From: Nathan Cournia <nac2b AT frank DOT mtsu DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Inheritance Problem
Date: Fri, 01 May 1998 14:20:11 -0500
Organization: Middle Tennessee State University
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Message-ID: <354A206B.586A3F60@frank.mtsu.edu>
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To: djgpp AT delorie DOT com
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 I'm having a problem with inheritance.  In my client file I have this
line:

wordTree Word;

 I also have this line:

Word.Search(Item, Success);

 The previous line calls a public Search function which in turn calls a
private recursive function.  The problem is that the public function is
calling the private function for the parent class instead of the derived

class.  Can anybody help.  Here are the header file for the two classes
and
the server file for the derived class.

 Thanks,
 Nathan Cournia

//FILE: BSTree.h
template <class T> struct bstNode;

template <class T> class bstClass
{
 public:
    bstClass(); //default constructor

    virtual ~bstClass(); //destructor

    bstClass(const bstClass<T>& Tree); //copy constructor

    virtual bool Empty(); //checks of tree is empty

    virtual void Insert(T& NewItem, bool& Success);
                                   //inserts item in tree

    virtual void PrintInorder(); //prints tree inorder

    virtual void PrintPostorder(); //prints tree postorder

    virtual void PrintPreorder(); //prints tree preorder

    virtual void Search(T Item, bool Success); //searches tree for item

 protected:
    void InsertData(bstNode<T>*& P,T& NewItem, bool& Success);
                                          //recursive insert function

    void Inorder(bstNode<T>* P); //inorder recursice function

    void Postorder(bstNode<T>* P); //postorder recursive function

    void Preorder(bstNode<T>* P); // preorder recursive function

    void CopyTree(bstNode<T>* P, bstNode<T>* NewP);
                         //copies tree at P to NewP

    void SearchTree(bstNode<T>* P, T Item, bool Success);
                              //searches for Item in tree

    void DestroyTree(bstNode<T>*& P); //recursive function to destroy
tree

 public:
    bstNode<T>* Root; //root of the tree
}; //end of bstClass
#include "BSTree.cc"

//FILE: WordTree.h

#include "Word.h" //for wordClass
#include "BSTree.h"

class wordTree: public bstClass<wordClass>
{
 protected:
    void SearchTree(bstNode<wordClass>* P, wordClass Item, bool
Success);
}; //end of wordTree
#include "WordTree.cc"


//FILE:      WordTree.cc

void wordTree::SearchTree(bstNode<wordClass>* P, wordClass Item, bool
Success)
{
    if(P==NULL) //check if the list is empty
        Success=0;
    else if(Item==P->Data) //item found
         {
             Success=1;
             P->Data.IncFreq();
             P->Data.AddLineNumber();
         }
    else if(Item<P->Data)
             SearchTree(P->LChild, Item, Success); //search left tree
    else
        SearchTree(P->RChild, Item, Success); //search right tree
} //end of SearchItem()