`sig val find : f:('a -> bool) -> 'a BatLazyList.t -> 'a option val rfind : f:('a -> bool) -> 'a BatLazyList.t -> 'a option val findi : f:(int -> 'a -> bool) -> 'a BatLazyList.t -> (int * 'a) option val rfindi : f:(int -> 'a -> bool) -> 'a BatLazyList.t -> (int * 'a) option val split_at : int -> 'a BatLazyList.t -> [ `Invalid_index of int | `Ok of 'a BatLazyList.t * 'a BatLazyList.t ] val at : 'a BatLazyList.t -> int -> [ `Invalid_index of int | `Ok of 'a ] val assoc : 'a -> ('a * 'b) BatLazyList.t -> 'b option val assq : 'a -> ('a * 'b) BatLazyList.t -> 'b option end`