feat: add Fut.for_list

src/fut.ml

@@ -318,6 +318,10 @@ let for_ ~on n f : unit t =
 let for_array ~on arr f : unit t =
   for_ ~on (Array.length arr) (fun i -> f i arr.(i))
 
+let for_list ~on l f : unit t =
+  let futs = List.rev_map (fun x -> spawn ~on (fun () -> f x)) l in
+  wait_list futs
+
 (* ### blocking ### *)
 
 let wait_block (self : 'a t) : 'a or_error =

src/fut.mli

@@ -141,6 +141,10 @@ val for_array : on:Pool.t -> 'a array -> (int -> 'a -> unit) -> unit t
     or fails if any of them fails.
     @since 0.2 *)
 
+val for_list : on:Pool.t -> 'a list -> ('a -> unit) -> unit t
+(** [for_list ~on l f] is like [for_array ~on (Array.of_list l) f].
+    @since 0.2 *)
+
 (** {2 Blocking} *)
 
 val wait_block : 'a t -> 'a or_error

test/t_futs1.ml

@@ -132,3 +132,14 @@ let () =
 let () =
   let x = [| Fut.return 1 |] |> Fut.join_array |> Fut.wait_block_exn in
   assert (x = [| 1 |])
+
+let () =
+  let run_for n =
+    let l = List.init n (fun x -> x) in
+    let sum = Atomic.make 0 in
+    Fut.for_list ~on:pool l (fun x -> ignore (Atomic.fetch_and_add sum x : int))
+    |> Fut.wait_block_exn;
+    assert (Atomic.get sum = List.fold_left ( + ) 0 l)
+  in
+
+  List.iter run_for [ 1; 10; 50; 1_000 ]