my ziglings
improvements for async-io
Chris Boesch
(Apr 5, 2026, 4:13 PM +0200)
5e474ea5
2acf1927
+17
-25
+11
-12
exercises/087_async3.zig
+11
-12
exercises/087_async3.zig
···
5
5
// them all. The Io backend may run them concurrently:
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//
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// var f1 = io.async(taskA, .{});
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+
// defer _ = f1.cancel(io);
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// var f2 = io.async(taskB, .{});
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-
//
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-
// // Both tasks may be running now!
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+
// defer _ = f2.cancel(io);
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// const a = f1.await(io);
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// const b = f2.await(io);
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//
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-
// There's also io.concurrent() which provides a STRONGER guarantee:
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-
// it ensures the function gets its own unit of concurrency (e.g. a
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-
// real OS thread). But it can fail with error.ConcurrencyUnavailable
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-
// if resources are exhausted.
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-
//
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// io.async() is more portable: if no thread is available, it simply
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-
// runs the function synchronously. This makes it the right default
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-
// for most code.
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+
// Notice the defer pattern: each async call is immediately
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+
// followed by a defer cancel. This ensures cleanup even if
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+
// we return early or hit an error before reaching await.
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+
// Since await/cancel are idempotent, the defer is harmless
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+
// if we've already awaited.
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//
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// Fix this program to launch both tasks and collect their results.
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//
···
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const io = init.io;
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// Launch both tasks asynchronously.
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-
var future_a = io.async(slowAdd, .{ 10, 20 });
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+
var future_a = io.async(slowAdd, .{ 1, 2 });
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+
defer _ = future_a.cancel(io);
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var future_b = ???(slowMul, .{ 6, 7 });
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+
defer _ = future_b.cancel(io);
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// Await both results.
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const sum = future_a.await(io);
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-
const product = future_b.???(io);
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+
const product = future_b.await(io);
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print("{} + {} = {}\n", .{ 1, 2, sum });
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print("{} * {} = {}\n", .{ 6, 7, product });
+6
-13
patches/patches/087_async3.patch
+6
-13
patches/patches/087_async3.patch
···
1
-
--- exercises/087_async3.zig 2026-04-01 22:51:05.540094851 +0200
2
-
+++ answers/087_async3.zig 2026-04-01 22:50:44.579669189 +0200
3
-
@@ -29,12 +29,12 @@
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-
const io = init.io;
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-
1
+
--- exercises/087_async3.zig 2026-04-05 16:12:48.317265515 +0200
2
+
+++ answers/087_async3.zig 2026-04-05 16:12:52.269343030 +0200
3
+
@@ -28,7 +28,7 @@
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4
// Launch both tasks asynchronously.
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-
- var future_a = io.async(slowAdd, .{ 10, 20 });
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+
var future_a = io.async(slowAdd, .{ 1, 2 });
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+
defer _ = future_a.cancel(io);
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7
- var future_b = ???(slowMul, .{ 6, 7 });
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-
+ var future_a = io.async(slowAdd, .{ 1, 2 });
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8
+ var future_b = io.async(slowMul, .{ 6, 7 });
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+
defer _ = future_b.cancel(io);
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// Await both results.
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-
const sum = future_a.await(io);
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-
- const product = future_b.???(io);
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-
+ const product = future_b.await(io);
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-
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-
print("{} + {} = {}\n", .{ 1, 2, sum });
18
-
print("{} * {} = {}\n", .{ 6, 7, product });