POV's mod(-3, 10) returns -3.  I don't have a problem with the
documentation: mod() works as described, returning ((A/B)-int(A/B))*B where
int(A) is not further from 0 than A on a number line.

However I do think that POV's mod() should behave like Perl's, and with
common (I thought) practice, where mod(A,B) lies in the range [0,B) for all
positive B.

Compare the gradient pattern: it used to be mirrored about 0, but post-3.5,
it is a continuous saw-tooth.  This new behaviour is what I expect from
mod().

Behaviour for B<0 seems to be debated but for the far more common case of
B>0, I believe mod(A,B) should be >= 0 for all A.

I'm sure the mathematicians in the audience will have their own references,
but here is another: http://en.wikipedia.org/wiki/Modulo_arithmetic

Anybody agree?  Anybody care?

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