1 files changed, 20 insertions, 0 deletions
diff --git a/src/map-editor/src/Util/List.elm b/src/map-editor/src/Util/List.elm
index 2bc5217..1f914b1 100644
--- a/src/map-editor/src/Util/List.elm
+++ b/src/map-editor/src/Util/List.elm
@@ -14,3 +14,23 @@ pop l =
 get_first : (a -> Bool) -> (List a) -> (Maybe a)
 get_first fun list =
    (List.head (List.filter fun list))
+
+product_map : (a -> b -> c) -> (List a) -> (List b) -> (List c)
+product_map product_fun list_a list_b =
+   (product_map_rec (product_fun) list_a list_b [])
+
+product_map_rec : (a -> b -> c) -> (List a) -> (List b) -> (List c) -> (List c)
+product_map_rec product_fun list_a list_b result =
+   case (pop list_a) of
+      Nothing -> result
+      (Just (head, tail)) ->
+         (product_map_rec
+            (product_fun)
+            tail
+            list_b
+            (List.append
+               (List.map (product_fun head) list_b)
+               result
+            )
+         )
+