Path: utzoo!attcan!uunet!lll-winken!ames!sun-barr!apple!rutgers!att!westmark!mole-end!mat
From: mat@mole-end.UUCP (Mark A Terribile)
Newsgroups: comp.lang.c++
Subject: Re: address of virtual function (revisited)
Summary: Rape is only rape in the absence of consent
Message-ID: <183@mole-end.UUCP>
Date: 11 May 89 11:38:34 GMT
References: <8905100026.AA27112@yahi.stanford.edu>
Organization: mole-end--private system.  admin: mole-end!newtnews
Lines: 48


	[The debate about how to store and access the size of an
	 object in an inheritance tree ... or anything else that
	 is constant per base or derived type ...]

>    So, for example, right now, with my combination of cfront and back end
>    compiler, Jerry's approach, where you violate the encapsulation of an
>    object, access its instance variables directly, and lock future
>    derived classes into using one approach to returning "size", and force
>    a syntax of p->size rather than p->size() --

First, I think that Jerry's article about the protected interface and its
intended customers answers this.  It is often reasonable to make a design
decision, in a particular circumstance, that constrains you later in some
way.

OOP people would like to have total code reusability.  The problem with this
approach is that the underlying algorithms have widely varying time and
space properties and one solution is *rarely* correct for everything.  See
grep(1) on a version of ``The UNIX (tm, etc.) Time Sharing System.''  See
the debate now raging on comp.lang.c about free store management.  Sometimes
you have to pay a price in generality to get performance.  C++ allows you to
make these decisions; it does not force the answers on you.

> For crying out loud!  If you are so concerned about performance that
> you would be willing to rape your code if it saved you a few cycles,
> how about this radical approach: write in the object oriented style,
> AND GET A REAL MACHINE.  ...

The job of the engineer is to move those cost/performance/reliability curves
that he can to the best advantage.  That doesn't mean that he can change
his environment.  If there is a glut of cheap 8088s around, he can build a
cheaper product, sell more, and thereby pay for more effort to improve the
performance and reliability.  He can also return more money to the
stockholders, who will respond by asking him to do something else that they
find useful (i.e. profitable to them and *presumably* to the people who buy
the product because they find it useful).

The discussions here show that C++, by not imposing its own ``compleat''
definition of OOP, is engendering all sorts of interesting debate about
how OOP can be used to real effect in the real world.  THIS IS GOOD.  On
the other hand, using the word ``rape'' to describe consensual union
between those who (presumably) have the right to that union is distortion
and pointless inflammation of passions.
-- 

(This man's opinions are his own.)
From mole-end				Mark Terribile