use std::collections::HashMap;

fn get_default(v: &Vec<u32>, i: usize, default_value: &u32) -> u32 {
    match v.get(i) {
        Some(value) => *value,
        None => *default_value,
    }
}

fn get_default_2(v: &Vec<u32>, i: usize, default_value: &u32) -> u32 {
    *v.get(i).unwrap_or(default_value)
}

fn vec_example() {
    let mut v = Vec::new();
    v.push(2);

    v.push(5);
    println!("v[0] = {:?}", v.get(6)); // OK, returns an Option
    println!("v[0] = {}", v[6]); // stops the program
}

fn map_example() {
    let mut map = HashMap::new();
    map.insert(1, String::from("1"));
    let key = &1;

    // checks that the key is in the map
    // but hashes the key twice:
    // - to check if it is in the map
    // - to get the value from the map
    if map.contains_key(key) {
        // sure that it exists
        let val = map.get(key).expect("something weird happened here");

        // example of unsafe code
        // avoid writing unsafe code for now
        // (very easy to shoot yourself in the foot...)
        // let val = unsafe {
        //     // it is up to you to be extra carefull here
        //     map.get(key).unwrap_unchecked()
        // };
    }

    // usefull API here: the `entry` method of map
    let uppercase = map.entry(2).or_insert(String::from("2")).to_uppercase();
}