Make length a tail-recursive function

Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/my_list.mli b/my_list.mli
index b21aa5d..9229064 100644
--- a/my_list.mli
+++ b/my_list.mli
@@ -3,9 +3,12 @@ type 'a my_list =
     | None
 
 (** Return the length (number of elements) of a given list. *)
-let rec length = function
-    | Item (_, tail) -> 1 + (length (tail))
-    | None -> 0
+let length my_list =
+    let rec aux l n =
+        match l with
+        | Item (_, tl) -> aux tl (n + 1)
+        | None -> n
+    in aux my_list 0
 
 (** Return the first element of the given list.
  * Raise [Failure "hd"] if the list is empty.