qsort example
=============

#include   <stdio.h>
#include   <stdlib.h>

#define   M   32         /* size of a[] */
#define   N   11         /* size of b[] */

#define   decimal_part(x)   (x - (int) x)
#define   random_char()     (rand() % 26 + 'a')
#define   random_float()    (rand() % 100 / 10.0)

#define   FILL(a, n, type)   \
   for (i = 0; i < n; ++i)   \
      a[i] = (*type == 'c') ? random_char() : random_float()

#define   PRINT(a, n, cntrl_string)   \
   for (i = 0; i < n; ++i)            \
      printf(cntrl_string, a[i]);     \
   putchar('\n')

main()
{
   char    a[M];
   float   b[N];
   int     i;
   int     lexico(void *, void *);
   int     compare_decimal_part(void *, void *);

   FILL(a, M , "char");
   PRINT(a, M, "%-2c");
   qsort(a, M, sizeof(char), lexico);
   PRINT(a, M, "%-2c"); /* left justifed 2 positions */
   printf("---\n");
   FILL(b, N, "float");
   PRINT(b, N, "%-6.1f");
   qsort(b, N, sizeof(float), compare_decimal_part);
   PRINT(b, N, "%-6.1f");
}

int lexico(void *vp, void *vq)
{
   char   *p = vp, *q = vq;

   return (*p - *q);
}

int compare_decimal_part(void *vp, void *vq)
{
   float   *p = vp, *q = vq, x;

   x = decimal_part(*p) - decimal_part(*q);
   return ((x == 0.0) ? 0 : (x < 0.0) ? -1 : +1);
}

Output
======

w f a z y z a z o h s n g h c x s f u b s n s n w f u j e l g t 
a a b c e f f f g g h h j l n n n o s s s s t u u w w x y z z z 
---
2.2   1.5   4.0   8.5   2.2   7.9   0.4   6.5   6.6   5.9   2.4   
4.0   2.2   2.2   0.4   2.4   8.5   1.5   6.5   6.6   5.9   7.9