Rust - Rustlings Write Up

写在前面

最近学长推荐我去学一下 Rust，考虑了一下，决定从 Rust 官方的学习文档 —— 也就是 Rustlings 入手，我一共用了两天的时间来完成 Rustlings，下面是我的题解(截至 2023.9.2)

Rust 给我的感觉就是生态好，打包方便，有便捷的包管理器；但是 Rust 的语法是非常严苛，通过严格的语法规范来减少程序运行时内存错误的发生

Rustlings

intro

intro1.rs

// intro1.rs
//
// About this `I AM NOT DONE` thing:
// We sometimes encourage you to keep trying things on a given exercise, even
// after you already figured it out. If you got everything working and feel
// ready for the next exercise, remove the `I AM NOT DONE` comment below.
//
// If you're running this using `rustlings watch`: The exercise file will be
// reloaded when you change one of the lines below! Try adding a `println!`
// line, or try changing what it outputs in your terminal. Try removing a
// semicolon and see what happens!
//
// Execute `rustlings hint intro1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    println!("Hello and");
    println!(r#"       welcome to...                      "#);
    println!(r#"                 _   _ _                  "#);
    println!(r#"  _ __ _   _ ___| |_| (_)_ __   __ _ ___  "#);
    println!(r#" | '__| | | / __| __| | | '_ \ / _` / __| "#);
    println!(r#" | |  | |_| \__ \ |_| | | | | | (_| \__ \ "#);
    println!(r#" |_|   \__,_|___/\__|_|_|_| |_|\__, |___/ "#);
    println!(r#"                               |___/      "#);
    println!();
    println!("This exercise compiles successfully. The remaining exercises contain a compiler");
    println!("or logic error. The central concept behind Rustlings is to fix these errors and");
    println!("solve the exercises. Good luck!");
    println!();
    println!("The source for this exercise is in `exercises/intro/intro1.rs`. Have a look!");
    println!(
        "Going forward, the source of the exercises will always be in the success/failure output."
    );
    println!();
    println!(
        "If you want to use rust-analyzer, Rust's LSP implementation, make sure your editor is set"
    );
    println!("up, and then run `rustlings lsp` before continuing.")
}

intro2.rs

// intro2.rs
//
// Make the code print a greeting to the world.
//
// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let world = "world";
    println!("Hello {}!", world);
}

variables

variables1.rs

// variables1.rs
//
// Make me compile!
//
// Execute `rustlings hint variables1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let x = 5;
    println!("x has the value {}", x);
}

variables2.rs

// variables2.rs
//
// Execute `rustlings hint variables2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let x = 10;
    if x == 10 {
        println!("x is ten!");
    } else {
        println!("x is not ten!");
    }
}

variables3.rs

// variables3.rs
//
// Execute `rustlings hint variables3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let x: i32 = 0;
    println!("Number {}", x);
}

variables4.rs

// variables4.rs
//
// Execute `rustlings hint variables4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let mut x = 3;
    println!("Number {}", x);
    x = 5; // don't change this line
    println!("Number {}", x);
}

variables5.rs

// variables5.rs
//
// Execute `rustlings hint variables5` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let number = "T-H-R-E-E"; // don't change this line
    println!("Spell a Number : {}", number);
    let number = 3; // don't rename this variable
    println!("Number plus two is : {}", number + 2);
}

variables6.rs

// variables6.rs
//
// Execute `rustlings hint variables6` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

const NUMBER : i32 = 3;
fn main() {
    println!("Number {}", NUMBER);
}

functions

functions1.rs

// functions1.rs
//
// Execute `rustlings hint functions1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn call_me(){
    return;
}

fn main() {
    call_me();
}

functions2.rs

// functions2.rs
//
// Execute `rustlings hint functions2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    call_me(3);
}

fn call_me(num: i32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

functions3.rs

// functions3.rs
//
// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    call_me(10);
}

fn call_me(num: u32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

functions4.rs

// functions4.rs
//
// This store is having a sale where if the price is an even number, you get 10
// Rustbucks off, but if it's an odd number, it's 3 Rustbucks off. (Don't worry
// about the function bodies themselves, we're only interested in the signatures
// for now. If anything, this is a good way to peek ahead to future exercises!)
//
// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let original_price = 51;
    println!("Your sale price is {}", sale_price(original_price));
}

fn sale_price(price: i32) -> i32 {
    if is_even(price) {
        price - 10
    } else {
        price - 3
    }
}

fn is_even(num: i32) -> bool {
    num % 2 == 0
}

functions5.rs

// functions5.rs
//
// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let answer = square(3);
    println!("The square of 3 is {}", answer);
}

fn square(num: i32) -> i32 {
    num * num
}

if

if1.rs

// if1.rs
//
// Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.

// I AM DONE

pub fn bigger(a: i32, b: i32) -> i32 {
    // Complete this function to return the bigger number!
    // Do not use:
    // - another function call
    // - additional variables
    if a > b {
        a
    }else{
        b
    }
}

// Don't mind this for now :)
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn ten_is_bigger_than_eight() {
        assert_eq!(10, bigger(10, 8));
    }

    #[test]
    fn fortytwo_is_bigger_than_thirtytwo() {
        assert_eq!(42, bigger(32, 42));
    }
}

if2.rs

// if2.rs
//
// Step 1: Make me compile!
// Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
//
// Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.

// I AM DONE

pub fn foo_if_fizz(fizzish: &str) -> &str {
    if fizzish == "fizz" {
        "foo"
    } else if fizzish == "fuzz" {
        "bar"
    } else {
        "baz"
    }
}

// No test changes needed!
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn foo_for_fizz() {
        assert_eq!(foo_if_fizz("fizz"), "foo")
    }

    #[test]
    fn bar_for_fuzz() {
        assert_eq!(foo_if_fizz("fuzz"), "bar")
    }

    #[test]
    fn default_to_baz() {
        assert_eq!(foo_if_fizz("literally anything"), "baz")
    }
}

if3.rs

// if3.rs
//
// Execute `rustlings hint if3` or use the `hint` watch subcommand for a hint.

// I AM DONE

pub fn animal_habitat(animal: &str) -> &'static str {
    let identifier = if animal == "crab" {
        1
    } else if animal == "gopher" {
        2
    } else if animal == "snake" {
        3
    } else {
        0
    };

    // DO NOT CHANGE THIS STATEMENT BELOW
    let habitat = if identifier == 1 {
        "Beach"
    } else if identifier == 2 {
        "Burrow"
    } else if identifier == 3 {
        "Desert"
    } else {
        "Unknown"
    };

    habitat
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn gopher_lives_in_burrow() {
        assert_eq!(animal_habitat("gopher"), "Burrow")
    }

    #[test]
    fn snake_lives_in_desert() {
        assert_eq!(animal_habitat("snake"), "Desert")
    }

    #[test]
    fn crab_lives_on_beach() {
        assert_eq!(animal_habitat("crab"), "Beach")
    }

    #[test]
    fn unknown_animal() {
        assert_eq!(animal_habitat("dinosaur"), "Unknown")
    }
}

primitive_types

primitive_types1.rs

// primitive_types1.rs
//
// Fill in the rest of the line that has code missing! No hints, there's no
// tricks, just get used to typing these :)
//
// Execute `rustlings hint primitive_types1` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    // Booleans (`bool`)

    let is_morning = true;
    if is_morning {
        println!("Good morning!");
    }

    let is_evening = false; // Finish the rest of this line like the example! Or make it be false!
    if is_evening {
        println!("Good evening!");
    }
}

primitive_types2.rs

// primitive_types2.rs
//
// Fill in the rest of the line that has code missing! No hints, there's no
// tricks, just get used to typing these :)
//
// Execute `rustlings hint primitive_types2` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    // Characters (`char`)

    // Note the _single_ quotes, these are different from the double quotes
    // you've been seeing around.
    let my_first_initial = 'C';
    if my_first_initial.is_alphabetic() {
        println!("Alphabetical!");
    } else if my_first_initial.is_numeric() {
        println!("Numerical!");
    } else {
        println!("Neither alphabetic nor numeric!");
    }

    let your_character = '1'; // Finish this line like the example! What's your favorite character?
    // Try a letter, try a number, try a special character, try a character
    // from a different language than your own, try an emoji!
    if your_character.is_alphabetic() {
        println!("Alphabetical!");
    } else if your_character.is_numeric() {
        println!("Numerical!");
    } else {
        println!("Neither alphabetic nor numeric!");
    }
}

primitive_types3.rs

// primitive_types3.rs
//
// Create an array with at least 100 elements in it where the ??? is.
//
// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let a = 0..200;

    if a.len() >= 100 {
        println!("Wow, that's a big array!");
    } else {
        println!("Meh, I eat arrays like that for breakfast.");
    }
}

primitive_types4.rs

// primitive_types4.rs
//
// Get a slice out of Array a where the ??? is so that the test passes.
//
// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

#[test]
fn slice_out_of_array() {
    let a = [1, 2, 3, 4, 5];

    let nice_slice = &a[1..4];

    assert_eq!([2, 3, 4], nice_slice)
}

primitive_types5.rs

// primitive_types5.rs
//
// Destructure the `cat` tuple so that the println will work.
//
// Execute `rustlings hint primitive_types5` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let cat = ("Furry McFurson", 3.5);
    let (name, age) /* your pattern here */ = cat;

    println!("{} is {} years old.", name, age);
}

primitive_types6.rs

// primitive_types6.rs
//
// Use a tuple index to access the second element of `numbers`. You can put the
// expression for the second element where ??? is so that the test passes.
//
// Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

#[test]
fn indexing_tuple() {
    let numbers = (1, 2, 3);
    // Replace below ??? with the tuple indexing syntax.
    let second = numbers.1;

    assert_eq!(2, second,
        "This is not the 2nd number in the tuple!")
}

vec

vec1.rs

// vecs1.rs
//
// Your task is to create a `Vec` which holds the exact same elements as in the
// array `a`.
//
// Make me compile and pass the test!
//
// Execute `rustlings hint vecs1` or use the `hint` watch subcommand for a hint.

// I AM DONE

fn array_and_vec() -> ([i32; 4], Vec<i32>) {
    let a = [10, 20, 30, 40]; // a plain array
    let v : Vec<i32> = vec![10, 20, 30, 40]; // TODO: declare your vector here with the macro for vectors

    (a, v)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_array_and_vec_similarity() {
        let (a, v) = array_and_vec();
        assert_eq!(a, v[..]);
    }
}

vec1.rs

// vecs2.rs
//
// A Vec of even numbers is given. Your task is to complete the loop so that
// each number in the Vec is multiplied by 2.
//
// Make me pass the test!
//
// Execute `rustlings hint vecs2` or use the `hint` watch subcommand for a hint.

