Roadtype section = {enter : int;hold : int;leave : int;curve : Playground.number;hill : Playground.number;}val straight : int -> sectionval curve : int -> Playground.number -> sectionval hill : int -> Playground.number -> sectionval curve_hill : int -> Playground.number -> Playground.number -> sectionval coast : section listtype segment = {index : int;y1 : Playground.number;y2 : Playground.number;curve : Playground.number;}val build : Playground.number -> section list -> tval length : t -> Playground.numberval segment_at : t -> Playground.number -> segmenttype point = {x : Playground.number;y : Playground.number;z : Playground.number;heading : Playground.number;}val centerline : Playground.number -> t -> point array