anchor.diff:  module internal Constants =
       //
       let [<Literal>] defaultStackCapacity = 16
  +    //
  +    let [<Literal>] balanceTolerance = 2u   //1u
   
   
   (*  NOTE :  The core functions implementing the AVL tree algorithm were extracted into OCaml
  
positive.code:                         t2r)
              | _ -> failwith "rebalance"
  
          elif t1h > t2h + 2u then // left is heavier than right
              match t1 with
              | Node (t1l, t1r, t1k, _) ->
                  // one of the nodes must have height > height t2 + 1
  
negative.code:         | _, Empty ->
              AvlTree.Insert (comparer, l, root)
          | Node (ll, lr, lx, lh), Node (rl, rr, rx, rh) ->
              if lh > rh + balanceTolerance then
                  AvlTree.Balance (comparer, ll, AvlTree.Join comparer root lr r, lx)
              else if rh > lh + balanceTolerance then
                  AvlTree.Balance (comparer, AvlTree.Join comparer root l rl, rr, rx)
              else
                  AvlTree.Create (root, l, r)
  