I made Intuitive Rust Examples that made me understand the concepts of Option

and_then_vs_map.rs

// difference between and_then vs map for `Option`

fn increment(n: i32) -> Option<i32> {
    Some(n).map(|x| x + 1)
}

fn main() {
    let one = Some(1);
    let four = one
        .map(|one| one + 1)
        .map(|two| two + 1)
        .and_then(|three| increment(three));

    println!("{}", four.unwrap()); // 4
}

as_ref.rs

// the point of using `as_ref` for `Option`

fn this_wont_work() {
    let lower: Option<String> = Some(String::from("case"));
    let upper: Option<String> = lower.map(|x| x.to_uppercase());

    println!("UPPER: {}", upper.unwrap());
    println!("lower: {}", lower.unwrap()); // lower is moved, can't be used
}

fn this_work() {
    let lower: Option<String> = Some(String::from("case"));
    let upper: Option<String> = lower.as_ref().map(|x| x.to_uppercase());

    println!("UPPER: {}", upper.unwrap());
    println!("lower: {}", lower.unwrap());
}

fn main() {
    this_wont_work();
    this_work();
}

gates.rs

mod gates {
    pub fn and() {
        let x = Some("x");
        let y = None::<&str>;

        println!("x & y = {}", x.and(y).unwrap_or("y"));
        println!("y & x = {}", y.and(x).unwrap_or("y"));
        println!("x & x = {}", x.and(x).unwrap_or("None"));
        println!("y & y = {}", y.and(y).unwrap_or("None"));
    }

    pub fn or() {
        let x = Some("x");
        let y = None::<&str>;

        println!("x | y = {}", x.or(y).unwrap_or("y"));
        println!("y | x = {}", y.or(x).unwrap_or("y"));
        println!("x | x = {}", x.or(x).unwrap_or("None"));
        println!("y | y = {}", y.or(y).unwrap_or("None"));
    }

    pub fn xor() {
        let x = Some("x");
        let y = None::<&str>;

        println!("x ⊕ y = {}", x.xor(y).unwrap_or("y"));
        println!("y ⊕ x = {}", y.xor(x).unwrap_or("y"));
        println!("x ⊕ x = {}", x.xor(x).unwrap_or("None"));
        println!("y ⊕ y = {}", y.xor(y).unwrap_or("None"));
    }
}

fn main() {
    println!("x = Some(x)");
    println!("y = None");
    println!();

    gates::and();
    println!();
    gates::or();
    println!();
    gates::xor();
}