anchor.diff:          // Preconditions
           //assert (AvlTree.AvlInvariant l)
           //assert (AvlTree.AvlInvariant r)
  -        assert (AvlTree.Height l <= AvlTree.Height r + balanceTolerance)
  +        //assert (AvlTree.Height l <= AvlTree.Height r + balanceTolerance)
   
           if AvlTree.Height l = AvlTree.Height r + balanceTolerance then
               match l with
  
positive.code:             when streamHeight > inputHeight ->
              union stream input
          | _, _ ->
              #if DEBUG
              let inputCount = count input
              let streamCount = count stream
              /// The minimum possible number of elements in the resulting set.
              let minPossibleResultCount =
                  max inputCount streamCount
              /// The maximum possible number of elements in the resulting set.
              let maxPossibleResultCount =
                  inputCount + streamCount
              #endif
  
              let result =
                  let result, head', stream'' =
  
negative.code:         | _, Empty ->
              input
          | _, _ ->
  //            #if DEBUG
  //            /// The maximum possible number of elements in the resulting set.
  //            let maxPossibleResultCount = count input
  //            #endif
  
              let result, _, _ =
                  CharDiet.TryDeleteMin stream
                  ||> diffImpl input
              
  //            Debug.Assert (
  //                dietInvariant result,
  //                "The DIET invariant does not hold for the result.")
  //            Debug.Assert (
  //                intervalsDisjoint result,
  //                "The intervals in the DIET are not disjoint.")
  
  //            #if DEBUG
  //            let resultCount = count result
  //            Debug.Assert (
  //                resultCount <= maxPossibleResultCount,
  //                sprintf "The result set should not contain more than %i elements, but it contains %i elements."
  //                    maxPossibleResultCount resultCount)
  //            #endif
              result
  
      /// Applies the given accumulating function to all elements in a DIET.
  