约束与静态检查
在运行前验证参数
约束与静态检查 是 CoddyKit 上的免费 Mojo Academy 课时。 这是第 4 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 Mojo Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Mojo 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。
Catching Mistakes Before Runtime
A constraint is a rule the compiler verifies about your parameters, stopping a bad build before the program ever runs. ⚙️
The constrained Function
Call constrained with a compile-time condition; if it is false, compilation fails with the message you supply.
fn half[n: Int]():
constrained[n % 2 == 0, "n must be even"]()Conditions Are Compile-Time
The condition must use parameters or aliases, so the check is settled while building, not while the program executes.
fn lanes[w: Int]():
constrained[w > 0, "width must be positive"]()Clear Error Messages
The string you pass becomes the error shown at the call site, so misuse is explained instead of failing in some confusing later way.
Guarding Valid Widths
Constraints shine for SIMD code: require a power-of-two width so the kernel never gets an impossible vector size.
constrained[w & (w - 1) == 0, "width must be a power of two"]()Constraints Document Intent
A clear constraint tells future readers exactly what a parameter expects, acting as machine-checked documentation that can never drift.
Static Asserts in Algorithms
Sprinkle checks through a parametric algorithm so every specialization is validated, catching one bad combination without testing every input.
Cheaper Than Runtime Checks
Because the test runs at compile time, the shipped code carries no if-statement to verify the rule, so there is zero runtime cost.
Pair With Conditional Compilation
Combine constraints with @parameter if: branch on what is supported, and reject the unsupported cases outright with a clear error.
Safer Metaprogramming
Constraints turn flexible parameters into a contract: powerful specialization stays safe because the compiler enforces every rule for you. 🚀
Fail Early, Fail Clearly
Place a constrained check near the top of a function so an invalid parameter is rejected immediately, with the reason stated up front.
Quick Check
Recall what constrained does in Mojo.
Recap
You used constraints: constrained validates parameters at compile time with clear errors, making powerful metaprogramming safe at zero runtime cost. 🎯
常见问题解答
「约束与静态检查」课时是免费的吗？
是的 — 「约束与静态检查」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 Mojo Academy 课程的其余内容，请升级到 CoddyKit PRO。 Mojo Academy 课程共包含 4 节课。
「约束与静态检查」这节课中我会学到什么？
在运行前验证参数 你通过在浏览器中直接运行的动手代码来练习 Mojo 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 Mojo Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Mojo 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 4 节课，共 4 节。
「约束与静态检查」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 Mojo Academy 课中编写并运行代码吗？
能。每节 Mojo 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。