// I AM DONE

fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
    for element in v.iter_mut() {
        // TODO: Fill this up so that each element in the Vec `v` is
        // multiplied by 2.
        *element *= 2;
    }

    // At this point, `v` should be equal to [4, 8, 12, 16, 20].
    v
}

fn vec_map(v: &Vec<i32>) -> Vec<i32> {
    v.iter().map(|element| {
        // TODO: Do the same thing as above - but instead of mutating the
        // Vec, you can just return the new number!
        *element * 2
    }).collect()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vec_loop() {
        let v: Vec<i32> = (1..).filter(|x| x % 2 == 0).take(5).collect();
        let ans = vec_loop(v.clone());

        assert_eq!(ans, v.iter().map(|x| x * 2).collect::<Vec<i32>>());
    }

    #[test]
    fn test_vec_map() {
        let v: Vec<i32> = (1..).filter(|x| x % 2 == 0).take(5).collect();
        let ans = vec_map(&v);

        assert_eq!(ans, v.iter().map(|x| x * 2).collect::<Vec<i32>>());
    }
}

move_semantics

move_semantics1.rs

// move_semantics1.rs
//
// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let vec0 = Vec::new();

    let mut vec1 = fill_vec(vec0);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
}

fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
    let mut vec = vec;

    vec.push(22);
    vec.push(44);
    vec.push(66);

    vec
}

move_semantics2.rs

// move_semantics2.rs
//
// Expected output:
// vec0 has length 3, with contents `[22, 44, 66]`
// vec1 has length 4, with contents `[22, 44, 66, 88]`
//
// Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let vec0 = Vec::new();

    let mut vec1 = fill_vec(vec0);
    let mut vec0 = vec1.clone();

    println!("{} has length {}, with contents: `{:?}`", "vec0", vec0.len(), vec0);

    vec1.push(88);

    println!("{} has length {}, with contents `{:?}`", "vec1", vec1.len(), vec1);
}

fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
    let mut vec = vec;

    vec.push(22);
    vec.push(44);
    vec.push(66);

    vec
}

move_semantics3.rs

// move_semantics3.rs
//
// Make me compile without adding new lines-- just changing existing lines! (no
// lines with multiple semicolons necessary!)
//
// Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let vec0 = Vec::new();

    let mut vec1 = fill_vec(vec0);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
}

fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
    let mut vec = vec;

    vec.push(22);
    vec.push(44);
    vec.push(66);

    vec
}

move_semantics4.rs

// move_semantics4.rs
//
// Refactor this code so that instead of passing `vec0` into the `fill_vec`
// function, the Vector gets created in the function itself and passed back to
// the main function.
//
// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let mut vec1 = fill_vec();

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
}

// `fill_vec()` no longer takes `vec: Vec<i32>` as argument
fn fill_vec() -> Vec<i32> {
    let mut vec : Vec<i32> = Vec::new();

    vec.push(22);
    vec.push(44);
    vec.push(66);

    vec
}

move_semantics5.rs

// move_semantics5.rs
//
// Make me compile only by reordering the lines in `main()`, but without adding,
// changing or removing any of them.
//
// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let mut x = 100;
    let y = &mut x;
    *y += 100;
    let z = &mut x;
    *z += 1000;
    assert_eq!(x, 1200);
}

move_semantics6.rs

// move_semantics6.rs
//
// You can't change anything except adding or removing references.
//
// Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand
// for a hint.

// I AM DONE

fn main() {
    let data = "Rust is great!".to_string();

    get_char(&data);

    string_uppercase(&data);
}

// Should not take ownership
fn get_char(data: &String) -> char {
    data.chars().last().unwrap()
}

// Should take ownership
fn string_uppercase(mut data: &String) {
    let data = data.to_uppercase();

    println!("{}", data);
}

struct

struct1.rs

// structs1.rs
//
// Address all the TODOs to make the tests pass!
//
// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

struct ColorClassicStruct {
    red : i32,
    green : i32,
    blue : i32,
}

struct ColorTupleStruct(i32, i32, i32);

#[derive(Debug)]
struct UnitLikeStruct;

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn classic_c_structs() {
        // TODO: Instantiate a classic c struct!
        let green = ColorClassicStruct{
            red : 0,
            green : 255,
            blue : 0,
        };

        assert_eq!(green.red, 0);
        assert_eq!(green.green, 255);
        assert_eq!(green.blue, 0);
    }

    #[test]
    fn tuple_structs() {
        // TODO: Instantiate a tuple struct!
        let green = ColorTupleStruct(0, 255, 0);

        assert_eq!(green.0, 0);
        assert_eq!(green.1, 255);
        assert_eq!(green.2, 0);
    }

    #[test]
    fn unit_structs() {
        // TODO: Instantiate a unit-like struct!
        let unit_like_struct = UnitLikeStruct;
        let message = format!("{:?}s are fun!", unit_like_struct);

        assert_eq!(message, "UnitLikeStructs are fun!");
    }
}

struct2.rs

// structs2.rs
//
// Address all the TODOs to make the tests pass!
//
// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[derive(Debug)]
struct Order {
    name: String,
    year: u32,
    made_by_phone: bool,
    made_by_mobile: bool,
    made_by_email: bool,
    item_number: u32,
    count: u32,
}

fn create_order_template() -> Order {
    Order {
        name: String::from("Bob"),
        year: 2019,
        made_by_phone: false,
        made_by_mobile: false,
        made_by_email: true,
        item_number: 123,
        count: 0,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn your_order() {
        let order_template = create_order_template();
        // TODO: Create your own order using the update syntax and template above!
        let your_order = Order{
            name : "Hacker in Rust".to_string(),
            count : 1,
            ..order_template
        };
        assert_eq!(your_order.name, "Hacker in Rust");
        assert_eq!(your_order.year, order_template.year);
        assert_eq!(your_order.made_by_phone, order_template.made_by_phone);
        assert_eq!(your_order.made_by_mobile, order_template.made_by_mobile);
        assert_eq!(your_order.made_by_email, order_template.made_by_email);
        assert_eq!(your_order.item_number, order_template.item_number);
        assert_eq!(your_order.count, 1);
    }
}

struct3.rs

// structs3.rs
//
// Structs contain data, but can also have logic. In this exercise we have
// defined the Package struct and we want to test some logic attached to it.
// Make the code compile and the tests pass!
//
// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[derive(Debug)]
struct Package {
    sender_country: String,
    recipient_country: String,
    weight_in_grams: u32,
}

impl Package {
    fn new(sender_country: String, recipient_country: String, weight_in_grams: u32) -> Package {
        if weight_in_grams < 10 {
            // This is not how you should handle errors in Rust,
            // but we will learn about error handling later.
            panic!("Can not ship a package with weight below 10 grams.")
        } else {
            Package {
                sender_country,
                recipient_country,
                weight_in_grams,
            }
        }
    }

    fn is_international(&self) -> bool {
        // Something goes here...
        self.sender_country != self.recipient_country
    }

    fn get_fees(&self, cents_per_gram: u32) -> u32 {
        // Something goes here...
        self.weight_in_grams * cents_per_gram
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    #[should_panic]
    fn fail_creating_weightless_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Austria");

        Package::new(sender_country, recipient_country, 5);
    }

    #[test]
    fn create_international_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Russia");

        let package = Package::new(sender_country, recipient_country, 1200);

        assert!(package.is_international());
    }

    #[test]
    fn create_local_package() {
        let sender_country = String::from("Canada");
        let recipient_country = sender_country.clone();

        let package = Package::new(sender_country, recipient_country, 1200);

        assert!(!package.is_international());
    }

    #[test]
    fn calculate_transport_fees() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Spain");

        let cents_per_gram = 3;

        let package = Package::new(sender_country, recipient_country, 1500);

        assert_eq!(package.get_fees(cents_per_gram), 4500);
        assert_eq!(package.get_fees(cents_per_gram * 2), 9000);
    }
}

enum

enum1.rs

// enums1.rs
//
// No hints this time! ;)

// I AM DONE

#[derive(Debug)]
enum Message {
    // TODO: define a few types of messages as used below
    Quit,
    Echo,
    Move,
    ChangeColor,
}

fn main() {
    println!("{:?}", Message::Quit);
    println!("{:?}", Message::Echo);
    println!("{:?}", Message::Move);
    println!("{:?}", Message::ChangeColor);
}

enum2.rs

// enums2.rs
//
// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[derive(Debug)]
enum Message {
    // TODO: define the different variants used below
    Move{x:u8, y:u8},
    Echo(String),
    ChangeColor(u8, u8, u8),
    Quit,
}

impl Message {
    fn call(&self) {
        println!("{:?}", self);
    }
}

fn main() {
    let messages = [
        Message::Move { x: 10, y: 30 },
        Message::Echo(String::from("hello world")),
        Message::ChangeColor(200, 255, 255),
        Message::Quit,
    ];

    for message in &messages {
        message.call();
    }
}

enum3.rs

// enums3.rs
//
// Address all the TODOs to make the tests pass!
//
// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

enum Message {
    // TODO: implement the message variant types based on their usage below
    ChangeColor(u8, u8, u8),
    Move(Point),
    Echo(String),
    Quit,
}

struct Point {
    x: u8,
    y: u8,
}

struct State {
    color: (u8, u8, u8),
    position: Point,
    quit: bool,
    message: String
}

impl State {
    fn change_color(&mut self, color: (u8, u8, u8)) {
        self.color = color;
    }

    fn quit(&mut self) {
        self.quit = true;
    }

    fn echo(&mut self, s: String) { self.message = s }

    fn move_position(&mut self, p: Point) {
        self.position = p;
    }

    fn process(&mut self, message: Message) {
        // TODO: create a match expression to process the different message
        // variants
        // Remember: When passing a tuple as a function argument, you'll need
        // extra parentheses: fn function((t, u, p, l, e))
        match message {
            Message::ChangeColor(r, g, b) => self.change_color((r, g, b)),
            Message::Echo(s) => self.echo(s),
            Message::Move(p) => self.move_position(p),
            Message::Quit => self.quit(),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_match_message_call() {
        let mut state = State {
            quit: false,
            position: Point { x: 0, y: 0 },
            color: (0, 0, 0),
            message: "hello world".to_string(),
        };
        state.process(Message::ChangeColor(255, 0, 255));
        state.process(Message::Echo(String::from("hello world")));
        state.process(Message::Move(Point { x: 10, y: 15 }));
        state.process(Message::Quit);

        assert_eq!(state.color, (255, 0, 255));
        assert_eq!(state.position.x, 10);
        assert_eq!(state.position.y, 15);
        assert_eq!(state.quit, true);
        assert_eq!(state.message, "hello world");
    }
}

string

string1.rs

// strings1.rs
//
// Make me compile without changing the function signature!
//
// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a
// hint.

// I AM ONE

fn main() {
    let answer = current_favorite_color();
    println!("My current favorite color is {}", answer);
}

fn current_favorite_color() -> String {
    "blue".to_string()
}

string2.rs

// strings2.rs
//
// Make me compile without changing the function signature!
//
// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let word = String::from("green"); // Try not changing this line :)
    if is_a_color_word(word) {
        println!("That is a color word I know!");
    } else {
        println!("That is not a color word I know.");
    }
}

fn is_a_color_word(attempt: String) -> bool {
    attempt == "green" || attempt == "blue" || attempt == "red"
}

string3.rs

// strings3.rs
//
// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn trim_me(input: &str) -> String {
    // TODO: Remove whitespace from both ends of a string!
    input.trim().to_string()
}

fn compose_me(input: &str) -> String {
    // TODO: Add " world!" to the string! There's multiple ways to do this!
    format!("{input} world!")
}

fn replace_me(input: &str) -> String {
    // TODO: Replace "cars" in the string with "balloons"!
    input.replace("cars", "balloons")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn trim_a_string() {
        assert_eq!(trim_me("Hello!     "), "Hello!");
        assert_eq!(trim_me("  What's up!"), "What's up!");
        assert_eq!(trim_me("   Hola!  "), "Hola!");
    }

    #[test]
    fn compose_a_string() {
        assert_eq!(compose_me("Hello"), "Hello world!");
        assert_eq!(compose_me("Goodbye"), "Goodbye world!");
    }

    #[test]
    fn replace_a_string() {
        assert_eq!(replace_me("I think cars are cool"), "I think balloons are cool");
        assert_eq!(replace_me("I love to look at cars"), "I love to look at balloons");
    }
}

string4.rs

// strings4.rs
//
// Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
// task is to call one of these two functions on each value depending on what
// you think each value is. That is, add either `string_slice` or `string`
// before the parentheses on each line. If you're right, it will compile!
//
// No hints this time!

