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//
// We've been using io.async() to launch tasks. But there's a
// stronger variant: io.concurrent().
//
// The difference:
//
// io.async():
// * The function MAY run on another thread, or it may run
// immediately on the current thread (synchronously).
// * Never fails — if no thread is available, it just runs
// the function right away.
// * More portable, works with all Io backends.
//
// io.concurrent():
// * GUARANTEES a separate unit of concurrency (a real thread
// in the Threaded backend).
// * Can fail with error.ConcurrencyUnavailable if resources
// are exhausted or the backend doesn't support it.
// * Use when you NEED true parallelism.
//
// Because concurrent() can fail, you must handle the error:
//
// var future = try io.concurrent(myFn, .{args});
// const result = future.await(io);
//
// Notice the 'try' — that's the key difference in usage!
//
// Fix this program to launch the computation concurrently.
//
const std = @import("std");
const print = std.debug.print;
pub fn main(init: std.process.Init) !void {
const io = init.io;
// Launch with a guaranteed separate thread.
// Which Io method guarantees true concurrency?
// (Hint: unlike io.async, this one can fail!)
var future = try io.???(compute, .{io});
print("Main thread continues...\n", .{});
// Wait 100 millisecond so the output order is deterministic.
io.sleep(std.Io.Duration.fromMilliseconds(100), .awake) catch {};
print("Main thread done waiting.\n", .{});
const result = future.await(io);
print("Result: {}\n", .{result});
}
fn compute(io: std.Io) u32 {
print("Computing on a separate thread!\n", .{});
// Simulate some work.
io.sleep(std.Io.Duration.fromMilliseconds(200), .awake) catch return 0;
return 123;
}
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