Add solutions to functions

solutions/01_variables/variables4.rs

@@ -4,6 +4,6 @@ fn main() {
     let mut x = 3;
     println!("Number {x}");
 
-    x = 5; // Don't change this line
+    x = 5;
     println!("Number {x}");
 }

solutions/01_variables/variables5.rs

@@ -1,5 +1,5 @@
 fn main() {
-    let number = "T-H-R-E-E"; // Don't change this line
+    let number = "T-H-R-E-E";
     println!("Spell a number: {}", number);
 
     // Using variable shadowing

solutions/02_functions/functions1.rs

@@ -1 +1,8 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Some function with the name `call_me` without arguments or a return value.
+fn call_me() {
+    println!("Hello world!");
+}
+
+fn main() {
+    call_me();
+}

solutions/02_functions/functions2.rs

@@ -1 +1,11 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// The type of function arguments must be annotated.
+// Added the type annotation `u64`.
+fn call_me(num: u64) {
+    for i in 0..num {
+        println!("Ring! Call number {}", i + 1);
+    }
+}
+
+fn main() {
+    call_me(3);
+}

solutions/02_functions/functions3.rs

@@ -1 +1,10 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn call_me(num: u32) {
+    for i in 0..num {
+        println!("Ring! Call number {}", i + 1);
+    }
+}
+
+fn main() {
+    // `call_me` expects an argument.
+    call_me(5);
+}

solutions/02_functions/functions4.rs

@@ -1 +1,17 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn is_even(num: i64) -> bool {
+    num % 2 == 0
+}
+
+// The return type must always be annotated.
+fn sale_price(price: i64) -> i64 {
+    if is_even(price) {
+        price - 10
+    } else {
+        price - 3
+    }
+}
+
+fn main() {
+    let original_price = 51;
+    println!("Your sale price is {}", sale_price(original_price));
+}

solutions/02_functions/functions5.rs

@@ -1 +1,9 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn square(num: i32) -> i32 {
+    // Removed the semicolon `;` at the end of the line below to implicitely return the result.
+    num * num
+}
+
+fn main() {
+    let answer = square(3);
+    println!("The square of 3 is {answer}");
+}