record progress: tests, lifetimes, iterators

.rustlings-state.txt

@@ -1,6 +1,6 @@
 DON'T EDIT THIS FILE!
 
-lifetimes1
+iterators2
 
 intro1
 intro2
@@ -66,3 +66,10 @@ traits3
 traits4
 traits5
 quiz3
+lifetimes1
+lifetimes2
+lifetimes3
+tests1
+tests2
+tests3
+iterators1

exercises/16_lifetimes/lifetimes1.rs

@@ -4,7 +4,7 @@
 // not own their own data. What if their owner goes out of scope?
 
 // TODO: Fix the compiler error by updating the function signature.
-fn longest(x: &str, y: &str) -> &str {
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x
     } else {

exercises/16_lifetimes/lifetimes2.rs

@@ -15,6 +15,7 @@ fn main() {
     {
         let string2 = String::from("xyz");
         result = longest(&string1, &string2);
-    }
         println!("The longest string is '{result}'");
     }
+
+}

exercises/16_lifetimes/lifetimes3.rs

@@ -1,9 +1,9 @@
 // Lifetimes are also needed when structs hold references.
 
 // TODO: Fix the compiler errors about the struct.
-struct Book {
-    author: &str,
-    title: &str,
+struct Book<'a > {
+    author: &'a str,
+    title: &'a str,
 }
 
 fn main() {

exercises/17_tests/tests1.rs

@@ -14,10 +14,12 @@ mod tests {
     // TODO: Import `is_even`. You can use a wildcard to import everything in
     // the outer module.
 
+    use crate::is_even;
+
     #[test]
     fn you_can_assert() {
         // TODO: Test the function `is_even` with some values.
-        assert!();
-        assert!();
+        assert!(is_even(4));
+        assert!(is_even(6));
     }
 }

exercises/17_tests/tests2.rs

@@ -15,9 +15,9 @@ mod tests {
     #[test]
     fn you_can_assert_eq() {
         // TODO: Test the function `power_of_2` with some values.
-        assert_eq!();
-        assert_eq!();
-        assert_eq!();
-        assert_eq!();
+        assert_eq!(power_of_2(2), 4);
+        assert_eq!(power_of_2(2), 4);
+        assert_eq!(power_of_2(2), 4);
+        assert_eq!(power_of_2(2), 4);
     }
 }

exercises/17_tests/tests3.rs

@@ -26,23 +26,20 @@ mod tests {
 
     #[test]
     fn correct_width_and_height() {
-        // 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!(todo!(), 10); // Check width
-        assert_eq!(todo!(), 20); // Check height
+        assert_eq!(rect.width, 10); // Check width
+        assert_eq!(rect.height, 20); // Check height
     }
 
-    // TODO: This test should check if the program panics when we try to create
-    // a rectangle with negative width.
     #[test]
+    #[should_panic]
     fn negative_width() {
         let _rect = Rectangle::new(-10, 10);
+
     }
 
-    // TODO: This test should check if the program panics when we try to create
-    // a rectangle with negative height.
     #[test]
+    #[should_panic]
     fn negative_height() {
         let _rect = Rectangle::new(10, -10);
     }

exercises/18_iterators/iterators1.rs

@@ -13,13 +13,13 @@ mod tests {
         let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
 
         // TODO: Create an iterator over the array.
-        let mut fav_fruits_iterator = todo!();
+        let mut fav_fruits_iterator = my_fav_fruits.iter();
 
         assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"custard apple"));
         assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"peach"));
         assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), None);
     }
 }

exercises/18_iterators/iterators2.rs

@@ -1,28 +1,35 @@
 // In this exercise, you'll learn some of the unique advantages that iterators
 // can offer.
 
-// TODO: Complete the `capitalize_first` function.
+// Complete the `capitalize_first` function.
 // "hello" -> "Hello"
 fn capitalize_first(input: &str) -> String {
     let mut chars = input.chars();
     match chars.next() {
         None => String::new(),
-        Some(first) => todo!(),
+        Some(first) => {
+            let mut new = String::from(first.to_uppercase().to_string());
+            new.push_str(&input[1..]);
+
+            new
+        },
     }
 }
 
-// TODO: 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(|i| {
+        capitalize_first(i)
+    }).collect()
 }
 
-// TODO: 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(|i| {
+        capitalize_first(i)
+    }).collect::<Vec<String>>().join("")
 }
 
 fn main() {

exercises/18_iterators/iterators3.rs

@@ -1,3 +1,5 @@
+use std::f32::consts::E;
+
 #[derive(Debug, PartialEq, Eq)]
 enum DivisionError {
     // Example: 42 / 0
@@ -8,24 +10,43 @@ enum DivisionError {
     NotDivisible,
 }
 
-// TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
 fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
-    todo!();
+    if b == 0 {
+        return Err(DivisionError::DivideByZero)
+    }
+    match a.checked_rem(b) {
+        None => {
+            Err(DivisionError::IntegerOverflow)
+        }
+        Some(0) => {
+            let division = a.checked_div(b);
+            if let Some(result) = division {
+                Ok(result)
+            } else {
+                Err(DivisionError::IntegerOverflow)
+            }
+        },
+        Some(_) => {
+            Err(DivisionError::NotDivisible)
+        }
+    }
 }
 
-// TODO: Add the correct return type and complete the function body.
 // Desired output: `Ok([1, 11, 1426, 3])`
-fn result_with_list() {
+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));
+    Ok(division_results.map(|i| {
+        i.unwrap()
+    }).collect::<Vec<i64>>())
 }
 
