Path: utzoo!mnetor!uunet!tektronix!tekcrl!jans
From: jans@tekcrl.TEK.COM (Jan Steinman)
Newsgroups: comp.lang.smalltalk
Subject: Re: Object Orientation and The Truth
Message-ID: <2343@tekcrl.TEK.COM>
Date: 23 Feb 88 18:06:17 GMT
Organization: Tektronix Inc., Beaverton, Or.
Lines: 46

(Quoted sections from johnson@uiucdcsp.cs.uiuc.edu are enclosed in "<>".)

<...almost nobody makes use of the fact that classes are objects in 
Smalltalk...>

An evolving style of programming here at Tek (best summarized as "Class 
Variables Considered Harmful To Inheritance"), involves making heavy use of 
class instance variables for encapsulating information common to all instances 
of a class.  For instance, individual Strings need to know how to concatenate 
themselves with each other, find Characters in themselves, and other things 
that are unique to individual Strings.  But if one considers that the state of 
being a String involves some knowledge of line termination conventions on a 
particular system, then it becomes obvious that String class (which is where 
the information concerning the state-of-being-a-String, or "Stringedness", is 
stored) should maintain that information.

In the past, we would have stuffed a line terminator in a class variable and 
been happy -- Strings and their subclasses could access it directly -- very 
efficient.  But what about an application that needs to cross boundaries -- 
have Unix Strings and MS-DOS Strings at the same time?  Class variables are 
shared among subclasses.  By forcing Strings to treat their class as an object 
by asking it for line termination information, subclassing easily handles the 
situation.  The subclass, say "PcString", is a bona-fide object, with its own 
instance variables, one of which contains the line termination sequence unique 
to MSDOS.  Inherited methods that deal with lines work with either Strings or 
PcStrings.

<Smalltalk is better than C++ because it has... classes as objects (the tricks 
one can do!)...>

This has gotten a bit long-winded, but to summarize: classes-as-objects is an 
under-utilized, under-appreciated concept in Smalltalk, that has practical, 
intuitive applications.  It is also misunderstood and misused, and people 
exploring "the tricks one can do" with it have tended to give it a bad rap by 
writing obscure, "tricky" code.

<To forstall arguments, C++ is better than Smalltalk because it is faster, you 
can make standalone executables with it, and it is more portable...  I am 
writing an operating system in C++. Otherwise I use Smalltalk.>

Here, here!  When you need a screwdriver, don't try to make do with a hammer!  
And if you pound nails with that screwdriver, you deserve the results!

:::::: Software Productivity Technologies    ---    Smalltalk   Project ::::::
:::::: Jan Steinman N7JDB	Box 500, MS 50-470	(w)503/627-5881 ::::::
:::::: jans@tekcrl.TEK.COM	Beaverton, OR 97077	(h)503/657-7703 ::::::