CCList.Ref to help use references on lists

core/CCList.ml

@@ -510,6 +510,39 @@ module Zipper = struct
     | _, [] -> raise Not_found
 end
 
+(** {2 References on Lists} *)
+
+module Ref = struct
+  type 'a t = 'a list ref
+
+  let push l x = l := x :: !l
+
+  let pop l = match !l with
+    | [] -> None
+    | x::tail ->
+        l := tail;
+        Some x
+
+  let pop_exn l = match !l with
+    | [] -> failwith "CCList.Ref.pop_exn"
+    | x::tail ->
+        l := tail;
+        x
+
+  let create() = ref []
+
+  let clear l = l := []
+
+  let lift f l = f !l
+
+  let push_list r l =
+    r := List.rev_append l !r
+
+  (*$T
+    let l = Ref.create() in Ref.push l 1; Ref.push_list l [2;3]; !l = [3;2;1]
+  *)
+end
+
 (** {2 Monadic Operations} *)
 module type MONAD = sig
   type 'a t

core/CCList.mli

@@ -225,6 +225,34 @@ module Zipper : sig
       @raise Not_found if the zipper is at an end *)
 end
 
+(** {2 References on Lists}
+@since NEXT_RELEASE *)
+
+module Ref : sig
+  type 'a t = 'a list ref
+
+  val push : 'a t -> 'a -> unit
+
+  val pop : 'a t -> 'a option
+
+  val pop_exn : 'a t -> 'a
+  (** Unsafe version of {!pop}.
+      @raise Failure if the list is empty *)
+
+  val create : unit -> 'a t
+  (** Create a new list reference *)
+
+  val clear : _ t -> unit
+  (** Remove all elements *)
+
+  val lift : ('a list -> 'b) -> 'a t -> 'b
+  (** Apply a list function to the content *)
+
+  val push_list : 'a t -> 'a list -> unit
+  (** Add elements of the list at the beginning of the list ref. Elements
+      at the end of the list will be at the beginning of the list ref *)
+end
+
 (** {2 Monadic Operations} *)
 module type MONAD = sig
   type 'a t