progress through generics and traits

.rustlings-state.txt

@@ -1,6 +1,6 @@
 DON'T EDIT THIS FILE!
 
-generics1
+lifetimes1
 
 intro1
 intro2
@@ -57,4 +57,12 @@ errors2
 errors3
 errors4
 errors5
-errors6
+errors6
+generics1
+generics2
+traits1
+traits2
+traits3
+traits4
+traits5
+quiz3

exercises/14_generics/generics1.rs

@@ -6,7 +6,7 @@ fn main() {
     // TODO: Fix the compiler error by annotating the type of the vector
     // `Vec<T>`. Choose `T` as some integer type that can be created from
     // `u8` and `i8`.
-    let mut numbers = Vec::new();
+    let mut numbers: Vec<i32> = Vec::new();
 
     // Don't change the lines below.
     let n1: u8 = 42;

exercises/14_generics/generics2.rs

@@ -1,12 +1,12 @@
 // This powerful wrapper provides the ability to store a positive integer value.
 // TODO: Rewrite it using a generic so that it supports wrapping ANY type.
-struct Wrapper {
+struct Wrapper<T> {
-    value: u32,
+    value: T,
 }
 
 // TODO: Adapt the struct's implementation to be generic over the wrapped value.
-impl Wrapper {
+impl <T> Wrapper<T> {
-    fn new(value: u32) -> Self {
+    fn new(value: T) -> Self {
         Wrapper { value }
     }
 }

exercises/15_traits/traits1.rs

@@ -5,7 +5,10 @@ trait AppendBar {
 }
 
 impl AppendBar for String {
-    // TODO: Implement `AppendBar` for the type `String`.
+    fn append_bar(mut self) -> Self {
+        self.push_str("Bar");
+        self
+    }
 }
 
 fn main() {

exercises/15_traits/traits2.rs

@@ -4,6 +4,12 @@ trait AppendBar {
 
 // TODO: Implement the trait `AppendBar` for a vector of strings.
 // `append_bar` should push the string "Bar" into the vector.
+impl AppendBar for Vec<String> {
+    fn append_bar(mut self) -> Self {
+        self.push(String::from("Bar"));
+        self
+    }
+}
 
 fn main() {
     // You can optionally experiment here.

exercises/15_traits/traits3.rs

@@ -5,7 +5,9 @@ trait Licensed {
     // implementors like the two structs below can share that default behavior
     // without repeating the function.
     // The default license information should be the string "Default license".
-    fn licensing_info(&self) -> String;
+    fn licensing_info(&self) -> String {
+        return String::from("Default license")
+    }
 }
 
 struct SomeSoftware {

exercises/15_traits/traits4.rs

@@ -11,7 +11,8 @@ impl Licensed for SomeSoftware {}
 impl Licensed for OtherSoftware {}
 
 // TODO: Fix the compiler error by only changing the signature of this function.
-fn compare_license_types(software1: ???, software2: ???) -> bool {
+fn compare_license_types<T, F>(software1: T, software2: F) -> bool
+    where T: Licensed, F: Licensed{
     software1.licensing_info() == software2.licensing_info()
 }
 

exercises/15_traits/traits5.rs

@@ -19,7 +19,8 @@ impl SomeTrait for OtherStruct {}
 impl OtherTrait for OtherStruct {}
 
 // TODO: Fix the compiler error by only changing the signature of this function.
-fn some_func(item: ???) -> bool {
+fn some_func<T>(item: T) -> bool
+    where T: OtherTrait + SomeTrait{
     item.some_function() && item.other_function()
 }
 

exercises/quizzes/quiz3.rs

@@ -11,15 +11,17 @@
 // Make the necessary code changes in the struct `ReportCard` and the impl
 // block to support alphabetical report cards in addition to numerical ones.
 
