anchor.diff:              model.Status <- "Opened File: " + path.Value
   
       member this.ParentPath (model: MainModel) =
  -        let path = model.Path
  +        let oldPath = model.Path
           this.OpenPath (fileSys.Parent model.Path) 0 model
  -        let index = model.Nodes |> Seq.tryFindIndex (fun n -> n.Path = path)
  -        match index with
  -            | Some i -> model.Cursor <- i
  +        match model.Nodes |> Seq.tryFindIndex (fun n -> n.Path = oldPath) with
  +            | Some index -> model.Cursor <- index
               | None -> ()
   
       member this.Back (model: MainModel) =
  
positive.code:             |> Seq.choose (fun (i, n) -> if predicate n then Some i else None)
              |> Seq.tryHead
          match firstMatch with
          | Some index -> this.SetCursor index model
          | None -> ()
  
      member this.OpenPath path cursor (model: MainModel) =
          try
  
negative.code: open System.Text.RegularExpressions
  
  type MainController(fileSys: IFileSystemService, settingsFactory: unit -> Mvc<SettingsEvents, SettingsModel>) =
      interface IController<MainEvents, MainModel> with
          member this.InitModel model =
              model.Path <- fileSys.Root
  