// I AM DONE

fn string_slice(arg: &str) {
    println!("{}", arg);
}
fn string(arg: String) {
    println!("{}", arg);
}

fn main() {
    string_slice("blue");
    string("red".to_string());
    string(String::from("hi"));
    string("rust is fun!".to_owned());
    string_slice("nice weather".into());
    string(format!("Interpolation {}", "Station"));
    string_slice(&String::from("abc")[0..1]);
    string_slice("  hello there ".trim());
    string("Happy Monday!".to_string().replace("Mon", "Tues"));
    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
}

modules

modules1.rs

// modules1.rs
//
// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

mod sausage_factory {
    // Don't let anybody outside of this module see this!
    fn get_secret_recipe() -> String {
        String::from("Ginger")
    }

    pub fn make_sausage() {
        get_secret_recipe();
        println!("sausage!");
    }
}

fn main() {
    sausage_factory::make_sausage();
}

modules2.rs

// modules2.rs
//
// You can bring module paths into scopes and provide new names for them with
// the 'use' and 'as' keywords. Fix these 'use' statements to make the code
// compile.
//
// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

mod delicious_snacks {
    // TODO: Fix these use statements
    pub use self::fruits::PEAR as fruit;
    pub use self::veggies::CUCUMBER as veggie;

    mod fruits {
        pub const PEAR: &'static str = "Pear";
        pub const APPLE: &'static str = "Apple";
    }

    mod veggies {
        pub const CUCUMBER: &'static str = "Cucumber";
        pub const CARROT: &'static str = "Carrot";
    }
}

fn main() {
    println!(
        "favorite snacks: {} and {}",
        delicious_snacks::fruit,
        delicious_snacks::veggie
    );
}

modules3.rs

// modules3.rs
//
// You can use the 'use' keyword to bring module paths from modules from
// anywhere and especially from the Rust standard library into your scope. Bring
// SystemTime and UNIX_EPOCH from the std::time module. Bonus style points if
// you can do it with one line!
//
// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

// TODO: Complete this use statement
use std::time::{SystemTime, UNIX_EPOCH};

fn main() {
    match SystemTime::now().duration_since(UNIX_EPOCH) {
        Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
        Err(_) => panic!("SystemTime before UNIX EPOCH!"),
    }
}

hashmap

hashmap1.rs

// hashmaps1.rs
//
// A basket of fruits in the form of a hash map needs to be defined. The key
// represents the name of the fruit and the value represents how many of that
// particular fruit is in the basket. You have to put at least three different
// types of fruits (e.g apple, banana, mango) in the basket and the total count
// of all the fruits should be at least five.
//
// Make me compile and pass the tests!
//
// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::collections::HashMap;

fn fruit_basket() -> HashMap<String, u32> {
    let mut basket = HashMap::new();

    // Two bananas are already given for you :)
    basket.insert(String::from("banana"), 2);

    // TODO: Put more fruits in your basket here.
    basket.insert(String::from("apple"), 2);
    basket.insert(String::from("mango"), 2);

    basket
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn at_least_three_types_of_fruits() {
        let basket = fruit_basket();
        assert!(basket.len() >= 3);
    }

    #[test]
    fn at_least_five_fruits() {
        let basket = fruit_basket();
        assert!(basket.values().sum::<u32>() >= 5);
    }
}

hashmap2.rs

// hashmaps2.rs
//
// We're collecting different fruits to bake a delicious fruit cake. For this,
// we have a basket, which we'll represent in the form of a hash map. The key
// represents the name of each fruit we collect and the value represents how
// many of that particular fruit we have collected. Three types of fruits -
// Apple (4), Mango (2) and Lychee (5) are already in the basket hash map. You
// must add fruit to the basket so that there is at least one of each kind and
// more than 11 in total - we have a lot of mouths to feed. You are not allowed
// to insert any more of these fruits!
//
// Make me pass the tests!
//
// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::collections::HashMap;

#[derive(Hash, PartialEq, Eq)]
enum Fruit {
    Apple,
    Banana,
    Mango,
    Lychee,
    Pineapple,
}

fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
    let fruit_kinds = vec![
        Fruit::Apple,
        Fruit::Banana,
        Fruit::Mango,
        Fruit::Lychee,
        Fruit::Pineapple,
    ];

    for fruit in fruit_kinds {
        // TODO: Insert new fruits if they are not already present in the
        // basket. Note that you are not allowed to put any type of fruit that's
        // already present!
        basket.entry(fruit).or_insert(1);
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    // Don't modify this function!
    fn get_fruit_basket() -> HashMap<Fruit, u32> {
        let mut basket = HashMap::<Fruit, u32>::new();
        basket.insert(Fruit::Apple, 4);
        basket.insert(Fruit::Mango, 2);
        basket.insert(Fruit::Lychee, 5);

        basket
    }

    #[test]
    fn test_given_fruits_are_not_modified() {
        let mut basket = get_fruit_basket();
        fruit_basket(&mut basket);
        assert_eq!(*basket.get(&Fruit::Apple).unwrap(), 4);
        assert_eq!(*basket.get(&Fruit::Mango).unwrap(), 2);
        assert_eq!(*basket.get(&Fruit::Lychee).unwrap(), 5);
    }

    #[test]
    fn at_least_five_types_of_fruits() {
        let mut basket = get_fruit_basket();
        fruit_basket(&mut basket);
        let count_fruit_kinds = basket.len();
        assert!(count_fruit_kinds >= 5);
    }

    #[test]
    fn greater_than_eleven_fruits() {
        let mut basket = get_fruit_basket();
        fruit_basket(&mut basket);
        let count = basket.values().sum::<u32>();
        assert!(count > 11);
    }
    
    #[test]
    fn all_fruit_types_in_basket() {
        let mut basket = get_fruit_basket();
        fruit_basket(&mut basket);
        for amount in basket.values() {
            assert_ne!(amount, &0);
        }
    }
}

hashmap3.rs

// hashmaps3.rs
//
// A list of scores (one per line) of a soccer match is given. Each line is of
// the form : "<team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>"
// Example: England,France,4,2 (England scored 4 goals, France 2).
//
// You have to build a scores table containing the name of the team, goals the
// team scored, and goals the team conceded. One approach to build the scores
// table is to use a Hashmap. The solution is partially written to use a
// Hashmap, complete it to pass the test.
//
// Make me pass the tests!
//
// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::collections::HashMap;

// A structure to store the goal details of a team.
struct Team {
    goals_scored: u8,
    goals_conceded: u8,
}

fn build_scores_table(results: String) -> HashMap<String, Team> {
    // The name of the team is the key and its associated struct is the value.
    let mut scores: HashMap<String, Team> = HashMap::new();

    for r in results.lines() {
        let v: Vec<&str> = r.split(',').collect();
        let team_1_name = v[0].to_string();
        let team_1_score: u8 = v[2].parse().unwrap();
        let team_2_name = v[1].to_string();
        let team_2_score: u8 = v[3].parse().unwrap();
        // TODO: Populate the scores table with details extracted from the
        // current line. Keep in mind that goals scored by team_1
        // will be the number of goals conceded from team_2, and similarly
        // goals scored by team_2 will be the number of goals conceded by
        // team_1.
        scores.entry(team_1_name.clone()).or_insert(Team{
            goals_scored : 0,
            goals_conceded : 0,
        });
        scores.get_mut(&team_1_name).unwrap().goals_scored += team_1_score;
        scores.get_mut(&team_1_name).unwrap().goals_conceded += team_2_score;

        scores.entry(team_2_name.clone()).or_insert(Team{
            goals_scored : 0,
            goals_conceded : 0,
        });
        scores.get_mut(&team_2_name).unwrap().goals_scored += team_2_score;
        scores.get_mut(&team_2_name).unwrap().goals_conceded += team_1_score;
    }
    scores
}

#[cfg(test)]
mod tests {
    use super::*;

    fn get_results() -> String {
        let results = "".to_string()
            + "England,France,4,2\n"
            + "France,Italy,3,1\n"
            + "Poland,Spain,2,0\n"
            + "Germany,England,2,1\n";
        results
    }

    #[test]
    fn build_scores() {
        let scores = build_scores_table(get_results());

        let mut keys: Vec<&String> = scores.keys().collect();
        keys.sort();
        assert_eq!(
            keys,
            vec!["England", "France", "Germany", "Italy", "Poland", "Spain"]
        );
    }

    #[test]
    fn validate_team_score_1() {
        let scores = build_scores_table(get_results());
        let team = scores.get("England").unwrap();
        assert_eq!(team.goals_scored, 5);
        assert_eq!(team.goals_conceded, 4);
    }

    #[test]
    fn validate_team_score_2() {
        let scores = build_scores_table(get_results());
        let team = scores.get("Spain").unwrap();
        assert_eq!(team.goals_scored, 0);
        assert_eq!(team.goals_conceded, 2);
    }
}

option

option1.rs

// options1.rs
//
// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

// This function returns how much icecream there is left in the fridge.
// If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
// all, so there'll be no more left :(
fn maybe_icecream(time_of_day: u16) -> Option<u16> {
    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
    // value of 0 The Option output should gracefully handle cases where
    // time_of_day > 23.
    // TODO: Complete the function body - remember to return an Option!
    if time_of_day <= 10 {
        Some(5)
    } else if time_of_day > 23 {
        None
    } else {
        Some(0)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn check_icecream() {
        assert_eq!(maybe_icecream(9), Some(5));
        assert_eq!(maybe_icecream(10), Some(5));
        assert_eq!(maybe_icecream(23), Some(0));
        assert_eq!(maybe_icecream(22), Some(0));
        assert_eq!(maybe_icecream(25), None);
    }

    #[test]
    fn raw_value() {
        // TODO: Fix this test. How do you get at the value contained in the
        // Option?
        let icecreams = maybe_icecream(10).unwrap();
        assert_eq!(icecreams, 5);
    }
}

option2.rs

// options2.rs
//
// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[cfg(test)]
mod tests {
    #[test]
    fn simple_option() {
        let target = "rustlings";
        let optional_target = Some(target);

        // TODO: Make this an if let statement whose value is "Some" type
        if let Some(word) = optional_target {
            assert_eq!(word, target);
        }
    }

    #[test]
    fn layered_option() {
        let range = 10;
        let mut optional_integers: Vec<Option<i8>> = vec![None];

        for i in 1..(range + 1) {
            optional_integers.push(Some(i));
        }

        let mut cursor = range;

        // TODO: make this a while let statement - remember that vector.pop also
        // adds another layer of Option<T>. You can stack `Option<T>`s into
        // while let and if let.
        while let Some(Some(integer)) = optional_integers.pop() {
            assert_eq!(integer, cursor);
            cursor -= 1;
        }

        assert_eq!(cursor, 0);
    }
}

option3.rs

// options3.rs
//
// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let y: Option<Point> = Some(Point { x: 100, y: 200 });

    let y = match y {
        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
        None => panic!("no match!"),
    };

    y; // Fix without deleting this line.
}

error

error1.rs

// errors1.rs
//
// This function refuses to generate text to be printed on a nametag if you pass
// it an empty string. It'd be nicer if it explained what the problem was,
// instead of just sometimes returning `None`. Thankfully, Rust has a similar
// construct to `Option` that can be used to express error conditions. Let's use
// it!
//
// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub fn generate_nametag_text(name: String) -> Result<String, String> {
    if name.is_empty() {
        // Empty names aren't allowed.
        Err("`name` was empty; it must be nonempty.".into())
    } else {
        Ok(format!("Hi! My name is {}", name))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn generates_nametag_text_for_a_nonempty_name() {
        assert_eq!(
            generate_nametag_text("Beyoncé".into()),
            Ok("Hi! My name is Beyoncé".into())
        );
    }

