#include <stdio.h>                                                        /* addAssoc.c */
int main () {                               /* x + (x + y) =?= (x + x) + y */
  float x = 1e-16, y = 1.0; xx = x+x, xy = x+y;
  printf("%.18f =?= %.18f\n", x + xy, xx + y);
  double a = 1e-16, b = 1.0; aa = a+a, ab = a+b;
  printf("%.18f =?= %.18f\n", a + ab, aa + b);
  return 0;
}