anchor.diff:      let empty : AvlTree<'T> = AvlTree.Empty
   
       /// Returns the height of an AVL tree's root node.
  -    let private ht (tree : AvlTree<'T>) =
  +    let inline height (tree : AvlTree<'T>) =
           match tree with
           | Empty -> 0u
           | Node (_,_,_,h) -> h
  
positive.code:         | Node (_,_,_,_) -> false
  
      /// Implementation. Returns the height of an AVL tree.
      let rec private heightRec (tree : AvlTree<'T>) cont =
          match tree with
          | Empty ->
              cont 0u
          | Node (_, l, r, _) ->
              heightRec l <| fun height_l ->
              heightRec r <| fun height_r ->
                  (max height_l height_r) + 1u
                  |> cont
  
      /// Returns the height of an AVL tree.
      let height (tree : AvlTree<'T>) =
          heightRec tree id
  
      /// Determines if an AVL tree is correctly formed.
      /// It isn't necessary to call this at run-time, though it may be useful for asserting
  
negative.code:     /// Creates an AVL tree whose root node holds the specified value
      /// and the specified left and right subtrees.
      let inline internal create value l (r : AvlTree<'T>) =
          Node (value, l, r, (max (height l) (height r)) + 1u)
  
      let rec private mkt_bal_l n l (r : AvlTree<'T>) =
          if height l = height r + 2u then
              match l with
              | Empty ->
                  failwith "mkt_bal_l"
              | Node (ln, ll, lr, _) ->
                  if height ll < height lr then
                      match lr with
                      | Empty ->
                          failwith "mkt_bal_l"
  