box1 solution

exercises/17_tests/tests3.rs

@@ -29,8 +29,8 @@ mod tests {
         // TODO: This test should check if the rectangle has the size that we
         // pass to its constructor.
         let rect = Rectangle::new(10, 20);
-        assert_eq!(???, 10); // Check width
+        assert_eq!(todo!(), 10); // Check width
-        assert_eq!(???, 20); // Check height
+        assert_eq!(todo!(), 20); // Check height
     }
 
     // TODO: This test should check if the program panics when we try to create

exercises/18_iterators/iterators1.rs

@@ -1,8 +1,6 @@
 // When performing operations on elements within a collection, iterators are
 // essential. This module helps you get familiar with the structure of using an
 // iterator and how to go through elements within an iterable collection.
-//
-// Make me compile by filling in the `???`s
 
 fn main() {
     // You can optionally experiment here.
@@ -10,19 +8,18 @@ fn main() {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-
     #[test]
     fn iterators() {
-        let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
+        let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
 
-        let mut my_iterable_fav_fruits = ???;   // TODO: Step 1
+        // TODO: Create an iterator over the array.
+        let mut fav_fruits_iterator = todo!();
 
-        assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
-        assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
-        assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
-        assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 3
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
-        assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
-        assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 4
+        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
     }
 }

exercises/18_iterators/iterators2.rs

@@ -1,31 +1,28 @@
 // In this exercise, you'll learn some of the unique advantages that iterators
-// can offer. Follow the steps to complete the exercise.
+// can offer.
 
-// Step 1.
+// TODO: Complete the `capitalize_first` function.
-// Complete the `capitalize_first` function.
 // "hello" -> "Hello"
 fn capitalize_first(input: &str) -> String {
-    let mut c = input.chars();
+    let mut chars = input.chars();
-    match c.next() {
+    match chars.next() {
         None => String::new(),
-        Some(first) => ???,
+        Some(first) => todo!(),
     }
 }
 
-// Step 2.
+// TODO: Apply the `capitalize_first` function to a slice of string slices.
-// Apply the `capitalize_first` function to a slice of string slices.
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    vec![]
+    // ???
 }
 
-// Step 3.
+// TODO: Apply the `capitalize_first` function again to a slice of string
-// Apply the `capitalize_first` function again to a slice of string slices.
+// slices. Return a single string.
-// Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 fn capitalize_words_string(words: &[&str]) -> String {
-    String::new()
+    // ???
 }
 
 fn main() {

exercises/18_iterators/iterators3.rs

@@ -1,40 +1,26 @@
-// This is a bigger exercise than most of the others! You can do it! Here is
-// your mission, should you choose to accept it:
-// 1. Complete the divide function to get the first four tests to pass.
-// 2. Get the remaining tests to pass by completing the result_with_list and
-//    list_of_results functions.
-
 #[derive(Debug, PartialEq, Eq)]
 enum DivisionError {
-    NotDivisible(NotDivisibleError),
     DivideByZero,
+    NotDivisible,
 }
 
-#[derive(Debug, PartialEq, Eq)]
+// TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
-struct NotDivisibleError {
-    dividend: i32,
-    divisor: i32,
-}
-
-// Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
 fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
     todo!();
 }
 
-// Complete the function and return a value of the correct type so the test
+// TODO: Add the correct return type and complete the function body.
-// passes.
+// Desired output: `Ok([1, 11, 1426, 3])`
-// Desired output: Ok([1, 11, 1426, 3])
+fn result_with_list() {
-fn result_with_list() -> () {
+    let numbers = [27, 297, 38502, 81];
-    let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
-// Complete the function and return a value of the correct type so the test
+// TODO: Add the correct return type and complete the function body.
-// passes.
+// Desired output: `[Ok(1), Ok(11), Ok(1426), Ok(3)]`
-// Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
+fn list_of_results() {
-fn list_of_results() -> () {
+    let numbers = [27, 297, 38502, 81];
-    let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
@@ -52,19 +38,13 @@ mod tests {
     }
 
