////   This file contains the C++ code from Program 10.2 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C++"//   by Bruno R. Preiss.////   Copyright (c) 1998 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.pads.uwaterloo.ca/Bruno.Preiss/books/opus4/programs/pgm10_02.cpp//class BST : public BinaryTree, public SearchTree{protected:    virtual void AttachKey (Object&);    virtual Object& DetachKey ();    virtual void Balance ();public:    BST& Left () const;    BST& Right () const;    // ...};