From: Geert Bosch <geert@gonzo.sun3.iaf.nl>
Subject: Re: Depending on passing mechanism
Date: 1997/10/15
Date: 1997-10-15T00:00:00+00:00 [thread overview]
Message-ID: <622b4t$nhe$1@gonzo.sun3.iaf.nl> (raw)
In-Reply-To: hbaker-1410971205270001@10.0.2.1
Robert Dewar <dewar@gnat.com> wrote:
``Yes, it may change program behavior, but program behavior is
occasionally non-deterministic in Ada, and this is one of those
cases.''
Henry Baker <hbaker@netcom.com> replied:
``This is another one of those cases that give standards bodies such a
bad name -- the behavior is well-defined as 'non-deterministic', but
non-functional.''
Although it would be nice te remove non-determinism from programming
languages I do not believe this is practical even for programs with
a single thread of control.
For example, large data-structures have to be passed by reference
for efficiency reasons. A fundamental problem in this case is
aliasing of subprogram parameters. When a subprogram is called
with two parameters that are passed by reference and these actually
refer to the same object the program execution may be non-deterministic.
In general this cannot be detected at compile time. Solving this
aliasing problem in the language (for example using reference
counting) will result in significant extra complexity and distributed
overhead. This added complexity and overhead would be two strong
reasons not to use the "improved" language for embedded systems
like those in the Boeing 777 you mentioned.
Do you have a proposal to remove the non-determinism without affecting
performance and flexibility too much? I think many readers in this
group might be interested in such ideas, at least I am.
Regards,
Geert
next prev parent reply other threads:[~1997-10-15 0:00 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-10-13 0:00 Depending on passing mechanism Andre Spiegel
1997-10-13 0:00 ` Matthew Heaney
1997-10-14 0:00 ` Robert Dewar
1997-10-14 0:00 ` Henry Baker
1997-10-15 0:00 ` Geert Bosch [this message]
1997-10-15 0:00 ` Henry Baker
1997-10-15 0:00 ` Jon S Anthony
1997-10-15 0:00 ` Robert Dewar
1997-10-16 0:00 ` Brian Rogoff
1997-10-17 0:00 ` Henry Baker
1997-10-18 0:00 ` Brian Rogoff
1997-10-18 0:00 ` Matthew Heaney
1997-10-19 0:00 ` Brian Rogoff
1997-10-21 0:00 ` Robert A Duff
1997-10-22 0:00 ` Robert Dewar
1997-10-22 0:00 ` Brian Rogoff
[not found] ` <dewar.877601826@merv>
1997-10-23 0:00 ` Brian Rogoff
1997-10-23 0:00 ` Henry Baker
1997-10-23 0:00 ` Brian Rogoff
1997-10-19 0:00 ` Fergus Henderson
1997-10-19 0:00 ` Brian Rogoff
1997-10-20 0:00 ` Fergus Henderson
1997-10-20 0:00 ` Henry Baker
1997-10-20 0:00 ` Tucker Taft
1997-10-21 0:00 ` Geert Bosch
1997-10-18 0:00 ` Fergus Henderson
1997-10-15 0:00 ` Robert Dewar
1997-10-15 0:00 ` Robert Dewar
1997-10-17 0:00 ` Andre Spiegel
1997-10-17 0:00 ` Henry Baker
1997-10-17 0:00 ` Robert I. Eachus
1997-10-17 0:00 ` Jon S Anthony
1997-10-21 0:00 ` Robert A Duff
1997-10-21 0:00 ` Peter Hermann
1997-10-22 0:00 ` Robert A Duff
1997-10-22 0:00 ` Brian Rogoff
1997-10-22 0:00 ` Henry Baker
1997-10-21 0:00 ` Robert Dewar
1997-10-22 0:00 ` Brian Rogoff
1997-10-22 0:00 ` Jon S Anthony
1997-10-15 0:00 ` Brian Rogoff
1997-10-19 0:00 ` Robert Dewar
1997-10-22 0:00 ` Henry Baker
1997-10-15 0:00 ` JP Thornley
1997-10-21 0:00 ` Robert A Duff
1997-10-22 0:00 ` Henry Baker
1997-10-21 0:00 ` Matthew Heaney
1997-10-22 0:00 ` Simon Wright
1997-10-23 0:00 ` Henry Baker
1997-10-23 0:00 ` Pat Rogers
1997-10-24 0:00 ` Robert Dewar
1997-10-23 0:00 ` Robert A Duff
1997-10-21 0:00 ` Keith Thompson
1997-10-14 0:00 ` Robert Dewar
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