Learning Zig, day 2 [deploy]
Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>
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categories = ["zig"]
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date = 2021-05-15
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description = "Onwards in our quest to learn Zig"
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slug = "learning-zig--day-2"
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tags = ["zig", "learn"]
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title = "Learning Zig - Day 2"
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+++
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In the [previous post] I documented how I went about setting up my Zig environment, and it's now time to start learning things.
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My preferred method of learning new languages is rebuilding an existing project in them, like I did when going from [Python] to [Kotlin] to [Rust]. For Zig, I've elected to rebuild my [healthchecks-rs] library. It's something I use on a day-to-day basis for keeping an eye on my backup jobs, and it would be a great addition to the [healthchecks.io ecosystem].
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# Getting the basics down
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Among the resources enlisted on the Zig [getting started] page, I opted to go with [ziglearn.org] for learning the ropes of the language. It is concise yet detailed, and the chapter-wise breakdown makes for great mental "checkpoints", much like the [Rust book].
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For this post I'm going through [chapter 1].
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# Thoughts™️
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I'm going to use this section to jot down my thoughts about Zig, broken down by the sections on ZigLearn. I'll skip the parts that I don't have anything to say on.
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## Assignment
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The presence of `undefined` is *very* interesting to me. It appears to be functionally identical to Rust's [Default trait], as shown in this snippet (had to skip to structs for this since I was so curious about it).
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```zig
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const std = @import("std");
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const Vec3 = struct {
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x: f32,
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y: f32,
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z: f32,
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};
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pub fn main() void {
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const inferred_constant: Vec3 = undefined;
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std.debug.print("Hello, {d}!\n", .{inferred_constant});
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}
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```
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which prints:
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```
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➜ zig build run
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Hello, Vec3{ .x = 0, .y = 0, .z = 0 }!
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```
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I have clearly not gotten very far yet, but initial thoughts here: Rust's trait-based implementation means I can customize the "default" values for my structs, which I'm not seeing in this implicit coercion yet. Guess we'll find out soon whether or not this can be handled explicitly :D
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## Arrays
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The syntax for array declarations is quite clear and explicit, which I like. Notably, while you can do this:
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```zig
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const implicitly_sized_array = [_]u8{}; // _ means "infer the size"
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```
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you cannot have an inferred size reference as the type:
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```zig
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const implicitly_sized_array[_]u8 = {};
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```
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Rust also [disallows this](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=f27a1a0b20feebe3e6d0a3417f25ce45), but the error is surprisingly worse than with Zig. Rust's resident diagnostics magician Esteban [assures me](https://twitter.com/ekuber/status/1393566561005314048) this is a regression and is being tracked.
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The only problem I encountered here was that I can't figure out how to print an array!
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```zig
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const implicitly_sized_array = [_]u8{0, 1, 2, 3};
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std.debug.print("This is an array: {}\n", .{implicitly_sized_array});
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// Outputs: "This is an array: "
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```
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I found a [PR that overhauls formatting] but nothing there gave me any pointers on why my code doesn't work. Hopefully this'll get cleared up later.
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## If
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Nothing special here, aside from the early introduction to testing, which is slightly more pleasant than with Rust. I do however have qualms about the test output, which is unnecessarily noisy:
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```shell
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Test [2/2] test "while with continue expression"... expected 2080, found 10
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/nix/store/nhd75c4sr3l9wlaspilkwawx5ixkn74w-zig-0.7.1/lib/zig/std/testing.zig:74:32: 0x206f9a in std.testing.expectEqual (test)
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std.debug.panic("expected {}, found {}", .{ expected, actual });
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^
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/home/msfjarvis/git-repos/zig-playground/src/main.zig:29:24: 0x205abd in test "while with continue expression" (test)
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testing.expectEqual(sum, 10);
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^
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/nix/store/nhd75c4sr3l9wlaspilkwawx5ixkn74w-zig-0.7.1/lib/zig/std/special/test_runner.zig:61:28: 0x22e161 in std.special.main (test)
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} else test_fn.func();
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^
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/nix/store/nhd75c4sr3l9wlaspilkwawx5ixkn74w-zig-0.7.1/lib/zig/std/start.zig:334:37: 0x20749d in std.start.posixCallMainAndExit (test)
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const result = root.main() catch |err| {
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^
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/nix/store/nhd75c4sr3l9wlaspilkwawx5ixkn74w-zig-0.7.1/lib/zig/std/start.zig:162:5: 0x2071d2 in std.start._start (test)
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@call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
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^
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error: the following test command crashed:
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./src/zig-cache/o/5a647f3d3394214b30b3861a6b0ffbbb/test
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```
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## Defer
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The `defer` language feature is something I've always been curious about since seeing it in Go, so I'm excited to discover use-cases for it when I finally have it available. Through ZigLearn I discovered that `defer` calls can be stacked to be executed in LIFO order, and Golang does it in the exact same fashion.
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## Errors
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I like how easy it is to define errors, but the syntax feels kinda icky. Having each error enum I declare 'magically' become a property on the `error` keyword doesn't sit right with me :(
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```zig
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const NumericError = error{};
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fn mayError(shouldError: bool) anyerror!u32 {
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return if (shouldError)
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// This is different from what I'm accustomed to as a user of
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// Either/Result type monads.
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error.NumericError
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else
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10;
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}
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```
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## Runtime Safety
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Being able to turn off runtime safety features (like bounds checking) in specific blocks is pretty interesting! Not sure if I'll ever have a valid use for it though...
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## Conclusion
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I like most of what I've seen so far in Zig. Aside from the issues I mentioned above, the lack of string type is a very confusing thing for me. I've kinda come to expect it everywhere based on my previous experiences with Python, Java, Kotlin, and Rust; but maybe I'll now learn to appreciate how every character on my screen is just numbers :D.
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I was very easily distracted today, so I only made it a third of the way in 3 hours for a chapter that is supposed to take 1 hour for the whole thing. Hoping to finish it tomorrow!
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[previous post]: /posts/first-steps-with-zig
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[Python]: https://msfjarvis.dev/g/walls-manager
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[Kotlin]: https://msfjarvis.dev/g/walls-bot
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[Rust]: https://msfjarvis.dev/g/walls-bot-rs
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[healthchecks-rs]: https://msfjarvis.dev/g/healthchecks-rs
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[healthchecks.io ecosystem]: https://healthchecks.io/docs/resources/
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[getting started]: https://ziglang.org/learn/getting-started/
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[ziglearn.org]: https://ziglearn.org/
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[Rust book]: https://doc.rust-lang.org/book/
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[chapter 1]: https://ziglearn.org/chapter-1/
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[Default trait]: https://doc.rust-lang.org/std/default/trait.Default.html
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[PR that overhauls formatting]: https://github.com/ziglang/zig/pull/6870
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[`unreachable`]: https://ziglearn.org/chapter-1/#unreachable
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