anchor.diff:      // TODO : This is an experimental version of count which is optimized for performance.
       // It should work, but we need to do some tests to be sure. Once we're confident it's correct
       // we'll remove the original 'Count' function and use this once instead.
  -    static member FastCount t =
  -        match t with
  +    static member FastCount (map : PatriciaMap<'T>) =
  +        match map with
           | Empty -> 0u
           | Lf (_,_) -> 1u
           | Br (_,_,_,_) as t ->
  
positive.code:             stack.Push t
  
              /// Recursively processes the tree using the mutable stack.
              let rec fastCount acc =
                  if stack.Count = 0 then acc
                  else
  
negative.code: 
          elements.ToArray ()
  
      // TODO
      // choose
      // exists
  