Path: utzoo!utgpu!attcan!uunet!mcvax!enea!suadb!anders
From: anders@suadb.UUCP (Anders Bj|rnerstedt)
Newsgroups: comp.lang.c++
Subject: Re: A C++ revelation/question...
Message-ID: <509@suadb.UUCP>
Date: 25 Aug 88 08:31:46 GMT
References: <2767@pt.cs.cmu.edu>
Reply-To: anders@suadb.UUCP (Anders Bj|rnerstedt)
Organization: University of Stockholm, Sweden
Lines: 77

In article <2767@pt.cs.cmu.edu> dld@f.gp.cs.cmu.edu (David Detlefs) writes:
>
>
>C++ is of course an object-oriented language.  However, some OOL
>literature makes a subtle distinction between languages that are
>(truly) "object-based" and those that are "type-based."  The
>distinction is that in an object-based language, a member function
>(method) of a class only has access to the private members of the
>object it is invoked on.  If we neglect some hacks used for debugging,
>Smalltalk is an example of a language that is object-oriented in this
>way.  "Type-based" languages allow a member function of a class access
>to the private part of any object of that class (type) that it has
>access to.  CLU and OWL are examples of languages that are type-based
>in this sense.

I dont agree with your terminology ! 
Sure, Smalltalk is untyped and enforces encapsulation. This does not 
say anything about whether or how a strongly typed language should 
enforce encapsulation. Thus the distinction "object based" vs 
"type based" is misleading.

Wegner has done a lot of work on the classification of programming
languages. Look up one of the folowing:

***************************************************************
#2920      Date: Dec. 1985       Type: Journal article    

   * On Understanding Types, Data Abstraction and 
   * Polymorphism

Journal:   ACM Computing Surveys
Volume:    17
Number:    4
Pages:     471-522


AUTHORS
L. Cardelli
P. Wegner  
***************************************************************
#3035      Date: Oct. 1987       Type: Proceeding article 

   * Dimensions of Object-Based Design

Journal:   Object-Oriented Programming Systems, Languages and Applications
City:      Orlando, Florida
Pages:     168-182


AUTHORS                   
P. Wegner                                                   
***************************************************************
#3339      Date: 1987            Type: Article within book 

   * The Object-Oriented Classification Paradigm

Issuer:    The MIT Press
City:      Cambridge, Massachusetts
Booktitle: Research Directions in Object-Oriented Programming
Pages:     479-560


AUTHORS                                                     EDITORS
P. Wegner                                                   B. Shriver
                                                            P. Wegner

------------------------------------

  Anders Bjornerstedt
  Department of Computer & Systems Sciences
  University of Stockholm
  S-106 91  Stockholm
  Sweden


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