     #[test]
-    fn test_not_divisible() {
+    fn test_divide_by_0() {
-        assert_eq!(
+        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
-            divide(81, 6),
-            Err(DivisionError::NotDivisible(NotDivisibleError {
-                dividend: 81,
-                divisor: 6
-            }))
-        );
     }
 
     #[test]
-    fn test_divide_by_0() {
+    fn test_not_divisible() {
-        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
+        assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));
     }
 
     #[test]
@@ -74,14 +54,11 @@ mod tests {
 
     #[test]
     fn test_result_with_list() {
-        assert_eq!(format!("{:?}", result_with_list()), "Ok([1, 11, 1426, 3])");
+        assert_eq!(result_with_list().unwarp(), [1, 11, 1426, 3]);
     }
 
     #[test]
     fn test_list_of_results() {
-        assert_eq!(
+        assert_eq!(list_of_results(), [Ok(1), Ok(11), Ok(1426), Ok(3)]);
-            format!("{:?}", list_of_results()),
-            "[Ok(1), Ok(11), Ok(1426), Ok(3)]"
-        );
     }
 }

exercises/18_iterators/iterators4.rs

@@ -1,9 +1,9 @@
-fn factorial(num: u64) -> u64 {
+fn factorial(num: u8) -> u64 {
-    // Complete this function to return the factorial of num
+    // TODO: Complete this function to return the factorial of `num`.
     // Do not use:
     // - early returns (using the `return` keyword explicitly)
     // Try not to use:
-    // - imperative style loops (for, while)
+    // - imperative style loops (for/while)
     // - additional variables
     // For an extra challenge, don't use:
     // - recursion
@@ -19,20 +19,20 @@ mod tests {
 
     #[test]
     fn factorial_of_0() {
-        assert_eq!(1, factorial(0));
+        assert_eq!(factorial(0), 1);
     }
 
     #[test]
     fn factorial_of_1() {
-        assert_eq!(1, factorial(1));
+        assert_eq!(factorial(1), 1);
     }
     #[test]
     fn factorial_of_2() {
-        assert_eq!(2, factorial(2));
+        assert_eq!(factorial(2), 2);
     }
 
     #[test]
     fn factorial_of_4() {
-        assert_eq!(24, factorial(4));
+        assert_eq!(factorial(4), 24);
     }
 }

exercises/18_iterators/iterators5.rs

@@ -1,10 +1,8 @@
-// Let's define a simple model to track Rustlings exercise progress. Progress
+// Let's define a simple model to track Rustlings' exercise progress. Progress
 // will be modelled using a hash map. The name of the exercise is the key and
 // the progress is the value. Two counting functions were created to count the
 // number of exercises with a given progress. Recreate this counting
-// functionality using iterators. Try not to use imperative loops (for, while).
+// functionality using iterators. Try to not use imperative loops (for/while).
-// Only the two iterator methods (count_iterator and count_collection_iterator)
-// need to be modified.
 
 use std::collections::HashMap;
 
@@ -18,24 +16,25 @@ enum Progress {
 fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
     let mut count = 0;
     for val in map.values() {
-        if val == &value {
+        if *val == value {
             count += 1;
         }
     }
     count
 }
 
+// TODO: Implement the functionality of `count_for` but with an iterator instead
+// of a `for` loop.
 fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
-    // map is a hashmap with String keys and Progress values.
+    // `map` is a hash map with `String` keys and `Progress` values.
-    // map = { "variables1": Complete, "from_str": None, ... }
+    // map = { "variables1": Complete, "from_str": None, … }
-    todo!();
 }
 
 fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
     let mut count = 0;
     for map in collection {
         for val in map.values() {
-            if val == &value {
+            if *val == value {
                 count += 1;
             }
         }
@@ -43,11 +42,12 @@ fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progres
     count
 }
 
