List.searchM and ListPair.unzip

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 10877420..b38097b7 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -293,6 +293,20 @@ fun search [a] [b] f =
         search'
     end
 
+fun searchM [m] (_ : monad m) [a] [b] f =
+    let
+        fun search' ls =
+            case ls of
+                [] => return None
+              | x :: ls =>
+                o <- f x;
+                case o of
+                    None => search' ls
+                  | v => return v
+    in
+        search'
+    end
+
 fun foldlM [m] (_ : monad m) [a] [b] f =
     let
         fun foldlM' acc ls =