[PoC] Use async with the savvy framework

This repository is an experiment to use ALTREP to wrap async with the power of my savvy framework.

Implementation

This function returns c(1L, 2L, 3L) after sleeping for 3 seconds.

async fn vec_i32_async() -> Vec<i32> {
    async {
        Timer::after(std::time::Duration::from_secs(3)).await;
        vec![1, 2, 3]
    }
    .await
}

// ...snip...

/// @export
#[savvy]
fn sleepy_vec() -> savvy::Result<savvy::Sexp> {
    let f = smol::spawn(vec_i32_async());
    SleepyVec {
        future: Box::pin(f),
        result: None,
    }
    .into_altrep()
}

Behavior

library(savvyAsyncPoC)

x <- sleepy_vec()

# While I'm waiting for 1 second, the task is executed in background.
Sys.sleep(1)

# It takes 3 seconds to finish the task, and 1 second has passed.
# So, this should take about 2 seconds.
system.time(x[1])
#>    user  system elapsed 
#>    0.00    0.00    1.95

# After that, the result is cached.
system.time(sum(x))
#>    user  system elapsed 
#>       0       0       0