10.6.1 Starting at the First Node

To find the first (least) item in the tree, we just descend all the way to the left, as usual. In an RTBST, as in a BST, this involves checking for null pointers.

396. <RTBST traverser first initializer 396> =
void *
rtbst_t_first (struct rtbst_traverser *trav, struct rtbst_table *tree) 
{
  assert (tree != NULL && trav != NULL);

  trav->rtbst_table = tree;
  trav->rtbst_node = tree->rtbst_root;
  if (trav->rtbst_node != NULL) 
    {
      while (trav->rtbst_node->rtbst_link[0] != NULL)
        trav->rtbst_node = trav->rtbst_node->rtbst_link[0];
      return trav->rtbst_node->rtbst_data;
    }
  else 
    return NULL;
}

This code is included in 395.