anchor.diff:  
   let leer nomarch = seq {
       use fr = new StreamReader(new FileStream(nomarch, FileMode.Open, FileAccess.Read, FileShare.Read, BUF_SIZE))
  +    let mutable nl = 0
       while not fr.EndOfStream do 
  -        yield fr.ReadLine()
  +        yield (nl, fr.ReadLine())
  +        nl <- nl + 1
   }
   
   let escribir nomarch (lineas : string seq) =
  
positive.code:         p <- p + TAM_PERIODO
  }
      
      
  let ordenar_periodos (linea:string) = 
      let periodos = separar_periodos linea |> Seq.distinct |> Seq.toList  
  
      let len = Seq.length periodos
      if len = 0 then "N".PadRight(TAM_VECTOR+1)
      else if len > ELEMENTOS_VECTOR then "S".PadRight(TAM_VECTOR+1)
      else ("D" + (periodos |> Seq.sortDescending |> String.Concat)).PadRight(TAM_VECTOR+1)
  
  
  let filtrar_linea n (linea : string)=
      if String.length linea <> LARGO_LINEA then 
          printfn "error en linea: %d" n
          linea
  
negative.code: 
  
  let procesar_vectores entrada salida =
     leer entrada |> Seq.map filtrar_linea |> escribir salida
  
  [<EntryPoint>]
  let main(argv: string[]) = 
  