[MPlayer-dev-eng] [PATCH] cropdetect

[Torinthiel]

On Mon, Aug 09, 2004 at 11:12:39PM -0400, Adrian wrote:
> 
> > > Also, this is not true:
> > > > (a - b) % c = (a % c) - (b % c)
> > 
> > this is, though, correct?
> > 
> > (a - b) % c = ((a % c) - (b % c)) % c
> 
> Nope.
> 
> a = 2
> b = 4
> c = 3

Now, that's something contrary to 'normal' mathematical modulus
operator. In mathematics output of -1 mod 3 is 2. So the example would
be correct. In C however % operator does not change sign, and
-1%3=-4%3=-1.
So a % b is like mathematical sgn(a)*(abs(a) mod b)
sgn of course returns -1 if a<0, 1 if a>0 and 0 if a=0.
Torinthiel

-- 
 Waclaw "Torinthiel" Schiller       GG#: 542916, 3073512
   torinthiel(at)megapolis(dot)pl
   gpg: B06901F1 fpr: FAA3 559F CAE9 34DE CDC8  7346 2B6E 39F2 B069 01F1
 "No classmates may be used during this examination"
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