anchor.diff:  
   type private Direction = FORWARD=0 | BACKWARD=1 | WANDERING=2
   
  -type MultiCursor private (_subcursors:IEnumerable<ICursor>) =
  +type MultiCursor private (_subcursors:seq<ICursor>) =
       let subcursors = List.ofSeq _subcursors
       let mutable cur:ICursor option = None
       let mutable dir = Direction.WANDERING
  
positive.code:         let sortfunc (a:ICursor) (b:ICursor) = b.KeyCompare(a.Key())
          find sortfunc
  
      static member Create(_subcursors:IEnumerable<ICursor>) :ICursor =
          upcast (MultiCursor _subcursors)
                 
      static member Create([<ParamArray>] _subcursors: ICursor[]) :ICursor =
  
negative.code: 
  open System
  open System.IO
  
  open Zumero.LSM
  
  