Merge pull request #1372 from rust-lang/all-contributors/add-black-puppydog

docs: add black-puppydog as a contributor for content

.all-contributorsrc

@@ -1839,6 +1839,15 @@
       "contributions": [
         "content"
       ]
+    },
+    {
+      "login": "black-puppydog",
+      "name": "Daan Wynen",
+      "avatar_url": "https://avatars.githubusercontent.com/u/189241?v=4",
+      "profile": "https://github.com/black-puppydog",
+      "contributions": [
+        "content"
+      ]
     }
   ],
   "contributorsPerLine": 8,

AUTHORS.md

@@ -262,6 +262,7 @@ authors.
     </tr>
     <tr>
       <td align="center" valign="top" width="12.5%"><a href="https://grzegorz-zur.com/"><img src="https://avatars.githubusercontent.com/u/5297583?v=4?s=100" width="100px;" alt="Grzegorz Żur"/><br /><sub><b>Grzegorz Żur</b></sub></a><br /><a href="#content-grzegorz-zur" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/black-puppydog"><img src="https://avatars.githubusercontent.com/u/189241?v=4?s=100" width="100px;" alt="Daan Wynen"/><br /><sub><b>Daan Wynen</b></sub></a><br /><a href="#content-black-puppydog" title="Content">🖋</a></td>
     </tr>
   </tbody>
 </table>

exercises/clippy/clippy1.rs

@@ -6,10 +6,12 @@
 // 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 NOT DONE
+
 use std::f32;
 
 fn main() {
-    let pi = std::f32::consts::PI;
+    let pi = 3.14f32;
     let radius = 5.00f32;
 
     let area = pi * f32::powi(radius, 2);

exercises/clippy/clippy2.rs

@@ -1,10 +1,12 @@
 // clippy2.rs
 // Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let mut res = 42;
     let option = Some(12);
-    if let Some(x) = option {
+    for x in option {
         res += x;
     }
     println!("{}", res);

exercises/clippy/clippy3.rs

@@ -1,24 +1,28 @@
 // clippy3.rs
 // Here's a couple more easy Clippy fixes, so you can see its utility.
 
+// I AM NOT DONE
+
 #[allow(unused_variables, unused_assignments)]
 fn main() {
     let my_option: Option<()> = None;
-    my_option.unwrap();
+    if my_option.is_none() {
+        my_option.unwrap();
+    }
 
     let my_arr = &[
-        -1, -2, -3,
+        -1, -2, -3
         -4, -5, -6
     ];
     println!("My array! Here it is: {:?}", my_arr);
 
-    let my_empty_vec: std::vec::Vec<i32> = vec![];
+    let my_empty_vec = vec![1, 2, 3, 4, 5].resize(0, 5);
     println!("This Vec is empty, see? {:?}", my_empty_vec);
 
     let mut value_a = 45;
     let mut value_b = 66;
     // Let's swap these two!
     value_a = value_b;
-    std::mem::swap(&mut value_a, &mut value_b);
+    value_b = value_a;
     println!("value a: {}; value b: {}", value_a, value_b);
 }

exercises/conversions/as_ref_mut.rs

@@ -3,19 +3,25 @@
 // 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 NOT DONE
+
 // Obtain the number of bytes (not characters) in the given argument.
-fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
+// TODO: Add the AsRef trait appropriately as a trait bound.
+fn byte_counter<T>(arg: T) -> usize {
     arg.as_ref().as_bytes().len()
 }
 
 // Obtain the number of characters (not bytes) in the given argument.
-fn char_counter<T: AsRef<str>>(arg: T) -> usize {
+// TODO: Add the AsRef trait appropriately as a trait bound.
+fn char_counter<T>(arg: T) -> usize {
     arg.as_ref().chars().count()
 }
 
 // Squares a number using as_mut().
-fn num_sq<T: AsMut<u32>>(arg: &mut T) {
+// TODO: Add the appropriate trait bound.
-    *arg.as_mut() = *arg.as_mut() * *arg.as_mut();
+fn num_sq<T>(arg: &mut T) {
+    // TODO: Implement the function body.
+    ???
 }
 
 #[cfg(test)]

exercises/conversions/from_into.rs

@@ -35,16 +35,10 @@ impl Default for Person {
 // 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 NOT DONE
+
 impl From<&str> for Person {
     fn from(s: &str) -> Person {
-        let vec: Vec<&str> = s.split(",").collect();
-        let name = vec[0].trim(); 
-        let age = vec[vec.len() - 1].parse::<usize>();
-        if vec.len() == 2 && name.len() > 0 && age.is_ok() {
-            Person { name: name.to_string(), age: age.unwrap() }
-        } else {
-            Person::default()
-        }
     }
 }
 

exercises/conversions/from_str.rs

@@ -28,6 +28,8 @@ enum ParsePersonError {
     ParseInt(ParseIntError),
 }
 
+// I AM NOT 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
@@ -44,22 +46,6 @@ enum ParsePersonError {
 impl FromStr for Person {
     type Err = ParsePersonError;
     fn from_str(s: &str) -> Result<Person, Self::Err> {
-        let vec: Vec<&str> = s.split(",").collect();
-        let name = vec[0].trim(); 
-        let age = vec[vec.len() - 1].parse::<usize>();
-        if vec.len() == 2 && name.len() > 0 && age.is_ok() {
-            Ok(Person { name: name.to_string(), age: age.unwrap() })
-        } else {
-            if s.trim().len() == 0 {
-                Err(ParsePersonError::Empty)
-            } else if vec.len() != 2 {
-                Err(ParsePersonError::BadLen)
-            } else if name.len() == 0 {
-                Err(ParsePersonError::NoName)
-            } else {
-                Err(ParsePersonError::ParseInt(age.unwrap_err()))
-            }
-        }
     }
 }
 

exercises/conversions/try_from_into.rs

@@ -23,6 +23,8 @@ enum IntoColorError {
     IntConversion,
 }
 
+// I AM NOT 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,
@@ -32,30 +34,10 @@ enum IntoColorError {
 // 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.
 
