From: Brian Rogoff <bpr@shell5.ba.best.com>
Subject: Re: Future Ada language revisions?
Date: 1998/10/21
Date: 1998-10-21T00:00:00+00:00 [thread overview]
Message-ID: <Pine.BSF.4.05.9810212137240.17208-100000@shell5.ba.best.com> (raw)
In-Reply-To: wccsoghbg1d.fsf@world.std.com
On Thu, 22 Oct 1998, Robert A Duff wrote:
> vsnyder@vanpcjpl.nasa.gov (Van Snyder) writes:
>
> > The reason that internal procedures can't be used for actual arguments seems
> > to revolve around the possibility that their "addresses" might be copied,
> > because when they appear as formal arguments they're "access to procedure"
> > with no additional restrictions. Right?
>
> Right.
>
> > Could we have another annotation for access formal arguments that prohibits
> > using them for anything other than actual arguments, and dereferencing them?
> > Say, "limited"?
>
> The Ada 9X team proposed exactly that. As an alternative, we also
> proposed a set of rules that would allow copying, but not to a
> more-global place. Both of these proposals were rejected, primarily on
> the grounds that they are hard to implement if the compiler uses a
> "display" to implement a procedure's environment, rather than a "static
> link".
>
> I think it was a mistake. I liked the "limited" idea best. It matches
> Pascal's semantics for passing procedures as parameters. This is the
> only case I can think of where Ada is less powerful than Pascal.
I take it that you've changed your mind then, since you were the author
of the "limited access to subprogram" proposal, and at the end of that
proposal you had recommended that it not be adopted. What changed your
mind?
I have mixed feelings; on one hand I *really* wish that Ada had this
feature, on the other I think that penalizing implementors who used
displays wouldn't have been such a good idea. If there is a future
enhanced Ada, this is one of those things that I hope makes it in there,
so I hope all implementors are at least looking at it now so the argument
of "too much change in too little time" no longer applies.
-- Brian
next prev parent reply other threads:[~1998-10-21 0:00 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-10-21 0:00 Future Ada language revisions? Van Snyder
1998-10-22 0:00 ` Robert A Duff
1998-10-21 0:00 ` Brian Rogoff [this message]
1998-10-23 0:00 ` Robert I. Eachus
1998-10-29 0:00 ` Robert A Duff
1998-10-30 0:00 ` Brian Rogoff
-- strict thread matches above, loose matches on Subject: below --
1998-09-27 0:00 bpr5549
1998-09-27 0:00 ` Larry Kilgallen
1998-09-27 0:00 ` Brian Rogoff
1998-09-28 0:00 ` dewarr
1998-09-28 0:00 ` Brian Rogoff
1998-09-29 0:00 ` Michael F Brenner
1998-10-02 0:00 ` Fergus Henderson
1998-09-29 0:00 ` Larry Kilgallen
1998-09-28 0:00 ` Michael F Brenner
1998-09-28 0:00 ` dewarr
1998-09-28 0:00 ` Arthur Evans Jr
1998-09-28 0:00 ` dewarr
1998-09-28 0:00 ` dewar
1998-10-05 0:00 ` Alfred Hilscher
1998-10-05 0:00 ` Brian Rogoff
1998-10-05 0:00 ` dewarr
1998-10-05 0:00 ` dewarr
1998-10-06 0:00 ` Alfred Hilscher
1998-10-05 0:00 ` Tucker Taft
1998-10-02 0:00 ` Robert I. Eachus
1998-10-03 0:00 ` Brian Rogoff
1998-10-05 0:00 ` dewarr
1998-10-04 0:00 ` Brian Rogoff
1998-10-05 0:00 ` Martin Dowie
1998-10-05 0:00 ` dewarr
1998-10-05 0:00 ` Niklas Holsti
1998-10-05 0:00 ` Martin Dowie
1998-10-06 0:00 ` r_barton1
1998-10-06 0:00 ` dennison
1998-10-06 0:00 ` Martin Dowie
1998-10-06 0:00 ` dewarr
1998-10-06 0:00 ` Martin Dowie
1998-10-06 0:00 ` dennison
1998-10-06 0:00 ` Matthew Heaney
1998-10-06 0:00 ` Robert I. Eachus
1998-10-06 0:00 ` Brian Rogoff
1998-10-07 0:00 ` dewarr
[not found] ` <tgmF02yDo.A84@netcom.com>
1998-10-06 0:00 ` Matthew Heaney
1998-10-08 0:00 ` dennison
1998-10-08 0:00 ` Pat Rogers
1998-10-08 0:00 ` Brian Rogoff
1998-10-09 0:00 ` dennison
1998-10-16 0:00 ` Robert A Duff
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