sig type 'a t = 'a CamlinternalLazy.t exception Undefined external force : 'a Lazy.t -> 'a = "%lazy_force" val force_val : 'a Lazy.t -> 'a val from_fun : (unit -> 'a) -> 'a Lazy.t val from_val : 'a -> 'a Lazy.t val is_val : 'a Lazy.t -> bool val lazy_from_fun : (unit -> 'a) -> 'a Lazy.t val lazy_from_val : 'a -> 'a Lazy.t val lazy_is_val : 'a Lazy.t -> bool end