Re: Virtual << operator?

I would like to force all the classes in my hierarchy to implement the
<< operator for testing purposes. My base class is a pure virtual
class.

I started out by working with operator overloading in the derived
class. I have been trying to use what I learned there to create an
appropriate virtual class to force overloading.

class Base{

  // Can't define operator with two arguments inside Base class
  virtual std::ostream& operator<<(std::ostream& s, Base& b) = 0;

  // When I did this for the concrete derived class, it failed because
the
  // compiler doesn't seem to 'find' the implementation of << for Base
  virtual std::ostream& operator<<(std::ostream& s) = 0;
}

// For the concrete derived class, I got this two-argument approach to
work.
// However, you can't declare virtual functions outside a class.
virtual std::ostream& operator<<(std::ostream& s, Base& b) = 0;

Any suggestions are appreciated.

Rob