-// TODO: Add the correct return type and complete the function body.
 // Desired output: `[Ok(1), Ok(11), Ok(1426), Ok(3)]`
-fn list_of_results() {
+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));
+    division_results.collect()
 }
 
 fn main() {

exercises/18_iterators/iterators4.rs

@@ -10,6 +10,9 @@ fn factorial(num: u64) -> u64 {
     // - additional variables
     // For an extra challenge, don't use:
     // - recursion
+    (1..=num).fold(1, |acc, v| {
+        acc * v
+    })
 }
 
 fn main() {

exercises/18_iterators/iterators5.rs

@@ -23,11 +23,14 @@ fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
     count
 }
 
-// TODO: Implement the functionality of `count_for` but with an iterator instead
+//  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 hash map with `String` keys and `Progress` values.
     // map = { "variables1": Complete, "from_str": None, … }
+    map.iter().filter(|p| {
+        *p.1 == value
+    }).count()
 }
 
 fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
@@ -42,12 +45,13 @@ fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progres
     count
 }
 
-// TODO: Implement the functionality of `count_collection_for` but with an
+// 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 hash maps.
     // collection = [{ "variables1": Complete, "from_str": None, … },
     //               { "variables2": Complete, … }, … ]
+    collection.iter().map(|i| {count_iterator(i, value)}).sum()
 }
 
 fn main() {

solutions/16_lifetimes/lifetimes1.rs

@@ -1,4 +1,28 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+// The Rust compiler needs to know how to check whether supplied references are
+// valid, so that it can let the programmer know if a reference is at risk of
+// going out of scope before it is used. Remember, references are borrows and do
+// not own their own data. What if their owner goes out of scope?
+
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    //    ^^^^     ^^          ^^          ^^
+    if x.len() > y.len() {
+        x
+    } else {
+        y
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_longest() {
+        assert_eq!(longest("abcd", "123"), "abcd");
+        assert_eq!(longest("abc", "1234"), "1234");
+    }
 }

solutions/16_lifetimes/lifetimes2.rs

@@ -1,4 +1,33 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    if x.len() > y.len() {
+        x
+    } else {
+        y
+    }
+}
+
+fn main() {
+    let string1 = String::from("long string is long");
+    // Solution1: You can move `strings2` out of the inner block so that it is
+    // not dropped before the print statement.
+    let string2 = String::from("xyz");
+    let result;
+    {
+        result = longest(&string1, &string2);
+    }
+    println!("The longest string is '{result}'");
+    // `string2` dropped at the end of the function.
+
+    // =========================================================================
+
+    let string1 = String::from("long string is long");
+    let result;
+    {
+        let string2 = String::from("xyz");
+        result = longest(&string1, &string2);
+        // Solution2: You can move the print statement into the inner block so
+        // that it is executed before `string2` is dropped.
+        println!("The longest string is '{result}'");
+        // `string2` dropped here (end of the inner scope).
+    }
 }

solutions/16_lifetimes/lifetimes3.rs

@@ -1,4 +1,18 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+// Lifetimes are also needed when structs hold references.
+
+struct Book<'a> {
+    //     ^^^^ added a lifetime annotation
+    author: &'a str,
+    //       ^^
+    title: &'a str,
+    //      ^^
+}
+
+fn main() {
+    let book = Book {
+        author: "George Orwell",
+        title: "1984",
+    };
+
+    println!("{} by {}", book.title, book.author);
 }

solutions/17_tests/tests1.rs

@@ -1,4 +1,24 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+// Tests are important to ensure that your code does what you think it should
+// do.
+
+fn is_even(n: i64) -> bool {
+    n % 2 == 0
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    // When writing unit tests, it is common to import everything from the outer
+    // module (`super`) using a wildcard.
+    use super::*;
+
+    #[test]
+    fn you_can_assert() {
+        assert!(is_even(0));
+        assert!(!is_even(-1));
+        //      ^ You can assert `false` using the negation operator `!`.
+    }
 }

solutions/17_tests/tests2.rs

@@ -1,4 +1,22 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+// Calculates the power of 2 using a bit shift.
+// `1 << n` is equivalent to "2 to the power of n".
+fn power_of_2(n: u8) -> u64 {
+    1 << n
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn you_can_assert_eq() {
+        assert_eq!(power_of_2(0), 1);
+        assert_eq!(power_of_2(1), 2);
+        assert_eq!(power_of_2(2), 4);
+        assert_eq!(power_of_2(3), 8);
+    }
 }

solutions/17_tests/tests3.rs

@@ -1,4 +1,45 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+struct Rectangle {
+    width: i32,
+    height: i32,
+}
+
+impl Rectangle {
+    // Don't change this function.
+    fn new(width: i32, height: i32) -> Self {
+        if width <= 0 || height <= 0 {
+            // Returning a `Result` would be better here. But we want to learn
+            // how to test functions that can panic.
+            panic!("Rectangle width and height must be positive");
+        }
+
+        Rectangle { width, height }
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn correct_width_and_height() {
+        let rect = Rectangle::new(10, 20);
+        assert_eq!(rect.width, 10); // Check width
+        assert_eq!(rect.height, 20); // Check height
+    }
+
+    #[test]
+    #[should_panic] // Added this attribute to check that the test panics.
+    fn negative_width() {
+        let _rect = Rectangle::new(-10, 10);
+    }
+
+    #[test]
+    #[should_panic] // Added this attribute to check that the test panics.
+    fn negative_height() {
+        let _rect = Rectangle::new(10, -10);
+    }
 }

solutions/18_iterators/iterators1.rs

@@ -1,4 +1,26 @@
+// 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() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    // 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

@@ -1,4 +1,56 @@
-fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+// 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");
+    }
 }