anchor.diff:          let result = CharDiet.remove value charSet.Tree
           //assert (CharDiet.dietInvariant result)
           //assert (CharDiet.intervalsDisjoint result)
  -        if charSet.Tree === result then charSet
  +        if charSet.Tree == result then charSet
           else CharSet (result)
   
       //
  
positive.code:                 let l' = AvlTree.Insert (comparer, l, value)
  
                  // Only rebalance the tree if an element was actually inserted.
                  if l' === l then tree
                  else AvlTree.mkt_bal_l (n, l', r)
              else
                  // x > n
                  let r' = AvlTree.Insert (comparer, r, value)
                  
                  // Only rebalance the tree if an element was actually inserted.
                  if r' === r then tree
                  else AvlTree.mkt_bal_r (n, l, r')
  
      /// Counts the number of elements in the tree.
  
negative.code:         let result = CharDiet.add value charSet.Tree
          //assert (CharDiet.dietInvariant result)
          //assert (CharDiet.intervalsDisjoint result)
          if charSet.Tree == result then charSet
          else CharSet (result)
  
      //
  