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-rw-r--r--lib/future.ml9
1 files changed, 9 insertions, 0 deletions
diff --git a/lib/future.ml b/lib/future.ml
index 6001da30d7..c1fb176df6 100644
--- a/lib/future.ml
+++ b/lib/future.ml
@@ -47,6 +47,10 @@ let is_val x = match !x with
| Val _ -> true
| Exn _ | Closure _ | Delegated | Dropped -> false
+let is_exn x = match !x with
+ | Exn _ -> true
+ | Val _ | Closure _ | Delegated | Dropped -> false
+
let peek_val x = match !x with
| Val (v, _) -> Some v
| Exn _ | Closure _ | Delegated | Dropped -> None
@@ -103,6 +107,11 @@ let chain ?(id="none") ?(pure=false) c f = ref (match !c with
let create_here f = chain ~pure:false (from_here ()) f
+let replace x y =
+ match !x with
+ | Exn _ -> x := Closure (fun () -> force ~pure:false y)
+ | _ -> Errors.anomaly (Pp.str "Only Exn futures can be replaced")
+
let purify f x =
let state = !freeze () in
try