#include <cmath>
#include <iostream>

struct Index {
        Index(int i) : i_(i) {}
        int i_;
};

Index operator*(Index &I)
{
    return I;
}

int operator*(int i, Index I)
{
        return std::pow(i,I.i_);
}

int main()
{
        Index I(2);
        std::cout << 2**I << std::endl;  // prints 8
}