Require a main function in all exercises

38 files changed, 162 insertions, 8 deletions

diff --git a/exercises/03_if/if1.rs b/exercises/03_if/if1.rs
index a1df66b..dbd0d28 100644
--- a/exercises/03_if/if1.rs
+++ b/exercises/03_if/if1.rs
@@ -10,6 +10,10 @@ pub fn bigger(a: i32, b: i32) -> i32 {
     // - additional variables
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 // Don't mind this for now :)
 #[cfg(test)]
 mod tests {
diff --git a/exercises/03_if/if2.rs b/exercises/03_if/if2.rs
index 7b9c05f..a1ed5c8 100644
--- a/exercises/03_if/if2.rs
+++ b/exercises/03_if/if2.rs
@@ -13,6 +13,10 @@ pub fn foo_if_fizz(fizzish: &str) -> &str {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 // No test changes needed!
 #[cfg(test)]
 mod tests {
diff --git a/exercises/03_if/if3.rs b/exercises/03_if/if3.rs
index caba172..0b44c5a 100644
--- a/exercises/03_if/if3.rs
+++ b/exercises/03_if/if3.rs
@@ -27,6 +27,10 @@ pub fn animal_habitat(animal: &str) -> &'static str {
     habitat
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 // No test changes needed.
 #[cfg(test)]
 mod tests {
diff --git a/exercises/04_primitive_types/primitive_types4.rs b/exercises/04_primitive_types/primitive_types4.rs
index 8ed0a82..f99d889 100644
--- a/exercises/04_primitive_types/primitive_types4.rs
+++ b/exercises/04_primitive_types/primitive_types4.rs
@@ -5,6 +5,10 @@
 // Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand
 // for a hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[test]
 fn slice_out_of_array() {
     let a = [1, 2, 3, 4, 5];
diff --git a/exercises/04_primitive_types/primitive_types6.rs b/exercises/04_primitive_types/primitive_types6.rs
index 5f82f10..48e84d3 100644
--- a/exercises/04_primitive_types/primitive_types6.rs
+++ b/exercises/04_primitive_types/primitive_types6.rs
@@ -6,6 +6,10 @@
 // Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand
 // for a hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[test]
 fn indexing_tuple() {
     let numbers = (1, 2, 3);
diff --git a/exercises/05_vecs/vecs1.rs b/exercises/05_vecs/vecs1.rs
index c64acbb..5f44cb2 100644
--- a/exercises/05_vecs/vecs1.rs
+++ b/exercises/05_vecs/vecs1.rs
@@ -14,6 +14,10 @@ fn array_and_vec() -> ([i32; 4], Vec<i32>) {
     (a, v)
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/05_vecs/vecs2.rs b/exercises/05_vecs/vecs2.rs
index d64d3d1..1b16f0b 100644
--- a/exercises/05_vecs/vecs2.rs
+++ b/exercises/05_vecs/vecs2.rs
@@ -26,6 +26,10 @@ fn vec_map(v: &Vec<i32>) -> Vec<i32> {
     }).collect()
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/07_structs/structs1.rs b/exercises/07_structs/structs1.rs
index 2978121..cd8b81c 100644
--- a/exercises/07_structs/structs1.rs
+++ b/exercises/07_structs/structs1.rs
@@ -14,6 +14,10 @@ struct ColorTupleStruct(/* TODO: Something goes here */);
 #[derive(Debug)]
 struct UnitLikeStruct;
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/07_structs/structs2.rs b/exercises/07_structs/structs2.rs
index a7a2dec..7e61e75 100644
--- a/exercises/07_structs/structs2.rs
+++ b/exercises/07_structs/structs2.rs
@@ -28,6 +28,10 @@ fn create_order_template() -> Order {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/07_structs/structs3.rs b/exercises/07_structs/structs3.rs
index 9835b81..bd562a1 100644
--- a/exercises/07_structs/structs3.rs
+++ b/exercises/07_structs/structs3.rs
@@ -38,6 +38,10 @@ impl Package {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/08_enums/enums3.rs b/exercises/08_enums/enums3.rs
index 580a553..56c04fe 100644
--- a/exercises/08_enums/enums3.rs
+++ b/exercises/08_enums/enums3.rs
@@ -45,6 +45,10 @@ impl State {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/09_strings/strings3.rs b/exercises/09_strings/strings3.rs
index dedc081..d53f654 100644
--- a/exercises/09_strings/strings3.rs
+++ b/exercises/09_strings/strings3.rs
@@ -18,6 +18,10 @@ fn replace_me(input: &str) -> String {
     ???
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/11_hashmaps/hashmaps1.rs b/exercises/11_hashmaps/hashmaps1.rs
index 5a52f61..51146df 100644
--- a/exercises/11_hashmaps/hashmaps1.rs
+++ b/exercises/11_hashmaps/hashmaps1.rs
@@ -24,6 +24,10 @@ fn fruit_basket() -> HashMap<String, u32> {
     basket
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/11_hashmaps/hashmaps2.rs b/exercises/11_hashmaps/hashmaps2.rs
index 2730643..47983f6 100644
--- a/exercises/11_hashmaps/hashmaps2.rs
+++ b/exercises/11_hashmaps/hashmaps2.rs
@@ -41,6 +41,10 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -79,7 +83,7 @@ mod tests {
         let count = basket.values().sum::<u32>();
         assert!(count > 11);
     }
-    
+
     #[test]
     fn all_fruit_types_in_basket() {
         let mut basket = get_fruit_basket();
diff --git a/exercises/11_hashmaps/hashmaps3.rs b/exercises/11_hashmaps/hashmaps3.rs
index 775a401..3322909 100644
--- a/exercises/11_hashmaps/hashmaps3.rs
+++ b/exercises/11_hashmaps/hashmaps3.rs
@@ -5,9 +5,9 @@
 // Example: England,France,4,2 (England scored 4 goals, France 2).
 //
 // You have to build a scores table containing the name of the team, the total
-// number of goals the team scored, and the total number of goals the team 
-// conceded. One approach to build the scores table is to use a Hashmap. 
-// The solution is partially written to use a Hashmap, 
+// number of goals the team scored, and the total number of goals the team
+// conceded. One approach to build the scores table is to use a Hashmap.
+// The solution is partially written to use a Hashmap,
 // complete it to pass the test.
 //
 // Make me pass the tests!
@@ -42,6 +42,10 @@ fn build_scores_table(results: String) -> HashMap<String, Team> {
     scores
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/12_options/options1.rs b/exercises/12_options/options1.rs
index ba4b1cd..aecb123 100644
--- a/exercises/12_options/options1.rs
+++ b/exercises/12_options/options1.rs
@@ -14,6 +14,10 @@ fn maybe_icecream(time_of_day: u16) -> Option<u16> {
     ???
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/12_options/options2.rs b/exercises/12_options/options2.rs
index 73f707e..d183d1d 100644
--- a/exercises/12_options/options2.rs
+++ b/exercises/12_options/options2.rs
@@ -3,6 +3,10 @@
 // Execute `rustlings hint options2` or use the `hint` watch subcommand for a
 // hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     #[test]
diff --git a/exercises/13_error_handling/errors1.rs b/exercises/13_error_handling/errors1.rs
index 9767f2c..7991c42 100644
--- a/exercises/13_error_handling/errors1.rs
+++ b/exercises/13_error_handling/errors1.rs
@@ -9,6 +9,10 @@
 // Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
 // hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 pub fn generate_nametag_text(name: String) -> Option<String> {
     if name.is_empty() {
         // Empty names aren't allowed.
diff --git a/exercises/13_error_handling/errors2.rs b/exercises/13_error_handling/errors2.rs
index 88d1bf4..051516b 100644
--- a/exercises/13_error_handling/errors2.rs
+++ b/exercises/13_error_handling/errors2.rs
@@ -29,6 +29,10 @@ pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     Ok(qty * cost_per_item + processing_fee)
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/13_error_handling/errors4.rs b/exercises/13_error_handling/errors4.rs
index 0e5c08b..9449417 100644
--- a/exercises/13_error_handling/errors4.rs
+++ b/exercises/13_error_handling/errors4.rs
@@ -19,6 +19,10 @@ impl PositiveNonzeroInteger {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[test]
 fn test_creation() {
     assert!(PositiveNonzeroInteger::new(10).is_ok());
diff --git a/exercises/13_error_handling/errors6.rs b/exercises/13_error_handling/errors6.rs
index de73a9a..363a3b9 100644
--- a/exercises/13_error_handling/errors6.rs
+++ b/exercises/13_error_handling/errors6.rs
@@ -54,6 +54,10 @@ impl PositiveNonzeroInteger {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
diff --git a/exercises/14_generics/generics2.rs b/exercises/14_generics/generics2.rs
index d50ed17..068468b 100644
--- a/exercises/14_generics/generics2.rs
+++ b/exercises/14_generics/generics2.rs
@@ -16,6 +16,10 @@ impl Wrapper {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/15_traits/traits2.rs b/exercises/15_traits/traits2.rs
index 9a2bc07..18ebcb0 100644
--- a/exercises/15_traits/traits2.rs
+++ b/exercises/15_traits/traits2.rs
@@ -14,6 +14,10 @@ trait AppendBar {
 
