/* BST traverser structure. */
struct bst_traverser
  {
    struct bst_table *bst_table;        /* Tree being traversed. */
    struct bst_node *bst_node;          /* Current node in tree. */
    struct bst_node *bst_stack[BST_MAX_HEIGHT];
                                        /* All the nodes above |bst_node|. */
    size_t bst_height;                  /* Number of nodes in |bst_parent|. */
    unsigned long bst_generation;       /* Generation number. */
  };