QueueExample | IDisposable

[mozesa]

Hello Paul,

first of all I would like to say Thank you for your enormous effort to keep it up.

I am at the beginning of my FP journey, so sorry for all the questions coming. 😃

Here is QueueExample from Samples in a bit modified version.

I have two issues:

• I wont see this line from _2 in Eff(fun(() => Console.WriteLine("I can't see this line"))), probably forked task never gets cancelled.
• I have an IDisposable object new TcpClient("127.0.0.1", 23), but I don't know how to use use (I tried, but it was already closed).

An additional question, in WriteToQueue I have to use ternary operator to check whether x is empty or not. Why the more elegant guard(notEmpty(x), Errors.Cancelled) is not work for me (Type arguments cannot be inferred...)?

Thanks for your help in advance.

Best Regards,
András

public class QueueExample<RT>
    where RT : struct,
    HasCancel<RT>,
    HasConsole<RT>
{
    public static Aff<RT, Unit> Main()
    {
        var queue = Queue<RT, string>();

        return
            from stream in Eff(() => new TcpClient("127.0.0.1", 23).GetStream())
            from c in fork(queue | WriteToClient(stream))
            from x in repeat(Console<RT>.readLines) | WriteToQueue(queue)
            from _2 in Eff(fun(() => Console.WriteLine("I can't see this line")))
            from _1 in c // cancels the forked task
            select unit;
    }

    private static Consumer<RT, string, Unit> WriteToQueue(Queue<RT, string, Unit> queue) =>
        from x in awaiting<string>()
        // from _ in guard(notEmpty(x), Errors.Cancelled) 
        from _ in notEmpty(x)
            ? queue.EnqueueEff(x)
            : FailEff<Unit>(Errors.Cancelled)
        select unit;

    private static Consumer<RT, string, Unit> WriteToClient(Stream stream) =>
        from l in awaiting<string>()
        from _1 in Console<RT>.writeLine(l)
        from _2 in Eff(fun(() => stream.Write(Encoding.ASCII.GetBytes(l))))
        select unit;
}