////   This file contains the C++ code from Program 9.17 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/pgm09_17.cpp//BinaryTree::BinaryTree () :    key (0),    left (0),    right (0)    {}BinaryTree::BinaryTree (Object& _key) :    key (&_key),    left (new BinaryTree ()),    right (new BinaryTree ())    {}