F Sharp (programming language): Difference between revisions

Revision as of 11:52, 15 January 2024

Revision as of 12:18, 15 January 2024

Line 539:

===Agent programming===

F# supports a variation of the [[Actor model|Actor]] programming model through the in-memory implementation of lightweight asynchronous agents. For example, the following code defines an agent and posts 2 messages:

<syntaxhighlight lang="fsharp">

type Message =

let counter =

| Enqueue of string

MailboxProcessor.Start(fun inbox ->

| Dequeue of AsyncReplyChannel<Option<string>>

let rec loop n =

async { do printfn "n = %d, waiting..." n

// Provides threads concurrent access to a list of strings

let! msg = inbox.Receive()

let listManager = MailboxProcessor.Start(fun inbox ->

return! loop(n+msg) }

looplet 0)rec messageLoop list = async {

let! msg = inbox.Receive()

match msg with

| Enqueue item ->

return! messageLoop (item :: list)

| Dequeue replyChannel ->

match list with

| [] ->

replyChannel.Reply None

return! loop(n+msg)messageLoop }list

| head :: tail ->

replyChannel.Reply (Some head)

return! messageLoop tail

}

// Start the loop with an empty list

messageLoop []

)

// Usage

async {

// Enqueue some strings

listManager.Post(Enqueue "Hello")

listManager.Post(Enqueue "World")

// Dequeue and process the strings

let! str = listManager.PostAndAsyncReply(Dequeue)

str |> Option.iter (printfn "Dequeued: %s")

}

|> Async.Start

</syntaxhighlight>