anchor.diff:  
     ///
     member private x.PutLength(newLength) =
  -    if x.IsDense then
  +    if isDense then
         
         while newLength < length do
           length <- length - 1u
  
positive.code:       sparse.GetAllIndexProperties(dict, length)
  
    ///
    member internal x.IsDense = 
      FSharp.Utils.notNull dense 
  
    ///
    member internal x.HasIndex(index:uint32) = 
      if index < length then
        if x.IsDense then 
          index < uint32 dense.Length && dense.[int index].HasValue
  
        else
  
negative.code:       base.Put(string index, value)
  
      else
        if isDense then
          let ii = int index
          let denseLength = uint32 dense.Length
  
  