//* Testing numerical undefined *
#include <stdio.h>
#include <math.h>

int main() {
    double x=1.0, y=0.0;
    // try: double, float

    printf("%lf\n",  x/y*y );
    printf("%lf\n",  -x/y*y );
    printf("%lf\n",  (x/y*y) - (x/y*y) );
    printf("%lf\n",  sqrt(-x) );

    return(0);
}