////   This file contains the C++ code from Program 10.20 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/pgm10_20.cpp//void BTree::Insert (Object& object){    if (IsEmpty ())    {	if (parent == 0)	{	    AttachSubtree (0, *new BTree (m, *this));	    AttachKey (1, object);	    AttachSubtree (1, *new BTree (m, *this));	    numberOfKeys = 1;	}	else	    parent->InsertPair (object, *new BTree (m, *parent));    }    else    {	unsigned int const index = FindIndex (object);	if (index != 0 && object == *key [index])	    throw invalid_argument ("duplicate key");	subtree [index]->Insert (object);    }}