+use std::fmt::Display;
+
 // TODO: Adjust the struct as described above.
-struct ReportCard {
+struct ReportCard<T> where T: Display {
-    grade: f32,
+    grade: T,
     student_name: String,
     student_age: u8,
 }
 
 // TODO: Adjust the impl block as described above.
-impl ReportCard {
+impl <T: Display>ReportCard<T> {
     fn print(&self) -> String {
         format!(
             "{} ({}) - achieved a grade of {}",

solutions/14_generics/generics1.rs

@@ -1,4 +1,17 @@
+// `Vec<T>` is generic over the type `T`. In most cases, the compiler is able to
+// infer `T`, for example after pushing a value with a concrete type to the vector.
+// But in this exercise, the compiler needs some help through a type annotation.
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
+    // `u8` and `i8` can both be converted to `i16`.
-    // It will be automatically filled after you finish the exercise.
+    let mut numbers: Vec<i16> = Vec::new();
+    //             ^^^^^^^^^^ added
+
+    // Don't change the lines below.
+    let n1: u8 = 42;
+    numbers.push(n1.into());
+    let n2: i8 = -1;
+    numbers.push(n2.into());
+
+    println!("{numbers:?}");
 }

solutions/14_generics/generics2.rs

@@ -1,4 +1,28 @@
-fn main() {
+struct Wrapper<T> {
-    // DON'T EDIT THIS SOLUTION FILE!
+    value: T,
-    // It will be automatically filled after you finish the exercise.
+}
+
+impl<T> Wrapper<T> {
+    fn new(value: T) -> Self {
+        Wrapper { value }
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn store_u32_in_wrapper() {
+        assert_eq!(Wrapper::new(42).value, 42);
+    }
+
+    #[test]
+    fn store_str_in_wrapper() {
+        assert_eq!(Wrapper::new("Foo").value, "Foo");
+    }
 }

solutions/15_traits/traits1.rs

@@ -1,4 +1,32 @@
-fn main() {
+// The trait `AppendBar` has only one function which appends "Bar" to any object
-    // DON'T EDIT THIS SOLUTION FILE!
+// implementing this trait.
-    // It will be automatically filled after you finish the exercise.
+trait AppendBar {
+    fn append_bar(self) -> Self;
+}
+
+impl AppendBar for String {
+    fn append_bar(self) -> Self {
+        self + "Bar"
+    }
+}
+
+fn main() {
+    let s = String::from("Foo");
+    let s = s.append_bar();
+    println!("s: {s}");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_foo_bar() {
+        assert_eq!(String::from("Foo").append_bar(), "FooBar");
+    }
+
+    #[test]
+    fn is_bar_bar() {
+        assert_eq!(String::from("").append_bar().append_bar(), "BarBar");
+    }
 }

solutions/15_traits/traits2.rs

@@ -1,4 +1,27 @@
-fn main() {
+trait AppendBar {
-    // DON'T EDIT THIS SOLUTION FILE!
+    fn append_bar(self) -> Self;
-    // It will be automatically filled after you finish the exercise.
+}
+
+impl AppendBar for Vec<String> {
+    fn append_bar(mut self) -> Self {
+        //        ^^^ this is important
+        self.push(String::from("Bar"));
+        self
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_vec_pop_eq_bar() {
+        let mut foo = vec![String::from("Foo")].append_bar();
+        assert_eq!(foo.pop().unwrap(), "Bar");
+        assert_eq!(foo.pop().unwrap(), "Foo");
+    }
 }

solutions/15_traits/traits3.rs

@@ -1,4 +1,38 @@
-fn main() {
+#![allow(dead_code)]
-    // DON'T EDIT THIS SOLUTION FILE!
+
-    // It will be automatically filled after you finish the exercise.
+trait Licensed {
+    fn licensing_info(&self) -> String {
+        "Default license".to_string()
+    }
+}
+
+struct SomeSoftware {
+    version_number: i32,
+}
+
+struct OtherSoftware {
+    version_number: String,
+}
+
+impl Licensed for SomeSoftware {}
+impl Licensed for OtherSoftware {}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_licensing_info_the_same() {
+        let licensing_info = "Default license";
+        let some_software = SomeSoftware { version_number: 1 };
+        let other_software = OtherSoftware {
+            version_number: "v2.0.0".to_string(),
+        };
+        assert_eq!(some_software.licensing_info(), licensing_info);
+        assert_eq!(other_software.licensing_info(), licensing_info);
+    }
 }

