Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!usc!wuarchive!uunet!mcsun!hp4nl!targon!ruud
From: ruud@targon.UUCP (Ruud Harmsen)
Newsgroups: comp.lang.c++
Subject: Re: object-oriented design (was Re: are 'friend's really necessary ??)
Message-ID: <1114@targon.UUCP>
Date: 5 Apr 90 09:59:06 GMT
References: <169@pollux.kulcs.uucp> <10589@alice.UUCP> <1082@targon.UUCP> <1110@targon.UUCP> <4593@pegasus.ATT.COM>
Reply-To: ruud@targon.UUCP (Ruud Harmsen)
Organization: Nixdorf Computer BV., SWP, P.O. Box 29,Vianen, The Netherlands
Lines: 35

In article <4593@pegasus.ATT.COM> psrc@pegasus.ATT.COM (Paul S. R. Chisholm) writes:
>I wrote:
>> >A "thing" in this case may be a whole class.  If you're careful, only a
>> >few functions in class B (e.g., member function foo and static member
>> >function bar) will need to know about the implementation of class A; in
>> >which case, only B::foo and B::bar will need be friends of A.  This is
>> >a Good Thing; it specifically limits what software can mess with an A,
>> >and what code must be looked at when the implementation of A changes.
>
I wrote:
>> In theory, this is correct.  But if in practice, in a particular
>> application 70 to 80 percent *has* to mess with a class A, then you can't
>> do very much limiting.
>
>Exactly right.  That's the signature of a poor design.  You have to
>*try*, hard, to hide the implementation of your data types.  Twenty
>years of programming have taught me that it's worth the effort.  Lots
>of other believe it, too.

I really hope you, and the other believers, are right.  But I'm not
convinced.  I don't think the trouble is in bad design, I think it's
in the nature of things.  The world simply isn't simple, cannot be
forced into strict hierarchical models (remember hierachical databases,
how much trouble they cause(d) in designing a system?), and any design
method that ignores or simplifies these facts, will eventually fail.

But I am always willing to learn, and I will keep on trying to apply
the theories, because I do believe the principles you mention are
themselves useful, and will help a bit, only not as much as many
people seem to think.

>I'm not speaking for the company, I'm just speaking my mind.
So am I.

	Ruud Harmsen.