p_rust 0.1.0

My rust practice
Documentation 
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#[derive(Debug, PartialEq, Copy, Clone)]
enum ShirtColor {
    Red,
    Blue,
}

struct Inventory {
    shirts: Vec<ShirtColor>,
}

impl Inventory {
    fn giveaway(&self, user_preference: Option<ShirtColor>) -> ShirtColor {
        user_preference.unwrap_or_else(|| self.most_stocked())
    }

    fn most_stocked(&self) -> ShirtColor {
        let mut num_red = 0;
        let mut num_blue = 0;

        for color in &self.shirts {
            match color {
                ShirtColor::Red => num_red += 1,
                ShirtColor::Blue => num_blue += 1,
            }
        }
        if num_red > num_blue {
            ShirtColor::Red
        } else {
            ShirtColor::Blue
        }
    }
}

#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

fn main() {
    let store = Inventory {
        shirts: vec![ShirtColor::Blue, ShirtColor::Red, ShirtColor::Blue],
    };

    let user_pref1 = Some(ShirtColor::Red);
    let giveaway1 = store.giveaway(user_pref1);
    println!(
        "The user with preference {:?} gets {:?}",
        user_pref1, giveaway1
    );

    let user_pref2 = None;
    let giveaway2 = store.giveaway(user_pref2);
    println!(
        "The user with preference {:?} gets {:?}",
        user_pref2, giveaway2
    );

    let expensive_closure = |num: u32| -> u32 {
        println!("calculating slowly...");
        // thread::sleep(Duration::from_secs(2));
        num
    };
    println!("expensive_closure: {}", expensive_closure(226));

    let example_closure = |x| x;
    let s = example_closure(String::from("hello"));
    // let n = example_closure(5);
    println!("s: {:?}", s);

    let list = vec![1, 2, 3];
    println!("Before defining closure: {:?}", list);

    let only_borrows = || println!("From closure: {:?}", list);

    println!("Before calling closure: {:?}", list);
    only_borrows();
    println!("After calling closure: {:?}", list);

    let mut list = vec![1, 2, 3];
    println!("Before defining closure: {:?}", list);

    let mut borrows_mutably = || list.push(7);

    // println!("Before calling closure: {:?}", list); // cannot borrow `list` as immutable because it is also borrowed as mutable
    borrows_mutably();
    println!("After calling closure: {:?}", list);

    let mut list = [
        Rectangle {
            width: 10,
            height: 1,
        },
        Rectangle {
            width: 7,
            height: 19,
        },
        Rectangle {
            width: 7,
            height: 12,
        }
    ];

    list.sort_by_key(|r| r.width);
    list.sort_by(|a, b| {
        a.width.cmp(&b.width)
            .then(a.height.cmp(&b.height))
    });
    println!("{:#?}", list);

    // let mut sort_operations = vec![];
    // let value = String::from("by key called");

    list.sort_by_key(|r| {
        // sort_operations.push(value); // won't work
        r.width
    });
    println!("{:#?}", list);

    let mut num_sort_operations = 0;
    list.sort_by_key(|r| {
        num_sort_operations += 1;
        r.width
    });
    println!("{:#?}, sorted in {num_sort_operations} operations", list);

    let v1 = vec![1, 2, 3];
    for val in &v1 {
        println!("Got: {}", val);
    }

    let v1_iter = v1.iter();
    for val in v1_iter {
        println!("Got: {}", val);
    }

    let v1 = vec![1, 2, 3];
    let v2: Vec<_> = v1.iter().map(|x| x + 1).collect();
    assert_eq!(v2, vec![2, 3, 4]);
}