void swap(void *v[], int , int);
void quicksort(void *v[], int left, int right,	       int (*comp) (void *, void *)){  int i, last;  void swap(void *v[], int , int);  if(left >= right) /*do nothing if array contains */    return;         /*fewer than two elements*/    swap(v, left, (left+right)/2);  last = left;  for(i=left+1; i<=right; i++)    if((*comp)(v[i], v[left])<0)      swap(v, ++last, i);  swap(v, left, last);  quicksort(v, left, last-1, comp);  quicksort(v, last+1, right, comp);}