expr

#include <vector>
#include <iostream>
#include <functional>

class Function {
public:
    virtual float eval(float x) {return 0;};
};

class Expr {
public:
    std::vector<Function*> functions;
    Expr() {}
    Expr(Function* f) {
        functions.push_back(f);
    }

    void addFunc(Function* f) {
        functions.push_back(f);
    }

    float eval(float x) {
        float ret = 1.0;
        for (int i = 0; i < functions.size(); i++) {
            ret *= functions[i]->eval(x);
        }
        return ret;
    }

};

Expr* prod(Expr* f, Expr* g) {
    Expr* h = new Expr();
    for (int i = 0; i < f->functions.size(); i++)
        h->addFunc(f->functions[i]);
    for (int i = 0; i < g->functions.size(); i++)
        h->functions.push_back(g->functions[i]);
    return h;
}

class Polynomial : public Function {
private:
    std::vector<float> coefs;
public:
    float eval(float x) {
        float ret = 0.0;
        for (int i = 0; i < coefs.size(); i++) {
            ret += coefs[i] * pow(x, i);

        }
        return ret;
    }

    Polynomial(std::vector<float> &v) {
        for (int i = 0; i < v.size(); i++) {
            coefs.push_back(v[i]);
        }
    }
};

class Sin : public Function {
public:
    float eval(float x) {
        return sin(x);
    }
};

int main() {
    Function* kovi = new Sin();
    std::vector<float> coeffs = {1,2,3,4,5};
    Function* mester = new Polynomial(coeffs);

    Expr* koviExpr = new Expr(kovi);
    Expr* mesterExpr = new Expr(mester);

    std::cout << "Kovi: " << koviExpr->eval(4.0) << std::endl;
    std::cout << "mester: " << mesterExpr->eval(4.0) << std::endl;
    std::cout << "Kovimester: " << prod(koviExpr, mesterExpr)->eval(4.0) << std::endl;

    int a; std::cin >> a;
    return 0;
}