class T {
public:
    double execute();
};

T t;
int a = 0, b = 1;
t.execute([a,b]()->double{return (3*a + 5*b);});

class T {
public:
    double execute(double (*expression)()) {
        return expression();
    }
};

int main() {
    T t;
    double result = t.execute([]() -> double {return 1 + 1;});
    return 0;
}

class T {
public:
    template<typename Func>
    double execute(Func expression) {
        return expression();
    }
};

int main() {
    T t;
    int a = 0, b = 1;
    double result = t.execute([&a,&b]() -> double {return 3 * a + 5 * b;});
    return 0;
}

class T {
public:
    double execute(std::function<double()> expression) {
        // sem templates, expression pode ser "armazenada" em qualquer lugar
        return expression();
    }
};

int main() {
    T t;
    int a = 0, b = 1;
    // [&] captura qualquer variavel por referencia
    std::function<double()> func = [&]() -> double {return 3 * a + 5 * b;};
    double result = t.execute(func);
    return 0;
}

class T {
private:
    double (*expression)();
public:
    T(double (*exp)()) : expression(exp) {}
    double execute() {
        return this->expression();
    }
};

int main() {
    T t([]()->double {return 1+1;});
    double val = t.execute(); // val = 2
    return 0;
}