Question

Consider the following definition

let test =
    Async.FromContinuations(
        fun (cont,econt,ccont) ->
            let rec inner () =
                async {
                    do printfn "looping..."
                    do! Async.Sleep 1000
                    return! inner ()
                }

            Async.Start(inner ())
            cont ())

Suppose I want to try the computation like so

let cts = new CancellationTokenSource ()
Async.Start(test, cts.Token)
cts.Cancel()

This will naturally not make the inner loop stop, since I have not passed the suitable cancellation token. Is there any way I can obtain the outer cancellation token through Async.FromContinuations? I could rewrite this using the async builder and Async.CancellationToken, but then I would lose the ability to pass continuations to the inner expression.

Answer 1

smth like this?

let test =
    async {
        let! ct = Async.CancellationToken
        return! Async.FromContinuations(
            fun (cont,econt,ccont) ->
                let rec inner () =
                    async {
                        do printfn "looping..."
                        do! Async.Sleep 1000
                        return! inner ()
                    }

                Async.Start(inner (), cancellationToken = ct)
                cont ())
    }
let cts = new CancellationTokenSource ()
Async.Start(test, cts.Token)
cts.CancelAfter(1000)