Comments
- Rust course
- Beginner
- Lesson 5/115
- 4 min
Document your code with // and /* */ comments.
Comments
Rust has three kinds of comments: // single line, /* ... */ multi-line, and /// doc comments. Doc comments become HTML documentation with cargo doc, and the code examples inside them run as tests.
/// İki sayıyı toplar.
/// ```
/// assert_eq!(topla(2, 3), 5);
/// ```
fn topla(a: i32, b: i32) -> i32 {
a + b // the result is returned as an expression
}Good comments
A good comment explains why the code does something, not what it does. The code itself should already say what it does through readable names. //! at the top of a file or crate documents the whole module.
// Bad: increment i
i += 1;
// Good: skip the header line
i += 1;Practice Documented function
Write a fn kare(n: i32) -> i32 function documented with ///, and in main call println!("{}", kare(9)); under a // comment.
Starter code
fn main() {
// buraya yaz
}Sample solution
/// Sayının karesini döndürür.
fn kare(n: i32) -> i32 {
n * n
}
fn main() {
// 9'un karesini yazdır
println!("{}", kare(9));
}Expected output
81
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What happens to code examples in <code>///</code> comments?
- Only the IDE shows them
- They run as tests with cargo test Correct answer
- They are ignored
- They cause a compile error
Explanation: This feature, called doc tests, guarantees that the examples in the documentation stay current and correct.
2 Doc comment
____ Dairenin alanını hesaplar.
fn alan(r: f64) -> f64 { 3.14 * r * r }/// Dairenin alanını hesaplar.
fn alan(r: f64) -> f64 { 3.14 * r * r }Explanation: Text after /// becomes the function's documentation.
3 Comment kind
| Term | Meaning |
|---|---|
// |
Single line |
/* */ |
Multi-line |
/// |
Item documentation |
//! |
Module documentation |