anchor.diff:  
           (Empty, source)
           ||> Array.fold (fun trie (key, value) ->
  -            PatriciaMap.Insert (uint32 key, value, trie))
  +            PatriciaMap.Add (uint32 key, value, trie))
   
       //
       static member OfMap (source : Map<int, 'T>) : PatriciaMap<'T> =
  
positive.code:         | Br (p, m, t0, t1) as t ->
              if matchPrefix (key, p, m) then
                  if zeroBit (key, m) then
                      let left = PatriciaMap.Insert (key, value, t0)
                      Br (p, m, left, t1)
                  else
                      let right = PatriciaMap.Insert (key, value, t1)
                      Br (p, m, t0, right)
              else
                  PatriciaMap.Join (key, Lf (key, value), p, t)
  
      /// Insert a binding (key-value pair) into a map, returning a new, updated map.
      static member private InsertOverwrite (key, value : 'T, map) =
          match map with
          | Empty ->
              Lf (key, value)
  
negative.code: 
          (Empty, source)
          ||> Map.fold (fun trie key value ->
              PatriciaMap.Add (uint32 key, value, trie))
  
      //
      member this.Iterate (action : int -> 'T -> unit) : unit =
  