First commit

solutions/00_intro/intro1.rs

@@ -0,0 +1,5 @@
+fn main() {
+    // Congratulations, you finished the first exercise 🎉
+    // As an introduction to Rustlings, the first exercise only required
+    // entering `n` in the terminal to go to the next exercise.
+}

solutions/00_intro/intro2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // `println!` instead of `printline!`.
+    println!("Hello world!");
+}

solutions/01_variables/variables1.rs

@@ -0,0 +1,6 @@
+fn main() {
+    // Declaring variables requires the `let` keyword.
+    let x = 5;
+
+    println!("x has the value {x}");
+}

solutions/01_variables/variables2.rs

@@ -0,0 +1,16 @@
+fn main() {
+    // The easiest way to fix the compiler error is to initialize the
+    // variable `x`. By setting its value to an integer, Rust infers its type
+    // as `i32` which is the default type for integers.
+    let x = 42;
+
+    // But we can enforce a type different from the default `i32` by adding
+    // a type annotation:
+    // let x: u8 = 42;
+
+    if x == 10 {
+        println!("x is ten!");
+    } else {
+        println!("x is not ten!");
+    }
+}

solutions/01_variables/variables3.rs

@@ -0,0 +1,15 @@
+#![allow(clippy::needless_late_init)]
+
+fn main() {
+    // Reading uninitialized variables isn't allowed in Rust!
+    // Therefore, we need to assign a value first.
+    let x: i32 = 42;
+
+    println!("Number {x}");
+
+    // It is possible to declare a variable and initialize it later.
+    // But it can't be used before initialization.
+    let y: i32;
+    y = 42;
+    println!("Number {y}");
+}

solutions/01_variables/variables4.rs

@@ -0,0 +1,9 @@
+fn main() {
+    // In Rust, variables are immutable by default.
+    // Adding the `mut` keyword after `let` makes the declared variable mutable.
+    let mut x = 3;
+    println!("Number {x}");
+
+    x = 5;
+    println!("Number {x}");
+}

solutions/01_variables/variables5.rs

@@ -0,0 +1,9 @@
+fn main() {
+    let number = "T-H-R-E-E";
+    println!("Spell a number: {number}");
+
+    // Using variable shadowing
+    // https://doc.rust-lang.org/book/ch03-01-variables-and-mutability.html#shadowing
+    let number = 3;
+    println!("Number plus two is: {}", number + 2);
+}

solutions/01_variables/variables6.rs

@@ -0,0 +1,6 @@
+// The type of constants must always be annotated.
+const NUMBER: u64 = 3;
+
+fn main() {
+    println!("Number: {NUMBER}");
+}

solutions/02_functions/functions1.rs

@@ -0,0 +1,8 @@
+// Some function with the name `call_me` without arguments or a return value.
+fn call_me() {
+    println!("Hello world!");
+}
+
+fn main() {
+    call_me();
+}

solutions/02_functions/functions2.rs

@@ -0,0 +1,11 @@
+// The type of function arguments must be annotated.
+// Added the type annotation `u64`.
+fn call_me(num: u64) {
+    for i in 0..num {
+        println!("Ring! Call number {}", i + 1);
+    }
+}
+
+fn main() {
+    call_me(3);
+}

solutions/02_functions/functions3.rs

@@ -0,0 +1,10 @@
+fn call_me(num: u8) {
+    for i in 0..num {
+        println!("Ring! Call number {}", i + 1);
+    }
+}
+
+fn main() {
+    // `call_me` expects an argument.
+    call_me(5);
+}

solutions/02_functions/functions4.rs

@@ -0,0 +1,17 @@
+fn is_even(num: i64) -> bool {
+    num % 2 == 0
+}
+
+// The return type must always be annotated.
+fn sale_price(price: i64) -> i64 {
+    if is_even(price) {
+        price - 10
+    } else {
+        price - 3
+    }
+}
+
+fn main() {
+    let original_price = 51;
+    println!("Your sale price is {}", sale_price(original_price));
+}