-fn into_color(collection: Vec<i16>) -> Result<Color, IntoColorError> {
-    let mut color = Color {red: 0, green: 0, blue: 0};
-    if collection.len() < 3 { return Err(IntoColorError::BadLen) }
-    for (i, num) in collection.iter().enumerate() {
-        if *num >= 0 && *num <= 255 {
-            let val = *num as u8;
-            match i {
-                0 => color.red = val,
-                1 => color.green = val,
-                2 => color.blue = val,
-                _ => return Err(IntoColorError::BadLen),
-            }
-        } else {
-            return Err(IntoColorError::IntConversion);
-        }
-    }
-    Ok(color)
-}
-
 // Tuple implementation
 impl TryFrom<(i16, i16, i16)> for Color {
     type Error = IntoColorError;
     fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
-        into_color(vec![tuple.0, tuple.1, tuple.2])
     }
 }
 
@@ -63,7 +45,6 @@ impl TryFrom<(i16, i16, i16)> for Color {
 impl TryFrom<[i16; 3]> for Color {
     type Error = IntoColorError;
     fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
-        into_color(arr.to_vec())
     }
 }
 
@@ -71,7 +52,6 @@ impl TryFrom<[i16; 3]> for Color {
 impl TryFrom<&[i16]> for Color {
     type Error = IntoColorError;
     fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
-        into_color(slice.to_vec())
     }
 }
 

exercises/conversions/using_as.rs

@@ -6,9 +6,11 @@
 // and returns the proper type.
 // Execute `rustlings hint using_as` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn average(values: &[f64]) -> f64 {
     let total = values.iter().sum::<f64>();
-    total / values.len() as f64
+    total / values.len()
 }
 
 fn main() {

exercises/enums/enums1.rs

@@ -1,12 +1,11 @@
 // enums1.rs
 // No hints this time! ;)
 
+// I AM NOT DONE
+
 #[derive(Debug)]
 enum Message {
-    Quit,
+    // TODO: define a few types of messages as used below
-    Echo,
-    Move,
-    ChangeColor,
 }
 
 fn main() {

exercises/enums/enums2.rs

@@ -1,12 +1,11 @@
 // enums2.rs
 // Execute `rustlings hint enums2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(Debug)]
 enum Message {
-    Move {x: i32, y: i32},
+    // TODO: define the different variants used below
-    Echo(String),
-    ChangeColor(u32, u32, u32),
-    Quit
 }
 
 impl Message {

exercises/enums/enums3.rs

@@ -2,11 +2,10 @@
 // Address all the TODOs to make the tests pass!
 // Execute `rustlings hint enums3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 enum Message {
-    Move(Point),
+    // TODO: implement the message variant types based on their usage below
-    Echo(String),
-    ChangeColor(u8, u8, u8),
-    Quit,
 }
 
 struct Point {
@@ -38,13 +37,8 @@ impl State {
     }
 
     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::Quit => self.quit(),
-            Message::Echo(string) => self.echo(string),
-            Message::Move(point) => self.move_position(point),
-            Message::ChangeColor(r, g, b) => self.change_color((r, g, b)),
-        }
     }
 }
 

exercises/error_handling/errors1.rs

@@ -5,12 +5,14 @@
 // 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.
 
-pub fn generate_nametag_text(name: String) -> Result<String, String> {
+// I AM NOT DONE
+
+pub fn generate_nametag_text(name: String) -> Option<String> {
     if name.is_empty() {
         // Empty names aren't allowed.
-        Err("`name` was empty; it must be nonempty.".to_string())
+        None
     } else {
-        Ok(format!("Hi! My name is {}", name))
+        Some(format!("Hi! My name is {}", name))
     }
 }
 

exercises/error_handling/errors2.rs

@@ -17,12 +17,14 @@
 // one is a lot shorter!
 // Execute `rustlings hint errors2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT 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>()?;
+    let qty = item_quantity.parse::<i32>();
 
     Ok(qty * cost_per_item + processing_fee)
 }

exercises/error_handling/errors3.rs

@@ -4,9 +4,11 @@
 // Why not? What should we do to fix it?
 // Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::num::ParseIntError;
 
-fn main() -> Result<(), ParseIntError> {
+fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -18,7 +20,6 @@ fn main() -> Result<(), ParseIntError> {
         tokens -= cost;
         println!("You now have {} tokens.", tokens);
     }
-    Ok(())
 }
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {

exercises/error_handling/errors4.rs

@@ -1,6 +1,8 @@
 // errors4.rs
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
 
@@ -12,13 +14,8 @@ enum CreationError {
 
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        if value < 0 {
+        // Hmm...? Why is this only returning an Ok value?
-          Err(CreationError::Negative)
+        Ok(PositiveNonzeroInteger(value as u64))
-        } else if value == 0 {
-          Err(CreationError::Zero)
-        }else {
-          Ok(PositiveNonzeroInteger(value as u64))
-        }
     }
 }
 

exercises/error_handling/errors5.rs

@@ -16,11 +16,14 @@
 
 // Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::error;
 use std::fmt;
 use std::num::ParseIntError;
 
-fn main() -> Result<(), Box<dyn error::Error>> {
+// TODO: update the return type of `main()` to make this compile.
+fn main() -> Result<(), Box<dyn ???>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);

exercises/error_handling/errors6.rs

@@ -8,6 +8,8 @@
 
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::num::ParseIntError;
 
 // This is a custom error type that we will be using in `parse_pos_nonzero()`.
@@ -21,13 +23,14 @@ impl ParsePosNonzeroError {
     fn from_creation(err: CreationError) -> ParsePosNonzeroError {
         ParsePosNonzeroError::Creation(err)
     }
-    fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
+    // TODO: add another error conversion function here.
-        ParsePosNonzeroError::ParseInt(err)
+    // fn from_parseint...
-    }
 }
 
 fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
-    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
+    // TODO: change this to return an appropriate error instead of panicking
+    // when `parse()` returns an error.
+    let x: i64 = s.parse().unwrap();
     PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
 }
 

exercises/functions/functions1.rs

@@ -1,9 +1,7 @@
 // functions1.rs
 // Execute `rustlings hint functions1` or use the `hint` watch subcommand for a hint.
 
-fn call_me() {
+// I AM NOT DONE
-
-}
 
 fn main() {
     call_me();

exercises/functions/functions2.rs

@@ -1,11 +1,13 @@
 // functions2.rs
 // Execute `rustlings hint functions2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     call_me(3);
 }
 
-fn call_me(num:i32) {
+fn call_me(num:) {
     for i in 0..num {
         println!("Ring! Call number {}", i + 1);
     }

exercises/functions/functions3.rs

@@ -1,8 +1,10 @@
 // functions3.rs
 // Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    call_me(10);
+    call_me();
 }
 
 fn call_me(num: u32) {

exercises/functions/functions4.rs

@@ -7,12 +7,14 @@
 // in the signatures for now. If anything, this is a good way to peek ahead
 // to future exercises!)
 
