Provide range checking for operator [] : overload square bracket « Operator Overloading « C++ Tutorial

1. C++ Tutorial
2. Operator Overloading
3. overload square bracket

#include <iostream>
#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;
}

2 25Boundary Error