////   This file contains the C++ code from Program 7.6 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/pgm07_06.cpp//class ListAsArray::Pos : public Position{protected:    ListAsArray const& list;    unsigned int offset;public:    // ...    friend class ListAsArray;    friend class SortedListAsArray;};