solutions/15_traits/traits4.rs

@@ -1,4 +1,35 @@
-fn main() {
+trait Licensed {
-    // DON'T EDIT THIS SOLUTION FILE!
+    fn licensing_info(&self) -> String {
-    // It will be automatically filled after you finish the exercise.
+        "Default license".to_string()
+    }
+}
+
+struct SomeSoftware;
+struct OtherSoftware;
+
+impl Licensed for SomeSoftware {}
+impl Licensed for OtherSoftware {}
+
+fn compare_license_types(software1: impl Licensed, software2: impl Licensed) -> bool {
+    //                              ^^^^^^^^^^^^^             ^^^^^^^^^^^^^
+    software1.licensing_info() == software2.licensing_info()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn compare_license_information() {
+        assert!(compare_license_types(SomeSoftware, OtherSoftware));
+    }
+
+    #[test]
+    fn compare_license_information_backwards() {
+        assert!(compare_license_types(OtherSoftware, SomeSoftware));
+    }
 }

solutions/15_traits/traits5.rs

@@ -1,4 +1,39 @@
-fn main() {
+trait SomeTrait {
-    // DON'T EDIT THIS SOLUTION FILE!
+    fn some_function(&self) -> bool {
-    // It will be automatically filled after you finish the exercise.
+        true
+    }
+}
+
+trait OtherTrait {
+    fn other_function(&self) -> bool {
+        true
+    }
+}
+
+struct SomeStruct;
+impl SomeTrait for SomeStruct {}
+impl OtherTrait for SomeStruct {}
+
+struct OtherStruct;
+impl SomeTrait for OtherStruct {}
+impl OtherTrait for OtherStruct {}
+
+fn some_func(item: impl SomeTrait + OtherTrait) -> bool {
+    //             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    item.some_function() && item.other_function()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_some_func() {
+        assert!(some_func(SomeStruct));
+        assert!(some_func(OtherStruct));
+    }
 }

solutions/quizzes/quiz3.rs

@@ -1,4 +1,65 @@
-fn main() {
+// An imaginary magical school has a new report card generation system written
-    // DON'T EDIT THIS SOLUTION FILE!
+// in Rust! Currently, the system only supports creating report cards where the
-    // It will be automatically filled after you finish the exercise.
+// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
+// school also issues alphabetical grades (A+ -> F-) and needs to be able to
+// print both types of report card!
+//
+// Make the necessary code changes in the struct `ReportCard` and the impl
+// block to support alphabetical report cards in addition to numerical ones.
+
+use std::fmt::Display;
+
+// Make the struct generic over `T`.
+struct ReportCard<T> {
+    //           ^^^
+    grade: T,
+    //     ^
+    student_name: String,
+    student_age: u8,
+}
+
+// To be able to print the grade, it has to implement the `Display` trait.
+impl<T: Display> ReportCard<T> {
+    //  ^^^^^^^ require that `T` implements `Display`.
+    fn print(&self) -> String {
+        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::*;
+
+    #[test]
+    fn generate_numeric_report_card() {
+        let report_card = ReportCard {
+            grade: 2.1,
+            student_name: "Tom Wriggle".to_string(),
+            student_age: 12,
+        };
+        assert_eq!(
+            report_card.print(),
+            "Tom Wriggle (12) - achieved a grade of 2.1",
+        );
+    }
+
+    #[test]
+    fn generate_alphabetic_report_card() {
+        let report_card = ReportCard {
+            grade: "A+",
+            student_name: "Gary Plotter".to_string(),
+            student_age: 11,
+        };
+        assert_eq!(
+            report_card.print(),
+            "Gary Plotter (11) - achieved a grade of A+",
+        );
+    }
 }