/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
void traverse(link h, void (*visit)(link))
  {
    QUEUEinit(max); QUEUEput(h);
    while (!QUEUEempty())
      {
        (*visit)(h = QUEUEget());
        if (h->l != NULL) QUEUEput(h->l); 
        if (h->r != NULL) QUEUEput(h->r); 
      }
  }