anchor.diff:              store.Resize 0n
   
           member x.Add(range : Range1l, view : BufferView) =
  -            lock x (fun () ->
  +            let mutable isNew = false
  +            let res = lock x (fun () ->
                   let count = range.Size + 1L
   
                   let writer = 
                       bufferWriters.GetOrCreate(view, fun view ->
  +                        isNew <- true
                           let remove w =
                               x.Dirty.Remove w |> ignore
                               bufferWriters.Remove view |> ignore
  
positive.code:                         store.Resize(Fun.NextPowerOfTwo(int64 min) |> nativeint)
                              
                      lock writer (fun () -> 
                          if writer.OutOfDate then
                              writer.Write(range)
                      )
  
  
                          
  
negative.code:                         writer.RemoveRef range |> ignore
                  }
              )
              if isNew then
                  transact (fun () -> x.MarkOutdated ())
              res
  
          member x.Set(range : Range1l, value : byte[]) =
              let count = range.Size + 1L
  