#include <stdlib.h>

#define ARRAY_LEN 5

int double_greater(const void *r1, const void* r2) {
    return (*(double *)r1 > *(double *)r2) ? 1 : 0;
}

int main()
{
    /* usage */
    int i;
    double array[ARRAY_LEN] = { 1.2, 24.2, 4.2, 9.0, 17.3 };

    qsort(array, ARRAY_LEN, sizeof(double), double_greater);

    for (i=0; i<ARRAY_LEN; i++) {
        printf("%lf\n", array[i]);
    }

    return 0;
}