Hyperparameter mutation

#include <vector>
#include <cmath>
#include <random>

class GHPM {
public:
    struct HyperParameter{
    private:
        double gradient;
        std::vector<double> s1;
        std::vector<double> s2;

        double calculate_gradient(std::vector<double> s2, std::vector<double> s1) {
            unsigned int size_1 = s1.size();

        }

    public:
        void append_hyper_parameter(double input) {
            s2.append(input);
        }
    };
private:

};