Fix another list unurlification segfault bug; List.foldlMi

2 files changed, 15 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 =
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index 851d74bc..2a28d148 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -43,6 +43,9 @@ val exists : a ::: Type -> (a -> bool) -> t a -> bool
 val foldlM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type
              -> (a -> b -> m b) -> b -> t a -> m b
 
+val foldlMi : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type
+             -> (int -> a -> b -> m b) -> b -> t a -> m b
+
 val foldlMap : a ::: Type -> b ::: Type -> c ::: Type
                -> (a -> b -> c * b) -> b -> t a -> t c * b