8.1 Data Types

The TAVL node structure takes the basic fields for a BST and adds a balance factor for AVL balancing and a pair of tag fields to allow for threading.

301. <TAVL node structure 301> =
/* Characterizes a link as a child pointer or a thread. */
enum tavl_tag 
  {
    TAVL_CHILD,                     /* Child pointer. */
    TAVL_THREAD                     /* Thread. */
  };

/* An TAVL tree node. */
struct tavl_node 
  {
    struct tavl_node *tavl_link[2]; /* Subtrees. */
    void *tavl_data;                /* Pointer to data. */
    unsigned char tavl_tag[2];      /* Tag fields. */
    signed char tavl_balance;       /* Balance factor. */
  };

This code is included in 299.

Exercises:

1. struct avl_node contains three pointer members and a single character member, whereas struct tavl_node additionally contains an array of two characters. Is struct tavl_node necessarily larger than struct avl_node? [answer]