module Ivar: sig .. end
Ivars are like write-once refs. They are initially undetermined, but you
can fill them. They are useful for creating Deferreds that you can
determine whenever you want.
type 'a t
val create : unit -> 'a t
Create a new unfilled Ivar.t
val read : 'a t -> 'a Deferred.t
read iv returns the Deferred.t associated with iv. This deferred
becomes determined when the Ivar is filled.
val fill : 'a t -> 'a -> unit
Fill the given Ivar.t. Raises an exception if the Ivar is already full.
val fill_if_empty : 'a t -> 'a -> unit
Fill the given Ivar.t. Does nothing if the Ivar is already full.
val is_full : 'a t -> bool
Return true if the Ivar.t is full.
val is_empty : 'a t -> bool
Return true if the Ivar.t is empty.