Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!bloom-beacon!eru!luth!sunic!tut!tukki!sakkinen
From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.lang.c++
Subject: Re: private to a class or to an object?
Message-ID: <1334@tukki.jyu.fi>
Date: 20 Sep 89 07:14:24 GMT
References: <517@wizard.UUCP>
Reply-To: markku@jytko.jyu.fi (Markku Sakkinen)
          SAKKINEN@FINJYU.bitnet (alternative)
Organization: University of Jyvaskyla, Finland
Lines: 25

In article <517@wizard.UUCP> john@wizard.UUCP (John Danner) writes:
> [example deleted]
>
>Shouldn't private data be private to a single object and not accessible
>to any object of that class?  Is this something that is safe to take
>advantage of as far as compatibility with future versions of cfront?

There are object-oriented languages in which the unit of encapsulation
is an object (e.g. Smalltalk), and those in which it is a class.
Both approaches have their pros and cons.
C++ belongs to the latter camp, and this is part of the fundamental
philosophy of C++, so you can safely rely upon it.

However:
The new restriction on access to _protected_ parts of objects from
subclass objects in C++ release 2.0 has been recently criticised
in this newsgroup, because some of us think it violates the clear
principle of class-level encapsulation.

Markku Sakkinen
Department of Computer Science
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland