setInterval in Rust

[alice]

Continuing the discussion from Is Rust getting it's message out?:

@ZiCog

Many thanks for that. But wow, it's likely to take me a year of study to grasp all of that!

Most of the complexity comes from the use of abortable from the futures crate. Hopefully this version without cancellation is easier to understand:

fn set_interval<F, Fut>(mut f: F, dur: Duration)
where
    F: Send + 'static + FnMut() -> Fut,
    Fut: Future<Output = ()> + Send + 'static,
{
    // Create stream of intervals.
    let mut interval = time::interval(dur);
    
    tokio::spawn(async move {
        // Skip the first tick at 0ms.
        interval.tick().await;
        loop {
            // Wait until next tick.
            interval.tick().await;
            // Spawn a task for this tick.
            tokio::spawn(f());
        }
    });
}

playground

[govardhangdg]

Any reason for using FnMut closure? The Fn closures work as well. It just felt oddly specific - using FnMut...

[alice]

Yes. All Fn closures are also FnMut, but there are FnMut closures that are not Fn. For example, a closure that contains an integer and increments it on each call is FnMut, but not Fn.