package current

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A monitor is an input pipeline stage that can watch for external events.

type 'a t

An 'a t is a monitor that outputs values of type 'a.

val create : read:(unit -> 'a or_error Lwt.t) -> watch:((unit -> unit) -> (unit -> unit Lwt.t) Lwt.t) -> pp:(Stdlib.Format.formatter -> unit) -> 'a t

create ~read ~watch ~pp is a monitor that uses read to read the current value of some external resource and watch to watch for changes. When the monitor is needed, it first calls watch refresh to start watching the resource. When this completes, it uses read () to read the current value. Whenever the watch thread calls refresh it marks the value as being out-of-date and will call read to get a new value. When the monitor is no longer required, it will call the shutdown function returned by watch to stop watching the resource. If it is needed later, it will run watch to start watching it again. This function takes care to perform only one user action (installing the watch, reading the value, or turning off the watch) at a time. For example, if refresh is called while already reading a value then it will wait for the current read to complete and then perform a second one.

val get : 'a t -> 'a Primitive.t

get t enables t and returns the primitive for it. When the primitive is released, the monitor will be disabled. Call this in your let> block.


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