Path: news.daimi.aau.dk!news.uni-c.dk!sunic!trane.uninett.no!eunet.no!nuug!EU.net!uunet!MathWorks.Com!europa.eng.gtefsd.com!swiss.ans.net!news.dfn.de!news.belwue.de!news.uni-stuttgart.de!rz.uni-karlsruhe.de!news.rz.uni-karlsruhe.de!hf
From: hf@informatik.uni-karlsruhe.de (Harald Fuchs)
Newsgroups: comp.lang.beta
Subject: Re: unsafe virtual patterns?
Date: 21 Sep 1994 15:18:09 GMT
Organization: Telematics Dept., Karlsruhe University, Germany
Lines: 9
Message-ID: <HF.94Sep21171809@faustino.informatik.uni-karlsruhe.de>
References: <35nlra$t2@rosie.next.com> <35nubg$74o@engnews2.Eng.Sun.COM>
Reply-To: hf@tk.telematik.informatik.uni-karlsruhe.de
NNTP-Posting-Host: faustino.telematik.informatik.uni-karlsruhe.de
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
In-reply-to: olm@Eng.Sun.COM's message of 21 Sep 1994 00:22:08 GMT
hf/
X-PGP-Public-Key: finger -l hf@tk.telematik.informatik.uni-karlsruhe.de
X-PGP-Fingerprint: 09 4E C4 A2 B2 C5 33 1A  79 80 5D 39 BD 9B 89 39
kiz#%J_T\[o"W6$r~=>bUG3}]662E7^t)&e'X!i<80mK`#8_COdRHrEG'[sT
  i<DN@!?oL&8,,U0L9o%^$sh*mo`nY7%uri56H_1Ka{L+`XGq7iV[1];7H"&89-;PH)TricUmwsj]AK
  NtAw+L&FKto;o0N88D8O:YzU

> Simula has the run-time check for reverse assignments.
> In Eiffel it corresponds to aBus?=aVehicle
> and for C++ it is the repsonsibility of the programmer (correct me if
> I am wrong!)

Yes and no.  A recent addition to C++ is the "dynamic_cast" operator
which does roughly the same as "?=" in Eiffel.  The difference is that
it won't work for non-polymorphic objects, i.e. objects without
virtual member functions.