////   This file contains the C++ code from Program 8.5 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/pgm08_05.cpp//class HashingVisitor : public Visitor{    HashValue value;public:    HashingVisitor (HashValue _value) : value (_value)	{}    void Visit (Object& object)	{ value += object.Hash (); }    HashValue Value () const	{ return value; }};HashValue Container::Hash () const{    HashingVisitor visitor (::Hash (typeid (*this).name ()));    Accept (visitor);    return visitor.Value ();}