#include <iostream>
using namespace std;

//it takes a "stateless functor class"
template <class UtilFunctor>
class UseUtil
{
    public:

  UseUtil() {
  }
  
  int useCalculate(UtilFunctor calculate, int someVal)
  {
    return calculate(someVal);
  }

};

//out of line way
//int UseUtil::useCalculate(
//                        UtilFunctor calculate, int someVal)
//{
//    return calculate(someVal);
//}

//first functor class
class Cal1
{
    public:
        int operator()(int val)
        {
            return val*val;
        };
};

//second functor class
class Cal2
{
    public:
        int operator()(int val)
        {
            return val+val;
        }
};

int main()
{
    Cal1 calObj1;
    UseUtil<Cal1> useUtilObj1;

    cout << "Using Cal1 = " << 
        useUtilObj1.useCalculate(calObj1, 10) << "\n";

    UseUtil<Cal2> useUtilObj2;
    Cal2 calObj2;

    cout << "Using Cal2 = " << 
        useUtilObj2.useCalculate(calObj2, 10) << "\n";
    return 0;
}