Fix another list unurlification segfault bug; List.foldlMi

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 35440de2..6a754287 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -255,6 +255,18 @@ fun foldlM [m] (_ : monad m) [a] [b] f =
         foldlM'
     end
 
+fun foldlMi [m] (_ : monad m) [a] [b] f =
+    let
+        fun foldlMi' i acc ls =
+            case ls of
+                [] => return acc
+              | x :: ls =>
+                acc <- f i x acc;
+                foldlMi' (i + 1) acc ls
+    in
+        foldlMi' 0
+    end
+
 fun all [m] f =
     let
         fun all' ls =