solutions/02_functions/functions5.rs

@@ -0,0 +1,9 @@
+fn square(num: i32) -> i32 {
+    // Removed the semicolon `;` at the end of the line below to implicitly return the result.
+    num * num
+}
+
+fn main() {
+    let answer = square(3);
+    println!("The square of 3 is {answer}");
+}

solutions/03_if/if1.rs

@@ -0,0 +1,28 @@
+fn bigger(a: i32, b: i32) -> i32 {
+    if a > b { a } else { b }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+// 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));
+    }
+
+    #[test]
+    fn equal_numbers() {
+        assert_eq!(42, bigger(42, 42));
+    }
+}

solutions/03_if/if2.rs

@@ -0,0 +1,35 @@
+fn picky_eater(food: &str) -> &str {
+    if food == "strawberry" {
+        "Yummy!"
+    } else if food == "potato" {
+        "I guess I can eat that."
+    } else {
+        "No thanks!"
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn yummy_food() {
+        assert_eq!(picky_eater("strawberry"), "Yummy!");
+    }
+
+    #[test]
+    fn neutral_food() {
+        assert_eq!(picky_eater("potato"), "I guess I can eat that.");
+    }
+
+    #[test]
+    fn default_disliked_food() {
+        assert_eq!(picky_eater("broccoli"), "No thanks!");
+        assert_eq!(picky_eater("gummy bears"), "No thanks!");
+        assert_eq!(picky_eater("literally anything"), "No thanks!");
+    }
+}

solutions/03_if/if3.rs

@@ -0,0 +1,53 @@
+fn animal_habitat(animal: &str) -> &str {
+    let identifier = if animal == "crab" {
+        1
+    } else if animal == "gopher" {
+        2
+    } else if animal == "snake" {
+        3
+    } else {
+        // Any unused identifier.
+        4
+    };
+
+    // Instead of such an identifier, you would use an enum in Rust.
+    // But we didn't get into enums yet.
+    if identifier == 1 {
+        "Beach"
+    } else if identifier == 2 {
+        "Burrow"
+    } else if identifier == 3 {
+        "Desert"
+    } else {
+        "Unknown"
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[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")
+    }
+}

solutions/04_primitive_types/primitive_types1.rs

@@ -0,0 +1,11 @@
+fn main() {
+    let is_morning = true;
+    if is_morning {
+        println!("Good morning!");
+    }
+
+    let is_evening = !is_morning;
+    if is_evening {
+        println!("Good evening!");
+    }
+}

solutions/04_primitive_types/primitive_types2.rs

@@ -0,0 +1,21 @@
+fn main() {
+    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!");
+    }
+
+    // Example with an emoji.
+    let your_character = '🦀';
+
+    if your_character.is_alphabetic() {
+        println!("Alphabetical!");
+    } else if your_character.is_numeric() {
+        println!("Numerical!");
+    } else {
+        println!("Neither alphabetic nor numeric!");
+    }
+}

solutions/04_primitive_types/primitive_types3.rs

@@ -0,0 +1,11 @@
+fn main() {
+    // An array with 100 elements of the value 42.
+    let a = [42; 100];
+
+    if a.len() >= 100 {
+        println!("Wow, that's a big array!");
+    } else {
+        println!("Meh, I eat arrays like that for breakfast.");
+        panic!("Array not big enough, more elements needed");
+    }
+}

solutions/04_primitive_types/primitive_types4.rs

@@ -0,0 +1,23 @@
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn slice_out_of_array() {
+        let a = [1, 2, 3, 4, 5];
+        //       0  1  2  3  4  <- indices
+        //          -------
+        //             |
+        //             +--- slice
+
+        // Note that the upper index 4 is excluded.
+        let nice_slice = &a[1..4];
+        assert_eq!([2, 3, 4], nice_slice);
+
+        // The upper index can be included by using the syntax `..=` (with `=` sign)
+        let nice_slice = &a[1..=3];
+        assert_eq!([2, 3, 4], nice_slice);
+    }
+}

solutions/04_primitive_types/primitive_types5.rs

@@ -0,0 +1,8 @@
+fn main() {
+    let cat = ("Furry McFurson", 3.5);
+
+    // Destructuring the tuple.
+    let (name, age) = cat;
+
+    println!("{name} is {age} years old");
+}