+// TODO: Implement the functionality of `count_collection_for` but with an
+// iterator instead of a `for` loop.
 fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
-    // collection is a slice of hashmaps.
+    // `collection` is a slice of hash maps.
-    // collection = [{ "variables1": Complete, "from_str": None, ... },
+    // collection = [{ "variables1": Complete, "from_str": None, … },
-    //     { "variables2": Complete, ... }, ... ]
+    //               { "variables2": Complete, … }, … ]
-    todo!();
 }
 
 fn main() {
@@ -58,70 +58,6 @@ fn main() {
 mod tests {
     use super::*;
 
-    #[test]
-    fn count_complete() {
-        let map = get_map();
-        assert_eq!(3, count_iterator(&map, Progress::Complete));
-    }
-
-    #[test]
-    fn count_some() {
-        let map = get_map();
-        assert_eq!(1, count_iterator(&map, Progress::Some));
-    }
-
-    #[test]
-    fn count_none() {
-        let map = get_map();
-        assert_eq!(2, count_iterator(&map, Progress::None));
-    }
-
-    #[test]
-    fn count_complete_equals_for() {
-        let map = get_map();
-        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
-        for progress_state in progress_states {
-            assert_eq!(
-                count_for(&map, progress_state),
-                count_iterator(&map, progress_state)
-            );
-        }
-    }
-
-    #[test]
-    fn count_collection_complete() {
-        let collection = get_vec_map();
-        assert_eq!(
-            6,
-            count_collection_iterator(&collection, Progress::Complete)
-        );
-    }
-
-    #[test]
-    fn count_collection_some() {
-        let collection = get_vec_map();
-        assert_eq!(1, count_collection_iterator(&collection, Progress::Some));
-    }
-
-    #[test]
-    fn count_collection_none() {
-        let collection = get_vec_map();
-        assert_eq!(4, count_collection_iterator(&collection, Progress::None));
-    }
-
-    #[test]
-    fn count_collection_equals_for() {
-        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
-        let collection = get_vec_map();
-
-        for progress_state in progress_states {
-            assert_eq!(
-                count_collection_for(&collection, progress_state),
-                count_collection_iterator(&collection, progress_state)
-            );
-        }
-    }
-
     fn get_map() -> HashMap<String, Progress> {
         use Progress::*;
 
@@ -150,4 +86,68 @@ mod tests {
 
         vec![map, other]
     }
+
+    #[test]
+    fn count_complete() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::Complete), 3);
+    }
+
+    #[test]
+    fn count_some() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::Some), 1);
+    }
+
+    #[test]
+    fn count_none() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::None), 2);
+    }
+
+    #[test]
+    fn count_complete_equals_for() {
+        let map = get_map();
+        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+        for progress_state in progress_states {
+            assert_eq!(
+                count_for(&map, progress_state),
+                count_iterator(&map, progress_state),
+            );
+        }
+    }
+
+    #[test]
+    fn count_collection_complete() {
+        let collection = get_vec_map();
+        assert_eq!(
+            count_collection_iterator(&collection, Progress::Complete),
+            6,
+        );
+    }
+
+    #[test]
+    fn count_collection_some() {
+        let collection = get_vec_map();
+        assert_eq!(count_collection_iterator(&collection, Progress::Some), 1);
+    }
+
+    #[test]
+    fn count_collection_none() {
+        let collection = get_vec_map();
+        assert_eq!(count_collection_iterator(&collection, Progress::None), 4);
+    }
+
+    #[test]
+    fn count_collection_equals_for() {
+        let collection = get_vec_map();
+        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+
+        for progress_state in progress_states {
+            assert_eq!(
+                count_collection_for(&collection, progress_state),
+                count_collection_iterator(&collection, progress_state),
+            );
+        }
+    }
 }

exercises/19_smart_pointers/box1.rs

@@ -4,45 +4,43 @@
 // `Box` - a smart pointer used to store data on the heap, which also allows us
 // to wrap a recursive type.
 //
-// The recursive type we're implementing in this exercise is the `cons list` - a
+// The recursive type we're implementing in this exercise is the "cons list", a
 // data structure frequently found in functional programming languages. Each
-// item in a cons list contains two elements: the value of the current item and
+// item in a cons list contains two elements: The value of the current item and
 // the next item. The last item is a value called `Nil`.
-//
-// Step 1: use a `Box` in the enum definition to make the code compile
-// Step 2: create both empty and non-empty cons lists by replacing `todo!()`
-//
-// Note: the tests should not be changed
 
