- Added function for updating dictionary.

1 files changed, 6 insertions, 0 deletions

diff --git a/stdlib/source/lux/data/coll/dictionary/ordered.lux b/stdlib/source/lux/data/coll/dictionary/ordered.lux
index 16412e648..aec44d943 100644
--- a/stdlib/source/lux/data/coll/dictionary/ordered.lux
+++ b/stdlib/source/lux/data/coll/dictionary/ordered.lux
@@ -519,6 +519,12 @@
       (set@ #root (#.Some (blacken root)) dict)
       )))
 
+(def: #export (update key transform dict)
+  (All [k v] (-> k (-> v v) (Dict k v) (Maybe (Dict k v))))
+  (do maybe.Monad<Maybe>
+    [old (get key dict)]
+    (wrap (put key (transform old) dict))))
+
 (def: #export (from-list Order<l> list)
   (All [k v] (-> (Order k) (List [k v]) (Dict k v)))
   (L/fold (function (_ [key value] dict)