////   This file contains the C++ code from Program 5.21 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/pgm05_21.cpp//class SearchableContainer : public virtual Container{public:    virtual bool IsMember (Object const&) const = 0;    virtual void Insert (Object&) = 0;    virtual void Withdraw (Object&) = 0;    virtual Object& Find (Object const&) const = 0;};