+// TODO: Use a `Box` in the enum definition to make the code compile.
 #[derive(PartialEq, Debug)]
 enum List {
     Cons(i32, List),
     Nil,
 }
 
-fn main() {
+// TODO: Create an empty cons list.
-    println!("This is an empty cons list: {:?}", create_empty_list());
-    println!(
-        "This is a non-empty cons list: {:?}",
-        create_non_empty_list()
-    );
-}
-
 fn create_empty_list() -> List {
     todo!()
 }
 
+// TODO: Create a non-empty cons list.
 fn create_non_empty_list() -> List {
     todo!()
 }
 
+fn main() {
+    println!("This is an empty cons list: {:?}", create_empty_list());
+    println!(
+        "This is a non-empty cons list: {:?}",
+        create_non_empty_list(),
+    );
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn test_create_empty_list() {
-        assert_eq!(List::Nil, create_empty_list());
+        assert_eq!(create_empty_list(), List::Nil);
     }
 
     #[test]

rustlings-macros/info.toml

@@ -886,28 +886,15 @@ https://doc.rust-lang.org/stable/book/ch11-01-writing-tests.html#checking-for-pa
 name = "iterators1"
 dir = "18_iterators"
 hint = """
-Step 1:
-
-We need to apply something to the collection `my_fav_fruits` before we start to
-go through it. What could that be? Take a look at the struct definition for a
-vector for inspiration:
-https://doc.rust-lang.org/std/vec/struct.Vec.html
-
-Step 2 & step 3:
-
-Very similar to the lines above and below. You've got this!
-
-Step 4:
-
 An iterator goes through all elements in a collection, but what if we've run
 out of elements? What should we expect here? If you're stuck, take a look at
-https://doc.rust-lang.org/std/iter/trait.Iterator.html for some ideas."""
+https://doc.rust-lang.org/std/iter/trait.Iterator.html"""
 
 [[exercises]]
 name = "iterators2"
 dir = "18_iterators"
 hint = """
-Step 1:
+`capitalize_first`:
 
 The variable `first` is a `char`. It needs to be capitalized and added to the
 remaining characters in `c` in order to return the correct `String`.
@@ -918,12 +905,15 @@ The remaining characters in `c` can be viewed as a string slice using the
 The documentation for `char` contains many useful methods.
 https://doc.rust-lang.org/std/primitive.char.html
 
-Step 2:
+Use `char::to_uppercase`. It returns an iterator that can be converted to a
+`String`.
+
+`capitalize_words_vector`:
 
 Create an iterator from the slice. Transform the iterated values by applying
 the `capitalize_first` function. Remember to `collect` the iterator.
 
-Step 3:
+`capitalize_words_string`:
 
 This is surprisingly similar to the previous solution. `collect` is very
 powerful and very general. Rust just needs to know the desired type."""
@@ -932,8 +922,8 @@ powerful and very general. Rust just needs to know the desired type."""
 name = "iterators3"
 dir = "18_iterators"
 hint = """
-The `divide` function needs to return the correct error when even division is
+The `divide` function needs to return the correct error when the divisor is 0 or
-not possible.
+when even division is not possible.
 
 The `division_results` variable needs to be collected into a collection type.
 
@@ -944,7 +934,7 @@ The `list_of_results` function needs to return a vector of results.
 
 See https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.collect for
 how the `FromIterator` trait is used in `collect()`. This trait is REALLY
-powerful! It can make the solution to this exercise infinitely easier."""
+powerful! It can make the solution to this exercise much easier."""
 
 [[exercises]]
 name = "iterators4"
@@ -952,10 +942,10 @@ dir = "18_iterators"
 hint = """
 In an imperative language, you might write a `for` loop that updates a mutable
 variable. Or, you might write code utilizing recursion and a match clause. In
-Rust you can take another functional approach, computing the factorial
+Rust, you can take another functional approach, computing the factorial
 elegantly with ranges and iterators.
 
