/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
#define leaf(A) (((A)->l == z) && ((A)->r == z))
Item searchR(link h, Key v, int w)
  { Key t = key(h->item);
    if (h == z) return NULLitem;
    if (leaf(h))
      return eq(v, t) ? h->item : NULLitem;
    if (bit(v, w) == 0)
         return searchR(h->l, v, w+1);
    else return searchR(h->r, v, w+1);
  }
Item STsearch(Key v) 
  { return searchR(head, v, 0); }