- : unit = ()
type ('a, 'container) iterator = ('a -> unit) -> 'container -> unit
type 'a generator = unit -> 'a option
type ('a, 'container) iter2gen =
    ('a, 'container) iterator -> 'container -> 'a generator
type _ Stdlib.Effect.t += Hold : unit Effect.t
val iter2gen : (int, 'a) iter2gen = <fun>
val f : unit -> unit = <fun>
Hold 1
1
Hold 2
Exception: Stdlib.Effect.Continuation_already_resumed.