Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!cs.utexas.edu!ut-emx!lad-shrike!aihaug
From: aihaug@AUSTIN.LOCKHEED.COM (Daniel A Haug)
Newsgroups: comp.object
Subject: Re: Understanding the Object-Oriented Life-Cycle
Message-ID: <315@shrike.AUSTIN.LOCKHEED.COM>
Date: 10 Nov 89 07:43:42 GMT
References: <5026@internal.Apple.COM>
Organization: Lockheed Austin Div.
Lines: 39

In article <5026@internal.Apple.COM>, chewy@apple.com (Paul Snively) writes:

> Speaking of criticisms, I'm interested in a good discussion on why 
> statically-typed hybrid languages like Object Pascal and C++ aren't useful 
> in some contexts where dynamically-typed languages such as Common Lisp 
> w/CLOS are.  Any takers?

Having just completed a project with 100+ thousand lines of
CLOS-based code, yeah I can think of a few places where dynamic
typing was useful... and a few dozen other things that would
have made this project VERY hard in C++.

By far (IMHO), the largest advantage to this is in code extensibility,
or reusability.  It is so incredibly useful to define an algorithm
that doesn't care about the types on which it operates.  For example,
I need only implement a priority queue ADT once.  The algorithm is the
same, but the types can be whatever.  As result, I only need to write
one QUEUE and DEQUE procedure that don't depend on any typing.  Then,
every object that is passed into the queue would need to support 
some sort of comparison method that QUEUE would call to determine
proper placement.

Although you, Paul, have barked at people referring to Lisp as
typeless (understandably), I still think of this as being an example
of a typeless function.  The functions QUEUE and DEQUE know nothing
about the types of objects on which they are operating.  This is VERY
typical of the style of design in our applications.  The ability to
reuse major segments of code because of their `typeless' characteristics
saved us man-years of effort.

----------

On a naive note, does C++ or any other C-based OO extensions support
different types of method combination?  In our applications, we only
used this capability in CLOS a few times.  However, it was immensely
useful when we DID use it.

-- 
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