functor (Ord : OrderedType) ->
sig
type key = Ord.t
type 'a t
val empty : 'a t
val is_empty : 'a t -> bool
val cardinal : 'a t -> int
val mem : key -> 'a t -> bool
val find : key -> 'a t -> 'a
val singleton : key -> 'a -> 'a t
val add : key -> 'a -> 'a t -> 'a t
val remove : key -> 'a t -> 'a t
val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
end