solutions/04_primitive_types/primitive_types6.rs

@@ -0,0 +1,16 @@
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn indexing_tuple() {
+        let numbers = (1, 2, 3);
+
+        // Tuple indexing syntax.
+        let second = numbers.1;
+
+        assert_eq!(second, 2, "This is not the 2nd number in the tuple!");
+    }
+}

solutions/05_vecs/vecs1.rs

@@ -0,0 +1,23 @@
+fn array_and_vec() -> ([i32; 4], Vec<i32>) {
+    let a = [10, 20, 30, 40]; // Array
+
+    // Used the `vec!` macro.
+    let v = vec![10, 20, 30, 40];
+
+    (a, v)
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_array_and_vec_similarity() {
+        let (a, v) = array_and_vec();
+        assert_eq!(a, *v);
+    }
+}

solutions/05_vecs/vecs2.rs

@@ -0,0 +1,55 @@
+fn vec_loop(input: &[i32]) -> Vec<i32> {
+    let mut output = Vec::new();
+
+    for element in input {
+        output.push(2 * element);
+    }
+
+    output
+}
+
+fn vec_map_example(input: &[i32]) -> Vec<i32> {
+    // An example of collecting a vector after mapping.
+    // We map each element of the `input` slice to its value plus 1.
+    // If the input is `[1, 2, 3]`, the output is `[2, 3, 4]`.
+    input.iter().map(|element| element + 1).collect()
+}
+
+fn vec_map(input: &[i32]) -> Vec<i32> {
+    // We will dive deeper into iterators, but for now, this is all what you
+    // had to do!
+    // Advanced note: This method is more efficient because it automatically
+    // preallocates enough capacity. This can be done manually in `vec_loop`
+    // using `Vec::with_capacity(input.len())` instead of `Vec::new()`.
+    input.iter().map(|element| 2 * element).collect()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_vec_loop() {
+        let input = [2, 4, 6, 8, 10];
+        let ans = vec_loop(&input);
+        assert_eq!(ans, [4, 8, 12, 16, 20]);
+    }
+
+    #[test]
+    fn test_vec_map_example() {
+        let input = [1, 2, 3];
+        let ans = vec_map_example(&input);
+        assert_eq!(ans, [2, 3, 4]);
+    }
+
+    #[test]
+    fn test_vec_map() {
+        let input = [2, 4, 6, 8, 10];
+        let ans = vec_map(&input);
+        assert_eq!(ans, [4, 8, 12, 16, 20]);
+    }
+}

solutions/06_move_semantics/move_semantics1.rs

@@ -0,0 +1,25 @@
+fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
+    let mut vec = vec;
+    //  ^^^ added
+
+    vec.push(88);
+
+    vec
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics1() {
+        let vec0 = vec![22, 44, 66];
+        let vec1 = fill_vec(vec0);
+        // `vec0` can't be accessed anymore because it is moved to `fill_vec`.
+        assert_eq!(vec1, vec![22, 44, 66, 88]);
+    }
+}

solutions/06_move_semantics/move_semantics2.rs

@@ -0,0 +1,28 @@
+fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
+    let mut vec = vec;
+
+    vec.push(88);
+
+    vec
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics2() {
+        let vec0 = vec![22, 44, 66];
+
+        // Cloning `vec0` so that the clone is moved into `fill_vec`, not `vec0`
+        // itself.
+        let vec1 = fill_vec(vec0.clone());
+
+        assert_eq!(vec0, [22, 44, 66]);
+        assert_eq!(vec1, [22, 44, 66, 88]);
+    }
+}

solutions/06_move_semantics/move_semantics3.rs

@@ -0,0 +1,22 @@
+fn fill_vec(mut vec: Vec<i32>) -> Vec<i32> {
+    //      ^^^ added
+    vec.push(88);
+
+    vec
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics3() {
+        let vec0 = vec![22, 44, 66];
+        let vec1 = fill_vec(vec0);
+        assert_eq!(vec1, [22, 44, 66, 88]);
+    }
+}

