現在我們寫了一些函數，是時候學習一下注釋了。注釋是你幫助其他程序猿理解你的代碼的備注。編譯器基本上會忽略它們。 Rust有兩種需要你了解的注釋格式：_行注釋_（_line comments_）和_文檔注釋_（_doc comments_）。 ~~~ // Line comments are anything after '//' and extend to the end of the line. let x = 5; // this is also a line comment. // If you have a long explanation for something, you can put line comments next // to each other. Put a space between the // and your comment so that it's // more readable. ~~~ 另一種注釋是文檔注釋。文檔注釋使用`///`而不是`//`，并且內建Markdown標記支持： ~~~ /// `hello` is a function that prints a greeting that is personalized based on /// the name given. /// /// # Arguments /// /// * `name` - The name of the person you'd like to greet. /// /// # Example /// /// ```rust /// let name = "Steve"; /// hello(name); // prints "Hello, Steve!" /// ~~~ fn hello(name: &str) { println!("Hello, {}!", name); } ``` 當書寫文檔注釋時，加上參數和返回值部分并提供一些用例將是非常有幫助的。不要擔心那個`&str`，我們馬上會提到它。 你可以使用[rustdoc](http://kaisery.gitbooks.io/rust-book-chinese/content/content/4.4.Documentation%20%E6%96%87%E6%A1%A3.md)工具來將文檔注釋生成為HTML文檔。