//<--- delta - function --->
enum class delta_function_type { encode, decode };

template<delta_function_type T>
class delta_function {
public:
    int operator()(int in);
private:
    int last = 0;
};

template <>
int inline delta_function<delta_function_type::encode>::operator()(int in) {
    int current = in;
    int res = current - last;
    last = current;
    return res;
}

template <>
int inline delta_function<delta_function_type::decode>::operator()(int in) {
    int res = in + last;
    last = res;
    return res;
}