    #[test]
    fn explains_why_generating_nametag_text_fails() {
        assert_eq!(
            generate_nametag_text("".into()),
            // Don't change this line
            Err("`name` was empty; it must be nonempty.".into())
        );
    }
}

error2.rs

// errors2.rs
//
// Say we're writing a game where you can buy items with tokens. All items cost
// 5 tokens, and whenever you purchase items there is a processing fee of 1
// token. A player of the game will type in how many items they want to buy, and
// the `total_cost` function will calculate the total cost of the tokens. Since
// the player typed in the quantity, though, we get it as a string-- and they
// might have typed anything, not just numbers!
//
// Right now, this function isn't handling the error case at all (and isn't
// handling the success case properly either). What we want to do is: if we call
// the `total_cost` function on a string that is not a number, that function
// will return a `ParseIntError`, and in that case, we want to immediately
// return that error from our function and not try to multiply and add.
//
// There are at least two ways to implement this that are both correct-- but one
// is a lot shorter!
//
// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::num::ParseIntError;

pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
    let processing_fee = 1;
    let cost_per_item = 5;
    let qty = item_quantity.parse::<i32>()?;

    Ok(qty * cost_per_item + processing_fee)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn item_quantity_is_a_valid_number() {
        assert_eq!(total_cost("34"), Ok(171));
    }

    #[test]
    fn item_quantity_is_an_invalid_number() {
        assert_eq!(
            total_cost("beep boop").unwrap_err().to_string(),
            "invalid digit found in string"
        );
    }
}

error3.rs

// errors3.rs
//
// This is a program that is trying to use a completed version of the
// `total_cost` function from the previous exercise. It's not working though!
// Why not? What should we do to fix it?
//
// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::num::ParseIntError;

fn main() {
    let mut tokens = 100;
    let pretend_user_input = "8";

    let cost = total_cost(pretend_user_input);

    match cost {
        Ok(c) => {
            if c > tokens {
                println!("You can't afford that many!");
            } else {
                tokens -= c;
                println!("You now have {} tokens.", tokens);
            }
        },
        Err(e) => {},
    }
    
}

pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
    let processing_fee = 1;
    let cost_per_item = 5;
    let qty = item_quantity.parse::<i32>()?;

    Ok(qty * cost_per_item + processing_fee)
}

error4.rs

// errors4.rs
//
// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64);

#[derive(PartialEq, Debug)]
enum CreationError {
    Negative,
    Zero,
}

impl PositiveNonzeroInteger {
    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
        // Hmm... Why is this always returning an Ok value?
        if value < 0 {
            Err(CreationError::Negative)
        } else if value == 0 {
            Err(CreationError::Zero)
        } else {
            Ok(PositiveNonzeroInteger(value as u64))
        }
    }
}

#[test]
fn test_creation() {
    assert!(PositiveNonzeroInteger::new(10).is_ok());
    assert_eq!(
        Err(CreationError::Negative),
        PositiveNonzeroInteger::new(-10)
    );
    assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
}

error5.rs

// errors5.rs
//
// This program uses an altered version of the code from errors4.
//
// This exercise uses some concepts that we won't get to until later in the
// course, like `Box` and the `From` trait. It's not important to understand
// them in detail right now, but you can read ahead if you like. For now, think
// of the `Box<dyn ???>` type as an "I want anything that does ???" type, which,
// given Rust's usual standards for runtime safety, should strike you as
// somewhat lenient!
//
// In short, this particular use case for boxes is for when you want to own a
// value and you care only that it is a type which implements a particular
// trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is
// the trait the compiler looks for on any value used in that context. For this
// exercise, that context is the potential errors which can be returned in a
// Result.
//
// What can we use to describe both errors? In other words, is there a trait
// which both errors implement?
//
// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::error;
use std::fmt;
use std::num::ParseIntError;

// TODO: update the return type of `main()` to make this compile.
fn main() -> Result<(), Box<dyn error::Error>> {
    let pretend_user_input = "42";
    let x: i64 = pretend_user_input.parse()?;
    println!("output={:?}", PositiveNonzeroInteger::new(x)?);
    Ok(())
}

// Don't change anything below this line.

#[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64);

#[derive(PartialEq, Debug)]
enum CreationError {
    Negative,
    Zero,
}

impl PositiveNonzeroInteger {
    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
        match value {
            x if x < 0 => Err(CreationError::Negative),
            x if x == 0 => Err(CreationError::Zero),
            x => Ok(PositiveNonzeroInteger(x as u64)),
        }
    }
}

// This is required so that `CreationError` can implement `error::Error`.
impl fmt::Display for CreationError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let description = match *self {
            CreationError::Negative => "number is negative",
            CreationError::Zero => "number is zero",
        };
        f.write_str(description)
    }
}

impl error::Error for CreationError {}

error6.rs

// errors6.rs
//
// Using catch-all error types like `Box<dyn error::Error>` isn't recommended
// for library code, where callers might want to make decisions based on the
// error content, instead of printing it out or propagating it further. Here, we
// define a custom error type to make it possible for callers to decide what to
// do next when our function returns an error.
//
// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::num::ParseIntError;

// This is a custom error type that we will be using in `parse_pos_nonzero()`.
#[derive(PartialEq, Debug)]
enum ParsePosNonzeroError {
    Creation(CreationError),
    ParseInt(ParseIntError),
}

impl ParsePosNonzeroError {
    fn from_creation(err: CreationError) -> ParsePosNonzeroError {
        ParsePosNonzeroError::Creation(err)
    }
    // TODO: add another error conversion function here.
    fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
        ParsePosNonzeroError::ParseInt(err)
    }
}

fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
    // TODO: change this to return an appropriate error instead of panicking
    // when `parse()` returns an error.
    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
    PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
}

// Don't change anything below this line.

#[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64);

#[derive(PartialEq, Debug)]
enum CreationError {
    Negative,
    Zero,
}

impl PositiveNonzeroInteger {
    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
        match value {
            x if x < 0 => Err(CreationError::Negative),
            x if x == 0 => Err(CreationError::Zero),
            x => Ok(PositiveNonzeroInteger(x as u64)),
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_parse_error() {
        // We can't construct a ParseIntError, so we have to pattern match.
        assert!(matches!(
            parse_pos_nonzero("not a number"),
            Err(ParsePosNonzeroError::ParseInt(_))
        ));
    }

    #[test]
    fn test_negative() {
        assert_eq!(
            parse_pos_nonzero("-555"),
            Err(ParsePosNonzeroError::Creation(CreationError::Negative))
        );
    }

    #[test]
    fn test_zero() {
        assert_eq!(
            parse_pos_nonzero("0"),
            Err(ParsePosNonzeroError::Creation(CreationError::Zero))
        );
    }

    #[test]
    fn test_positive() {
        let x = PositiveNonzeroInteger::new(42);
        assert!(x.is_ok());
        assert_eq!(parse_pos_nonzero("42"), Ok(x.unwrap()));
    }
}

generics

generics1.rs

// generics1.rs
//
// This shopping list program isn't compiling! Use your knowledge of generics to
// fix it.
//
// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let mut shopping_list: Vec<&str> = Vec::new();
    shopping_list.push("milk");
}

generics1.rs

// generics2.rs
//
// This powerful wrapper provides the ability to store a positive integer value.
// Rewrite it using generics so that it supports wrapping ANY type.
//
// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

struct Wrapper<T> {
    value: T,
}

impl<T> Wrapper<T> {
    pub fn new(value: T) -> Self {
        Wrapper { value }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn store_u32_in_wrapper() {
        assert_eq!(Wrapper::new(42).value, 42);
    }

    #[test]
    fn store_str_in_wrapper() {
        assert_eq!(Wrapper::new("Foo").value, "Foo");
    }
}

traits

traits1.rs

// traits1.rs
//
// Time to implement some traits! Your task is to implement the trait
// `AppendBar` for the type `String`. The trait AppendBar has only one function,
// which appends "Bar" to any object implementing this trait.
//
// Execute `rustlings hint traits1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

trait AppendBar {
    fn append_bar(self) -> Self;
}

impl AppendBar for String {
    // TODO: Implement `AppendBar` for type `String`.
    fn append_bar(self) -> Self {
        format!("{self}Bar")
    }
}

fn main() {
    let s = String::from("Foo");
    let s = s.append_bar();
    println!("s: {}", s);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn is_foo_bar() {
        assert_eq!(String::from("Foo").append_bar(), String::from("FooBar"));
    }

    #[test]
    fn is_bar_bar() {
        assert_eq!(
            String::from("").append_bar().append_bar(),
            String::from("BarBar")
        );
    }
}

traits2.rs

// traits2.rs
//
// Your task is to implement the trait `AppendBar` for a vector of strings. To
// implement this trait, consider for a moment what it means to 'append "Bar"'
// to a vector of strings.
//
// No boiler plate code this time, you can do this!
//
// Execute `rustlings hint traits2` or use the `hint` watch subcommand for a hint.

// I AM DONE

trait AppendBar {
    fn append_bar(self) -> Self;
}

// TODO: Implement trait `AppendBar` for a vector of strings.
impl AppendBar for Vec<String> {
    fn append_bar(mut self) -> Self {
        self.push("Bar".to_string());
        self
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn is_vec_pop_eq_bar() {
        let mut foo = vec![String::from("Foo")].append_bar();
        assert_eq!(foo.pop().unwrap(), String::from("Bar"));
        assert_eq!(foo.pop().unwrap(), String::from("Foo"));
    }
}

traits3.rs

// traits3.rs
//
// Your task is to implement the Licensed trait for both structures and have
// them return the same information without writing the same function twice.
//
// Consider what you can add to the Licensed trait.
//
// Execute `rustlings hint traits3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub trait Licensed {
    fn licensing_info(&self) -> String {
        "Some information".to_string()
    }
}

struct SomeSoftware {
    version_number: i32,
}

struct OtherSoftware {
    version_number: String,
}

impl Licensed for SomeSoftware {} // Don't edit this line
impl Licensed for OtherSoftware {} // Don't edit this line

