Functor Pqueue.Make

module Make: 
functor (Ord : OrderedType) -> S  with type elt = Ord.t

type elt 

type t 

val empty : t

val is_empty : t -> bool

val add : elt -> t -> t

val union : t -> t -> t

val find_min : t -> elt

val remove_min : t -> t

val size : t -> int

val fold : ('a -> elt -> 'a) -> 'a -> t -> 'a