diff --git a/src/day13.ml b/src/day13.ml
index ad9c1ad..ddd52c0 100644
--- a/src/day13.ml
+++ b/src/day13.ml
@@ -1,63 +1,60 @@
 open Containers
 
-type packet =
-  | I of int
-  | L of packet list
-[@@deriving show { with_path = false }]
+module Packet = struct
+  type t =
+    | I of int
+    | L of t list
+  [@@deriving show { with_path = false }]
 
-let packet_of_str line =
-  let open Angstrom in
-  let int =
-    take_while1 (function
-      | '0' .. '9' -> true
-      | _ -> false)
-    >>= fun s -> return @@ I (int_of_string s) <?> "int"
-  in
-  let packet =
-    fix (fun packet ->
-      let lb, rb = char '[', char ']' in
-      let delim = sep_by (char ',') in
-      let list = lb *> delim packet <* rb >>= fun p -> return @@ L p <?> "list" in
-      choice [ int; list ])
-    <?> "packet"
-  in
-  Result.get_or_failwith @@ parse_string ~consume:All packet line
-;;
+  let of_str line =
+    let open Angstrom in
+    let int =
+      take_while1 (function
+        | '0' .. '9' -> true
+        | _ -> false)
+      >>= fun s -> return @@ I (int_of_string s) <?> "int"
+    in
+    let packet =
+      fix (fun packet ->
+        let lb, delimited, rb = char '[', sep_by (char ','), char ']' in
+        let list = lb *> delimited packet <* rb >>= fun p -> return @@ L p <?> "list" in
+        choice [ int; list ])
+      <?> "packet"
+    in
+    Result.get_or_failwith @@ parse_string ~consume:All packet line
+  ;;
 
-let rec is_ordered a b =
-  match a, b with
-  | I a, I b -> Int.compare a b
-  | L a, L b -> List.compare is_ordered a b
-  | (I _ as a), (L _ as b) -> is_ordered (L [ a ]) b
-  | (L _ as a), (I _ as b) -> is_ordered a (L [ b ])
-;;
+  let rec compare a b =
+    match a, b with
+    | I a, I b -> Int.compare a b
+    | L a, L b -> List.compare compare a b
+    | (I _ as a), (L _ as b) -> compare (L [ a ]) b
+    | (L _ as a), (I _ as b) -> compare a (L [ b ])
+  ;;
+end
 
 let%expect_test "Day 13.1" =
-  let result =
-    Utils.lines_of_input 13
-    |> List.filter Fun.(not % String.is_empty)
-    |> List.map packet_of_str
-    |> List.chunks 2
-    |> List.mapi (fun i packets ->
-      match packets with
-      | [ a; b ] when is_ordered a b < 0 -> i + 1
-      | _ -> 0)
-    |> List.reduce_exn ( + )
-  in
-  Printf.printf "%i" result;
+  Utils.lines_of_input 13
+  |> List.filter Fun.(not % String.is_empty)
+  |> List.map Packet.of_str
+  |> List.chunks 2
+  |> List.mapi (fun i packets ->
+    match packets with
+    | [ a; b ] when Packet.compare a b < 0 -> i + 1
+    | _ -> 0)
+  |> List.reduce_exn ( + )
+  |> print_int;
   [%expect {| 6272 |}]
 ;;
 
 let%expect_test "Day 13.2" =
-  let result =
-    Utils.lines_of_input 13
-    |> List.filter Fun.(not % String.is_empty)
-    |> List.map (fun line -> false, packet_of_str line)
-    |> List.append [ true, packet_of_str "[[2]]"; true, packet_of_str "[[6]]" ]
-    |> List.sort (fun (_, a) (_, b) -> is_ordered a b)
-    |> List.mapi (fun i (is_divider, _) -> if is_divider then i + 1 else 1)
-    |> List.reduce_exn ( * )
-  in
-  Printf.printf "%i" result;
+  Utils.lines_of_input 13
+  |> List.filter Fun.(not % String.is_empty)
+  |> List.map (fun line -> false, Packet.of_str line)
+  |> List.append [ true, Packet.of_str "[[2]]"; true, Packet.of_str "[[6]]" ]
+  |> List.sort (fun (_, a) (_, b) -> Packet.compare a b)
+  |> List.mapi (fun i (is_divider, _) -> if is_divider then i + 1 else 1)
+  |> List.reduce_exn ( * )
+  |> print_int;
   [%expect {| 22288 |}]
 ;;