1 files changed, 28 insertions, 0 deletions
diff --git a/ocaml/lib/year2025/day01/part02/turner.ml b/ocaml/lib/year2025/day01/part02/turner.ml
new file mode 100644
index 0000000..7477093
--- /dev/null
+++ b/ocaml/lib/year2025/day01/part02/turner.ml
@@ -0,0 +1,28 @@
+open Dial
+
+module Turner : sig
+  val turn : Dial.t -> int -> Dial.direction -> Dial.t * int
+  (** [turn dial direction] is the new state of the dial after turning [direction] on [dial] *)
+end = struct
+  (** [turn dial direction] is the new state of the dial after turning [direction] on [dial].
+      Raises: [dial_out_of_range] if the dial is moved to an invalid state. *)
+  let rec turn dial zero_count direction =
+    let open Dial in
+    match direction with
+    | Left 0 ->
+        (dial, zero_count)
+    | Left n ->
+        let dial' = prev dial in
+        let zero_count' =
+          if Dial.is_zero dial' then zero_count + 1 else zero_count
+        in
+        turn dial' zero_count' (Left (n - 1))
+    | Right 0 ->
+        (dial, zero_count)
+    | Right n ->
+        let dial' = next dial in
+        let zero_count' =
+          if Dial.is_zero dial' then zero_count + 1 else zero_count
+        in
+        turn dial' zero_count' (Right (n - 1))
+end