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From: richard@pantor.UUCP (Richard Sargent)
Newsgroups: comp.lang.c++
Subject: virtual and overloading
Message-ID: <58.UUL1.3#5109@pantor.UUCP>
Date: 20 Mar 90 14:41:40 GMT
Organization: Pansophic Systems Inc, Graphics Product Company
Lines: 35

(I apologize if this has made it out before. I have not seen any
indication that it has done so, hence the repost.)

A question came up recently here as to what is correct code for
a C++ 2.0 program.

We have a derived tree of classes of graphical objects, with the
base class defining a 'virtual void draw( some *obj )'. In one
derived class, a way down the tree of classes, we have a class
in which we want to have a function 'void draw( void )'. That is,
we want a function for that particular class which takes no
argument.

Attempting to do this the obvious way results in a type mismatch.

Q: is it necessary that the base class define 'virtual void draw( void )'
to overload it, even though the only class to use it is way down
the tree of classes?

If we do this then we get an error message on the derived classes
which define 'void draw( some *obj )', namely "sorry, not implemented:
virtual derclass::draw() overloaded in base class but not in derived
class". So, does this mean that we have to specify the overloading
of the 'void draw( void )' in all derived classes?

Q: exactly what do we need to do to make this work?


If anyone has done something like this in 2.0, we certainly would 
appreciate hearing how?

Thanks for your help.

Richard Sargent                   Internet: richard@pantor.UUCP
Systems Analyst                   UUCP:     ...!mnetor!becker!pantor!richard