study 4-6

exercises/04_primitive_types/primitive_types1.rs

@@ -9,6 +9,7 @@ fn main() {
     // TODO: Define a boolean variable with the name `is_evening` before the `if` statement below.
     // The value of the variable should be the negation (opposite) of `is_morning`.
     // let …
+    let is_evening: bool = false;
     if is_evening {
         println!("Good evening!");
     }

exercises/04_primitive_types/primitive_types2.rs

@@ -16,7 +16,7 @@ fn main() {
     // below with your favorite character.
     // Try a letter, try a digit (in single quotes), try a special character, try a character
     // from a different language than your own, try an emoji 😉
-    // let your_character = '';
+    let your_character = '1';
 
     if your_character.is_alphabetic() {
         println!("Alphabetical!");

exercises/04_primitive_types/primitive_types3.rs

@@ -1,6 +1,6 @@
 fn main() {
     // TODO: Create an array called `a` with at least 100 elements in it.
-    // let a = ???
+    let a = "12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890";
 
     if a.len() >= 100 {
         println!("Wow, that's a big array!");

exercises/04_primitive_types/primitive_types4.rs

@@ -9,7 +9,7 @@ mod tests {
         let a = [1, 2, 3, 4, 5];
 
         // TODO: Get a slice called `nice_slice` out of the array `a` so that the test passes.
-        // let nice_slice = ???
+        let nice_slice = &a[1..4];
 
         assert_eq!([2, 3, 4], nice_slice);
     }

exercises/04_primitive_types/primitive_types5.rs

@@ -2,7 +2,7 @@ fn main() {
     let cat = ("Furry McFurson", 3.5);
 
     // TODO: Destructure the `cat` tuple in one statement so that the println works.
-    // let /* your pattern here */ = cat;
+    let (name, age): (&str, f32) = cat;
 
     println!("{name} is {age} years old");
 }

exercises/04_primitive_types/primitive_types6.rs

@@ -10,7 +10,7 @@ mod tests {
 
         // TODO: Use a tuple index to access the second element of `numbers`
         // and assign it to a variable called `second`.
-        // let second = ???;
+        let second: i32 = numbers.1;
 
         assert_eq!(second, 2, "This is not the 2nd number in the tuple!");
     }

exercises/05_vecs/vecs1.rs

@@ -3,7 +3,7 @@ fn array_and_vec() -> ([i32; 4], Vec<i32>) {
 
     // TODO: Create a vector called `v` which contains the exact same elements as in the array `a`.
     // Use the vector macro.
-    // let v = ???;
+    let v = a.to_vec();
 
     (a, v)
 }

exercises/05_vecs/vecs2.rs

@@ -4,6 +4,7 @@ fn vec_loop(input: &[i32]) -> Vec<i32> {
     for element in input {
         // TODO: Multiply each element in the `input` slice by 2 and push it to
         // the `output` vector.
+        output.push(element * 2)
     }
 
     output
@@ -24,7 +25,7 @@ fn vec_map(input: &[i32]) -> Vec<i32> {
     input
         .iter()
         .map(|element| {
-            // ???
+            element * 2
         })
         .collect()
 }

exercises/06_move_semantics/move_semantics1.rs

@@ -1,6 +1,6 @@
 // TODO: Fix the compiler error in this function.
 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    let vec = vec;
+    let mut vec = vec;
 
     vec.push(88);
 

exercises/06_move_semantics/move_semantics2.rs

@@ -20,7 +20,7 @@ mod tests {
     fn move_semantics2() {
         let vec0 = vec![22, 44, 66];
 
-        let vec1 = fill_vec(vec0);
+        let vec1 = fill_vec(vec0.clone());
 
         assert_eq!(vec0, [22, 44, 66]);
         assert_eq!(vec1, [22, 44, 66, 88]);

exercises/06_move_semantics/move_semantics3.rs

@@ -1,5 +1,5 @@
 // TODO: Fix the compiler error in the function without adding any new line.
-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
+fn fill_vec(mut vec: Vec<i32>) -> Vec<i32> {
     vec.push(88);
 
     vec

exercises/06_move_semantics/move_semantics4.rs

@@ -10,8 +10,8 @@ mod tests {
     fn move_semantics4() {
         let mut x = 100;
         let y = &mut x;
-        let z = &mut x;
         *y += 100;
+        let z = &mut x;
         *z += 1000;
         assert_eq!(x, 1200);
     }

exercises/06_move_semantics/move_semantics5.rs

@@ -6,18 +6,18 @@
 fn main() {
     let data = "Rust is great!".to_string();
 
-    get_char(data);
+    get_char(&data);
 
-    string_uppercase(&data);
+    string_uppercase(data);
 }
 
 // Shouldn't 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();
 
     println!("{data}");

exercises/quizzes/quiz1.rs

@@ -10,7 +10,7 @@
 
 // TODO: Write a function that calculates the price of an order of apples given
 // the quantity bought.
-// fn calculate_price_of_apples(???) -> ??? { ??? }
+fn calculate_price_of_apples(num: i32) -> i32 { if num <= 40 { num * 2 } else { num } }
 
 fn main() {
     // You can optionally experiment here.