+// I AM NOT DONE
+
 fn main() {
     let original_price = 51;
     println!("Your sale price is {}", sale_price(original_price));
 }
 
-fn sale_price(price: u32) -> u32 {
+fn sale_price(price: i32) -> {
     if is_even(price) {
         price - 10
     } else {
@@ -20,6 +22,6 @@ fn sale_price(price: u32) -> u32 {
     }
 }
 
-fn is_even(num: u32) -> bool {
+fn is_even(num: i32) -> bool {
     num % 2 == 0
 }

exercises/functions/functions5.rs

@@ -1,11 +1,13 @@
 // functions5.rs
 // Execute `rustlings hint functions5` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let answer = square(3);
     println!("The square of 3 is {}", answer);
 }
 
 fn square(num: i32) -> i32 {
-    num * num
+    num * num;
 }

exercises/generics/generics1.rs

@@ -3,7 +3,9 @@
 
 // Execute `rustlings hint generics1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let mut shopping_list: Vec<&str> = Vec::new();
+    let mut shopping_list: Vec<?> = Vec::new();
     shopping_list.push("milk");
 }

exercises/generics/generics2.rs

@@ -3,12 +3,14 @@
 
 // Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
 
-struct Wrapper<T> {
+// I AM NOT DONE
-    value: T,
+
+struct Wrapper {
+    value: u32,
 }
 
-impl<T> Wrapper<T> {
+impl Wrapper {
-    pub fn new(value: T) -> Self {
+    pub fn new(value: u32) -> Self {
         Wrapper { value }
     }
 }

exercises/hashmaps/hashmaps1.rs

@@ -10,17 +10,17 @@
 //
 // Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::collections::HashMap;
 
 fn fruit_basket() -> HashMap<String, u32> {
-    let mut basket = HashMap::new();
+    let mut basket = // TODO: declare your hash map here.
 
     // Two bananas are already given for you :)
     basket.insert(String::from("banana"), 2);
 
-    basket.insert(String::from("avocado"), 2);
+    // TODO: Put more fruits in your basket here.
-    basket.insert(String::from("tomato"), 1);
-    basket.insert(String::from("potato"), 1);
 
     basket
 }

exercises/hashmaps/hashmaps2.rs

@@ -11,6 +11,8 @@
 //
 // Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::collections::HashMap;
 
 #[derive(Hash, PartialEq, Eq)]
@@ -32,7 +34,9 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
     ];
 
     for fruit in fruit_kinds {
-        basket.entry(fruit).or_insert(3);
+        // TODO: Put new fruits if not already present. Note that you
+        // are not allowed to put any type of fruit that's already
+        // present!
     }
 }
 

exercises/hashmaps/hashmaps3.rs

@@ -14,6 +14,8 @@
 
 // Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::collections::HashMap;
 
 // A structure to store team name and its goal details.
@@ -33,20 +35,11 @@ fn build_scores_table(results: String) -> HashMap<String, Team> {
         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();
-        let team_1 = scores.entry(team_1_name.clone()).or_insert(Team {
+        // TODO: Populate the scores table with details extracted from the
-          name: team_1_name,
+        // current line. Keep in mind that goals scored by team_1
-          goals_scored: 0,
+        // will be the number of goals conceded from team_2, and similarly
-          goals_conceded: 0,
+        // goals scored by team_2 will be the number of goals conceded by
-        });
+        // team_1.
-        team_1.goals_scored += team_1_score;
-        team_1.goals_conceded += team_2_score;
-        let team_2 = scores.entry(team_2_name.clone()).or_insert(Team {
-          name: team_2_name,
-          goals_scored: 0,
-          goals_conceded: 0,
-        });
-        team_2.goals_scored += team_2_score;
-        team_2.goals_conceded += team_1_score;
     }
     scores
 }

exercises/if/if1.rs

@@ -1,12 +1,13 @@
 // if1.rs
 // Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT 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 :)

exercises/if/if2.rs

@@ -4,13 +4,13 @@
 // 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 NOT DONE
+
 pub fn foo_if_fizz(fizzish: &str) -> &str {
     if fizzish == "fizz" {
         "foo"
-    } else if fizzish == "fuzz" {
-        "bar"
     } else {
-        "baz"
+        1
     }
 }
 

exercises/intro/intro1.rs

@@ -9,6 +9,8 @@
 // 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!
 
+// I AM NOT DONE
+
 fn main() {
     println!("Hello and");
     println!(r#"       welcome to...                      "#);

exercises/intro/intro2.rs

@@ -2,6 +2,8 @@
 // Make the code print a greeting to the world.
 // Execute `rustlings hint intro2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    println!("Hello {}!", "perro");
+    println!("Hello {}!");
 }

exercises/iterators/iterators1.rs

@@ -8,15 +8,17 @@
 //
 // Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main () {
     let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
 
-    let mut my_iterable_fav_fruits = my_fav_fruits.iter();
+    let mut my_iterable_fav_fruits = ???;   // TODO: Step 1
 
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
-    assert_eq!(my_iterable_fav_fruits.next(), Some(&"custard apple"));
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
-    assert_eq!(my_iterable_fav_fruits.next(), Some(&"peach"));
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 3
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
-    assert_eq!(my_iterable_fav_fruits.next(), None);
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 4
 }

exercises/iterators/iterators2.rs

@@ -3,6 +3,8 @@
 // can offer. Follow the steps to complete the exercise.
 // Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 // Step 1.
 // Complete the `capitalize_first` function.
 // "hello" -> "Hello"
@@ -10,7 +12,7 @@ pub fn capitalize_first(input: &str) -> String {
     let mut c = input.chars();
     match c.next() {
         None => String::new(),
-        Some(first) => format!("{}{}", first.to_uppercase(), c.as_str()),
+        Some(first) => ???,
     }
 }
 
@@ -19,11 +21,7 @@ pub fn capitalize_first(input: &str) -> String {
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    let mut replaced = vec![];
+    vec![]
-    for word in words.iter() {
-        replaced.push(capitalize_first(word));
-    }
-    replaced
 }
 
 // Step 3.
@@ -31,7 +29,7 @@ pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
 // Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 pub fn capitalize_words_string(words: &[&str]) -> String {
-    capitalize_words_vector(words).join("")
+    String::new()
 }
 
 #[cfg(test)]

exercises/iterators/iterators3.rs

@@ -6,6 +6,8 @@
 //    list_of_results functions.
 // Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(Debug, PartialEq, Eq)]
 pub enum DivisionError {
     NotDivisible(NotDivisibleError),
@@ -21,29 +23,21 @@ pub struct NotDivisibleError {
 // 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 a.checked_div(b).is_none() {
+    todo!();
-        Err(DivisionError::DivideByZero)
-    } else if a.checked_rem(b) != Some(0) {
-        Err(DivisionError::NotDivisible(NotDivisibleError {dividend: a, divisor: b}))
-    } else {
-        Ok(a / 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> {
+fn result_with_list() -> () {
     let numbers = vec![27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27).unwrap());
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
-    Ok(Vec::from_iter(division_results))
 }
 
 // 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>> {
+fn list_of_results() -> () {
     let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
-    Vec::from_iter(division_results)
 }
 
