Module CCList.Ref
val push : 'a t -> 'a -> unitval pop : 'a t -> 'a optionval pop_exn : 'a t -> 'aUnsafe version of
pop.- raises Failure
 if the list is empty.
val create : unit -> 'a tCreate a new list reference.
val clear : _ t -> unitRemove all elements.
val lift : ('a list -> 'b) -> 'a t -> 'bApply a list function to the content.
val push_list : 'a t -> 'a list -> unitAdd 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.