/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
Item search(int l, int r, Key v)
  { int m = (l+r)/2;
    if (l > r) return NULLitem;
    if eq(v, key(st[m])) return st[m];
    if (l == r) return NULLitem;
    if less(v, key(st[m])) 
         return search(l, m-1, v);
    else return search(m+1, r, v);
  }
Item STsearch(Key v)
  { return search(0, N-1, v); }