Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!brunix!sdm
From: sdm@brunix (Scott Meyers)
Newsgroups: comp.lang.c++
Subject: Re: Re^2: information hiding
Message-ID: <9437@brunix.UUCP>
Date: 27 Jun 89 17:04:42 GMT
References: <6031@watdcsu.waterloo.edu> <6590164@hplsla.HP.COM> <1421@cbnewsc.ATT.COM> <7709@spool.cs.wisc.edu> <1827@itivax.iti.org>
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Reply-To: sdm@sundry.UUCP (Scott Meyers)
Organization: Brown University Department of Computer Science
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Actually, it would have been very easy to design C++ in such a way that the
private data of a class didn't need to be specified in the class
definition: represent each class object as a pointer to the real object.
The price you pay, of course, is an extra indirect reference each time you
refer to an object.  There are other problems as well.  This very point is
discussed in THE C++ PROGRAMMING LANGUAGE at the end of section 5.3.1, page
145.

I was amused to read Stroustrup's discussion of this issue, because a year
or so ago this was the question I posed on the programming languages
portion of the Ph.D. comprehensive exam here at Brown University.  It's an
interesting problem, because it reveals how programming language design is
influenced by language implementation.

Scott