// http://tinodidriksen.com/2010/01/31/snippet-pointer-usage-polymorphism/
#include <iostream>

struct A {
    virtual void foo() {
        std::cout << "A::foo()" << std::endl;
    }
    virtual ~A() {
    }
};

struct B : public A {
    void foo() {
        std::cout << "B::foo()" << std::endl;
    }
};

int main() {
    A *a = new A;
    a->foo();
    delete a;

    a = new B;
    a->foo();
    delete a;
}