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn is_licensing_info_the_same() {
        let licensing_info = String::from("Some information");
        let some_software = SomeSoftware { version_number: 1 };
        let other_software = OtherSoftware {
            version_number: "v2.0.0".to_string(),
        };
        assert_eq!(some_software.licensing_info(), licensing_info);
        assert_eq!(other_software.licensing_info(), licensing_info);
    }
}

traits4.rs

// traits4.rs
//
// Your task is to replace the '??' sections so the code compiles.
//
// Don't change any line other than the marked one.
//
// Execute `rustlings hint traits4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub trait Licensed {
    fn licensing_info(&self) -> String {
        "some information".to_string()
    }
}

struct SomeSoftware {}

struct OtherSoftware {}

impl Licensed for SomeSoftware {}
impl Licensed for OtherSoftware {}

// YOU MAY ONLY CHANGE THE NEXT LINE
fn compare_license_types(software: impl Licensed, software_two: impl Licensed) -> bool {
    software.licensing_info() == software_two.licensing_info()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn compare_license_information() {
        let some_software = SomeSoftware {};
        let other_software = OtherSoftware {};

        assert!(compare_license_types(some_software, other_software));
    }

    #[test]
    fn compare_license_information_backwards() {
        let some_software = SomeSoftware {};
        let other_software = OtherSoftware {};

        assert!(compare_license_types(other_software, some_software));
    }
}

traits5.rs

// traits5.rs
//
// Your task is to replace the '??' sections so the code compiles.
//
// Don't change any line other than the marked one.
//
// Execute `rustlings hint traits5` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub trait SomeTrait {
    fn some_function(&self) -> bool {
        true
    }
}

pub trait OtherTrait {
    fn other_function(&self) -> bool {
        true
    }
}

struct SomeStruct {}
struct OtherStruct {}

impl SomeTrait for SomeStruct {}
impl OtherTrait for SomeStruct {}
impl SomeTrait for OtherStruct {}
impl OtherTrait for OtherStruct {}

// YOU MAY ONLY CHANGE THE NEXT LINE
fn some_func(item: impl SomeTrait + OtherTrait) -> bool {
    item.some_function() && item.other_function()
}

fn main() {
    some_func(SomeStruct {});
    some_func(OtherStruct {});
}

lifetime

lifetime1.rs

// lifetimes1.rs
//
// The Rust compiler needs to know how to check whether supplied references are
// valid, so that it can let the programmer know if a reference is at risk of
// going out of scope before it is used. Remember, references are borrows and do
// not own their own data. What if their owner goes out of scope?
//
// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

fn main() {
    let string1 = String::from("abcd");
    let string2 = "xyz";

    let result = longest(string1.as_str(), string2);
    println!("The longest string is '{}'", result);
}

lifetime2.rs

// lifetimes2.rs
//
// So if the compiler is just validating the references passed to the annotated
// parameters and the return type, what do we need to change?
//
// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

fn main() {
    let string1 = String::from("long string is long");
    let result;
    {
        let string2 = String::from("xyz");
        result = longest(string1.as_str(), string2.as_str());
        println!("The longest string is '{}'", result);
    }
}

lifetime3.rs

// lifetimes3.rs
//
// Lifetimes are also needed when structs hold references.
//
// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

struct Book<'a> {
    author: &'a str,
    title: &'a str,
}

fn main() {
    let name = String::from("Jill Smith");
    let title = String::from("Fish Flying");
    let book = Book { author: &name, title: &title };

    println!("{} by {}", book.title, book.author);
}

test

test1.rs

// tests1.rs
//
// Tests are important to ensure that your code does what you think it should
// do. Tests can be run on this file with the following command: rustlings run
// tests1
//
// This test has a problem with it -- make the test compile! Make the test pass!
// Make the test fail!
//
// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[cfg(test)]
mod tests {
    #[test]
    fn you_can_assert() {
        assert!(true);
    }
}

test2.rs

// tests2.rs
//
// This test has a problem with it -- make the test compile! Make the test pass!
// Make the test fail!
//
// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[cfg(test)]
mod tests {
    #[test]
    fn you_can_assert_eq() {
        assert_eq!(true, true);
    }
}

test3.rs

// tests3.rs
//
// This test isn't testing our function -- make it do that in such a way that
// the test passes. Then write a second test that tests whether we get the
// result we expect to get when we call `is_even(5)`.
//
// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub fn is_even(num: i32) -> bool {
    num % 2 == 0
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn is_true_when_even() {
        assert!(is_even(2));
    }

    #[test]
    fn is_false_when_odd() {
        assert!(!is_even(5));
    }
}

test4.rs

// tests4.rs
//
// Make sure that we're testing for the correct conditions!
//
// Execute `rustlings hint tests4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

struct Rectangle {
    width: i32,
    height: i32
}

impl Rectangle {
    // Only change the test functions themselves
    pub fn new(width: i32, height: i32) -> Self {
        if width <= 0 || height <= 0 {
            panic!("Rectangle width and height cannot be negative!")
        }
        Rectangle {width, height}
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn correct_width_and_height() {
        // This test should check if the rectangle is the size that we pass into its constructor
        let rect = Rectangle::new(10, 20);
        assert_eq!(rect.width, 10); // check width
        assert_eq!(rect.height, 20); // check height
    }

    #[test]
    #[should_panic (expected = "negative")]
    fn negative_width() {
        // This test should check if program panics when we try to create rectangle with negative width
        let _rect = Rectangle::new(-10, 10);
    }

    #[test]
    #[should_panic (expected = "negative")]
    fn negative_height() {
        // This test should check if program panics when we try to create rectangle with negative height
        let _rect = Rectangle::new(10, -10);
    }
}

iterators

iterators1.rs

// iterators1.rs
//
// When performing operations on elements within a collection, iterators are
// essential. This module helps you get familiar with the structure of using an
// iterator and how to go through elements within an iterable collection.
//
// Make me compile by filling in the `???`s
//
// Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];

    let mut my_iterable_fav_fruits = my_fav_fruits.iter();   // TODO: Step 1

    assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"custard apple"));     // TODO: Step 2
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"peach"));     // TODO: Step 3
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
    assert_eq!(my_iterable_fav_fruits.next(), None);     // TODO: Step 4
}

iterators2.rs

// iterators2.rs
//
// In this exercise, you'll learn some of the unique advantages that iterators
// can offer. Follow the steps to complete the exercise.
//
// Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

// Step 1.
// Complete the `capitalize_first` function.
// "hello" -> "Hello"
pub fn capitalize_first(input: &str) -> String {
    let mut c = input.chars();
    match c.next() {
        None => String::new(),
        Some(first) => first.to_uppercase().collect::<String>() + c.as_str(),
    }
}

// Step 2.
// Apply the `capitalize_first` function to a slice of string slices.
// Return a vector of strings.
// ["hello", "world"] -> ["Hello", "World"]
pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
    let mut res = vec![];
    for word in words {
        res.push(capitalize_first(word))
    }
    res
}

// Step 3.
// Apply the `capitalize_first` function again to a slice of string slices.
// Return a single string.
// ["hello", " ", "world"] -> "Hello World"
pub fn capitalize_words_string(words: &[&str]) -> String {
    let mut res = String::new();
    for word in words {
        res += &capitalize_first(word);
    }
    res
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_success() {
        assert_eq!(capitalize_first("hello"), "Hello");
    }

    #[test]
    fn test_empty() {
        assert_eq!(capitalize_first(""), "");
    }

    #[test]
    fn test_iterate_string_vec() {
        let words = vec!["hello", "world"];
        assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
    }

    #[test]
    fn test_iterate_into_string() {
        let words = vec!["hello", " ", "world"];
        assert_eq!(capitalize_words_string(&words), "Hello World");
    }
}

iterators3.rs

// iterators3.rs
//
// This is a bigger exercise than most of the others! You can do it! Here is
// your mission, should you choose to accept it:
// 1. Complete the divide function to get the first four tests to pass.
// 2. Get the remaining tests to pass by completing the result_with_list and
//    list_of_results functions.
//
// Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[derive(Debug, PartialEq, Eq)]
pub enum DivisionError {
    NotDivisible(NotDivisibleError),
    DivideByZero,
}

#[derive(Debug, PartialEq, Eq)]
pub struct NotDivisibleError {
    dividend: i32,
    divisor: i32,
}

// Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
// Otherwise, return a suitable error.
pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
    if b == 0 {
        Err(DivisionError::DivideByZero)
    } else if a % b == 0 {
        Ok(a / b)
    } else {
        Err(DivisionError::NotDivisible(NotDivisibleError{
            dividend : a,
            divisor  : b,
        }))
    }
}

// Complete the function and return a value of the correct type so the test
// passes.
// Desired output: Ok([1, 11, 1426, 3])
fn result_with_list() -> Result<Vec<i32>, DivisionError> {
    let numbers = vec![27, 297, 38502, 81];
    let mut res : Vec<i32> = vec![];
    for num in numbers {
        res.push(divide(num, 27)?)
    }
    Ok(res)
}

// Complete the function and return a value of the correct type so the test
// passes.
// Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
fn list_of_results() -> Vec<Result<i32, DivisionError>> {
    let numbers = vec![27, 297, 38502, 81];
    let mut res : Vec<Result<i32, DivisionError>> = vec![];
    for num in numbers {
        res.push(divide(num, 27))
    }
    res
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_success() {
        assert_eq!(divide(81, 9), Ok(9));
    }

    #[test]
    fn test_not_divisible() {
        assert_eq!(
            divide(81, 6),
            Err(DivisionError::NotDivisible(NotDivisibleError {
                dividend: 81,
                divisor: 6
            }))
        );
    }

    #[test]
    fn test_divide_by_0() {
        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
    }

    #[test]
    fn test_divide_0_by_something() {
        assert_eq!(divide(0, 81), Ok(0));
    }

    #[test]
    fn test_result_with_list() {
        assert_eq!(format!("{:?}", result_with_list()), "Ok([1, 11, 1426, 3])");
    }

    #[test]
    fn test_list_of_results() {
        assert_eq!(
            format!("{:?}", list_of_results()),
            "[Ok(1), Ok(11), Ok(1426), Ok(3)]"
        );
    }
}

iterators4.rs

// iterators4.rs
//
// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

pub fn factorial(num: u64) -> u64 {
    // Complete this function to return the factorial of num
    // Do not use:
    // - return
    // Try not to use:
    // - imperative style loops (for, while)
    // - additional variables
    // For an extra challenge, don't use:
    // - recursion
    // Execute `rustlings hint iterators4` for hints.
    if num <= 1 {
        1
    } else {
        num * factorial(num - 1)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn factorial_of_0() {
        assert_eq!(1, factorial(0));
    }

    #[test]
    fn factorial_of_1() {
        assert_eq!(1, factorial(1));
    }
    #[test]
    fn factorial_of_2() {
        assert_eq!(2, factorial(2));
    }

    #[test]
    fn factorial_of_4() {
        assert_eq!(24, factorial(4));
    }
}

iterators5.rs

// iterators5.rs
//
// Let's define a simple model to track Rustlings exercise progress. Progress
// will be modelled using a hash map. The name of the exercise is the key and
// the progress is the value. Two counting functions were created to count the
// number of exercises with a given progress. Recreate this counting
// functionality using iterators. Try not to use imperative loops (for, while).
// Only the two iterator methods (count_iterator and count_collection_iterator)
// need to be modified.
//
// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::collections::HashMap;

#[derive(Clone, Copy, PartialEq, Eq)]
enum Progress {
    None,
    Some,
    Complete,
}

fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
    let mut count = 0;
    for val in map.values() {
        if val == &value {
            count += 1;
        }
    }
    count
}

fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
    // map is a hashmap with String keys and Progress values.
    // map = { "variables1": Complete, "from_str": None, ... }
    let mut count = 0;
    for val in map.values() {
        if val == &value {
            count += 1;
        }
    }
    count
}

fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
    let mut count = 0;
    for map in collection {
        for val in map.values() {
            if val == &value {
                count += 1;
            }
        }
    }
    count
}

fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
    // collection is a slice of hashmaps.
    // collection = [{ "variables1": Complete, "from_str": None, ... },
    //     { "variables2": Complete, ... }, ... ]
    let mut count = 0;
    for map in collection {
        for val in map.values() {
            if val == &value {
                count += 1;
            }
        }
    }
    count
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn count_complete() {
        let map = get_map();
        assert_eq!(3, count_iterator(&map, Progress::Complete));
    }