-Hint 2: Check out the `fold` and `rfold` methods!"""
+Check out the `fold` and `rfold` methods!"""
 
 [[exercises]]
 name = "iterators5"
@@ -979,21 +969,16 @@ a different method that could make your code more compact than using `fold`."""
 name = "box1"
 dir = "19_smart_pointers"
 hint = """
-Step 1:
+The compiler's message should help: Since we cannot store the value of the
-
-The compiler's message should help: since we cannot store the value of the
 actual type when working with recursive types, we need to store a reference
 (pointer) to its value.
 
-We should, therefore, place our `List` inside a `Box`. More details in the book
+We should, therefore, place our `List` inside a `Box`. More details in The Book:
-here: https://doc.rust-lang.org/book/ch15-01-box.html#enabling-recursive-types-with-boxes
+https://doc.rust-lang.org/book/ch15-01-box.html#enabling-recursive-types-with-boxes
 
-Step 2:
+Creating an empty list should be fairly straightforward (Hint: Read the tests).
 
-Creating an empty list should be fairly straightforward (hint: peek at the
+For a non-empty list, keep in mind that we want to use our `Cons` list builder.
-assertions).
-
-For a non-empty list keep in mind that we want to use our `Cons` "list builder".
 Although the current list is one of integers (`i32`), feel free to change the
 definition and try other types!"""
 

solutions/18_iterators/iterators1.rs

@@ -1 +1,26 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// When performing operations on elements within a collection, iterators are
+// essential. This module helps you get familiar with the structure of using an
+// iterator and how to go through elements within an iterable collection.
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn iterators() {
+        let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
+
+        // Create an iterator over the array.
+        let mut fav_fruits_iterator = my_fav_fruits.iter();
+
+        assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"custard apple"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"peach"));
+        assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
+        assert_eq!(fav_fruits_iterator.next(), None);
+        //                                     ^^^^ reached the end
+    }
+}

solutions/18_iterators/iterators2.rs

@@ -1 +1,56 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// In this exercise, you'll learn some of the unique advantages that iterators
+// can offer.
+
+// "hello" -> "Hello"
+fn capitalize_first(input: &str) -> String {
+    let mut chars = input.chars();
+    match chars.next() {
+        None => String::new(),
+        Some(first) => first.to_uppercase().to_string() + chars.as_str(),
+    }
+}
+
+// Apply the `capitalize_first` function to a slice of string slices.
+// Return a vector of strings.
+// ["hello", "world"] -> ["Hello", "World"]
+fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
+    words.iter().map(|word| capitalize_first(word)).collect()
+}
+
+// Apply the `capitalize_first` function again to a slice of string
+// slices. Return a single string.
+// ["hello", " ", "world"] -> "Hello World"
+fn capitalize_words_string(words: &[&str]) -> String {
+    words.iter().map(|word| capitalize_first(word)).collect()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_success() {
+        assert_eq!(capitalize_first("hello"), "Hello");
+    }
+
+    #[test]
+    fn test_empty() {
+        assert_eq!(capitalize_first(""), "");
+    }
+
+    #[test]
+    fn test_iterate_string_vec() {
+        let words = vec!["hello", "world"];
+        assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
+    }
+
+    #[test]
+    fn test_iterate_into_string() {
+        let words = vec!["hello", " ", "world"];
+        assert_eq!(capitalize_words_string(&words), "Hello World");
+    }
+}

