From: John W Kennedy <jwkenne@...>
Date: 2009-03-20T11:07:21+09:00
Subject: Re: Modulo ?

On 3/19/09 6:03 PM, Sebastian Hungerecker wrote:
> Michael Malone wrote:
>> Many people I know and work with simplify the modulo operator to
>> themselves as remainder, so mentally (whether or not it is correct)
>> assume 0/7 = 0 r 7
>
> Maybe I'm slow, but I don't get it.
> You're saying that many people assume that x % y is the same as the remainder
> of dividing x by y, right? I don't see anything wrong with that.
> If I understand you correctly, you're also saying that this assumption is
> wrong in the case of 0%7. I don't understand why that should be the case. The
> remainder of 0/7 is 0, right? And 0%7 is also 0, so where's the problem?

Going by the usual definition of "remainder", there is a difference 
between modulo and remainder when negative numbers get involved.

   remainder(a,b) = a - trunc(a/b) * b
   modulo(a,b) = a - floor(a/b) * b