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From: Ketil Z Malde <ketil@imr.no>
Subject: Re: What is wrong with OO ?
Date: 1997/02/12
Message-ID: <KETIL-ytq20ammnxd.fsf@imr.no>#1/1
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Sender: ketil@simba
References: <5dopri$dei@news4.digex.net> <JSA.97Feb11200125@alexandria>
Organization: University of Bergen, Norway
Newsgroups: 
 comp.lang.c++,comp.lang.smalltalk,comp.lang.eiffel,comp.lang.ada,comp.object,comp.software-eng
Date: 1997-02-12T00:00:00+00:00
List-Id: <comp.lang.ada>


jsa@alexandria (Jon S Anthony) writes:

> Nick is correct here.  This is a problem in C++ (along with
> friendship) as it requires prescience on the part of the developer
> and/or various maintenance problems: if you later decide it should be
> virtual, you have to go back and _change_ the source of the parent
> thereby changing the semantics in various other places.  If you decide
> you need a new "friend" you have to go back and _change_ the source
> (which you may not even have accesss to!)

Yes, I agree, the developer of a class needs to think about how the
class is going to be used in the future.  Usually, I don't think this is
a great problem.

E.g. if you wish to provide an interface only, you go with a virtual
abstract method, if you wish to provide interface with a default (but
not absolute) implementation, you go with virtual, and if you want to
provide both interface and implementation (which usually means that the
method is closely tied to the attributes of the (base) class) you submit
a plain non-virtual method.  Simple!

Should the default case therefore be ``virtual''?

There is of course also an issue with MI, but we'll look at that next
period.  :-)

~kzm
-- 
If I haven't seen further, it is by standing in the footprints of giants