Full Example of Interface

#include <cmath>
#include <iostream>
#include <string>
#include <concepts>
#include <type_traits>
template <typename Base, typename Exponent>
concept HasPower = std::convertible_to<Exponent, int> &&
                    requires (Base base, Exponent exponent) {
    base.power(exponent);
};
//class having a conversion operator
class IntWithPower {
public:
    IntWithPower(int num) : m_num(num) {}
    int power(IntWithPower exp) {
       return pow(m_num, exp);
    }
    operator int() const { return m_num; }
private:
    int m_num;
};
//function on which concept is applied
template<typename Exponent>
void printPower(HasPower<Exponent> auto number, Exponent exponent) {
    std::cout << number.power(exponent) << '\n';
}
int main() {
    printPower(IntWithPower{5}, IntWithPower{4});
    printPower(IntWithPower{5}, 4L);
    printPower(IntWithPower{5}, 3.0);
}