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From: "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>
Subject: Re: GNAT messages and the not operator (pitfall alert!)
Date: 1996/10/30
Message-ID: <01bbc5fe$823691c0$308371a5@dhoossr.iquest.com>#1/1
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references: <dewar.846162354@merv> <dewar.846163972@merv>
 <32762A30.D2D@watson.ibm.com> <1996Oct29.145959.1@corning.com>
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Date: 1996-10-30T00:00:00+00:00
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whiting_ms@corning.com (Matt Whiting) wrote in article
<1996Oct29.145959.1@corning.com>...
> In article <32762A30.D2D@watson.ibm.com>, "Norman H. Cohen"
<ncohen@watson.ibm.com> writes:
> > Robert Dewar wrote:
> >> 
> >> Here is another pitfall, pretty horrible if it hits, but fortunately
rare.
> >> Ask an Ada expert what is the value of
> >> 
> >>     -5 mod 3
> > 
> > I agree this is a nasty one, and Ada as a Second Language explicitly
> > warns about it (bottom of page 245), as well as about the only slightly
> > less insidious
> 
> Relative to the page 245 warning and the table on page 246, I'm still
confused.
> I'm probably beating a dead horse here, but something still doesn't seem
right.
> If I'm reading the p. 246 table correctly, -5 mod 4 (row 1, column 4,
excluding
> the "header row and column"), should evaluate to 3.  However, I just
wrote a
> simple little program using ObjectAda V7.0 which evaluates to -1, which,
BTW,
> is what I would have expected.  Taking into account the warning on p.
245, I
> also tried -(5 mod 4).  It does give the identical -1 result.  Am I
reading the
> table incorrectly?
> 
> Matt
> 
-5 mod 4 = -(5 mod 4) = -1, but (-5) mod 4 = 3

Is it clear now?
-- 
David C. Hoos, Sr.,
http://www.dbhwww.com
http://www.ada95.com