How to Use Comments and Documentation Comments in Rust

Use // for single-line comments ignored by the compiler and /// for documentation comments that generate API docs. Place // anywhere to explain code logic, and place /// immediately before items like functions or structs to create public documentation.

// This is a regular comment ignored by the compiler
fn add(a: i32, b: i32) -> i32 {
    a + b
}

/// Adds two numbers and returns the result.
///
/// # Examples
///
/// ```
/// let result = add(2, 2);
/// assert_eq!(result, 4);
/// ```
fn multiply(a: i32, b: i32) -> i32 {
    a * b
}

Regular comments are like sticky notes for yourself that the computer ignores, while documentation comments are like a user manual that the computer reads to create help files. You use regular comments to explain tricky logic to other developers, and documentation comments to describe how to use your code for anyone reading the generated API docs. Think of it as the difference between a private diary entry and a public instruction manual.