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From: Martin <martin.dowie@btopenworld.com>
Newsgroups: comp.lang.ada
Subject: Re: About the F-22 software bug
Date: Fri, 5 Feb 2010 00:30:55 -0800 (PST)
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On Feb 5, 6:42=A0am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> declaimed the following in comp.lang.ada:
>
> > I know that the F-22 is 90% of Ada. Is there some public information
> > about this bug? Is that a design bug?
>
> =A0 =A0 =A0 =A0 So far as I recall -- from some years ago -- it was an al=
gorithm
> problem handling position information wrap-around from crossing, as
> mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> =A0 =A0 =A0 =A0 I didn't hear that they had to follow the tankers back --=
 was under
> the impression once they managed to cross back heading east a reboot of
> the navigation system started working again...
>
> --
> =A0 =A0 =A0 =A0 Wulfraed =A0 =A0 =A0 =A0 Dennis Lee Bieber =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 KD6MOG
> =A0 =A0 =A0 =A0 wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/

For some reason (that I don't get at all) lots of systems define long
as -180 <=3D x <=3D +180 degrees.

Having the potential to alias a position seems like a bad idea for a
start, so when I've been coding such systems up, I've always spent a
bit of time making it convert positions into the range -180 <=3D x <
+180 degrees and using a proper ADT.

I wonder if it was anything to do with that?...

Cheers
-- Martin