Message-ID: <354C6526.866A90FB@uol.com.br>
Date: Sun, 03 May 1998 09:37:58 -0300
From: "Juciê Dias Andrade" <jucie AT uol DOT com DOT br>
MIME-Version: 1.0
To: Nathan Cournia <nac2b AT frank DOT mtsu DOT edu>, djgpp AT delorie DOT com
Subject: Re: Inheritance Problem
References: <354A206B DOT 586A3F60 AT frank DOT mtsu DOT edu> <354B2DE4 DOT 9981F3C9 AT uol DOT com DOT br> <354BB946 DOT F6E8A824 AT frank DOT mtsu DOT edu>
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>In my bstClass I have the public search function declared as
>virtual.

It doesn't matter. The behavior that is to be overriden is
method SearchTree() and not Search(). Search() does always the
same, ok?

>I want to override the protected recursive function that it
>calls.

Yes, you know what you want.

virtual stands for "this method can have a different bahavior in
a derived class" and no "this method can call another method
that can have a different bahavior in a derived class".

>Do I declare the protected  function as virtual and is that
>allowed?

Yes, it is. Overriding has nothing to do with access control
(public, protected, private). SearchTree() could be private!

Nathan, I will tell you the whole history. If you take a look at
the generated assembly code you will se the difference is at the
method call. The compiler sees a method call and thinks "Is the
called method virtual?". If it is the case the compiler
generates a indirect call, a smart one. This call, at execution
time, gets the address of the proper method from a table that is
connected with the real class of the called object.

This issue is actually confusing sometimes. I hope this
explanation improves your understanding of what is "virtual".

[]s