Concurrency

Placeholder: Brief overview. For detailed specifications, see the concurrency specs.

No Function Coloring

Functions are just functions - no async/await split:

func fetch_user(id: u64) -> User {
    const response = try http_get(url)  // Pauses task, not thread
    return parse_user(response)
}

Spawning Tasks

func main() {
    with multitasking {
        const h = spawn { fetch_user(1) }
        const user = try h.join()
        println(user.name)
    }
}

Three spawn constructs:

• spawn { } - Green task (requires with multitasking)
• spawn_thread { } - Thread from pool (requires with threading)
• spawn_raw { } - Raw OS thread (no requirements)

Channels

with multitasking {
    const chan = Channel.buffered(10)

    spawn {
        try chan.sender.send(42)
    }.detach()

    const val = try chan.receiver.recv()
    println("Received: {}", val)
}

Channels transfer ownership - no shared mutable state between tasks.

Thread Pools

with threading(4) {
    const results = Vec.new()
    for i in 0..100 {
        const h = spawn_thread { compute(i) }
        try results.push(h)
    }

    for h in results {
        const val = try h.join()
        println(val)
    }
}

Next Steps

• Examples
• Formal async spec
• Formal sync spec