C++/Development/Mutable

#include <iostream>
using namespace std;
class Timer {
  int step;
  int target;
  mutable int current; 
public:
  Timer(int delay, int i=1) {
    target = delay;
    step = i;
    current = 0;
  }
  bool counting() const {
    current += step;
    if(current >= target) {
      cout << "\a";
      return false;
    }
    cout << current << " ";
    return true;
  }
};
int main()
{
  Timer ob(200, 4);
  while(ob.counting()) ;
  return 0;
}