C++ struct Inheritance

add.cpp

#include <iostream>

struct Perlin {
    float freq;

    explicit
    Perlin (float f = 1.0) {
        freq = f;
    }

    float getValue() {
        std::cout << "Perlin return " << this -> freq << std::endl;
        return this -> freq;
    };
};

struct Module {
    enum ModuleType { Perlin, Add };

    ModuleType type;
    void* modules[255];
    uint8_t index = 0;

    explicit
    Module (struct Perlin* noise) {
        this -> type = Perlin;
        this -> modules[0]  = (void *) noise;
    }

    explicit
    Module (struct Module* module, struct Module* module2) {
        this -> type = Add;

        this -> modules[0]   = (void *) module;
        this -> modules[1] = (void *) module2;
    }

    float getValue() const {

        switch (type) {

            case Perlin: {
                std::cout << "Case: Perlin" << std::endl;

                auto Perlin = (struct Perlin *) modules[0];
                return Perlin->getValue();
            }

            case Add: {
                std::cout << "Case: Add" << std::endl;

                auto m1 = (struct Module *) modules[0];
                auto m2 = (struct Module *) modules[1];

                auto a = m1->getValue();
                std::cout << "a = " << a  << std::endl;

                auto b = m2->getValue();
                std::cout << "b = " << b  << std::endl;

                return a + b;
            }
        }
    };
};

int main() {

    Perlin n0(5);
    Perlin n1(3);

    Module per1 (&n0);
    Module per2 (&n1);

    Module add  (&per1, &per2);

    std::cout << add.getValue()  << std::endl;
    std::cout << "Hello, Noise!" << std::endl;
    return 0;
}

main.cpp

//
//  main.cpp
//  Created by menangen on 22.10.2020.
//

#include <iostream>

struct Noise {
    float value;
    
    float getValue(float x) {
        return x * value;
    };
    
    void addNoise(Noise other) {
        value += other.value;
    };
    
    void powerTo(float to) { value = pow(value, to); }
};

struct Perlin: Noise {
    Perlin( float a = 1, float b = 2) { value = a + b; };
};

struct Billow: Noise {
    Billow( float a = 2, float b = 3, float c = 5) { value = a + b + c; };
};

int main(int argc, const char * argv[]) {
    
    Perlin p = Perlin(2);
    Billow n;
    
    std::cout << p.value << "\n";
    std::cout << n.value << "\n";
    
    p.powerTo(2.0);
    p.addNoise(n);
    
    std::cout
    << ".getValue(2) = [  " << p.getValue(2) << "  ]\n\n";
    
    return 0;
}