# Module Event

    module Event: sig .. end

First-class synchronous communication.

This module implements synchronous inter-thread communications over channels. As in John Reppy's Concurrent ML system, the communication events are first-class values: they can be built and combined independently before being offered for communication.

    type 'a channel

The type of communication channels carrying values of type `'a`.

    val new_channel : unit -> 'a channel

Return a new channel.

    type +'a event

The type of communication events returning a result of type `'a`.

    val send : 'a channel -> 'a -> unit event

`send ch v` returns the event consisting in sending the value `v` over the channel `ch`. The result value of this event is `()`.

    val receive : 'a channel -> 'a event

`receive ch` returns the event consisting in receiving a value from the channel `ch`. The result value of this event is the value received.

    val always : 'a -> 'a event

`always v` returns an event that is always ready for synchronization. The result value of this event is `v`.

    val choose : 'a event list -> 'a event

`choose evl` returns the event that is the alternative of all the events in the list `evl`.

    val wrap : 'a event -> ('a -> 'b) -> 'b event

`wrap ev fn` returns the event that performs the same communications as `ev`, then applies the post-processing function `fn` on the return value.

    val wrap_abort : 'a event -> (unit -> unit) -> 'a event

`wrap_abort ev fn` returns the event that performs the same communications as `ev`, but if it is not selected the function `fn` is called after the synchronization.

    val guard : (unit -> 'a event) -> 'a event

`guard fn` returns the event that, when synchronized, computes `fn()` and behaves as the resulting event. This enables computing events with side-effects at the time of the synchronization operation.

    val sync : 'a event -> 'a

'Synchronize' on an event: offer all the communication possibilities specified in the event to the outside world, and block until one of the communications succeed. The result value of that communication is returned.

    val select : 'a event list -> 'a

'Synchronize' on an alternative of events. `select evl` is shorthand for `sync(choose evl)`.

    val poll : 'a event -> 'a option

Non-blocking version of `Event.sync`: offer all the communication possibilities specified in the event to the outside world, and if one can take place immediately, perform it and return `Some r` where `r` is the result value of that communication. Otherwise, return `None` without blocking.