////   This file contains the C++ code from Program 6.18 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/pgm06_18.cpp//QueueAsLinkedList::QueueAsLinkedList () :    list ()    {}void QueueAsLinkedList::Purge (){    if (IsOwner ())    {	ListElement<Object*> const* ptr;	for (ptr = list.Head (); ptr != 0; ptr = ptr->Next ())	    delete ptr->Datum ();    }    list.Purge ();    count = 0;}QueueAsLinkedList::~QueueAsLinkedList ()    { Purge (); }