F# mailboxes

mailbox_chat.fs

open System.Threading

type ChatMessage =
    | SendMessage of string
    | GetContent of AsyncReplyChannel<string list>


let agent = MailboxProcessor.Start(fun agent ->
    let rec loop (state : string list) = async {
        printfn "List length is now %d" state.Length
        let! msg = agent.Receive()
        match msg with
        | SendMessage text ->
            return! loop (text :: state)
        | GetContent reply ->
            reply.Reply state
            return! loop state
    }

    loop []
)

for i in [1..10] do
    Thread.Sleep 500
    SendMessage (sprintf "Dave %d" i) |> agent.Post

let reply = agent.PostAndReply GetContent

reply |> List.rev |> String.concat ", " |> printfn "Messages: %s"