add a few functions to CCPersistentArray

src/data/CCPersistentArray.ml

@@ -80,3 +80,13 @@ let of_array a = init (Array.length a) (fun i -> a.(i))
 let to_list t = Array.to_list (reroot t)
 let of_list l = ref (Array (Array.of_list l))
 
+type 'a sequence = ('a -> unit) -> unit
+
+let to_seq a yield = iter yield a
+
+let of_seq seq =
+  let l = ref [] in
+  seq (fun x -> l := x :: !l);
+  of_list (List.rev !l)
+
+

src/data/CCPersistentArray.mli

@@ -96,4 +96,10 @@ val to_list : 'a t -> 'a list
 val of_list : 'a list -> 'a t
 (** [of_list l] returns a fresh persistent array containing the elements of [l]. *)
 
+type 'a sequence = ('a -> unit) -> unit
+
+val to_seq : 'a t -> 'a sequence
+
+val of_seq : 'a sequence -> 'a t
+