1 files changed, 9 insertions, 0 deletions
diff --git a/my_list.mli b/my_list.mli
index 4644a74..329efba 100644
--- a/my_list.mli
+++ b/my_list.mli
@@ -75,3 +75,12 @@ let rev_append l1 l2 =
 let rec flatten = function
     | Item(hd, tl) -> append hd (flatten tl)
     | None -> None
+
+(** Return true if the given elem is contained in the given list. *)
+let rec mem elem = function
+    | Item(hd, tl) -> (
+        match hd = elem with
+        | true -> true
+        | false -> mem elem tl
+    )
+    | None -> false