 #[cfg(test)]

exercises/iterators/iterators4.rs

@@ -1,6 +1,8 @@
 // iterators4.rs
 // Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 pub fn factorial(num: u64) -> u64 {
     // Complete this function to return the factorial of num
     // Do not use:
@@ -11,24 +13,6 @@ pub fn factorial(num: u64) -> u64 {
     // For an extra challenge, don't use:
     // - recursion
     // Execute `rustlings hint iterators4` for hints.
-    (1..num + 1).fold(1, |a, b| a * b)
-    // Explicación con ejemplo factorial(4):
-    // (1..num + 1) es la iteración (1, 2, 3, 4) porque:
-    // * La iteración tiene un límite de elementos igual a num + 1, en este caso 5:
-    // * (0, 1, 2, 3, 4) => 5 elementos
-    // * Sin embargo, solo toma a partir del elemento 1:
-    // * (1, 2, 3, 4)
-    // * Una manera más elegante es:
-    //   (1..=num), demostración:
-    //   assert_eq!((1..num + 1), (1..=num));
-    // De ahí el fold realiza la siguiente multiplicación:
-    // ((((1 * 1) * 2) * 3) * 4)
-    // * El primer argumento de fold es 1 y este corresponde al primer 1 en (1 * 1)
-    // * La variable 'a' es el resultado acumulativo de a * b
-    // * La variable 'b' es cada uno de los elementos del iterador (1, 2, 3, 4)
-    // Una opción más sintética hubiera sido:
-    // (1..=num).product()
-    // Sin embargo, el hint pidió revisar los métodos 'fold' y 'rfold'…
 }
 
 #[cfg(test)]

exercises/iterators/iterators5.rs

@@ -10,6 +10,8 @@
 //
 // Make the code compile and the tests pass.
 
+// I AM NOT DONE
+
 use std::collections::HashMap;
 
 #[derive(Clone, Copy, PartialEq, Eq)]
@@ -32,7 +34,7 @@ fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
 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, ... }
-    map.values().filter(|v| v == &&value).count()
+    todo!();
 }
 
 fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
@@ -51,7 +53,7 @@ fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Pr
     // collection is a slice of hashmaps.
     // collection = [{ "variables1": Complete, "from_str": None, ... },
     //     { "variables2": Complete, ... }, ... ]
-    collection.iter().map(|hm| count_iterator(&hm, value)).fold(0, |a, b| a + b)
+    todo!();
 }
 
 #[cfg(test)]

exercises/lifetimes/lifetimes1.rs

@@ -7,7 +7,9 @@
 //
 // Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a hint.
 
-fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+// I AM NOT DONE
+
+fn longest(x: &str, y: &str) -> &str {
     if x.len() > y.len() {
         x
     } else {

exercises/lifetimes/lifetimes2.rs

@@ -6,6 +6,8 @@
 //
 // Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x
@@ -17,7 +19,9 @@ fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
 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());
+        let string2 = String::from("xyz");
+        result = longest(string1.as_str(), string2.as_str());
+    }
     println!("The longest string is '{}'", result);
 }

exercises/lifetimes/lifetimes3.rs

@@ -4,9 +4,11 @@
 //
 // Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a hint.
 
-struct Book<'a> {
+// I AM NOT DONE
-    author: &'a str,
+
-    title: &'a str,
+struct Book {
+    author: &str,
+    title: &str,
 }
 
 fn main() {

exercises/macros/macros1.rs

@@ -1,6 +1,8 @@
 // macros1.rs
 // Execute `rustlings hint macros1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
@@ -8,5 +10,5 @@ macro_rules! my_macro {
 }
 
 fn main() {
-    my_macro!();
+    my_macro();
 }

exercises/macros/macros2.rs

@@ -1,11 +1,12 @@
 // macros2.rs
 // Execute `rustlings hint macros2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     my_macro!();
 }
 
-#[macro_export]
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");

exercises/macros/macros3.rs

@@ -2,8 +2,9 @@
 // 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 NOT DONE
+
 mod macros {
-    #[macro_export]
     macro_rules! my_macro {
         () => {
             println!("Check out my macro!");

exercises/macros/macros4.rs

@@ -1,10 +1,12 @@
 // macros4.rs
 // Execute `rustlings hint macros4` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
-    };
+    }
     ($val:expr) => {
         println!("Look at this other macro: {}", $val);
     }

exercises/modules/modules1.rs

@@ -1,13 +1,15 @@
 // modules1.rs
 // Execute `rustlings hint modules1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT 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() {
+    fn make_sausage() {
         get_secret_recipe();
         println!("sausage!");
     }

exercises/modules/modules2.rs

@@ -3,9 +3,12 @@
 // '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 NOT DONE
+
 mod delicious_snacks {
-    pub use self::fruits::PEAR as fruit;
+    // TODO: Fix these use statements
-    pub use self::veggies::CUCUMBER as veggie;
+    use self::fruits::PEAR as ???
+    use self::veggies::CUCUMBER as ???
 
     mod fruits {
         pub const PEAR: &'static str = "Pear";

exercises/modules/modules3.rs

@@ -5,7 +5,10 @@
 // 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.
 
-use std::time::{SystemTime, UNIX_EPOCH};
+// I AM NOT DONE
+
+// TODO: Complete this use statement
+use ???
 
 fn main() {
     match SystemTime::now().duration_since(UNIX_EPOCH) {

exercises/move_semantics/move_semantics1.rs

@@ -1,10 +1,12 @@
 // move_semantics1.rs
 // Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let vec0 = Vec::new();
 
-    let mut vec1 = fill_vec(vec0);
+    let vec1 = fill_vec(vec0);
 
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 

exercises/move_semantics/move_semantics2.rs

@@ -2,10 +2,12 @@
 // Make me compile without changing line 13 or moving line 10!
 // Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let vec0 = Vec::new();
 
-    let mut vec1 = fill_vec(vec0.clone());
+    let mut vec1 = fill_vec(vec0);
 
     // Do not change the following line!
     println!("{} has length {} content `{:?}`", "vec0", vec0.len(), vec0);

exercises/move_semantics/move_semantics3.rs

@@ -3,6 +3,8 @@
 // (no lines with multiple semicolons necessary!)
 // Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let vec0 = Vec::new();
 
@@ -15,7 +17,7 @@ fn main() {
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 }
 
-fn fill_vec(mut vec: Vec<i32>) -> Vec<i32> {
+fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
     vec.push(22);
     vec.push(44);
     vec.push(66);

exercises/move_semantics/move_semantics4.rs

@@ -4,8 +4,12 @@
 // function.
 // Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let mut vec1 = fill_vec();
+    let vec0 = Vec::new();
+
+    let mut vec1 = fill_vec(vec0);
 
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 
@@ -16,7 +20,7 @@ fn main() {
 
 // `fill_vec()` no longer takes `vec: Vec<i32>` as argument
 fn fill_vec() -> Vec<i32> {
-    let mut vec = Vec::new();
+    let mut vec = vec;
 
     vec.push(22);
     vec.push(44);

exercises/move_semantics/move_semantics5.rs

@@ -3,11 +3,13 @@
 // adding, changing or removing any of them.
 // Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let mut x = 100;
     let y = &mut x;
-    *y += 100;
     let z = &mut x;
+    *y += 100;
     *z += 1000;
     assert_eq!(x, 1200);
 }

exercises/move_semantics/move_semantics6.rs

@@ -2,22 +2,24 @@
 // Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand for a hint.
 // You can't change anything except adding or removing references.
 
