Xref: utzoo comp.lang.eiffel:1381 comp.object:2520
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!pyrltd!tetrauk!rick
From: rick@tetrauk.UUCP (Rick Jones)
Newsgroups: comp.lang.eiffel,comp.object
Subject: Re: Inheritance and Information Hiding
Message-ID: <1086@tetrauk.UUCP>
Date: 6 Feb 91 21:30:37 GMT
References: <808@puck.mrcu> <10612@pasteur.Berkeley.EDU> <1080@tetrauk.UUCP> <27A9AB0C.4794@tct.uucp>
Reply-To: rick@tetrauk.UUCP (Rick Jones)
Organization: Tetra Ltd., Maidenhead, UK
Lines: 30

In article <27A9AB0C.4794@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
>According to rick@tetrauk.UUCP (Rick Jones):
>>Given that this thread is starting to look like an Eiffel v C++ debate, there
>>is a significant aspect of Eiffel which has been overlooked - assertions.
>
>Please don't cloud discussions with irrelevant issues.
>
>Inheritance and information hiding issues are orthagonal to assertion
>issues.  A given language may support the former, the latter, both, or
>neither.  Let's keep the discussions clear.

A significant theme of this thread was the postulation by some that the notion
of "private" was essential in order to prevent subclasses from breaking their
parent's invariants.  The connection between assertion and information hiding
had already been made.

My point is that, as far as maintaining invariants is concerned, there is more
than one way to skin a cat.  In fact my view is that assertions are a superior
method.  If "private" is used to achieve this, then information hiding and
assertions are not being kept separate.  If assertions are used the two issues
are separated.

In summary, I agree with Chip on the orthogonality, but the issue is neither
irrelevant nor, it seems, entirely free of clouds.  A little discussion might
let in some light.
-- 
Rick Jones
Tetra Ltd.  Maidenhead, 	Was it something important?  Maybe not
Berks, UK			What was it you wanted?  Tell me again I forgot
rick@tetrauk.uucp					-- Bob Dylan