#include <iostream>
using namespace std;
struct Food {
    Food() { cout << "Food constructor" << endl; }
    ~Food() { cout << "Food destructor" << endl; }
};
struct Predator {
    void eat(Food& food) { food.~Food(); }
    void eat(Food* food) { delete food; }
};

int main()
{
    Predator p;
    Food *f1 = new Food;
    Food *f2 = new Food;
    p.eat(*f1);
    p.eat(f2);
    return 0;
}

#include <iostream>
using namespace std;
struct Food {
    Food() { cout << "Food constructor" << endl; }
    void die() { delete this; }
private:
    ~Food() { cout << "Food destructor" << endl; }
};
struct Predator {
    void eat(Food& food) { food.die(); }
    void eat(Food* food) { food->die(); }
};

int main()
{
    Predator p;
    Food *f1 = new Food;
    Food *f2 = new Food;
    // Food f3; --> compile time error
    p.eat(*f1);
    // delete f2; --> compile time error
    p.eat(f2);
    // f2->die(); --> а это скомпилируется, но UB, если f2 уже съеден
    return 0;
}

#include <iostream>

using namespace std;

struct Animal {
    virtual void die() = 0;
    virtual void eat(Animal*) = 0;
protected: virtual ~Animal() {}
};

struct Sheep : public Animal
{
    Sheep() { cout << "Sheep constructor" << endl; }
    void die() { delete this; }
    void eat(Animal* food) {/* овечка не может съесть животное */ cout << "impossible" << endl;}
private:
    ~Sheep() { cout << "Sheep destructor" << endl; }
};

struct Wolf : public Animal
{
    void eat(Animal* food) { food->die(); }
    void die() { delete this; }
private:
    ~Wolf() {}
};

int main()
{
    Animal *s1 = new Sheep, *s2 = new Sheep, *s3 = new Sheep;
    Animal *w1 = new Wolf, *w2 = new Wolf;
    w1->eat(s1);
    w2->eat(s2);
    s3->eat(w1); // Смело...
    s3->die(); // От старости... Или со страху.
    w1->eat(w2); // Не повезло 2-му.
    w1->die(); // От обжорства...
    return 0;
}