+// I AM NOT DONE
+
 fn main() {
     let data = "Rust is great!".to_string();
 
-    get_char(&data);
+    get_char(data);
 
-    string_uppercase(data);
+    string_uppercase(&data);
 }
 
 // Should not take ownership
-fn get_char(data: &String) -> char {
+fn get_char(data: String) -> char {
     data.chars().last().unwrap()
 }
 
 // Should take ownership
-fn string_uppercase(mut data: String) {
+fn string_uppercase(mut data: &String) {
-    data = data.to_uppercase();
+    data = &data.to_uppercase();
 
     println!("{}", data);
 }

exercises/options/options1.rs

@@ -1,19 +1,16 @@
 // options1.rs
 // Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT 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.
-    if time_of_day < 22 {
+    // TODO: Complete the function body - remember to return an Option!
-      Some(5)
+    ???
-    } else if time_of_day < 24 {
-      Some(0)
-    } else {
-      None
-    }
 }
 
 #[cfg(test)]
@@ -31,7 +28,8 @@ mod tests {
 
     #[test]
     fn raw_value() {
+        // TODO: Fix this test. How do you get at the value contained in the Option?
         let icecreams = maybe_icecream(12);
-        assert_eq!(icecreams, Some(5));
+        assert_eq!(icecreams, 5);
     }
 }

exercises/options/options2.rs

@@ -1,6 +1,8 @@
 // options2.rs
 // Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[cfg(test)]
 mod tests {
     #[test]
@@ -8,7 +10,8 @@ mod tests {
         let target = "rustlings";
         let optional_target = Some(target);
 
-        if let Some(word) = optional_target {
+        // TODO: Make this an if let statement whose value is "Some" type
+        word = optional_target {
             assert_eq!(word, target);
         }
     }
@@ -21,8 +24,10 @@ mod tests {
             optional_integers.push(Some(i));
         }
 
-        while let Some(integer) = optional_integers.pop() {
+        // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
-            assert_eq!(integer, Some(range));
+        // You can stack `Option<T>`'s into while let and if let
+        integer = optional_integers.pop() {
+            assert_eq!(integer, range);
             range -= 1;
         }
     }

exercises/options/options3.rs

@@ -1,6 +1,8 @@
 // options3.rs
 // Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 struct Point {
     x: i32,
     y: i32,
@@ -10,7 +12,7 @@ fn main() {
     let y: Option<Point> = Some(Point { x: 100, y: 200 });
 
     match y {
-        Some(ref p) => println!("Co-ordinates are {},{} ", p.x, p.y),
+        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
         _ => println!("no match"),
     }
     y; // Fix without deleting this line.

exercises/primitive_types/primitive_types1.rs

@@ -2,6 +2,8 @@
 // Fill in the rest of the line that has code missing!
 // No hints, there's no tricks, just get used to typing these :)
 
+// I AM NOT DONE
+
 fn main() {
     // Booleans (`bool`)
 
@@ -10,7 +12,7 @@ fn main() {
         println!("Good morning!");
     }
 
-    let is_evening  = false; // Finish the rest of this line like the example! Or make it be false!
+    let // Finish the rest of this line like the example! Or make it be false!
     if is_evening {
         println!("Good evening!");
     }

exercises/primitive_types/primitive_types2.rs

@@ -2,6 +2,8 @@
 // Fill in the rest of the line that has code missing!
 // No hints, there's no tricks, just get used to typing these :)
 
+// I AM NOT DONE
+
 fn main() {
     // Characters (`char`)
 
@@ -16,7 +18,7 @@ fn main() {
         println!("Neither alphabetic nor numeric!");
     }
 
-    let your_character = 'p'; // Finish this line like the example! What's your favorite character?
+    let // 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() {

exercises/primitive_types/primitive_types3.rs

@@ -2,8 +2,10 @@
 // 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 NOT DONE
+
 fn main() {
-    let a = ["Multiplicado cien veces"; 100]; 
+    let a = ???
 
     if a.len() >= 100 {
         println!("Wow, that's a big array!");

exercises/primitive_types/primitive_types4.rs

@@ -2,11 +2,13 @@
 // 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 NOT DONE
+
 #[test]
 fn slice_out_of_array() {
     let a = [1, 2, 3, 4, 5];
 
-    let nice_slice = &a[1..4];
+    let nice_slice = ???
 
     assert_eq!([2, 3, 4], nice_slice)
 }

exercises/primitive_types/primitive_types5.rs

@@ -2,9 +2,11 @@
 // 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 NOT DONE
+
 fn main() {
     let cat = ("Furry McFurson", 3.5);
-    let (name, age) = cat;
+    let /* your pattern here */ = cat;
 
     println!("{} is {} years old.", name, age);
 }

exercises/primitive_types/primitive_types6.rs

@@ -3,11 +3,13 @@
 // 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 NOT DONE
+
 #[test]
 fn indexing_tuple() {
     let numbers = (1, 2, 3);
     // Replace below ??? with the tuple indexing syntax.
-    let second = numbers.1;
+    let second = ???;
 
     assert_eq!(2, second,
         "This is not the 2nd number in the tuple!")

exercises/quiz1.rs

@@ -10,14 +10,10 @@
 // Write a function that calculates the price of an order of apples given
 // the quantity bought. No hints this time!
 
+// I AM NOT DONE
+
 // Put your function here!
-fn calculate_price_of_apples(apples:u32) -> u32 {
+// fn calculate_price_of_apples {
-    if apples > 40 {
-        apples * 1
-    } else {
-        apples * 2
-    }
-}
 
 // Don't modify this function!
 #[test]

exercises/quiz2.rs

@@ -18,6 +18,8 @@
 // - The output element is going to be a Vector of strings.
 // No hints this time!
 
