diff --git a/day4.ml b/day4.ml
index 49a1ebf..99aecaf 100644
--- a/day4.ml
+++ b/day4.ml
@@ -79,13 +79,15 @@ let%test_module _ = (module struct
 end)
 
 
-
-let main1 file =
-  let sets = chunk_input file |> List.map field_keys in
-  let len_all = List.length sets in
-  let len_valid = List.(length (filter valid_set sets)) in
+let main' make valid file =
+  let items = chunk_input file |> List.map make in
+  let len_all = List.length items in
+  let len_valid = List.(length (filter valid items)) in
   Printf.printf "%d valid out of %d\n" len_valid len_all
 
+
+let main1 = main' field_keys valid_set
+
 let%expect_test "part 1" =
   main1 "../../data/day4";
   [%expect{| 233 valid out of 288 |}]
@@ -223,11 +225,7 @@ let%test_module _ = (module struct
 end)
 
 
-let main2 file =
-  let maps = chunk_input file |> List.map fields in
-  let len_all = List.length maps in
-  let len_valid = List.(length (filter valid_map maps)) in
-  Printf.printf "%d valid out of %d\n" len_valid len_all
+let main2 = main' fields valid_map
 
 let%expect_test _ =
   main2 "../../data/day4";