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From: cok@islsun.Kodak.COM (David Cok)
Newsgroups: comp.lang.c++
Subject: Re: typesafe downward casting and contravariance
Message-ID: <1991Apr12.100854.18729@kodak.kodak.com>
Date: 12 Apr 91 10:08:54 GMT
References: <9104111419.AA08217@ucbvax.Berkeley.EDU>
Sender: news@kodak.kodak.com
Organization: Eastman Kodak Co., Rochester, NY
Lines: 33

In article <9104111419.AA08217@ucbvax.Berkeley.EDU> schweitz@lexvmc.vnet.ibm.com ("Eric Schweitz") writes:
....

>Sigh. Sorry for my poor example. It seems to have clouded rather than
>clarified my point.  I should have wrote:
>
>   int sin (number);
>   float sin (number);
>   complex sin (number);
>
>or even better just used something generic:
>
>   base func (base);
>   derived func (base);
>   morederived func (base);
>
	.....
>(Does this impose the restriction
>that sizeof(derived*) == sizeof(base*)?  Note: This isn't an attack,
>I'm just curious. :-))

The above would not be allowed either.  a) There is not enough info to
disambiguate; b) the return types are not pointers or references.  What
would be allowed is this:
	base* base::func();
	derived* derived::func();
	morederived* morederived::();

There is no need for the restriction on sizes.

David R. Cok
Eastman Kodak Company -- Imaging Science Lab
cok@Kodak.COM