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From: mitsu@well.UUCP
Newsgroups: comp.lang.c++
Subject: Re: OOPS Class Library Availability
Message-ID: <4489@well.UUCP>
Date: Thu, 19-Nov-87 20:13:08 EST
Article-I.D.: well.4489
Posted: Thu Nov 19 20:13:08 1987
Date-Received: Sun, 22-Nov-87 04:06:54 EST
References: <283@nih-csl.UUCP>
Reply-To: mitsu@well.UUCP (Mitsuharu Hadeishi)
Organization: Electronic Arts
Lines: 54
Keywords: C++, class library, OOPS, object-oriented programming
Summary: We want it, some comments about generic classes

In article <283@nih-csl.UUCP> keith@nih-csl.UUCP (keith gorlen) writes:
>
>The Object-Oriented Program Support (OOPS) class library for C++ will
>soon become easier to obtain.  In the past, it has been necessary to
>send us a letter of request and a mag tape.  However, we will submit
>the OOPS class library for distribution on the USENIX C++ library tape
>that is being assembled, and we will also make it available via
>anonymous ftp as soon as we get an Internet connection (probably
>during the first quarter of '88).
. . . . 
>	Keith Gorlen			phone: (301) 496-5363
>	Building 12A, Room 2017		uucp: uunet!mimsy!elsie!nih-csl!keith
>	National Institutes of Health
>	Bethesda, MD 20892

	We would like to find out how to get a hold of the USENIX C++
library tape.  (BTW, Keith, we never did get a copy of your OOPS library;
did you get our letter?)  We, too, have been thinking of using
a pure object-oriented approach to using C++, but we have run into some
difficulties.  How does your OOPS library handle dynamic binding?
I presume your Collection classes handle pointers to things of type
Object, is that right?  Does the caller have to type coerce the return
value of the Collection class to get the correctly typed object, or
do your objects handle that automatically via some sort of class object
pointer?  If your objects do have class object pointers, what's in those
class objects?  I presume some class variables and methods, but is there
also a table of method pointers for the class, or do you use virtual
functions to handle this?  Do all of your methods universally return
Object pointers (thus making the virtual function type difficulty moot?)
Do you declare ALL methods virtual in that case?  Can you handle multiple
inheritance?  How do you deal with the problems of virtual function
table offsets in that case?

	Now presuming you don't declare all methods of all subclasses
in class Object (thereby eliminating the type coercion problem and the
multiple-inheritance virtual function table offset difficulty at once)
what kind of macros do you use to do type coercion?  What methods do
you expect to be defined for all objects (aside from ==, =, Hash() or
whatever, !=)?  Do you use more general macros than those included
in generic.h?

	Finally, what is the performance hit in using instances of
class Float or Integer instead of built-in classes?  If you use
virtual functions heavily, do you feel this is an overly-large
memory hit?

				-Mitsu Hadeishi
				 CDI Research and Development
				 Electronic Arts
				 1820 Gateway Drive
				 San Mateo, CA 94404
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