class MyBumper : public Bumper
{
    public:
  	MyBumper()
  		: bumped( false )
  	{
  	}
  
  	void bumperEvent( bool hasContact )
  	{
  		bumped |= hasContact;
  		std::cout << "Bumper has " << ( hasContact ? "contact" : "no contact") << std::endl;
  	}
  
  	bool bumped;
};