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From: jsa@alexandria (Jon S Anthony)
Subject: Re: Any research putting c above ada?
Date: 1997/05/02
Message-ID: <JSA.97May2135942@alexandria>#1/1
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References: <5ih6i9$oct$1@waldorf.csc.calpoly.edu>
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 <EACHUS.97Apr30145510@spectre.mitre.org>
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Newsgroups: comp.lang.c++,comp.lang.c,comp.lang.ada
Date: 1997-05-02T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <EACHUS.97Apr30145510@spectre.mitre.org> eachus@spectre.mitre.org (Robert I. Eachus) writes:

> add state.  The final answer was a compromise:
> 
>    type Bar is new Foo with null record;
> 
>    Three keywords to indicate that the type could have been extended,
> but wasn't.  There needs to be something, and a lot of us wanted "with
> null;" instead of "with null record;" but that's what compromise is

Actually, I've always had a simple question about this area.  Why was
the "record" bit included in tagged types at all??  Why not simply:

    type T is tagged
        x: ...
        y: ...
        ...
    end T;

and

    type S is new T with
        ...
    end S;

and as you say above

    type R is new T with null;

Why was the "record" bit even there?  It's not a big deal, but IMO the
"record" part even is rather misleading - tagged things are very
different in all sorts of ways from regular old record types and
people can (and have - as evidenced by various threads in c.l.a) get
tripped up by this.


/Jon
-- 
Jon Anthony
Organon Motives, Inc.
Belmont, MA 02178
617.484.3383
jsa@organon.com