let print_gradelist_txt (hpr : string -> unit) (gl:student list) (padd:paddress) =
(* Print all grades *)
List.iter (fun stu ->
let gra = student_grade stu padd in
let sra = (if (gra >=0.) then (Printf.sprintf "%.1f" gra) else "") in
hpr (Printf.sprintf "%s\t%s\t%s\n" stu.name stu.pren sra)) gl