Need help regarding Async and fsi

Question

I\'d like to write some code that runs a sequence of F# scripts (.fsx). The thing is that I could have literally hundreds of scripts and if I do that:

let sh         


        

Answer 1

It is possible to simplify version of Subject from blogpost. instead of returning imitation of event, getSubject can return workflow.

Result workflow itself is state machine with two states 1. Event wasn't triggered yet: all pending listeners should be registered 2. Value is already set, listener is served immediately In code it will appear like this:

type SubjectState<'T> = Listen of ('T -> unit) list | Value of 'T

getSubject implementation is trivial

let getSubject (e : IEvent<_, _>) = 
    let state = ref (Listen [])
    let switchState v = 
        let listeners = 
            lock state (fun () ->
                match !state with
                | Listen ls -> 
                    state := Value v 
                    ls
                | _ -> failwith "Value is set twice"
            )
        for l in listeners do l v

    Async.StartWithContinuations(
        Async.AwaitEvent e,
        switchState,
        ignore,
        ignore
    )

Async.FromContinuations(fun (cont, _, _) ->
    let ok, v = lock state (fun () ->
        match !state with
        | Listen ls ->
            state := Listen (cont::ls)
            false, Unchecked.defaultof<_>
        | Value v ->
            true, v
        )
    if ok then cont v
    )