isleap.c

#define isleap(year)  ((!((year) % 4) && ((year) % 100)) || !((year) % 400))

int main(void){
  int year, isleap;

  for (year = 1898; year < 2050; year++) {
       isleap = (!(year % 4) && (year % 100)) || !(year % 400);
       printf("%4d: %d\n", year, isleap);
  }
}