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comptime 参数与值

传入在编译时就存在的值。

comptime 参数与值 是 CoddyKit 上的免费 Zig Academy 课时。这是第 2 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Zig Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Zig Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Some Arguments Must Be Known Early

Sometimes a function needs an argument the compiler can see, not just the running program. Zig lets you mark such a parameter comptime. 🧩

Marking a comptime Parameter

Write comptime before a parameter name to require that its value be known at compile-time. The caller must pass a known value.

fn repeat(comptime n: usize) void {}

The Caller Supplies a Known Value

A comptime parameter accepts only values the compiler already knows, like literals or other compile-time constants.

repeat(3);

Run-Time Values Are Rejected

Pass a value that is only known at run-time into a comptime parameter and Zig reports a clear compile error.

comptime Inside a Body

You can also force a local expression to evaluate early. A comptime block runs during compilation and produces a constant.

const table = comptime buildTable();

comptime var for Compile-Time State

A comptime var is a mutable variable that exists only during compilation. Use it to accumulate a value as compile-time code runs.

comptime var sum = 0;

Known Values Specialize Functions

Because a comptime argument is fixed, Zig can generate a tailored version of the function for that exact value.

Mix comptime and Normal Parameters

A function can take both kinds at once: a comptime parameter for the known part and ordinary parameters for run-time data.

fn scale(comptime factor: u8, x: u32) u32 {
    return x * factor;
}

Validate Arguments Early

Since the value is known, you can check it during compilation and stop the build if it is wrong, before the program ever runs. ✅

No Run-Time Cost

Work driven by a comptime parameter happens during the build. The resulting binary carries the answer with nothing left to compute.

Inside, the Parameter Is Constant

Within the function body a comptime parameter behaves like a fixed constant, so you may use it in array sizes and other compile-time spots.

fn buffer(comptime n: usize) [n]u8 {
    return undefined;
}

Quick Check

A function declares a parameter as comptime n: usize. What kind of value must the caller pass?

Recap

Mark a parameter comptime to demand a compile-time value. Zig can then validate it and specialize the function with no run-time cost. 🎯

常见问题解答

「comptime 参数与值」课时是免费的吗？

是的 — 「comptime 参数与值」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Zig Academy 课程的其余内容，请升级到 CoddyKit PRO。 Zig Academy 课程共包含 4 节课。

「comptime 参数与值」这节课中我会学到什么？

传入在编译时就存在的值。你通过在浏览器中直接运行的动手代码来练习 Zig Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Zig Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Zig Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 2 节课，共 4 节。

「comptime 参数与值」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Zig Academy 课中编写并运行代码吗？

能。每节 Zig Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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