format and where claude on fol

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/kernel/Generator.ml b/lib/kernel/Generator.ml
index b83de3b..a037b3d 100644
--- a/lib/kernel/Generator.ml
+++ b/lib/kernel/Generator.ml
@@ -53,3 +53,19 @@ class producer_cursor produce finally =
   end
 
 let cursor_of ?finally produce = new producer_cursor produce finally |> Protocols.Handle.make
+
+let filter keep cursor =
+  cursor_of
+    ~finally:(fun () -> Protocols.Handle.release cursor)
+    (fun ~yield ->
+      let open Utilities.Result in
+      let* scan = Protocols.Cursor.require cursor in
+      let rec pass () =
+        let* next = Protocols.Cursor.next scan in
+        match next with
+        | None -> Ok ()
+        | Some tuple ->
+            if keep tuple then yield tuple;
+            pass ()
+      in
+      pass () )