.TH "Event" 3 2024-05-31 OCamldoc "OCaml library"
.SH NAME
Event \- First-class synchronous communication.
.SH Module
Module   Event
.SH Documentation
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Module
.BI "Event"
 : 
.B sig end

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First\-class synchronous communication\&.
.sp
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\&.

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.sp
.sp
.I type 
.B 'a
.I channel 

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The type of communication channels carrying values of type 
.ft B
\&'a
.ft R
\&.

.sp

.I val new_channel 
: 
.B unit -> 'a channel
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Return a new channel\&.

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.I type 
.B +'a
.I event 

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The type of communication events returning a result of type 
.ft B
\&'a
.ft R
\&.

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.I val send 
: 
.B 'a channel -> 'a -> unit event
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.ft B
send ch v
.ft R
returns the event consisting in sending the value 
.ft B
v
.ft R
over the channel 
.ft B
ch
.ft R
\&. The result value of this event is 
.ft B
()
.ft R
\&.

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.I val receive 
: 
.B 'a channel -> 'a event
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.ft B
receive ch
.ft R
returns the event consisting in receiving a value
from the channel 
.ft B
ch
.ft R
\&. The result value of this event is the
value received\&.

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.I val always 
: 
.B 'a -> 'a event
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.ft B
always v
.ft R
returns an event that is always ready for
synchronization\&.  The result value of this event is 
.ft B
v
.ft R
\&.

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.I val choose 
: 
.B 'a event list -> 'a event
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.ft B
choose evl
.ft R
returns the event that is the alternative of
all the events in the list 
.ft B
evl
.ft R
\&.

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.I val wrap 
: 
.B 'a event -> ('a -> 'b) -> 'b event
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.ft B
wrap ev fn
.ft R
returns the event that performs the same communications
as 
.ft B
ev
.ft R
, then applies the post\-processing function 
.ft B
fn
.ft R
on the return value\&.

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.I val wrap_abort 
: 
.B 'a event -> (unit -> unit) -> 'a event
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.ft B
wrap_abort ev fn
.ft R
returns the event that performs
the same communications as 
.ft B
ev
.ft R
, but if it is not selected
the function 
.ft B
fn
.ft R
is called after the synchronization\&.

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.I val guard 
: 
.B (unit -> 'a event) -> 'a event
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.ft B
guard fn
.ft R
returns the event that, when synchronized, computes
.ft B
fn()
.ft R
and behaves as the resulting event\&. This enables
computing events with side\-effects at the time of the synchronization
operation\&.

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.I val sync 
: 
.B 'a event -> 'a
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\&'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\&.

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.I val select 
: 
.B 'a event list -> 'a
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\&'Synchronize\&' on an alternative of events\&.
.ft B
select evl
.ft R
is shorthand for 
.ft B
sync(choose evl)
.ft R
\&.

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.I val poll 
: 
.B 'a event -> 'a option
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Non\-blocking version of 
.ft B
Event\&.sync
.ft R
: offer all the communication
possibilities specified in the event to the outside world,
and if one can take place immediately, perform it and return
.ft B
Some r
.ft R
where 
.ft B
r
.ft R
is the result value of that communication\&.
Otherwise, return 
.ft B
None
.ft R
without blocking\&.

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