zig-journey

A repository that journals my initial explorations into The Zig Programming Language.

Installing

I'll be using VS Code on Windows, so here's what I did to install everything.

choco install zig -y
choco install vscode -y
code --install-extension ziglang.vscode-zig

Getting the first app running

mkdir your:\\folder
cd your:\\folder
zig init
zig build run
zig build test

After doing this, I can run zig in the cli. Easy!

Explorations

Structure

zig init creates both a main.zig which creates an executable, and root.zig, which creates a library.

Accessibility

It seems like a function can be declared private or public, a struct, and so on. Fields on that struct however seem to be always public. From what I'm reading, prefixing with underscore seems to be a preferred way to indicate that we prefer the member being private.

Imports

Without defining a module, we need to import from specific zig files, as such:

const core = @import("core.zig"); // todo: There must be better than this?
const consts = @import("consts.zig");

However, this feels wonky. Better would be an import that describes our grouped functionality. Hence, modules. In this case, in build.zig, we define the module and add as an import to the executable

    const core_mod = b.addModule("core", .{ .root_source_file = b.path("src/core.zig"), .target = target, .optimize = optimize });
    exe.root_module.addImport("core", core_mod);

Note however that we replaced both core.zig, and consts.zig. This seems to be because core.zig already imports consts.zig, and so main was complaining that consts was imported twice. Changing the visibility of consts from core, we have also included consts in our core module, accessible as core.consts. Nice 👍.

Initialization

It looks like I have taken some time to understand that creating views, grid, cells and so on in the init function, that they are created on the stack and released at the end of scope. This means that I was looking at pointers to essentially freed memory. Oops!

The below is the flawed implementation

    pub fn initEmpty_flawed(allocator: Allocator) SudokuPuzzle {

        var views = Views{ .rows = undefined, .columns = undefined, .blocks = undefined };
        var grid: CellGrid = undefined;

        for (0..consts.PUZZLE_MAXIMUM_VALUE) |row| {
            // Set up the views
        }

        for (0..consts.PUZZLE_MAXIMUM_VALUE) |row| {
            for (0..consts.PUZZLE_MAXIMUM_VALUE) |column| {
                grid[row][column] = Cell.initEmpty(allocator);
                // Set up the pointers
            }
        }

        return SudokuPuzzle{ .grid = grid, .views = views };
    }

Below, using the allocator.create to make sure that the initialized resources live beyond the scope of the init function. Note how allocator.Create(T) returns a *T.

 pub fn initEmpty(allocator: Allocator) !*SudokuPuzzle {
        var puzzle = try allocator.create(SudokuPuzzle);
        errdefer allocator.destroy(puzzle);

        for (0..consts.PUZZLE_MAXIMUM_VALUE) |row| {
            // Set up the views
        }

        for (0..consts.PUZZLE_MAXIMUM_VALUE) |row| {
            for (0..consts.PUZZLE_MAXIMUM_VALUE) |column| {
                puzzle.grid[row][column] = Cell.initEmpty(allocator);
                // Set up the pointers
            }
        }
        return puzzle;
    }

References

• Setting up VSCode for Zig
• Getting started with Zig