let string_of_list to_s list = 
  "[" ^ String.concat ", " (List.map to_s list) ^ "]"
let print_list to_s list = 
  print_newline (print_string (string_of_list to_s list))
let diff list = 
  List.map2 (-) (List.tl list) (List.rev (List.tl (List.rev list)))
let diff_rec list = 
  let rec aux acc = function
    | [] -> acc
    | _ :: [] -> acc
    | a :: (b :: _ as tail) -> aux (b - a :: acc) tail
  in
  List.rev (aux [] list)
let () = 
  let p = print_list string_of_int in
  p (diff [3;1;4;1;5;9;2;6;5]);
  p (diff_rec [3;1;4;1;5;9;2;6;5])
 

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