Xref: utzoo comp.lang.modula2:3786 comp.lang.modula3:210
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!sunic!news.funet.fi!jyu.fi!sakkinen
From: sakkinen@jyu.fi (Markku Sakkinen)
Newsgroups: comp.lang.modula2,comp.lang.modula3
Subject: Re: Two Oberon questions
Message-ID: <1991Apr17.125354.8444@jyu.fi>
Date: 17 Apr 91 12:53:54 GMT
References: <1991Apr12.104304.4194@jyu.fi>
Reply-To: sakkinen@jytko.jyu.fi (Markku Sakkinen)
Organization: University of Jyvaskyla, Finland
Lines: 40

In article <1991Apr12.104304.4194@jyu.fi> I asked:

>First question:
>How is the type equivalence of two objects really defined in Oberon?
> ...
>Wirth's original language definition in Software - Practice and Experience
>(July 1988) sidesteps this question rather completely.
> ...

It seems that this crucial issue really remains undefined!
I could not find any mention of it even in the newest revision
(Oct. 1990) of the language report, as available by anonymous FTP
from ETH Zurich.

>Second question:
>Can function procedures in Oberon return structured values?
> ...

Oh dear, already the original language report clearly said 'no'
in subsection 10.1;  how could I have failed to note it?
Therefore, no improvement over Pascal and Modula-2, unfortunately.
However, since SET is one basic type in Oberon (instead of constructed
set types as in Pascal and Modula-2), it is allowed as a return type.

>Common addition to both questions:
>Has the principle perhaps even been changed over the years?
>Do different implementations of Oberon differ?

According to the answers I received, implementations apply
"name equivalence" to types.

Thanks once again to everybody who sent answers or comments!

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