Under what circumstances is it advantageous to give an implementation of a pure virtual function?

Question

In C++, it is legal to give an implementation of a pure virtual function:

class C
{
public:
  virtual int f() = 0;
};

int C::f() 
{
  return 0;
}
         


        

Answer 1

Just found out that Herb Sutter answered the first part of this question in his Guru of the Week #31.