    #[test]
    fn count_some() {
        let map = get_map();
        assert_eq!(1, count_iterator(&map, Progress::Some));
    }

    #[test]
    fn count_none() {
        let map = get_map();
        assert_eq!(2, count_iterator(&map, Progress::None));
    }

    #[test]
    fn count_complete_equals_for() {
        let map = get_map();
        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
        for progress_state in progress_states {
            assert_eq!(
                count_for(&map, progress_state),
                count_iterator(&map, progress_state)
            );
        }
    }

    #[test]
    fn count_collection_complete() {
        let collection = get_vec_map();
        assert_eq!(
            6,
            count_collection_iterator(&collection, Progress::Complete)
        );
    }

    #[test]
    fn count_collection_some() {
        let collection = get_vec_map();
        assert_eq!(1, count_collection_iterator(&collection, Progress::Some));
    }

    #[test]
    fn count_collection_none() {
        let collection = get_vec_map();
        assert_eq!(4, count_collection_iterator(&collection, Progress::None));
    }

    #[test]
    fn count_collection_equals_for() {
        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
        let collection = get_vec_map();

        for progress_state in progress_states {
            assert_eq!(
                count_collection_for(&collection, progress_state),
                count_collection_iterator(&collection, progress_state)
            );
        }
    }

    fn get_map() -> HashMap<String, Progress> {
        use Progress::*;

        let mut map = HashMap::new();
        map.insert(String::from("variables1"), Complete);
        map.insert(String::from("functions1"), Complete);
        map.insert(String::from("hashmap1"), Complete);
        map.insert(String::from("arc1"), Some);
        map.insert(String::from("as_ref_mut"), None);
        map.insert(String::from("from_str"), None);

        map
    }

    fn get_vec_map() -> Vec<HashMap<String, Progress>> {
        use Progress::*;

        let map = get_map();

        let mut other = HashMap::new();
        other.insert(String::from("variables2"), Complete);
        other.insert(String::from("functions2"), Complete);
        other.insert(String::from("if1"), Complete);
        other.insert(String::from("from_into"), None);
        other.insert(String::from("try_from_into"), None);

        vec![map, other]
    }
}

smart_pointer

box1.rs

// box1.rs
//
// At compile time, Rust needs to know how much space a type takes up. This
// becomes problematic for recursive types, where a value can have as part of
// itself another value of the same type. To get around the issue, we can use a
// `Box` - a smart pointer used to store data on the heap, which also allows us
// to wrap a recursive type.
//
// The recursive type we're implementing in this exercise is the `cons list` - a
// data structure frequently found in functional programming languages. Each
// item in a cons list contains two elements: the value of the current item and
// the next item. The last item is a value called `Nil`.
//
// Step 1: use a `Box` in the enum definition to make the code compile
// Step 2: create both empty and non-empty cons lists by replacing `todo!()`
//
// Note: the tests should not be changed
//
// Execute `rustlings hint box1` or use the `hint` watch subcommand for a hint.

// I AM DONE

#[derive(PartialEq, Debug)]
pub enum List {
    Cons(i32, Box<List>),
    Nil,
}

fn main() {
    println!("This is an empty cons list: {:?}", create_empty_list());
    println!(
        "This is a non-empty cons list: {:?}",
        create_non_empty_list()
    );
}

pub fn create_empty_list() -> List {
    List::Nil
}

pub fn create_non_empty_list() -> List {
    List::Cons(0, Box::new(List::Nil))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_create_empty_list() {
        assert_eq!(List::Nil, create_empty_list())
    }

    #[test]
    fn test_create_non_empty_list() {
        assert_ne!(create_empty_list(), create_non_empty_list())
    }
}

rc1.rs

// rc1.rs
//
// In this exercise, we want to express the concept of multiple owners via the
// Rc<T> type. This is a model of our solar system - there is a Sun type and
// multiple Planets. The Planets take ownership of the sun, indicating that they
// revolve around the sun.
//
// Make this code compile by using the proper Rc primitives to express that the
// sun has multiple owners.
//
// Execute `rustlings hint rc1` or use the `hint` watch subcommand for a hint.

// I AM DONE

use std::rc::Rc;

#[derive(Debug)]
struct Sun {}

#[derive(Debug)]
enum Planet {
    Mercury(Rc<Sun>),
    Venus(Rc<Sun>),
    Earth(Rc<Sun>),
    Mars(Rc<Sun>),
    Jupiter(Rc<Sun>),
    Saturn(Rc<Sun>),
    Uranus(Rc<Sun>),
    Neptune(Rc<Sun>),
}

impl Planet {
    fn details(&self) {
        println!("Hi from {:?}!", self)
    }
}

fn main() {
    let sun = Rc::new(Sun {});
    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference

    let mercury = Planet::Mercury(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
    mercury.details();

    let venus = Planet::Venus(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
    venus.details();

    let earth = Planet::Earth(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
    earth.details();

    let mars = Planet::Mars(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
    mars.details();

    let jupiter = Planet::Jupiter(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
    jupiter.details();

    // TODO
    let saturn = Planet::Saturn(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
    saturn.details();

    // TODO
    let uranus = Planet::Uranus(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
    uranus.details();

    // TODO
    let neptune = Planet::Neptune(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
    neptune.details();

    assert_eq!(Rc::strong_count(&sun), 9);

    drop(neptune);
    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references

    drop(uranus);
    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references

    drop(saturn);
    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references

    drop(jupiter);
    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references

    drop(mars);
    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references

    // TODO
    drop(earth);
    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references

    // TODO
    drop(venus);
    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references

    // TODO
    drop(mercury);
    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference

    assert_eq!(Rc::strong_count(&sun), 1);
}

arc1.rs

// arc1.rs
//
// In this exercise, we are given a Vec of u32 called "numbers" with values
// ranging from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ] We would like to use this
// set of numbers within 8 different threads simultaneously. Each thread is
// going to get the sum of every eighth value, with an offset.
//
// The first thread (offset 0), will sum 0, 8, 16, ...
// The second thread (offset 1), will sum 1, 9, 17, ...
// The third thread (offset 2), will sum 2, 10, 18, ...
// ...
// The eighth thread (offset 7), will sum 7, 15, 23, ...
//
// Because we are using threads, our values need to be thread-safe.  Therefore,
// we are using Arc.  We need to make a change in each of the two TODOs.
//
// Make this code compile by filling in a value for `shared_numbers` where the
// first TODO comment is, and create an initial binding for `child_numbers`
// where the second TODO comment is. Try not to create any copies of the
// `numbers` Vec!
//
// Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.

// I AM DONE

#![forbid(unused_imports)] // Do not change this, (or the next) line.
use std::sync::Arc;
use std::thread;

fn main() {
    let numbers: Vec<_> = (0..100u32).collect();
    let shared_numbers = Arc::new(&numbers);
    let mut joinhandles = Vec::new();

    for offset in 0..8 {
        let child_numbers = numbers.clone();
        joinhandles.push(thread::spawn(move || {
            let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
            println!("Sum of offset {} is {}", offset, sum);
        }));
    }
    for handle in joinhandles.into_iter() {
        handle.join().unwrap();
    }
}

cow1.rs

// cow1.rs
//
// This exercise explores the Cow, or Clone-On-Write type. Cow is a
// clone-on-write smart pointer. It can enclose and provide immutable access to
// borrowed data, and clone the data lazily when mutation or ownership is
// required. The type is designed to work with general borrowed data via the
// Borrow trait.
//
// This exercise is meant to show you what to expect when passing data to Cow.
// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the
// TODO markers.
//
// Execute `rustlings hint cow1` or use the `hint` watch subcommand for a hint.

// I AM DONE

use std::borrow::Cow;

fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
    for i in 0..input.len() {
        let v = input[i];
        if v < 0 {
            // Clones into a vector if not already owned.
            input.to_mut()[i] = -v;
        }
    }
    input
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn reference_mutation() -> Result<(), &'static str> {
        // Clone occurs because `input` needs to be mutated.
        let slice = [-1, 0, 1];
        let mut input = Cow::from(&slice[..]);
        match abs_all(&mut input) {
            Cow::Owned(_) => Ok(()),
            _ => Err("Expected owned value"),
        }
    }

    #[test]
    fn reference_no_mutation() -> Result<(), &'static str> {
        // No clone occurs because `input` doesn't need to be mutated.
        let slice = [0, 1, 2];
        let mut input = Cow::from(&slice[..]);
        match abs_all(&mut input) {
            // TODO
            Cow::Borrowed(_) => Ok(()),
            _ => panic!("expected borrowed value"),
        }
    }

    #[test]
    fn owned_no_mutation() -> Result<(), &'static str> {
        // We can also pass `slice` without `&` so Cow owns it directly. In this
        // case no mutation occurs and thus also no clone, but the result is
        // still owned because it was never borrowed or mutated.
        let slice = vec![0, 1, 2];
        let mut input = Cow::from(slice);
        match abs_all(&mut input) {
            // TODO
            Cow::Owned(_) => Ok(()),
            _ => panic!("expected owned value"),
        }
    }

    #[test]
    fn owned_mutation() -> Result<(), &'static str> {
        // Of course this is also the case if a mutation does occur. In this
        // case the call to `to_mut()` returns a reference to the same data as
        // before.
        let slice = vec![-1, 0, 1];
        let mut input = Cow::from(slice);
        match abs_all(&mut input) {
            // TODO
            Cow::Owned(_) => Ok(()),
            _ => panic!("expected borrowed value"),
        }
    }
}

threads

threads1.rs

// threads1.rs
//
// This program spawns multiple threads that each run for at least 250ms, and
// each thread returns how much time they took to complete. The program should
// wait until all the spawned threads have finished and should collect their
// return values into a vector.
//
// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::thread;
use std::time::{Duration, Instant};

fn main() {
    let mut handles = vec![];
    for i in 0..10 {
        handles.push(thread::spawn(move || {
            let start = Instant::now();
            thread::sleep(Duration::from_millis(250));
            println!("thread {} is complete", i);
            start.elapsed().as_millis()
        }));
    }

    let mut results: Vec<u128> = vec![];
    for handle in handles {
        // TODO: a struct is returned from thread::spawn, can you use it?
        if let temp = handle.join() {
            results.push(temp.unwrap());
        }
    }

    if results.len() != 10 {
        panic!("Oh no! All the spawned threads did not finish!");
    }

    println!();
    for (i, result) in results.into_iter().enumerate() {
        println!("thread {} took {}ms", i, result);
    }
}

threads2.rs

// threads2.rs
//
// Building on the last exercise, we want all of the threads to complete their
// work but this time the spawned threads need to be in charge of updating a
// shared value: JobStatus.jobs_completed
//
// Execute `rustlings hint threads2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

struct JobStatus {
    jobs_completed: u32,
}

fn main() {
    let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));
    let mut handles = vec![];
    for _ in 0..10 {
        let status_shared = Arc::clone(&status);
        let handle = thread::spawn(move || {
            thread::sleep(Duration::from_millis(250));
            // TODO: You must take an action before you update a shared value
            let mut status_shared = status_shared.lock().unwrap();
            status_shared.jobs_completed += 1;
            status_shared.jobs_completed
        });
        handles.push(handle);
    }
    for handle in handles {
        let temp = handle.join().unwrap();
        // TODO: Print the value of the JobStatus.jobs_completed. Did you notice
        // anything interesting in the output? Do you have to 'join' on all the
        // handles?
        println!("jobs completed {}", temp);
    }
}

