Difficulties with Ocaml. Lists

Question

I wrote this function which was supposed to give me the before last element of a list, but it doesn't work? Do you know why? thanks!

let rec exo1= match l with |List.length l = 0 or 1 -> failwith exo1 |List.length l > 2 -> List.tl l in exo1 l |List.length l = 2 -> List.hd l ;;

Answer 1

Try something like below.. I commented out the answer.

let rec exo1 lst =
match lst with
| [] -> failwith "List is too short!"
(*| (*the magic happens here*) -> (*ans*)*)
| hd::tl -> exo1 tl