 // TODO: Implement trait `AppendBar` for a vector of strings.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/15_traits/traits3.rs b/exercises/15_traits/traits3.rs
index 357f1d7..8412afa 100644
--- a/exercises/15_traits/traits3.rs
+++ b/exercises/15_traits/traits3.rs
@@ -23,6 +23,10 @@ struct OtherSoftware {
 impl Licensed for SomeSoftware {} // Don't edit this line
 impl Licensed for OtherSoftware {} // Don't edit this line
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/15_traits/traits4.rs b/exercises/15_traits/traits4.rs
index 7242c48..18db0d6 100644
--- a/exercises/15_traits/traits4.rs
+++ b/exercises/15_traits/traits4.rs
@@ -25,6 +25,10 @@ fn compare_license_types(software: ??, software_two: ??) -> bool {
     software.licensing_info() == software_two.licensing_info()
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/17_tests/tests1.rs b/exercises/17_tests/tests1.rs
index bde2108..d32ace1 100644
--- a/exercises/17_tests/tests1.rs
+++ b/exercises/17_tests/tests1.rs
@@ -10,6 +10,10 @@
 // Execute `rustlings hint tests1` or use the `hint` watch subcommand for a
 // hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     #[test]
diff --git a/exercises/17_tests/tests2.rs b/exercises/17_tests/tests2.rs
index aea5c0e..501c44b 100644
--- a/exercises/17_tests/tests2.rs
+++ b/exercises/17_tests/tests2.rs
@@ -6,6 +6,10 @@
 // Execute `rustlings hint tests2` or use the `hint` watch subcommand for a
 // hint.
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     #[test]
diff --git a/exercises/17_tests/tests3.rs b/exercises/17_tests/tests3.rs
index d815e05..a2093cf 100644
--- a/exercises/17_tests/tests3.rs
+++ b/exercises/17_tests/tests3.rs
@@ -11,6 +11,10 @@ pub fn is_even(num: i32) -> bool {
     num % 2 == 0
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/17_tests/tests4.rs b/exercises/17_tests/tests4.rs
index 0972a5b..a50323c 100644
--- a/exercises/17_tests/tests4.rs
+++ b/exercises/17_tests/tests4.rs
@@ -7,7 +7,7 @@
 
