Oxford comma

let rec oxford (l : string list) : string =
	match l with
	| [] -> ""
	| x :: [] -> x
	| x :: y :: [] -> x ^ ", and " ^ y
	| x :: tl -> x ^ ", " ^ oxford tl

let () =
    print_endline @@ oxford [];
    print_endline @@ oxford ["a"];
    print_endline @@ oxford ["a"; "b"];
    print_endline @@ oxford ["a"; "b"; "c"]