+// I AM NOT DONE
+
 pub enum Command {
     Uppercase,
     Trim,
@@ -27,14 +29,12 @@ pub enum Command {
 mod my_module {
     use super::Command;
 
-    pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
+    // TODO: Complete the function signature!
-        let mut output: Vec<String> = vec![];
+    pub fn transformer(input: ???) -> ??? {
+        // TODO: Complete the output declaration!
+        let mut output: ??? = vec![];
         for (string, command) in input.iter() {
-            output.push(match command {
+            // TODO: Complete the function body. You can do it!
-               Command::Uppercase => string.to_uppercase(),  
-               Command::Trim => string.trim().to_string(),  
-               Command::Append(times) => format!("{}{}", string, "bar".repeat(*times)),  
-            })
         }
         output
     }
@@ -42,7 +42,8 @@ mod my_module {
 
 #[cfg(test)]
 mod tests {
-    use super::my_module::transformer;
+    // TODO: What do we need to import to have `transformer` in scope?
+    use ???;
     use super::Command;
 
     #[test]

exercises/quiz3.rs

@@ -13,15 +13,16 @@
 // to show that your changes allow alphabetical grades.
 
 // Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.
-use std::fmt::Display;
 
-pub struct ReportCard<T> {
+// I AM NOT DONE
-    pub grade: T,
+
+pub struct ReportCard {
+    pub grade: f32,
     pub student_name: String,
     pub student_age: u8,
 }
 
-impl<T: std::fmt::Display> ReportCard<T> {
+impl ReportCard {
     pub fn print(&self) -> String {
         format!("{} ({}) - achieved a grade of {}",
             &self.student_name, &self.student_age, &self.grade)
@@ -47,8 +48,9 @@ mod tests {
 
     #[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+",
+            grade: 2.1,
             student_name: "Gary Plotter".to_string(),
             student_age: 11,
         };

exercises/smart_pointers/arc1.rs

@@ -18,17 +18,19 @@
 // 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 NOT 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 shared_numbers = // TODO
     let mut joinhandles = Vec::new();
 
     for offset in 0..8 {
-        let child_numbers = Arc::clone(&shared_numbers);
+        let child_numbers = // TODO
         joinhandles.push(thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
             println!("Sum of offset {} is {}", offset, sum);

exercises/smart_pointers/box1.rs

@@ -16,9 +16,11 @@
 //
 // Execute `rustlings hint box1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(PartialEq, Debug)]
 pub enum List {
-    Cons(i32, Box<List>),
+    Cons(i32, List),
     Nil,
 }
 
@@ -31,11 +33,11 @@ fn main() {
 }
 
 pub fn create_empty_list() -> List {
-    List::Nil
+    todo!()
 }
 
 pub fn create_non_empty_list() -> List {
-    List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))))
+    todo!()
 }
 
 #[cfg(test)]

exercises/smart_pointers/cow1.rs

@@ -4,6 +4,11 @@
 // 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.
+
+// I AM NOT DONE
 
 use std::borrow::Cow;
 
@@ -18,28 +23,52 @@ fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
     input
 }
 
-fn main() {
+#[cfg(test)]
-    // No clone occurs because `input` doesn't need to be mutated.
+mod tests {
-    let slice = [0, 1, 2];
+    use super::*;
-    let mut input = Cow::from(&slice[..]);
+
-    match abs_all(&mut input) {
+    #[test]
-        Cow::Borrowed(_) => println!("I borrowed the slice!"),
+    fn reference_mutation() -> Result<(), &'static str> {
-        _ => panic!("expected borrowed value"),
+        // 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"),
+        }
     }
 
-    // Clone occurs because `input` needs to be mutated.
+    #[test]
-    let slice = [-1, 0, 1];
+    fn reference_no_mutation() -> Result<(), &'static str> {
-    let mut input = Cow::from(&slice[..]);
+        // No clone occurs because `input` doesn't need to be mutated.
-    match abs_all(&mut input) {
+        let slice = [0, 1, 2];
-        Cow::Owned(_) => println!("I modified the slice and now own it!"),
+        let mut input = Cow::from(&slice[..]);
-        _ => panic!("expected owned value"),
+        match abs_all(&mut input) {
+            // TODO
+        }
     }
 
-    // No clone occurs because `input` is already owned.
+    #[test]
-    let slice = vec![-1, 0, 1];
+    fn owned_no_mutation() -> Result<(), &'static str> {
-    let mut input = Cow::from(slice);
+        // We can also pass `slice` without `&` so Cow owns it directly.
-    match abs_all(&mut input) {
+        // In this case no mutation occurs and thus also no clone,
-        Cow::Owned(_) => println!("I own this slice!"),
+        // but the result is still owned because it always was.
-        _ => panic!("expected borrowed value"),
+        let slice = vec![0, 1, 2];
+        let mut input = Cow::from(slice);
+        match abs_all(&mut input) {
+            // TODO
+        }
+    }
+
+    #[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
+        }
     }
 }

exercises/smart_pointers/rc1.rs

@@ -5,6 +5,8 @@
 
 // Make this code compile by using the proper Rc primitives to express that the sun has multiple owners.
 
+// I AM NOT DONE
+
 use std::rc::Rc;
 
 #[derive(Debug)]
@@ -52,15 +54,18 @@ fn main() {
     println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
     jupiter.details();
 
-    let saturn = Planet::Saturn(Rc::clone(&sun));
+    // TODO
+    let saturn = Planet::Saturn(Rc::new(Sun {}));
     println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
     saturn.details();
 
-    let uranus = Planet::Uranus(Rc::clone(&sun));
+    // TODO
+    let uranus = Planet::Uranus(Rc::new(Sun {}));
     println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
     uranus.details();
 
-    let neptune = Planet::Neptune(Rc::clone(&sun));
+    // TODO
+    let neptune = Planet::Neptune(Rc::new(Sun {}));
     println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
     neptune.details();
 
@@ -81,13 +86,13 @@ fn main() {
     drop(mars);
     println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
-    drop(earth);
+    // TODO
     println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
-    drop(venus);
+    // TODO
     println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
-    drop(mercury);
+    // TODO
     println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
     assert_eq!(Rc::strong_count(&sun), 1);

exercises/strings/strings1.rs

@@ -2,11 +2,13 @@
 // Make me compile without changing the function signature!
 // Execute `rustlings hint strings1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let answer = current_favorite_color();
     println!("My current favorite color is {}", answer);
 }
 
 fn current_favorite_color() -> String {
-    String::from("blue")
+    "blue"
 }

exercises/strings/strings2.rs

@@ -2,9 +2,11 @@
 // Make me compile without changing the function signature!
 // Execute `rustlings hint strings2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let word = String::from("green"); // Try not changing this line :)
-    if is_a_color_word(&word) {
+    if is_a_color_word(word) {
         println!("That is a color word I know!");
     } else {
         println!("That is not a color word I know.");

exercises/strings/strings3.rs

@@ -1,16 +1,21 @@
 // strings3.rs
 // Execute `rustlings hint strings3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn trim_me(input: &str) -> String {
-    input.trim().to_string()
+    // TODO: Remove whitespace from both ends of a string!
+    ???
 }
 
 fn compose_me(input: &str) -> String {
-    format!("{}{}", input, " world!")
+    // TODO: Add " world!" to the string! There's multiple ways to do this!
+    ???
 }
 
 fn replace_me(input: &str) -> String {
-    input.replace("cars", "balloons")
+    // TODO: Replace "cars" in the string with "balloons"!
+    ???
 }
 
 #[cfg(test)]

exercises/strings/strings4.rs

@@ -6,6 +6,8 @@
 // before the parentheses on each line. If you're right, it will compile!
 // No hints this time!
 
