+ module type ResultSet =
+ sig
+ type t
+ val empty : t
+ val cons : Tree.t -> t -> t
+ val concat : t -> t -> t
+ val iter : (Tree.t -> unit) -> t -> unit
+ val fold : (Tree.t -> 'a -> 'a) -> t -> 'a -> 'a
+ val map : (Tree.t -> Tree.t) -> t -> t
+ val length : t -> int
+ end