solutions/06_move_semantics/move_semantics4.rs

@@ -0,0 +1,19 @@
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn move_semantics4() {
+        let mut x = Vec::new();
+        let y = &mut x;
+        // `y` used here.
+        y.push(42);
+        // The mutable reference `y` is not used anymore,
+        // therefore a new reference can be created.
+        let z = &mut x;
+        z.push(13);
+        assert_eq!(x, [42, 13]);
+    }
+}

solutions/06_move_semantics/move_semantics5.rs

@@ -0,0 +1,23 @@
+#![allow(clippy::ptr_arg)]
+
+// Borrows instead of taking ownership.
+// It is recommended to use `&str` instead of `&String` here. But this is
+// enough for now because we didn't handle strings yet.
+fn get_char(data: &String) -> char {
+    data.chars().last().unwrap()
+}
+
+// Takes ownership instead of borrowing.
+fn string_uppercase(mut data: String) {
+    data = data.to_uppercase();
+
+    println!("{data}");
+}
+
+fn main() {
+    let data = "Rust is great!".to_string();
+
+    get_char(&data);
+
+    string_uppercase(data);
+}

solutions/07_structs/structs1.rs

@@ -0,0 +1,49 @@
+struct ColorRegularStruct {
+    red: u8,
+    green: u8,
+    blue: u8,
+}
+
+struct ColorTupleStruct(u8, u8, u8);
+
+#[derive(Debug)]
+struct UnitStruct;
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn regular_structs() {
+        let green = ColorRegularStruct {
+            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() {
+        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() {
+        let unit_struct = UnitStruct;
+        let message = format!("{unit_struct:?}s are fun!");
+
+        assert_eq!(message, "UnitStructs are fun!");
+    }
+}

solutions/07_structs/structs2.rs

@@ -0,0 +1,51 @@
+#[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,
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn your_order() {
+        let order_template = create_order_template();
+
+        let your_order = Order {
+            name: String::from("Hacker in Rust"),
+            count: 1,
+            // Struct update syntax
+            ..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);
+    }
+}

solutions/07_structs/structs3.rs

@@ -0,0 +1,83 @@
+#[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) -> Self {
+        if weight_in_grams < 10 {
+            // This isn't how you should handle errors in Rust, but we will
+            // learn about error handling later.
+            panic!("Can't ship a package with weight below 10 grams");
+        }
+
+        Self {
+            sender_country,
+            recipient_country,
+            weight_in_grams,
+        }
+    }
+
+    fn is_international(&self) -> bool {
+        //                     ^^^^^^^ added
+        self.sender_country != self.recipient_country
+    }
+
+    fn get_fees(&self, cents_per_gram: u32) -> u32 {
+        //                                  ^^^^^^ added
+        self.weight_in_grams * cents_per_gram
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[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);
+    }
+}

solutions/08_enums/enums1.rs

@@ -0,0 +1,16 @@
+#[derive(Debug)]
+enum Message {
+    Resize,
+    Move,
+    Echo,
+    ChangeColor,
+    Quit,
+}
+
+fn main() {
+    println!("{:?}", Message::Resize);
+    println!("{:?}", Message::Move);
+    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::ChangeColor);
+    println!("{:?}", Message::Quit);
+}

solutions/08_enums/enums2.rs

@@ -0,0 +1,37 @@
+#[derive(Debug)]
+struct Point {
+    x: u64,
+    y: u64,
+}
+
+#[derive(Debug)]
+enum Message {
+    Resize { width: u64, height: u64 },
+    Move(Point),
+    Echo(String),
+    ChangeColor(u8, u8, u8),
+    Quit,
+}
+
+impl Message {
+    fn call(&self) {
+        println!("{self:?}");
+    }
+}
+
+fn main() {
+    let messages = [
+        Message::Resize {
+            width: 10,
+            height: 30,
+        },
+        Message::Move(Point { x: 10, y: 15 }),
+        Message::Echo(String::from("hello world")),
+        Message::ChangeColor(200, 255, 255),
+        Message::Quit,
+    ];
+
+    for message in &messages {
+        message.call();
+    }
+}