+// I AM NOT DONE
+
 fn string_slice(arg: &str) {
     println!("{}", arg);
 }
@@ -14,14 +16,14 @@ fn string(arg: String) {
 }
 
 fn main() {
-    string_slice("blue");
+    ???("blue");
-    string("red".to_string());
+    ???("red".to_string());
-    string(String::from("hi"));
+    ???(String::from("hi"));
-    string("rust is fun!".to_owned());
+    ???("rust is fun!".to_owned());
-    string("nice weather".into());
+    ???("nice weather".into());
-    string(format!("Interpolation {}", "Station"));
+    ???(format!("Interpolation {}", "Station"));
-    string_slice(&String::from("abc")[0..1]);
+    ???(&String::from("abc")[0..1]);
-    string_slice("  hello there ".trim());
+    ???("  hello there ".trim());
-    string("Happy Monday!".to_string().replace("Mon", "Tues"));
+    ???("Happy Monday!".to_string().replace("Mon", "Tues"));
-    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
+    ???("mY sHiFt KeY iS sTiCkY".to_lowercase());
 }

exercises/structs/structs1.rs

@@ -2,13 +2,13 @@
 // Address all the TODOs to make the tests pass!
 // Execute `rustlings hint structs1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 struct ColorClassicStruct {
-    red: u32,
+    // TODO: Something goes here
-    green: u32,
-    blue: u32,
 }
 
-struct ColorTupleStruct(u32, u32, u32);
+struct ColorTupleStruct(/* TODO: Something goes here */);
 
 #[derive(Debug)]
 struct UnitLikeStruct;
@@ -19,11 +19,8 @@ mod tests {
 
     #[test]
     fn classic_c_structs() {
-        let green = ColorClassicStruct {
+        // TODO: Instantiate a classic c struct!
-            red: 0,
+        // let green =
-            green: 255,
-            blue: 0,
-        };
 
         assert_eq!(green.red, 0);
         assert_eq!(green.green, 255);
@@ -32,7 +29,8 @@ mod tests {
 
     #[test]
     fn tuple_structs() {
-        let green = ColorTupleStruct(0, 255, 0);
+        // TODO: Instantiate a tuple struct!
+        // let green =
 
         assert_eq!(green.0, 0);
         assert_eq!(green.1, 255);
@@ -41,7 +39,8 @@ mod tests {
 
     #[test]
     fn unit_structs() {
-        let unit_like_struct = UnitLikeStruct;
+        // TODO: Instantiate a unit-like struct!
+        // let unit_like_struct =
         let message = format!("{:?}s are fun!", unit_like_struct);
 
         assert_eq!(message, "UnitLikeStructs are fun!");

exercises/structs/structs2.rs

@@ -2,6 +2,8 @@
 // Address all the TODOs to make the tests pass!
 // Execute `rustlings hint structs2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(Debug)]
 struct Order {
     name: String,
@@ -32,11 +34,8 @@ mod tests {
     #[test]
     fn your_order() {
         let order_template = create_order_template();
-        let your_order = Order {
+        // TODO: Create your own order using the update syntax and template above!
-            name: String::from("Hacker in Rust"),
+        // let your_order =
-            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);

exercises/structs/structs3.rs

@@ -4,6 +4,8 @@
 // Make the code compile and the tests pass!
 // Execute `rustlings hint structs3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[derive(Debug)]
 struct Package {
     sender_country: String,
@@ -24,12 +26,12 @@ impl Package {
         }
     }
 
-    fn is_international(&self) -> bool {
+    fn is_international(&self) -> ??? {
-        if self.sender_country == self.recipient_country { false } else { true }
+        // Something goes here...
     }
 
-    fn get_fees(&self, cents_per_gram: i32) -> i32 {
+    fn get_fees(&self, cents_per_gram: i32) -> ??? {
-        self.weight_in_grams * cents_per_gram
+        // Something goes here...
     }
 }
 

exercises/tests/tests1.rs

@@ -7,10 +7,12 @@
 // pass! Make the test fail!
 // Execute `rustlings hint tests1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[cfg(test)]
 mod tests {
     #[test]
     fn you_can_assert() {
-        assert!(true);
+        assert!();
     }
 }

exercises/tests/tests2.rs

@@ -3,10 +3,12 @@
 // pass! Make the test fail!
 // Execute `rustlings hint tests2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 #[cfg(test)]
 mod tests {
     #[test]
     fn you_can_assert_eq() {
-        assert_eq!(1 + 1, 2);
+        assert_eq!();
     }
 }

exercises/tests/tests3.rs

@@ -4,6 +4,8 @@
 // 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 NOT DONE
+
 pub fn is_even(num: i32) -> bool {
     num % 2 == 0
 }
@@ -14,11 +16,11 @@ mod tests {
 
     #[test]
     fn is_true_when_even() {
-        assert!(is_even(4));
+        assert!();
     }
 
     #[test]
     fn is_false_when_odd() {
-        assert!(!is_even(5));
+        assert!();
     }
 }

exercises/threads/threads1.rs

@@ -6,6 +6,8 @@
 // The program should wait until all the spawned threads have finished and
 // should collect their return values into a vector.
 
+// I AM NOT DONE
+
 use std::thread;
 use std::time::{Duration, Instant};
 
@@ -22,7 +24,7 @@ fn main() {
 
     let mut results: Vec<u128> = vec![];
     for handle in handles {
-        results.push(handle.join().unwrap());
+        // TODO: a struct is returned from thread::spawn, can you use it?
     }
 
     if results.len() != 10 {

exercises/threads/threads2.rs

@@ -3,7 +3,9 @@
 // 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
 
-use std::sync::{Arc, Mutex};
+// I AM NOT DONE
+
+use std::sync::Arc;
 use std::thread;
 use std::time::Duration;
 
