Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!ucbvax!agate!darkstar!ucschu.ucsc.edu!ericg
From: ericg@ucschu.ucsc.edu (Eric Goodman)
Newsgroups: comp.lang.c++
Subject: Re: Copying objects
Message-ID: <4853@darkstar.ucsc.edu>
Date: 2 Jul 90 23:48:26 GMT
References: <18753@well.sf.ca.us>
Sender: usenet@darkstar.ucsc.edu
Distribution: comp
Organization: Humanities Division, UC Santa Cruz
Lines: 29

In article <18753@well.sf.ca.us> mccarthy@well.sf.ca.us (Patrick McCarthy) 
writes:
> In other words, suppose you have a class called Base, and two classes
> Derived_1 and Derived_2 which inherit from Base.  Suppose further that p
> and q are of type Base *.  In order to make p point to a copy of q using
> q's copy constructor, you would have know q's type in advance as
> follows:

A virtual overloaded operator= should work (I'm assuming that virtual 
operators are legal); 
the problem is that you would have to define it backwards:

Class Base{
public:
virtual Base operator=(Base) { ... }
};

insures that the left operand of the = is of the correct type, so
*p=*q; // could be used to copy *p into *q with p's type insured.  
I don't see how you could do this to copy in the ordinary fashion, though 
so this may be useless.

Eric Goodman
Humanities Division
University of California, Santa Cruz
ericg@ucschu.ucsc.edu
ericg@ucschu.bitnet
Eric_Goodman.staff@macmail.ucsc.edu
...!ucbvax!ucscc!ucschu!ericg