2.23607 Surface of r: 2 Module of r: 2.23607

BIBILOGRAPHY / REFERENCE : - http://www.4p8.com/eric.brasseur/cppcen.html