Syntax

The Rust syntax is similar to other languages such as C and C++. However, here is a brief overview.

Variable declaration

Rust is a statically typed language, which means that the type of a variable needs to be known, either explicitly or implicitly. The basic syntax for variable declaration is let name: type = value;. E.g.,

fn main() {
    let x: usize = 0; // unsigned integer.
    let x: &str = "Hello, world!"; // string slice.
    let x: String = "Hello, world!".to_string(); // string.
    let x: &[u8] = b"Hello, world!"; // byte slice.
    let x: Vec<usize> = vec![1, 2, 3, 4, 5]; // vec.
}

Scopes

{ and } define scopes. E.g.,

fn main() { // start of function scope.
    println!("Hello, world!");
} // end of function scope.

We can also have nested scopes. E.g.,

fn main() {
    let x: &str = "Hello, world!";

    {
        println!("{x}");
    }
}

Scopes are important for ownership and lifetimes, which will be covered later on.

Statement delimiters

; is used for statement delimiters. E.g.,

fn main() {
    println!("Hello, world!"); // Defines the println! statement.
} // does not need a ";".

Note that scopes do not need a ; terminator.

Comments

// is used for code comments.
/// is used for docstrings.

/// This is a docstring.
fn main() {
    // This is a comment.
    println!("Hello, world");
}