Batteries_uni.Ref

`sig
type 'a t = 'a ref
external ref : 'a -> 'a ref = "%makemutable"
external ( ! ) : 'a ref -> 'a = "%field0"
external ( := ) : 'a ref -> 'a -> unit = "%setfield0"
external set : 'a ref -> 'a -> unit = "%setfield0"
external get : 'a ref -> 'a = "%field0"
val copy : 'a ref -> 'a ref
val pre : 'a ref -> ('a -> 'a) -> 'a
val post : 'a ref -> ('a -> 'a) -> 'a
val swap : 'a ref -> 'a ref -> unit
val post_incr : int ref -> int
val post_decr : int ref -> int
val pre_incr : int ref -> int
val pre_decr : int ref -> int
val protect : 'a ref -> 'a -> (unit -> 'b) -> 'b
val print :
('a BatInnerIO.output -> 'b -> unit) ->
'a BatInnerIO.output -> 'b t -> unit
end`