solutions/18_iterators/iterators3.rs

@@ -1 +1,73 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+#[derive(Debug, PartialEq, Eq)]
+enum DivisionError {
+    DivideByZero,
+    NotDivisible,
+}
+
+fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
+    if b == 0 {
+        return Err(DivisionError::DivideByZero);
+    }
+
+    if a % b != 0 {
+        return Err(DivisionError::NotDivisible);
+    }
+
+    Ok(a / b)
+}
+
+fn result_with_list() -> Result<Vec<i64>, DivisionError> {
+    //                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    let numbers = [27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    // Collects to the expected return type. Returns the first error in the
+    // division results (if one exists).
+    division_results.collect()
+}
+
+fn list_of_results() -> Vec<Result<i64, DivisionError>> {
+    //               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    let numbers = [27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    // Collects to the expected return type.
+    division_results.collect()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_success() {
+        assert_eq!(divide(81, 9), Ok(9));
+    }
+
+    #[test]
+    fn test_divide_by_0() {
+        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
+    }
+
+    #[test]
+    fn test_not_divisible() {
+        assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));
+    }
+
+    #[test]
+    fn test_divide_0_by_something() {
+        assert_eq!(divide(0, 81), Ok(0));
+    }
+
+    #[test]
+    fn test_result_with_list() {
+        assert_eq!(result_with_list().unwrap(), [1, 11, 1426, 3]);
+    }
+
+    #[test]
+    fn test_list_of_results() {
+        assert_eq!(list_of_results(), [Ok(1), Ok(11), Ok(1426), Ok(3)]);
+    }
+}

solutions/18_iterators/iterators4.rs

@@ -1 +1,71 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// 3 possible solutions are presented.
+
+// With `for` loop and a mutable variable.
+fn factorial_for(num: u64) -> u64 {
+    let mut result = 1;
+
+    for x in 2..=num {
+        result *= x;
+    }
+
+    result
+}
+
+// Equivalent to `factorial_for` but shorter and without a `for` loop and
+// mutable variables.
+fn factorial_fold(num: u64) -> u64 {
+    // Case num==0: The iterator 2..=0 is empty
+    //              -> The initial value of `fold` is returned which is 1.
+    // Case num==1: The iterator 2..=1 is also empty
+    //              -> The initial value 1 is returned.
+    // Case num==2: The iterator 2..=2 contains one element
+    //              -> The initial value 1 is multiplied by 2 and the result
+    //                 is returned.
+    // Case num==3: The iterator 2..=3 contains 2 elements
+    //              -> 1 * 2 is calculated, then the result 2 is multiplied by
+    //                 the second element 3 so the result 6 is returned.
+    // And so on…
+    (2..=num).fold(1, |acc, x| acc * x)
+}
+
+// Equivalent to `factorial_fold` but with a built-in method that is suggested
+// by Clippy.
+fn factorial_product(num: u64) -> u64 {
+    (2..=num).product()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn factorial_of_0() {
+        assert_eq!(factorial_for(0), 1);
+        assert_eq!(factorial_fold(0), 1);
+        assert_eq!(factorial_product(0), 1);
+    }
+
+    #[test]
+    fn factorial_of_1() {
+        assert_eq!(factorial_for(1), 1);
+        assert_eq!(factorial_fold(1), 1);
+        assert_eq!(factorial_product(1), 1);
+    }
+    #[test]
+    fn factorial_of_2() {
+        assert_eq!(factorial_for(2), 2);
+        assert_eq!(factorial_fold(2), 2);
+        assert_eq!(factorial_product(2), 2);
+    }
+
+    #[test]
+    fn factorial_of_4() {
+        assert_eq!(factorial_for(4), 24);
+        assert_eq!(factorial_fold(4), 24);
+        assert_eq!(factorial_product(4), 24);
+    }
+}

