Question

I have not programmed in c++ in a long time and want some simple behavior that no amount of virtual keywords has yet to produce:

class Base {
  public:
    int both() { return a(); }
};

class Derived : public Base {
  protected:
    int a();
};

class Problem : public Derived {
};

Problem* p = new Problem();
p.both();

Which gives me a compile-time error. Is this sort of behavior possible with c++? Do I just need forward declaration? Virtual keywords on everything?

Answer 1

No. You will have to use a pure virtual a in base.

class Base {
    virtual int a() = 0;
    int both() {
        return a();
    }
};