Complete functions exercises

exercises/02_functions/functions1.rs

@@ -3,8 +3,14 @@
 // Execute `rustlings hint functions1` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 fn main() {
+    println!("You define functions outside of main and call them here.");
+    println!("Call me.");
+    // Rust doesn't care where the function is defined, as long as it's within the scope.
     call_me();
 }
+
+fn call_me() {
+    println!("Beep me. If you wanna reach me.");
+}

exercises/02_functions/functions2.rs

@@ -3,13 +3,13 @@
 // 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:) {
+fn call_me(num: i8) {
+    // chose i8 because it's the smallest integer type
     for i in 0..num {
         println!("Ring! Call number {}", i + 1);
     }

exercises/02_functions/functions3.rs

@@ -3,10 +3,8 @@
 // Execute `rustlings hint functions3` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 fn main() {
-    call_me();
+    call_me(12);
 }
 
 fn call_me(num: u32) {

exercises/02_functions/functions4.rs

@@ -8,14 +8,13 @@
 // Execute `rustlings hint functions4` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 fn main() {
     let original_price = 51;
     println!("Your sale price is {}", sale_price(original_price));
 }
 
-fn sale_price(price: i32) -> {
+fn sale_price(price: i32) -> i32 {
     if is_even(price) {
         price - 10
     } else {

exercises/02_functions/functions5.rs

@@ -3,7 +3,6 @@
 // Execute `rustlings hint functions5` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 fn main() {
     let answer = square(3);
@@ -11,5 +10,8 @@ fn main() {
 }
 
 fn square(num: i32) -> i32 {
-    num * num;
+    // you can either add an explicit return to this expression
+    // or remove the semicolon to make it an implicit return
+    // you cannot just have an expression with a semicolon
+    return num * num;
 }