List.Lazy
type 'a t =
| Nil
| Cons of 'a * 'a t lazy_t
val map : f:('a -> 'b) -> 'a t -> 'b t
val to_strict : 'a t -> 'a t
val unfold : ('a -> 'a option) -> 'a -> 'a t
val filter_map : f:('a -> 'b option) -> 'a t -> 'b t