Module Xml.W type 'a tval return : 'a -> 'a ttype (-'a, 'b) ftval fmap : ('a, 'b) ft -> 'a t -> 'b ttype 'a tlistval nil : unit -> 'a tlistval singleton : 'a t -> 'a tlistval cons : 'a t -> 'a tlist -> 'a tlistval append : 'a tlist -> 'a tlist -> 'a tlistval map : ('a, 'b) ft -> 'a tlist -> 'b tlist