 struct Rectangle {
     width: i32,
-    height: i32
+    height: i32,
 }
 
 impl Rectangle {
@@ -16,10 +16,14 @@ impl Rectangle {
         if width <= 0 || height <= 0 {
             panic!("Rectangle width and height cannot be negative!")
         }
-        Rectangle {width, height}
+        Rectangle { width, height }
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/18_iterators/iterators2.rs b/exercises/18_iterators/iterators2.rs
index 4ca7742..0ebd69a 100644
--- a/exercises/18_iterators/iterators2.rs
+++ b/exercises/18_iterators/iterators2.rs
@@ -33,6 +33,10 @@ pub fn capitalize_words_string(words: &[&str]) -> String {
     String::new()
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/18_iterators/iterators3.rs b/exercises/18_iterators/iterators3.rs
index f7da049..3f5923c 100644
--- a/exercises/18_iterators/iterators3.rs
+++ b/exercises/18_iterators/iterators3.rs
@@ -43,6 +43,10 @@ fn list_of_results() -> () {
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/18_iterators/iterators4.rs b/exercises/18_iterators/iterators4.rs
index af3958c..8fc8792 100644
--- a/exercises/18_iterators/iterators4.rs
+++ b/exercises/18_iterators/iterators4.rs
@@ -15,6 +15,10 @@ pub fn factorial(num: u64) -> u64 {
     // Execute `rustlings hint iterators4` for hints.
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/18_iterators/iterators5.rs b/exercises/18_iterators/iterators5.rs
index ceec536..2604004 100644
--- a/exercises/18_iterators/iterators5.rs
+++ b/exercises/18_iterators/iterators5.rs
@@ -55,6 +55,10 @@ fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Pr
     todo!();
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/19_smart_pointers/cow1.rs b/exercises/19_smart_pointers/cow1.rs
index b24591b..51e5fdb 100644
--- a/exercises/19_smart_pointers/cow1.rs
+++ b/exercises/19_smart_pointers/cow1.rs
@@ -25,6 +25,10 @@ fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
     input
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/23_conversions/as_ref_mut.rs b/exercises/23_conversions/as_ref_mut.rs
index cd2c93b..6fb7c2f 100644
--- a/exercises/23_conversions/as_ref_mut.rs
+++ b/exercises/23_conversions/as_ref_mut.rs
@@ -26,6 +26,10 @@ fn num_sq<T>(arg: &mut T) {
     ???
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/quiz1.rs b/exercises/quiz1.rs
index b9e71f5..55bc61f 100644
--- a/exercises/quiz1.rs
+++ b/exercises/quiz1.rs
@@ -16,6 +16,10 @@
 // Put your function here!
 // fn calculate_price_of_apples {
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 // Don't modify this function!
 #[test]
 fn verify_test() {
diff --git a/exercises/quiz2.rs b/exercises/quiz2.rs
index 8ace3fe..1d73ab9 100644
--- a/exercises/quiz2.rs
+++ b/exercises/quiz2.rs
@@ -40,6 +40,10 @@ mod my_module {
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     // TODO: What do we need to import to have `transformer` in scope?
diff --git a/exercises/quiz3.rs b/exercises/quiz3.rs
index 24f7082..780e130 100644
--- a/exercises/quiz3.rs
+++ b/exercises/quiz3.rs
@@ -24,11 +24,17 @@ pub struct ReportCard {
 
 impl ReportCard {
     pub fn print(&self) -> String {
-        format!("{} ({}) - achieved a grade of {}",
-            &self.student_name, &self.student_age, &self.grade)
+        format!(
+            "{} ({}) - achieved a grade of {}",
+            &self.student_name, &self.student_age, &self.grade
+        )
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;