C++ Tutorial/Operator Overloading/overload square bracket

Overload [] operator for class

<source lang="cpp">#include <iostream> using namespace std; class Point {

 int a[3];

public:

 Point(int i, int j, int k) {
   a[0] = i;
   a[1] = j;
   a[2] = k;
 }
 int operator[](int i) { return a[i]; }

}; int main() {

 Point ob(1, 2, 3);
 cout << ob[1]; // displays 2
 return 0;

}</source>

2"

Provide range checking for operator []

<source lang="cpp">#include <iostream>

1. include <cstdlib>

using namespace std; class Point {

 int a[3];

public:

 Point(int i, int j, int k) {
   a[0] = i;
   a[1] = j;
   a[2] = k;
 }
 int &operator[](int i);

}; // Provide range checking for Point. int &Point::operator[](int i) {

 if(i<0 || i> 2) {
   cout << "Boundary Error\n";
   exit(1);
 }
 return a[i];

} int main() {

 Point ob(1, 2, 3);
 cout << ob[1]; // displays 2
 cout << " ";
 ob[1] = 25; // [] appears on left
 cout << ob[1]; // displays 25
 ob[3] = 44; // generates runtime error, 3 out-of-range
 return 0;

}</source>

2 25Boundary Error