threads3.rs

// threads3.rs
//
// Execute `rustlings hint threads3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::sync::mpsc;
use std::sync::Arc;
use std::thread;
use std::time::Duration;

struct Queue {
    length: u32,
    first_half: Vec<u32>,
    second_half: Vec<u32>,
}

impl Queue {
    fn new() -> Self {
        Queue {
            length: 10,
            first_half: vec![1, 2, 3, 4, 5],
            second_half: vec![6, 7, 8, 9, 10],
        }
    }
}

fn send_tx(q: Queue, tx: mpsc::Sender<u32>) -> () {
    let qc = Arc::new(q);
    let qc1 = Arc::clone(&qc);
    let qc2 = Arc::clone(&qc);

    let tc = Arc::new(tx);
    let tc1 = Arc::clone(&tc);
    let tc2 = Arc::clone(&tc);

    thread::spawn(move || {
        for val in &qc1.first_half {
            println!("sending {:?}", val);
            tc1.send(*val).unwrap();
            thread::sleep(Duration::from_secs(1));
        }
    });

    thread::spawn(move || {
        for val in &qc2.second_half {
            println!("sending {:?}", val);
            tc2.send(*val).unwrap();
            thread::sleep(Duration::from_secs(1));
        }
    });
}

fn main() {
    let (tx, rx) = mpsc::channel();
    let queue = Queue::new();
    let queue_length = queue.length;

    send_tx(queue, tx);

    let mut total_received: u32 = 0;
    for received in rx {
        println!("Got: {}", received);
        total_received += 1;
    }

    println!("total numbers received: {}", total_received);
    assert_eq!(total_received, queue_length)
}

macros

macros1.rs

// macros1.rs
//
// Execute `rustlings hint macros1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

macro_rules! my_macro {
    () => {
        println!("Check out my macro!");
    };
}

fn main() {
    my_macro!();
}

macros2.rs

// macros2.rs
//
// Execute `rustlings hint macros2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

macro_rules! my_macro {
    () => {
        println!("Check out my macro!");
    };
}

fn main() {
    my_macro!();
}

macros3.rs

// macros3.rs
//
// Make me compile, without taking the macro out of the module!
//
// Execute `rustlings hint macros3` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[macro_use]
mod macros {
    macro_rules! my_macro {
        () => {
            println!("Check out my macro!");
        };
    }
}

fn main() {
    my_macro!();
}

macros4.rs

// macros4.rs
//
// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

#[rustfmt::skip]
macro_rules! my_macro {
    () => {
        println!("Check out my macro!");
    };
    ($val:expr) => {
        println!("Look at this other macro: {}", $val);
    }
}

fn main() {
    my_macro!();
    my_macro!(7777);
}

clippy

clippy1.rs

// clippy1.rs
//
// The Clippy tool is a collection of lints to analyze your code so you can
// catch common mistakes and improve your Rust code.
//
// For these exercises the code will fail to compile when there are clippy
// warnings check clippy's suggestions from the output to solve the exercise.
//
// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

use std::f32;

fn main() {
    // let pi = 3.14f32;
    let pi = f32::consts::PI;
    let radius = 5.00f32;

    let area = pi * f32::powi(radius, 2);

    println!(
        "The area of a circle with radius {:.2} is {:.5}!",
        radius, area
    )
}

clippy2.rs

// clippy2.rs
// 
// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn main() {
    let mut res = 42;
    let option = Some(12);
    if let Some(x) = option {
        res += x;
    }
    println!("{}", res);
}

clippy3.rs

// clippy3.rs
// 
// Here's a couple more easy Clippy fixes, so you can see its utility.
//
// Execute `rustlings hint clippy3` or use the `hint` watch subcommand for a hint.

// I AM DONE

#[allow(unused_variables, unused_assignments)]
fn main() {
    let my_option: Option<()> = None;
    if my_option.is_none() {
        // let temp = my_option.unwrap();
    }

    let my_arr = &[
        -1, -2, -3,
        -4, -5, -6,
    ];
    println!("My array! Here it is: {:?}", my_arr);

    let mut my_empty_vec = vec![1, 2, 3, 4, 5];
    my_empty_vec.clear();
    println!("This Vec is empty, see? {:?}", my_empty_vec);

    let mut value_a = 45;
    let mut value_b = 66;
    // Let's swap these two!
    std::mem::swap(&mut value_a, &mut value_b);
    println!("value a: {}; value b: {}", value_a, value_b);
}

conversions

using_as.rs

// using_as.rs
//
// Type casting in Rust is done via the usage of the `as` operator. Please note
// that the `as` operator is not only used when type casting. It also helps with
// renaming imports.
//
// The goal is to make sure that the division does not fail to compile and
// returns the proper type.
//
// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

fn average(values: &[f64]) -> f64 {
    let total = values.iter().sum::<f64>();
    total / values.len() as f64
}

fn main() {
    let values = [3.5, 0.3, 13.0, 11.7];
    println!("{}", average(&values));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn returns_proper_type_and_value() {
        assert_eq!(average(&[3.5, 0.3, 13.0, 11.7]), 7.125);
    }
}

from_into.rs

// from_into.rs
//
// The From trait is used for value-to-value conversions. If From is implemented
// correctly for a type, the Into trait should work conversely. You can read
// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
//
// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
// hint.

#[derive(Debug)]
struct Person {
    name: String,
    age: usize,
}

// We implement the Default trait to use it as a fallback
// when the provided string is not convertible into a Person object
impl Default for Person {
    fn default() -> Person {
        Person {
            name: String::from("John"),
            age: 30,
        }
    }
}

// Your task is to complete this implementation in order for the line `let p =
// Person::from("Mark,20")` to compile Please note that you'll need to parse the
// age component into a `usize` with something like `"4".parse::<usize>()`. The
// outcome of this needs to be handled appropriately.
//
// Steps:
// 1. If the length of the provided string is 0, then return the default of
//    Person.
// 2. Split the given string on the commas present in it.
// 3. Extract the first element from the split operation and use it as the name.
// 4. If the name is empty, then return the default of Person.
// 5. Extract the other element from the split operation and parse it into a
//    `usize` as the age.
// If while parsing the age, something goes wrong, then return the default of
// Person Otherwise, then return an instantiated Person object with the results

// I AM DONE

impl From<&str> for Person {
    fn from(s: &str) -> Person {
        let (name, age) = match s.split_once(',') {
            Some((name, age)) => (name.trim(), age.trim()),
            _ => return Person::default(),
        };

        if let Ok(age) = age.parse::<usize>() {
            if name.len() > 0 {
                return Person {
                    name: String::from(name),
                    age,
                };
            }
        }

        Person::default()
    }
}

fn main() {
    // Use the `from` function
    let p1 = Person::from("Mark,20");
    // Since From is implemented for Person, we should be able to use Into
    let p2: Person = "Gerald,70".into();
    println!("{:?}", p1);
    println!("{:?}", p2);
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn test_default() {
        // Test that the default person is 30 year old John
        let dp = Person::default();
        assert_eq!(dp.name, "John");
        assert_eq!(dp.age, 30);
    }
    #[test]
    fn test_bad_convert() {
        // Test that John is returned when bad string is provided
        let p = Person::from("");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }
    #[test]
    fn test_good_convert() {
        // Test that "Mark,20" works
        let p = Person::from("Mark,20");
        assert_eq!(p.name, "Mark");
        assert_eq!(p.age, 20);
    }
    #[test]
    fn test_bad_age() {
        // Test that "Mark,twenty" will return the default person due to an
        // error in parsing age
        let p = Person::from("Mark,twenty");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_missing_comma_and_age() {
        let p: Person = Person::from("Mark");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_missing_age() {
        let p: Person = Person::from("Mark,");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_missing_name() {
        let p: Person = Person::from(",1");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_missing_name_and_age() {
        let p: Person = Person::from(",");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_missing_name_and_invalid_age() {
        let p: Person = Person::from(",one");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
    }

    #[test]
    fn test_trailing_comma() {
        let p: Person = Person::from("Mike,32");
        assert_eq!(p.name, "Mike");
        assert_eq!(p.age, 32);
    }

    #[test]
    fn test_trailing_comma_and_some_string() {
        let p: Person = Person::from("Mike,32");
        assert_eq!(p.name, "Mike");
        assert_eq!(p.age, 32);
    }
}

from_str.rs

// from_str.rs
//
// This is similar to from_into.rs, but this time we'll implement `FromStr` and
// return errors instead of falling back to a default value. Additionally, upon
// implementing FromStr, you can use the `parse` method on strings to generate
// an object of the implementor type. You can read more about it at
// https://doc.rust-lang.org/std/str/trait.FromStr.html
//
// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
// hint.

use std::num::ParseIntError;
use std::str::FromStr;

#[derive(Debug, PartialEq)]
struct Person {
    name: String,
    age: usize,
}

// We will use this error type for the `FromStr` implementation.
#[derive(Debug, PartialEq)]
enum ParsePersonError {
    // Empty input string
    Empty,
    // Incorrect number of fields
    BadLen,
    // Empty name field
    NoName,
    // Wrapped error from parse::<usize>()
    ParseInt(ParseIntError),
}

// I AM DONE

// Steps:
// 1. If the length of the provided string is 0, an error should be returned
// 2. Split the given string on the commas present in it
// 3. Only 2 elements should be returned from the split, otherwise return an
//    error
// 4. Extract the first element from the split operation and use it as the name
// 5. Extract the other element from the split operation and parse it into a
//    `usize` as the age with something like `"4".parse::<usize>()`
// 6. If while extracting the name and the age something goes wrong, an error
//    should be returned
// If everything goes well, then return a Result of a Person object
//
// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
// you want to return a string error message, you can do so via just using
// return `Err("my error message".into())`.

impl FromStr for Person {
    type Err = ParsePersonError;
    fn from_str(s: &str) -> Result<Person, Self::Err> {
        if s.is_empty() {
            return Err(ParsePersonError::Empty);
        }

        let splitted_item = s.split(',').collect::<Vec<&str>>();
        let (name, age) = match &splitted_item[..] {
            [name, age] => (
                name.to_string(),
                age.parse().map_err(ParsePersonError::ParseInt)?,
            ),
            _ => return Err(ParsePersonError::BadLen),
        };

        if name.is_empty() {
            return Err(ParsePersonError::NoName);
        }

        Ok(Person {
            name: name.into(),
            age,
        })
    }
}

fn main() {
    let p = "Mark,20".parse::<Person>().unwrap();
    println!("{:?}", p);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn empty_input() {
        assert_eq!("".parse::<Person>(), Err(ParsePersonError::Empty));
    }
    #[test]
    fn good_input() {
        let p = "John,32".parse::<Person>();
        assert!(p.is_ok());
        let p = p.unwrap();
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 32);
    }
    #[test]
    fn missing_age() {
        assert!(matches!(
            "John,".parse::<Person>(),
            Err(ParsePersonError::ParseInt(_))
        ));
    }

    #[test]
    fn invalid_age() {
        assert!(matches!(
            "John,twenty".parse::<Person>(),
            Err(ParsePersonError::ParseInt(_))
        ));
    }

    #[test]
    fn missing_comma_and_age() {
        assert_eq!("John".parse::<Person>(), Err(ParsePersonError::BadLen));
    }

    #[test]
    fn missing_name() {
        assert_eq!(",1".parse::<Person>(), Err(ParsePersonError::NoName));
    }

    #[test]
    fn missing_name_and_age() {
        assert!(matches!(
            ",".parse::<Person>(),
            Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
        ));
    }

    #[test]
    fn missing_name_and_invalid_age() {
        assert!(matches!(
            ",one".parse::<Person>(),
            Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
        ));
    }

    #[test]
    fn trailing_comma() {
        assert_eq!("John,32,".parse::<Person>(), Err(ParsePersonError::BadLen));
    }

    #[test]
    fn trailing_comma_and_some_string() {
        assert_eq!(
            "John,32,man".parse::<Person>(),
            Err(ParsePersonError::BadLen)
        );
    }
}

try_from_into.rs

// try_from_into.rs
//
// TryFrom is a simple and safe type conversion that may fail in a controlled
// way under some circumstances. Basically, this is the same as From. The main
// difference is that this should return a Result type instead of the target
// type itself. You can read more about it at
// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
//
// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for
// a hint.

use std::convert::{TryFrom, TryInto};

#[derive(Debug, PartialEq)]
struct Color {
    red: u8,
    green: u8,
    blue: u8,
}

// We will use this error type for these `TryFrom` conversions.
#[derive(Debug, PartialEq)]
enum IntoColorError {
    // Incorrect length of slice
    BadLen,
    // Integer conversion error
    IntConversion,
}

// I AM DONE

// Your task is to complete this implementation and return an Ok result of inner
// type Color. You need to create an implementation for a tuple of three
// integers, an array of three integers, and a slice of integers.
//
// Note that the implementation for tuple and array will be checked at compile
// time, but the slice implementation needs to check the slice length! Also note
// that correct RGB color values must be integers in the 0..=255 range.