@@ -12,18 +14,21 @@ struct JobStatus {
 }
 
 fn main() {
-    let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));
+    let status = Arc::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));
-            status_shared.lock().unwrap().jobs_completed += 1;
+            // TODO: You must take an action before you update a shared value
+            status_shared.jobs_completed += 1;
         });
         handles.push(handle);
     }
     for handle in handles {
         handle.join().unwrap();
-        println!("jobs completed {}", status.lock().unwrap().jobs_completed);
+        // 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 {}", ???);
     }
 }

exercises/threads/threads3.rs

@@ -1,6 +1,8 @@
 // threads3.rs
 // Execute `rustlings hint threads3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 use std::sync::mpsc;
 use std::sync::Arc;
 use std::thread;
@@ -26,12 +28,11 @@ 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 tx1 = tx.clone();
 
     thread::spawn(move || {
         for val in &qc1.first_half {
             println!("sending {:?}", val);
-            tx1.send(*val).unwrap();
+            tx.send(*val).unwrap();
             thread::sleep(Duration::from_secs(1));
         }
     });

exercises/traits/traits1.rs

@@ -9,14 +9,14 @@
 // implementing this trait.
 // Execute `rustlings hint traits1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 trait AppendBar {
     fn append_bar(self) -> Self;
 }
 
 impl AppendBar for String {
-    fn append_bar(self) -> String {
+    // TODO: Implement `AppendBar` for type `String`.
-        format!("{}Bar", self)
-    } 
 }
 
 fn main() {

exercises/traits/traits2.rs

@@ -11,16 +11,13 @@
 // you can do this!
 // Execute `rustlings hint traits2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 trait AppendBar {
     fn append_bar(self) -> Self;
 }
 
-impl AppendBar for Vec<String> {
+// TODO: Implement trait `AppendBar` for a vector of strings.
-    fn append_bar(mut self) -> Vec<String> {
-        self.push(String::from("Bar"));
-        self
-    }
-}
 
 #[cfg(test)]
 mod tests {

exercises/traits/traits3.rs

@@ -7,10 +7,10 @@
 // Consider what you can add to the Licensed trait.
 // Execute `rustlings hint traits3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 pub trait Licensed {
-    fn licensing_info(&self) -> String {
+    fn licensing_info(&self) -> String;
-        "Some information".to_string()
-    }
 }
 
 struct SomeSoftware {

exercises/traits/traits4.rs

@@ -4,6 +4,8 @@
 // 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 NOT DONE
+
 pub trait Licensed {
     fn licensing_info(&self) -> String {
         "some information".to_string()
@@ -18,7 +20,7 @@ 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 {
+fn compare_license_types(software: ??, software_two: ??) -> bool {
     software.licensing_info() == software_two.licensing_info()
 }
 

exercises/traits/traits5.rs

@@ -4,6 +4,8 @@
 // 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 NOT DONE
+
 pub trait SomeTrait {
     fn some_function(&self) -> bool {
         true
@@ -25,7 +27,7 @@ impl SomeTrait for OtherStruct {}
 impl OtherTrait for OtherStruct {}
 
 // YOU MAY ONLY CHANGE THE NEXT LINE
-fn some_func(item: impl SomeTrait + OtherTrait) -> bool {
+fn some_func(item: ??) -> bool {
     item.some_function() && item.other_function()
 }
 

exercises/variables/variables1.rs

@@ -2,7 +2,9 @@
 // Make me compile!
 // Execute `rustlings hint variables1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let x = 5;
+    x = 5;
     println!("x has the value {}", x);
 }

exercises/variables/variables2.rs

@@ -1,8 +1,10 @@
 // variables2.rs
 // Execute `rustlings hint variables2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let x = 10;
+    let x;
     if x == 10 {
         println!("x is ten!");
     } else {

exercises/variables/variables3.rs

@@ -1,7 +1,9 @@
 // variables3.rs
 // Execute `rustlings hint variables3` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let x: i32 = 0;
+    let x: i32;
     println!("Number {}", x);
 }

exercises/variables/variables4.rs

@@ -1,8 +1,10 @@
 // variables4.rs
 // Execute `rustlings hint variables4` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
-    let mut x = 3;
+    let x = 3;
     println!("Number {}", x);
     x = 5; // don't change this line
     println!("Number {}", x);

exercises/variables/variables5.rs

@@ -1,11 +1,11 @@
 // variables5.rs
 // Execute `rustlings hint variables5` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn main() {
     let number = "T-H-R-E-E"; // don't change this line
     println!("Spell a Number : {}", number);
-    {
+    number = 3; // don't rename this variable
-        let number = 3; // don't rename this variable
+    println!("Number plus two is : {}", number + 2);
-        println!("Number plus two is : {}", number + 2);
-    }
 }

exercises/variables/variables6.rs

@@ -1,7 +1,9 @@
 // variables6.rs
 // Execute `rustlings hint variables6` or use the `hint` watch subcommand for a hint.
 
-const NUMBER:i32 = 3;
+// I AM NOT DONE
+
+const NUMBER = 3;
 fn main() {
     println!("Number {}", NUMBER);
 }

exercises/vecs/README.md

@@ -13,3 +13,5 @@ the other useful data structure, hash maps, later.
 ## Further information
 
 - [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
+- [`iter_mut`](https://doc.rust-lang.org/std/primitive.slice.html#method.iter_mut)
+- [`map`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map)

exercises/vecs/vecs1.rs

@@ -4,10 +4,11 @@
 // Make me compile and pass the test!
 // Execute `rustlings hint vecs1` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn array_and_vec() -> ([i32; 4], Vec<i32>) {
     let a = [10, 20, 30, 40]; // a plain array
-    let v = a.to_vec();
+    let v = // TODO: declare your vector here with the macro for vectors
-    // let v = vec![10, 20, 30, 40];
 
     (a, v)
 }

exercises/vecs/vecs2.rs

@@ -6,9 +6,13 @@
 //
 // Execute `rustlings hint vecs2` or use the `hint` watch subcommand for a hint.
 
+// I AM NOT DONE
+
 fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
     for i in v.iter_mut() {
-        *i *= 2
+        // TODO: Fill this up so that each element in the Vec `v` is
+        // multiplied by 2.
+        ???
     }
 
     // At this point, `v` should be equal to [4, 8, 12, 16, 20].
@@ -17,7 +21,9 @@ fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
 
 fn vec_map(v: &Vec<i32>) -> Vec<i32> {
     v.iter().map(|num| {
-        num * 2
+        // TODO: Do the same thing as above - but instead of mutating the
+        // Vec, you can just return the new number!
+        ???
     }).collect()
 }
 

info.toml

@@ -1010,11 +1010,11 @@ https://doc.rust-lang.org/stable/book/ch16-00-concurrency.html
 [[exercises]]
 name = "cow1"
 path = "exercises/smart_pointers/cow1.rs"
-mode = "compile"
+mode = "test"
 hint = """
-Since the vector is already owned, the `Cow` type doesn't need to clone it.
+If Cow already owns the data it doesn't need to clone it when to_mut() is called.
 
-Checkout https://doc.rust-lang.org/std/borrow/enum.Cow.html for documentation
+Check out https://doc.rust-lang.org/std/borrow/enum.Cow.html for documentation
 on the `Cow` type.
 """