pub fn print_hello_world() {
    println!("Hello, world!");
}

pub mod maths {
    pub fn add(a: i32, b: i32) -> i32 {
        a + b
    }

    pub fn subtract(a: i32, b: i32) -> i32 {
        a - b
    }

    pub fn multiply(a: i32, b: i32) -> i32 {
        a * b
    }

    pub fn area(x: f32, y: f32) -> f32 {
        x * y
    }

    pub mod more_math {
        pub fn divide(a: f32, b: f32) -> f32 {
            a / b
        }
    }
}