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From: jsa@alexandria (Jon S Anthony)
Subject: Re: Unbounded strings (Was: Java vs Ada 95 (Was Re: Once again,
 Ada absent from DoD SBIR solicitation))
Date: 1996/11/20
Message-ID: <JSA.96Nov19210658@alexandria>#1/1
X-Deja-AN: 197556708
sender: news@organon.com (news)
references: <325BC3B3.41C6@hso.link.com> <dewar.848202876@merv>
organization: Organon Motives, Inc.
newsgroups: comp.lang.ada
Date: 1996-11-20T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <E14DCH.5EK@world.std.com> bobduff@world.std.com (Robert A Duff) writes:

> In article <dewar.848352010@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
> >"behave as if they are really (varying length) strings"
> >is meaningless, either we ignore the parenthetical remark, in which case
> >it is nonsense, since these do not behave like Ada strings, or we include
> >it, in which case we are talking about something not in the language and
> >so are defining varying length string semantics in terms of varying
> >length string semantics which is nonsense.
> 
> Whenever the RM uses a term that it doesn't define, which is quite
> often, you have to take the most reasonable meaning you know from plain
> English, or from general computer jargon.  Perhaps I interpret this

Criminey!  You better watch out Bob, you're beginning to sound just
like me in this sort of context! ;^)

There are indeed many of these and the worst of it is, they don't seem
all that "fundamental" or "primitive" or "intuitive" like "reasonable"
undefined terms.  As you say - you have to guess the best you can...


> And you still haven't answered my main objection to your reading -- if
> you read it that way, then why isn't practically everything in Annex A
> erroneous?  And lots of other stuff.  E.g:
> 
>     X, Y: Calendar.Time := Clock;
>     
>     X := Y; -- Erroneous?
> 
> (No tasks here.)  How do we know that the implementer has not evilly
> made the full type for Time controlled, with an Adjust routine that does
> something erroneous?  Or raises GNAT.Evil_Exceptions.Whatever_Error?  Or
> writes the value 17 into all integer variables in the program?  We know
> that, because the correct way to interpret the RM is that if it doesn't
> say any of those bad things happen, then they don't.  The same way we
> know that 1+1 of Integers doesn't have side effects.

Hmmmm.  Really.  I think Robert has been hoisted on his own petard, :-)

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