solutions/08_enums/enums3.rs

@@ -0,0 +1,92 @@
+struct Point {
+    x: u64,
+    y: u64,
+}
+
+enum Message {
+    Resize { width: u64, height: u64 },
+    Move(Point),
+    Echo(String),
+    ChangeColor(u8, u8, u8),
+    Quit,
+}
+
+struct State {
+    width: u64,
+    height: u64,
+    position: Point,
+    message: String,
+    color: (u8, u8, u8),
+    quit: bool,
+}
+
+impl State {
+    fn resize(&mut self, width: u64, height: u64) {
+        self.width = width;
+        self.height = height;
+    }
+
+    fn move_position(&mut self, point: Point) {
+        self.position = point;
+    }
+
+    fn echo(&mut self, s: String) {
+        self.message = s;
+    }
+
+    fn change_color(&mut self, red: u8, green: u8, blue: u8) {
+        self.color = (red, green, blue);
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
+    fn process(&mut self, message: Message) {
+        match message {
+            Message::Resize { width, height } => self.resize(width, height),
+            Message::Move(point) => self.move_position(point),
+            Message::Echo(string) => self.echo(string),
+            Message::ChangeColor(red, green, blue) => self.change_color(red, green, blue),
+            Message::Quit => self.quit(),
+        }
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_match_message_call() {
+        let mut state = State {
+            width: 0,
+            height: 0,
+            position: Point { x: 0, y: 0 },
+            message: String::from("hello world"),
+            color: (0, 0, 0),
+            quit: false,
+        };
+
+        state.process(Message::Resize {
+            width: 10,
+            height: 30,
+        });
+        state.process(Message::Move(Point { x: 10, y: 15 }));
+        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::ChangeColor(255, 0, 255));
+        state.process(Message::Quit);
+
+        assert_eq!(state.width, 10);
+        assert_eq!(state.height, 30);
+        assert_eq!(state.position.x, 10);
+        assert_eq!(state.position.y, 15);
+        assert_eq!(state.message, "Hello world!");
+        assert_eq!(state.color, (255, 0, 255));
+        assert!(state.quit);
+    }
+}

solutions/09_strings/strings1.rs

@@ -0,0 +1,9 @@
+fn current_favorite_color() -> String {
+    // Equivalent to `String::from("blue")`
+    "blue".to_string()
+}
+
+fn main() {
+    let answer = current_favorite_color();
+    println!("My current favorite color is {answer}");
+}

solutions/09_strings/strings2.rs

@@ -0,0 +1,15 @@
+fn is_a_color_word(attempt: &str) -> bool {
+    attempt == "green" || attempt == "blue" || attempt == "red"
+}
+
+fn main() {
+    let word = String::from("green");
+
+    if is_a_color_word(&word) {
+        //             ^ added to have `&String` which is automatically
+        //               coerced to `&str` by the compiler.
+        println!("That is a color word I know!");
+    } else {
+        println!("That is not a color word I know.");
+    }
+}

solutions/09_strings/strings3.rs

@@ -0,0 +1,49 @@
+fn trim_me(input: &str) -> &str {
+    input.trim()
+}
+
+fn compose_me(input: &str) -> String {
+    // The macro `format!` has the same syntax as `println!`, but it returns a
+    // string instead of printing it to the terminal.
+    // Equivalent to `input.to_string() + " world!"`
+    format!("{input} world!")
+}
+
+fn replace_me(input: &str) -> String {
+    input.replace("cars", "balloons")
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[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!");
+        assert_eq!(trim_me("Hi!"), "Hi!");
+    }
+
+    #[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",
+        );
+    }
+}

solutions/09_strings/strings4.rs

@@ -0,0 +1,38 @@
+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());
+
+    // Here, both answers work.
+    // `.into()` converts a type into an expected type.
+    // If it is called where `String` is expected, it will convert `&str` to `String`.
+    string("nice weather".into());
+    // But if it is called where `&str` is expected, then `&str` is kept `&str` since no conversion is needed.
+    // If you remove the `#[allow(…)]` line, then Clippy will tell you to remove `.into()` below since it is a useless conversion.
+    #[allow(clippy::useless_conversion)]
+    string_slice("nice weather".into());
+
+    string(format!("Interpolation {}", "Station"));
+
+    // WARNING: This is byte indexing, not character indexing.
+    // Character indexing can be done using `s.chars().nth(INDEX)`.
+    string_slice(&String::from("abc")[0..1]);
+
+    string_slice("  hello there ".trim());
+
+    string("Happy Monday!".replace("Mon", "Tues"));
+
+    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
+}