// Tuple implementation
impl TryFrom<(i16, i16, i16)> for Color {
    type Error = IntoColorError;
    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
        let (red, green, blue) = tuple;

        for color in [red, green, blue] {
            if !(0..=255).contains(&color) {
                return Err(IntoColorError::IntConversion);
            }
        }
        Ok(Self {
            red: tuple.0 as u8,
            green: tuple.1 as u8,
            blue: tuple.2 as u8,
        })
    }
}

// Array implementation
impl TryFrom<[i16; 3]> for Color {
    type Error = IntoColorError;
    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
        for color in arr {
            if !(0..=255).contains(&color) {
                return Err(IntoColorError::IntConversion);
            }
        }
        Ok(Self {
            red: arr[0] as u8,
            green: arr[1] as u8,
            blue: arr[2] as u8,
        })
    }
}

// Slice implementation
impl TryFrom<&[i16]> for Color {
    type Error = IntoColorError;
    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
        if slice.len() != 3 {
            return Err(IntoColorError::BadLen);
        }
        for color in slice {
            if !(0..=255).contains(color) {
                return Err(IntoColorError::IntConversion);
            }
        }
        Ok(Self {
            red: slice[0] as u8,
            green: slice[1] as u8,
            blue: slice[2] as u8,
        })
    }
}

fn main() {
    // Use the `try_from` function
    let c1 = Color::try_from((183, 65, 14));
    println!("{:?}", c1);

    // Since TryFrom is implemented for Color, we should be able to use TryInto
    let c2: Result<Color, _> = [183, 65, 14].try_into();
    println!("{:?}", c2);

    let v = vec![183, 65, 14];
    // With slice we should use `try_from` function
    let c3 = Color::try_from(&v[..]);
    println!("{:?}", c3);
    // or take slice within round brackets and use TryInto
    let c4: Result<Color, _> = (&v[..]).try_into();
    println!("{:?}", c4);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_tuple_out_of_range_positive() {
        assert_eq!(
            Color::try_from((256, 1000, 10000)),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_tuple_out_of_range_negative() {
        assert_eq!(
            Color::try_from((-1, -10, -256)),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_tuple_sum() {
        assert_eq!(
            Color::try_from((-1, 255, 255)),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_tuple_correct() {
        let c: Result<Color, _> = (183, 65, 14).try_into();
        assert!(c.is_ok());
        assert_eq!(
            c.unwrap(),
            Color {
                red: 183,
                green: 65,
                blue: 14
            }
        );
    }
    #[test]
    fn test_array_out_of_range_positive() {
        let c: Result<Color, _> = [1000, 10000, 256].try_into();
        assert_eq!(c, Err(IntoColorError::IntConversion));
    }
    #[test]
    fn test_array_out_of_range_negative() {
        let c: Result<Color, _> = [-10, -256, -1].try_into();
        assert_eq!(c, Err(IntoColorError::IntConversion));
    }
    #[test]
    fn test_array_sum() {
        let c: Result<Color, _> = [-1, 255, 255].try_into();
        assert_eq!(c, Err(IntoColorError::IntConversion));
    }
    #[test]
    fn test_array_correct() {
        let c: Result<Color, _> = [183, 65, 14].try_into();
        assert!(c.is_ok());
        assert_eq!(
            c.unwrap(),
            Color {
                red: 183,
                green: 65,
                blue: 14
            }
        );
    }
    #[test]
    fn test_slice_out_of_range_positive() {
        let arr = [10000, 256, 1000];
        assert_eq!(
            Color::try_from(&arr[..]),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_slice_out_of_range_negative() {
        let arr = [-256, -1, -10];
        assert_eq!(
            Color::try_from(&arr[..]),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_slice_sum() {
        let arr = [-1, 255, 255];
        assert_eq!(
            Color::try_from(&arr[..]),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_slice_correct() {
        let v = vec![183, 65, 14];
        let c: Result<Color, _> = Color::try_from(&v[..]);
        assert!(c.is_ok());
        assert_eq!(
            c.unwrap(),
            Color {
                red: 183,
                green: 65,
                blue: 14
            }
        );
    }
    #[test]
    fn test_slice_excess_length() {
        let v = vec![0, 0, 0, 0];
        assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
    }
    #[test]
    fn test_slice_insufficient_length() {
        let v = vec![0, 0];
        assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
    }
}

as_ref.rs

// as_ref_mut.rs
//
// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
//
// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
// hint.

// I AM DONE

// Obtain the number of bytes (not characters) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn byte_counter<T : AsRef<str>>(arg: T) -> usize {
    arg.as_ref().as_bytes().len()
}

// Obtain the number of characters (not bytes) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn char_counter<T : AsRef<str>>(arg: T) -> usize {
    arg.as_ref().chars().count()
}

// Squares a number using as_mut().
// TODO: Add the appropriate trait bound.
fn num_sq<T : AsMut<u32>>(arg: &mut T) {
    // TODO: Implement the function body.
    *arg.as_mut() *= *arg.as_mut()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn different_counts() {
        let s = "Café au lait";
        assert_ne!(char_counter(s), byte_counter(s));
    }

    #[test]
    fn same_counts() {
        let s = "Cafe au lait";
        assert_eq!(char_counter(s), byte_counter(s));
    }

    #[test]
    fn different_counts_using_string() {
        let s = String::from("Café au lait");
        assert_ne!(char_counter(s.clone()), byte_counter(s));
    }

    #[test]
    fn same_counts_using_string() {
        let s = String::from("Cafe au lait");
        assert_eq!(char_counter(s.clone()), byte_counter(s));
    }

    #[test]
    fn mult_box() {
        let mut num: Box<u32> = Box::new(3);
        num_sq(&mut num);
        assert_eq!(*num, 9);
    }
}

quiz

quiz1.rs

// quiz1.rs
//
// This is a quiz for the following sections:
// - Variables
// - Functions
// - If
//
// Mary is buying apples. The price of an apple is calculated as follows:
// - An apple costs 2 rustbucks.
// - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
// Write a function that calculates the price of an order of apples given the
// quantity bought.
//
// No hints this time ;)

// I AM DONE

// Put your function here!
fn calculate_price_of_apples(num : i32) -> i32 {
    if num > 40 {
        num
    } else {
        num * 2
    }
}

// Don't modify this function!
#[test]
fn verify_test() {
    let price1 = calculate_price_of_apples(35);
    let price2 = calculate_price_of_apples(40);
    let price3 = calculate_price_of_apples(41);
    let price4 = calculate_price_of_apples(65);

    assert_eq!(70, price1);
    assert_eq!(80, price2);
    assert_eq!(41, price3);
    assert_eq!(65, price4);
}

quiz2.rs

// quiz2.rs
//
// This is a quiz for the following sections:
// - Strings
// - Vecs
// - Move semantics
// - Modules
// - Enums
//
// Let's build a little machine in the form of a function. As input, we're going
// to give a list of strings and commands. These commands determine what action
// is going to be applied to the string. It can either be:
// - Uppercase the string
// - Trim the string
// - Append "bar" to the string a specified amount of times
// The exact form of this will be:
// - The input is going to be a Vector of a 2-length tuple,
//   the first element is the string, the second one is the command.
// - The output element is going to be a Vector of strings.
//
// No hints this time!

// I AM DONE

pub enum Command {
    Uppercase,
    Trim,
    Append(usize),
}

mod my_module {
    use super::Command;

    // TODO: Complete the function signature!
    pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
        // TODO: Complete the output declaration!
        let mut output: Vec<String> = vec![];
        for (string, command) in input.iter() {
            // TODO: Complete the function body. You can do it!
            match command {
                Command::Uppercase => output.push(string.to_uppercase()),
                Command::Trim => output.push(string.trim().to_string()),
                Command::Append(usize) => {
                    let mut res = string.clone();
                    for _ in 0..*usize {
                        res += &String::from("bar");
                    }
                    output.push(res)
                },
            }
        }
        output
    }
}

#[cfg(test)]
mod tests {
    // TODO: What do we need to import to have `transformer` in scope?
    use crate::my_module::transformer;
    use super::Command;

    #[test]
    fn it_works() {
        let output = transformer(vec![
            ("hello".into(), Command::Uppercase),
            (" all roads lead to rome! ".into(), Command::Trim),
            ("foo".into(), Command::Append(1)),
            ("bar".into(), Command::Append(5)),
        ]);
        assert_eq!(output[0], "HELLO");
        assert_eq!(output[1], "all roads lead to rome!");
        assert_eq!(output[2], "foobar");
        assert_eq!(output[3], "barbarbarbarbarbar");
    }
}

quiz3.rs

// quiz3.rs
//
// This quiz tests:
// - Generics
// - Traits
//
// An imaginary magical school has a new report card generation system written
// in Rust! Currently the system only supports creating report cards where the
// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
// school also issues alphabetical grades (A+ -> F-) and needs to be able to
// print both types of report card!
//
// Make the necessary code changes in the struct ReportCard and the impl block
// to support alphabetical report cards. Change the Grade in the second test to
// "A+" to show that your changes allow alphabetical grades.
//
// Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.

// I AM DONE

pub struct ReportCard<T> {
    pub grade: T,
    pub student_name: String,
    pub student_age: u8,
}

impl<T: std::fmt::Display> ReportCard<T> {
    pub fn print(&self) -> String {
        format!("{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn generate_numeric_report_card() {
        let report_card = ReportCard {
            grade: 2.1,
            student_name: "Tom Wriggle".to_string(),
            student_age: 12,
        };
        assert_eq!(
            report_card.print(),
            "Tom Wriggle (12) - achieved a grade of 2.1"
        );
    }

    #[test]
    fn generate_alphabetic_report_card() {
        // TODO: Make sure to change the grade here after you finish the exercise.
        let report_card = ReportCard {
            grade: "A+",
            student_name: "Gary Plotter".to_string(),
            student_age: 11,
        };
        assert_eq!(
            report_card.print(),
            "Gary Plotter (11) - achieved a grade of A+"
        );
    }
}

---