#include <iostream>

namespace exercise {

class A {
public:

    virtual void a() = 0;
    virtual void b() = 0;
    virtual void c() = 0;

};

class B : public A {

    void a() { std::cout << "a function @ B class"; }
    void b() { std::cout << "b function @ B class"; }
    void c() { std::cout << "c function @ B class"; }

};

class C : public A {

    void a() { std::cout << "a function @ C class"; }
    void b() { std::cout << "b function @ C class"; }
    void c() { std::cout << "c function @ C class"; }
};

using Pstd_mem = void(A::*)();

void foo(A* basePointer, Pstd_mem action) {

    basePointer->*action();

}
}

int main(void) {

using namespace exercise;

A* b = new B();
A* c = new C();

foo(b, &A::b);

}