Module Ivar

A write-once cell that can be empty or full (i.e. hold a single value).

One can read an ivar to obtain a deferred that becomes determined when the ivar is filled. An ivar is similar to an 'a option ref, except it is an error to fill an already full ivar.


type 'a t = 'a Types.Ivar.t
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t
type 'a ivar = 'a t
include Core_kernel.Std.Invariant.S1 with type 'a t := 'a t
type 'a t
val invariant : 'a Invariant_intf.inv -> 'a t Invariant_intf.inv
val equal : 'a t -> 'a t -> bool

equal t t' is physical equality of t and t'.

val create : unit -> 'a t

create () returns an empty ivar, create_full, a full one.

val create_full : 'a -> 'a t
val fill : 'a t -> 'a -> unit

fill t v fills t with value v if t was empty. If t was full, fill raises an exception.

It is guaranteed that immediately after calling fill t, is_some (Deferred.peek (read t)).

val fill_if_empty : 'a t -> 'a -> unit

fill_if_empty t v fills t with v if t is currently empty. If t is full, then fill_if_empty does nothing.

val is_empty : 'a t -> bool

is_empty t returns true if t is empty

val is_full : 'a t -> bool

is_full t returns true if t is full

val read : 'a t -> 'a Deferred0.t

read t returns a deferred that becomes enabled with value v after the ivar is filled with v.

val peek : 'a t -> 'a option

peek t returns Some v iff t is full with value v.

val value_exn : 'a t -> 'a

value_exn t returns v if t is full with value v, and raises otherwise.