WP 34S Modulo Bug

[Gerald H]

(06-22-2014 02:26 PM)Thomas Klemm Wrote:  Whatever the definition of MOD is, it should be idempotent:

Example in C:

Code:

#include <stdio.h>
int main()
{
    printf("%2d = %2d\n",  4 %  5, (  4 %  5) %  5);
    printf("%2d = %2d\n", -4 %  5, ( -4 %  5) %  5);
    printf("%2d = %2d\n",  4 % -5, (  4 % -5) % -5);
    printf("%2d = %2d\n", -4 % -5, ( -4 % -5) % -5);
}

Result:

Code:

 4 =  4
-4 = -4
 4 =  4
-4 = -4

This is clearly violated with the current implementation of MOD in the WP-34S:
-4 MOD 2 = 2
but
(-4 MOD 2) MOD 2 = 0

Cheers
Thomas

Yes, idempotency is required.

You seem to be willing to accept that remainder producing zero does not imply mod giving the same result?