/* Recursively verify tree structure. */
size_t count;
int height;

recurse_verify_tree (tree->avl_root, &okay, &count,
                     0, INT_MAX, &height);
if (count != n)
  {
    printf (" Tree has %lu nodes, but should have %lu.\n",
            (unsigned long) count, (unsigned long) n);
    okay = 0;
  }
