Sourceval get_lane : lane:int -> k:int -> t -> bool Sourceval get_right_of_lane : lane:int -> k:int -> m:int -> t -> bool Sourceval get_left_of_lane : lane:int -> k:int -> m:int -> t -> bool Sourceval pos_fold : f:(int -> 'a -> 'a) -> init:'a -> int -> 'a