AddClass.cpp

#include <iostream>

using std::cout;
using std::endl;

struct add {
    int sum;
    add& operator()(int val) {
        sum += val;
        return *this;
    }
    add(int initval): sum(initval) {}
    operator int() { return sum; }
};

int main(void)
{
    cout << add(3)(4)(5) << endl;
    if (add(3)(4)(5) == 12) 
        cout << "Perfect!" << endl;
    return 0;
}