Functions

Case

Rust uses snake case for function and variable names. Functions always start with fn

fn main() {
    println!("Hello, world!");
 
    another_function();
}
 
fn another_function() {
    println!("Another function.");
}

In rust you must declare parameter types

fn main() {
    another_function(5);
}
 
fn another_function(x: i32) {
    println!("The value of x is: {}", x);
}

Rust is an expressive language, so you have to do stuff like this:

fn main() {
    let _x = 5;
 
    let y = {
        let x = 3;
        x + 1
    };
 
    println!("The value of y is: {}", y);
}

Unless you add a return statement, most functions return the last expression implicitly:

fn five() -> i32 {
    5
}
 
fn main() {
    let x = five();
 
    println!("The value of x is: {}", x);
}