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From: hohl@hermes.informatik.uni-stuttgart.de (Fritz Hohl)
Subject: Re: Strong type checking...
Message-ID: <D5Dxo8.CA6@news.informatik.uni-stuttgart.de>
Sender: news@informatik.uni-stuttgart.de
Organization: IPVR, University of Stuttgart, Germany
References:  <markjrD55495.GLo@netcom.com>
Date: Mon, 13 Mar 1995 15:28:56 GMT
Lines: 50

>a) Add strong type checking to Smalltalk (this method only
>	   takes numbers, for example, and then have all the source code
>	   scanned to insure that this is the case).

The theme of my diploma thesis was "The use of typing in Smalltalk". 
Unfortunately it's written in german :)
Nevertheless, here's the URL: 
http://www.informatik.uni-stuttgart.de/zd/buecherei/studienarbeiten/FritzHohl.html

In my opinion, typing in Smalltalk is useful because 
it helps the programmer to read and understand existing code. In 
smalltalk programmers do programming mostly by reading existing 
methods. If they see a variable, they have to follow the source of the 
creation of the object which is bounded to this variable via other 
methods in other classes, a process which iterates usually some times.

With (strong) typing, one can see which object is bound to a variable 
simply by reading the type of the variable.

Unfortunately, Smalltalk programmers don't use typing because there 
is no type system in most ST-systems.

But there are some Smalltalk dialects with Strong Typing:

1) The TS-System of Johnson, Graver and Zurawski
see e.g.:
R. E. Johnson, J. Graver, L. Zurawski: TS: An Optimizing Compiler for Smalltalk,
                           in:
                           Proceedings of the ACM Conference on 
                           Object-Oriented Programming, Languages and Applications,
                           pages 18-25, 1988

2) Strongtalk (even if i don't know whether they have a product out now)
see e.g.:
  G. Bracha, D. Grisworld: Strongtalk: Typechecking Smalltalk in a 
                           Production Environment, in:
                           Proceedings of the ACM Conference on 
                           Object-Oriented Programming, Languages and Applications,
                           pages 215ff, 1993


A reference which might help you too is the following book:
J. Palsberg, M. I. Schwartzbach: Object-Oriented Type Systems, 
John Wiley & Sons, 1994

Greets, Fritz Hohl

-- 
Fritz Hohl      e-mail: hohl@hermes.informatik.uni-stuttgart.de
Rotebuehlstr. 108, 70197 Stuttgart