solutions/18_iterators/iterators5.rs

@@ -1 +1,150 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Let's define a simple model to track Rustlings' exercise progress. Progress
+// will be modelled using a hash map. The name of the exercise is the key and
+// the progress is the value. Two counting functions were created to count the
+// number of exercises with a given progress. Recreate this counting
+// functionality using iterators. Try to not use imperative loops (for/while).
+
+use std::collections::HashMap;
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum Progress {
+    None,
+    Some,
+    Complete,
+}
+
+fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
+    let mut count = 0;
+    for val in map.values() {
+        if *val == value {
+            count += 1;
+        }
+    }
+    count
+}
+
+fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
+    // `map` is a hash map with `String` keys and `Progress` values.
+    // map = { "variables1": Complete, "from_str": None, … }
+    map.values().filter(|val| **val == value).count()
+}
+
+fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
+    let mut count = 0;
+    for map in collection {
+        count += count_for(map, value);
+    }
+    count
+}
+
+fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
+    // `collection` is a slice of hash maps.
+    // collection = [{ "variables1": Complete, "from_str": None, … },
+    //               { "variables2": Complete, … }, … ]
+    collection
+        .iter()
+        .map(|map| count_iterator(map, value))
+        .sum()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn get_map() -> HashMap<String, Progress> {
+        use Progress::*;
+
+        let mut map = HashMap::new();
+        map.insert(String::from("variables1"), Complete);
+        map.insert(String::from("functions1"), Complete);
+        map.insert(String::from("hashmap1"), Complete);
+        map.insert(String::from("arc1"), Some);
+        map.insert(String::from("as_ref_mut"), None);
+        map.insert(String::from("from_str"), None);
+
+        map
+    }
+
+    fn get_vec_map() -> Vec<HashMap<String, Progress>> {
+        use Progress::*;
+
+        let map = get_map();
+
+        let mut other = HashMap::new();
+        other.insert(String::from("variables2"), Complete);
+        other.insert(String::from("functions2"), Complete);
+        other.insert(String::from("if1"), Complete);
+        other.insert(String::from("from_into"), None);
+        other.insert(String::from("try_from_into"), None);
+
+        vec![map, other]
+    }
+
+    #[test]
+    fn count_complete() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::Complete), 3);
+    }
+
+    #[test]
+    fn count_some() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::Some), 1);
+    }
+
+    #[test]
+    fn count_none() {
+        let map = get_map();
+        assert_eq!(count_iterator(&map, Progress::None), 2);
+    }
+
+    #[test]
+    fn count_complete_equals_for() {
+        let map = get_map();
+        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+        for progress_state in progress_states {
+            assert_eq!(
+                count_for(&map, progress_state),
+                count_iterator(&map, progress_state),
+            );
+        }
+    }
+
+    #[test]
+    fn count_collection_complete() {
+        let collection = get_vec_map();
+        assert_eq!(
+            count_collection_iterator(&collection, Progress::Complete),
+            6,
+        );
+    }
+
+    #[test]
+    fn count_collection_some() {
+        let collection = get_vec_map();
+        assert_eq!(count_collection_iterator(&collection, Progress::Some), 1);
+    }
+
+    #[test]
+    fn count_collection_none() {
+        let collection = get_vec_map();
+        assert_eq!(count_collection_iterator(&collection, Progress::None), 4);
+    }
+
+    #[test]
+    fn count_collection_equals_for() {
+        let collection = get_vec_map();
+        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+
+        for progress_state in progress_states {
+            assert_eq!(
+                count_collection_for(&collection, progress_state),
+                count_collection_iterator(&collection, progress_state),
+            );
+        }
+    }
+}

solutions/19_smart_pointers/box1.rs

@@ -1 +1,47 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// At compile time, Rust needs to know how much space a type takes up. This
+// becomes problematic for recursive types, where a value can have as part of
+// itself another value of the same type. To get around the issue, we can use a
+// `Box` - a smart pointer used to store data on the heap, which also allows us
+// to wrap a recursive type.
+//
+// The recursive type we're implementing in this exercise is the "cons list", a
+// data structure frequently found in functional programming languages. Each
+// item in a cons list contains two elements: The value of the current item and
+// the next item. The last item is a value called `Nil`.
+
+#[derive(PartialEq, Debug)]
+enum List {
+    Cons(i32, Box<List>),
+    Nil,
+}
+
+fn create_empty_list() -> List {
+    List::Nil
+}
+
+fn create_non_empty_list() -> List {
+    List::Cons(42, Box::new(List::Nil))
+}
+
+fn main() {
+    println!("This is an empty cons list: {:?}", create_empty_list());
+    println!(
+        "This is a non-empty cons list: {:?}",
+        create_non_empty_list(),
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_create_empty_list() {
+        assert_eq!(create_empty_list(), List::Nil);
+    }
+
+    #[test]
+    fn test_create_non_empty_list() {
+        assert_ne!(create_empty_list(), create_non_empty_list());
+    }
+}