add CCFQueue.rev

src/data/CCFQueue.ml

@@ -371,6 +371,16 @@ let of_seq seq =
     Sequence.of_list l |> of_seq |> to_list = l)
 *)
 
+let rev q =
+  let q' = ref empty in
+  iter (fun x -> q' := cons x !q') q;
+  !q'
+
+(*$Q
+  (Q.list Q.int) (fun l -> \
+    of_list l |> rev |> to_list = List.rev l)
+*)
+
 let _nil () = `Nil
 let _single x cont () = `Cons (x, cont)
 let _double x y cont () = `Cons (x, _single y cont)

src/data/CCFQueue.mli

@@ -110,6 +110,10 @@ val append : 'a t -> 'a t -> 'a t
       after elements of the first one.
       Linear in the size of the second queue. *)
 
+val rev : 'a t -> 'a t
+(** Reverse the queue, O(n) complexity
+    @since NEXT_RELEASE *)
+
 val map : ('a -> 'b) -> 'a t -> 'b t
 (** Map values *)
 
@@ -131,6 +135,7 @@ val of_list : 'a list -> 'a t
 val to_list : 'a t -> 'a list
 
 val add_seq_front : 'a sequence -> 'a t -> 'a t
+
 val add_seq_back : 'a t -> 'a sequence -> 'a t
 
 val to_seq : 'a t -> 'a sequence