sig
type key = pred
type 'a t
val is_empty : 'a t -> bool
val empty : 'a t
val add : key -> 'a -> 'a t -> 'a t
val mem : key -> 'a t -> bool
val find : key -> 'a t -> 'a
val remove : key -> 'a t -> 'a t
val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
val iter : (key -> 'a -> unit) -> 'a t -> unit
val map : (key -> 'a -> 'b) -> 'a t -> 'b t
val mapf : (key -> 'a -> 'b option) -> 'a t -> 'b t
val mapq : (key -> 'a -> 'a option) -> 'a t -> 'a t
val filter : (key -> 'a -> bool) -> 'a t -> 'a t
val partition : (key -> 'a -> bool) -> 'a t -> 'a t * 'a t
val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
val union : (key -> 'a -> 'a -> 'a) -> 'a t -> 'a t -> 'a t
val inter : (key -> 'a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
val interf : (key -> 'a -> 'b -> 'c option) -> 'a t -> 'b t -> 'c t
val interq : (key -> 'a -> 'a -> 'a option) -> 'a t -> 'a t -> 'a t
val diffq : (key -> 'a -> 'a -> 'a option) -> 'a t -> 'a t -> 'a t
val merge :
(key -> 'a option -> 'b option -> 'c option) -> 'a t -> 'b t -> 'c t
val insert : (key -> 'a -> 'a -> 'a) -> key -> 'a -> 'a t -> 'a t
val change :
(key -> 'b -> 'a option -> 'a option) -> key -> 'b -> 'a t -> 'a t
end