let chunk list =
    let rec aux current acc = function
      | [] -> []
      | [x] -> (x :: current) :: acc
      | a :: (b :: _ as t) ->
         if a = b then aux (a :: current) acc t
         else aux [] ((a :: current) :: acc) t in
    List.rev (aux [] [] list);;
let inspect to_s list = "["  ^ String.concat ";" (List.map to_s list) ^ "]";;
let p to_s list = print_string (inspect to_s list);print_string "\n";;
let roym list = List.map List.hd (chunk list);;
let a = [1;1;2;2;3;3;3;1];;
let pi = p string_of_int;;
let () = pi a;;
let () = pi (roym a);;
 

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