////   This file contains the C++ code from Program 10.3 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_03.cpp//BST& BST::Left () const    { return dynamic_cast<BST&> (BinaryTree::Left ()); }BST& BST::Right () const    { return dynamic_cast<BST&> (BinaryTree::Right ()); }