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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: maintenance of overriding subprograms
Date: 1997/09/09
Message-ID: <EG8tAB.Et5@world.std.com>#1/1
X-Deja-AN: 270995238
References: <340C2EA5.B9F@gsfc.nasa.gov> <341065D7.4D41@gsfc.nasa.gov>
 <EG54sG.D2F@world.std.com> <34145A2F.3659@pseserv3.fw.hac.com>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1997-09-09T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <34145A2F.3659@pseserv3.fw.hac.com>,
W. Wesley Groleau x4923 <wwgrol@pseserv3.fw.hac.com> wrote:
>If your names are well-chosen, and your hierarchy well-designed, 
>wouldn't it be unnecessary (except for the occasional extreme case)
>to hunt down a lot of other stuff to understand the item at hand?

I don't think so.  If I see:

    package P is
        type T is new Some_Parent with ...;
        procedure Foo(X: T);
    private
        ...
    end P;

How on Earth am I supposed to know about the 17 primitive operations of
type T?  If Some_Parent is heavily used, then maybe I've memorized them,
but otherwise, I can either go look them up, or use a tool that collects
them for me.  I prefer to have the latter, at least as an option.

>Conversely, if one has to study all the ancestors in great detail
>to do anything with a particular descendant, haven't we lost much of
>the reduced work alleged to be acheived by inheritance?

Well, not really.  For example, think of all those clients of the
*parent* type that happily use the derived type without even *knowing*
about it.

It depends who's doing the "alleging", I guess.  It ranges from "OOP is
a useful tool" to "OOP will cure all the world's ills".  ;-)

- Bob