Ideally, a program should be self-documenting by using descriptive variable names and easy-to-read code, but there are always cases where additional comments about a program's structure or algorithms are needed. Rust follows the C convention and has:
- // line comments; everything on the line after // is commentary and not compiled
- /* */block or multi-line comments; everything between the start /*and the end */ is not compiled
However, the preferred Rust style is to use only the // comment, also for multiple lines, as shown in the following code:
// see Chapter 2/code/comments.rs
fn main() {
// Here starts the execution of the Game.
// We begin with printing a welcome message:
println!("Welcome to the Game!");
}
Use the /* */ comments only to comment out code.
Rust also has a doc comment with ///, useful in larger projects that require an official documentation for customers and developers. Such comments have to appear before an item (like a function) on a separate line to document that item. In these comments, you can use Markdown formatting syntax (see https://en.wikipedia.org/wiki/Markdown).
Here is a doc comment:
/// Start of the Game
fn main() {
}
We'll see more relevant uses of /// in later code snippets. The rustdoc tool can compile these comments into project documentation.