solutions/10_modules/modules1.rs

@@ -0,0 +1,15 @@
+mod sausage_factory {
+    fn get_secret_recipe() -> String {
+        String::from("Ginger")
+    }
+
+    // Added `pub` before `fn` to make the function accessible outside the module.
+    pub fn make_sausage() {
+        get_secret_recipe();
+        println!("sausage!");
+    }
+}
+
+fn main() {
+    sausage_factory::make_sausage();
+}

solutions/10_modules/modules2.rs

@@ -0,0 +1,23 @@
+mod delicious_snacks {
+    // Added `pub` and used the expected alias after `as`.
+    pub use self::fruits::PEAR as fruit;
+    pub use self::veggies::CUCUMBER as veggie;
+
+    mod fruits {
+        pub const PEAR: &str = "Pear";
+        pub const APPLE: &str = "Apple";
+    }
+
+    mod veggies {
+        pub const CUCUMBER: &str = "Cucumber";
+        pub const CARROT: &str = "Carrot";
+    }
+}
+
+fn main() {
+    println!(
+        "favorite snacks: {} and {}",
+        delicious_snacks::fruit,
+        delicious_snacks::veggie,
+    );
+}

solutions/10_modules/modules3.rs

@@ -0,0 +1,8 @@
+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!"),
+    }
+}

solutions/11_hashmaps/hashmaps1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/11_hashmaps/hashmaps2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/11_hashmaps/hashmaps3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/12_options/options1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/12_options/options2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/12_options/options3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors4.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors5.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/13_error_handling/errors6.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/14_generics/generics1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/14_generics/generics2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/15_traits/traits1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/15_traits/traits2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/15_traits/traits3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/15_traits/traits4.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/15_traits/traits5.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/16_lifetimes/lifetimes1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/16_lifetimes/lifetimes2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/16_lifetimes/lifetimes3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/17_tests/tests1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/17_tests/tests2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/17_tests/tests3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/18_iterators/iterators1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/18_iterators/iterators2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/18_iterators/iterators3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/18_iterators/iterators4.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/18_iterators/iterators5.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/19_smart_pointers/arc1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/19_smart_pointers/box1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/19_smart_pointers/cow1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/19_smart_pointers/rc1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/20_threads/threads1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/20_threads/threads2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/20_threads/threads3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/21_macros/macros1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/21_macros/macros2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/21_macros/macros3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/21_macros/macros4.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/22_clippy/clippy1.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/22_clippy/clippy2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/22_clippy/clippy3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/23_conversions/as_ref_mut.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/23_conversions/from_into.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/23_conversions/from_str.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/23_conversions/try_from_into.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/23_conversions/using_as.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/README.md

@@ -0,0 +1,6 @@
+# Official Rustlings solutions
+
+Before you finish an exercise, its solution file will only contain an empty `main` function.
+The content of this file will be automatically replaced by the actual solution once you finish the exercise.
+
+Note that these solutions are often only _one possibility_ to solve an exercise.

solutions/quizzes/quiz1.rs

@@ -0,0 +1,30 @@
+// Mary is buying apples. The price of an apple is calculated as follows:
+// - An apple costs 2 rustbucks.
+// - However, if Mary buys more than 40 apples, the price of each apple in the
+// entire order is reduced to only 1 rustbuck!
+
+fn calculate_price_of_apples(n_apples: u64) -> u64 {
+    if n_apples > 40 {
+        n_apples
+    } else {
+        2 * n_apples
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+// Don't change the tests!
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn verify_test() {
+        assert_eq!(calculate_price_of_apples(35), 70);
+        assert_eq!(calculate_price_of_apples(40), 80);
+        assert_eq!(calculate_price_of_apples(41), 41);
+        assert_eq!(calculate_price_of_apples(65), 65);
+    }
+}

solutions/quizzes/quiz2.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}

solutions/quizzes/quiz3.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}