The keyword this is a pointer to the instance a method is acting upon

NOTE : -

THIS CONTENT IS NOT ORIGINAL

21. The keyword this is a pointer to the instance a method is acting upon

When a method is applied to an instance, that method may use the instance's variables, modify them... But sometimes it is necessary to know the address of the instance. No problem, the keyword this is intended for that purpose:

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);
  }

  void set_length (double a = 1)
  {
     double length;

     length = this->module();

     x = x / length * a;
     y = y / length * a;
  }
};

int main ()
{
  vector c (3, 5);

  cout << "The module of vector c: " << c.module() << endl;

  c.set_length(2);            // Transforms c in a vector of size 2.

  cout << "The module of vector c: " << c.module() << endl;

  c.set_length();             // Transforms b in an unitary vector.

  cout << "The module of vector c: " << c.module() << endl;

  return 0;
}

Output

The module of vector c: 5.83095 The module of vector c: 2 The module of vector c: 1

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