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Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!mcsun!news.funet.fi!tukki.jyu.fi!sakkinen
From: sakkinen@jyu.fi (Markku Sakkinen)
Newsgroups: comp.lang.eiffel,comp.object
Subject: Re: Reference Semantics
Message-ID: <1991Jun14.073249.1469@jyu.fi>
Date: 14 Jun 91 07:32:49 GMT
References: <133154@tut.cis.ohio-state.edu> <1991Jun12.072557.7282@jyu.fi> <133644@tut.cis.ohio-state.edu>
Organization: University of Jyvaskyla, Finland
Lines: 41

I am cross-posting this article and the following one to comp.object
because the question is interesting not only to the Eiffel community.

In article <133644@tut.cis.ohio-state.edu> ogden@seal.cis.ohio-state.edu (William F Ogden) writes:
>In article <1991Jun12.072557.7282@jyu.fi> sakkinen@jyu.fi (Markku Sakkinen) writes:
>>  ...
>It's true that analogies only suggest, but don't prove. In this case,
>the analogy suggests strongly that we examine very carefully whether
>the visible use of references is really that central to object oriented 
>design. A good example or two showing where references are fundamentally
>necessary could perhaps expose the deficiencies of the proposed [dangerous?]
>analogy.

class person
    export ... inherit ...
    feature
        mother: person;
        heart: human_heart;
    ... end

It is essential that several persons can have the same mother.
On the opposite, a heart cannot be shared.  I consider it a deficiency
of languages such as Lisp, Smalltalk, and Eiffel that this important
semantic difference cannot be expressed; and the main reason is that
references are used for "everything".

(Arrrgh: I already wrote and submitted something like this yesterday,
but some testing of the news system here caused all articles to get lost.)

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Markku Sakkinen (sakkinen@jytko.jyu.fi)
       SAKKINEN@FINJYU.bitnet (alternative network address)
Department of Computer Science and Information Systems
University of Jyvaskyla (a's with umlauts)
PL 35
SF-40351 Jyvaskyla (umlauts again)
Finland
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