Re: [Jscheme-user] Re: Modulo function (Ken Anderson)

[Timothy J. H. <ti...@cs...>]

On Jun 17, 2004, at 8:46 AM, Jonathan A Rees wrote:

>> From Scheme 48 (for heaven's sake don't even think about IP):
>
> (define (modulo x y)
>    (let ((r (remainder x y)))
>       (if (> y 0)
>           (if (< r 0)
>               (+ r y)
>               r)
>           (if (> r 0)
>               (+ r y)
>               r))))

Thanks!!

>
> Easily translated into Java.
I used something similar in Java ...

case MODULO: c=a1%b1; c= (((c==0)||((c>0)==(b1>0)))?c:c+b1); break;

Your code says that if y and r have opposite signs then add y to r, 
otherwise leave r alone.
Mine says the same, but tests first to see if r==0 which short circuits 
the tests.

Your's is easier to understand as well! I'll try to see which is 
faster....
---Tim---

>
> As I remember it took several iterations to get this right.
>
> -Jonathan
>
>
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