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From: preston@ariel.rice.edu (Preston Briggs)
Newsgroups: comp.lang.modula2,comp.lang.modula3
Subject: Re: Two Oberon questions
Message-ID: <1991Apr13.014229.27407@rice.edu>
Date: 13 Apr 91 01:42:29 GMT
References: <1991Apr12.104304.4194@jyu.fi>
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Organization: Rice University, Houston
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sakkinen@jytko.jyu.fi (Markku Sakkinen) writes:

>First question:
>How is the type equivalence of two objects really defined in Oberon?
>Modula-2 has "name equivalence", but Modula-3 has gone over to
>structural equivalence (in my opinion: unfortunately).
>Wirth's original language definition in Software - Practice and Experience
>(July 1988) sidesteps this question rather completely.

In a later paper, perhaps about the Oberon system, Wirth let slip that
Oberon (the language) uses name equivalence.  Of course, you have
to make these exceptions for procedure passed as parameters, and pretty
soon you end up wishing he had just said structural equivalence and
let it go at that.

>Can function procedures in Oberon return structured values?

Nope.  This one is in the report, somewhere.
Of course, I may be out of date.

Preston Briggs