Auto merge of rust-lang#224 - nyxtom:feat-enums, r=fmoko

feat: Add enums exercises

Creates an exhaustive list of enum exercises. This goes through the basics of different ways to derive enums with mixed data type variants, as well as the use of the all important `match` operator.

exercises/enums/README.md

@@ -0,0 +1,7 @@
+### Enums
+
+Rust allows you to define a type called `enums` which allow you to enumerate possible values. In combination with enums, we have the concept of `pattern matching` in Rust, which makes it easy to run different code for different values of an enumeration. Enums, while available in many languages, Rust's enums are most similar to `algebraic data types` in functional languages, such as F#, OCaml, and Haskell.
+
+#### Book Sections
+
+- [Enums](https://doc.rust-lang.org/book/ch06-00-enums.html)

exercises/enums/enums1.rs

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+// enums1.rs
+// Make me compile! Scroll down for hints!
+
+#[derive(Debug)]
+enum Message {
+    // TODO: define a few types of messages as used below
+}
+
+fn main() {
+    println!("{:?}", Message::Quit);
+    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::Move);
+    println!("{:?}", Message::ChangeColor);
+}
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+// Hint: The declaration of the enumeration type has not been defined yet.

exercises/enums/enums2.rs

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+// enums2.rs
+// Make me compile! Scroll down for hints
+
+#[derive(Debug)]
+enum Message {
+    // TODO: define the different variants used below
+}
+
+impl Message {
+    fn call(&self) {
+        println!("{:?}", &self);
+    }
+}
+
+fn main() {
+    let messages = [
+        Message::Move{ x: 10, y: 30 },
+        Message::Echo(String::from("hello world")),
+        Message::ChangeColor(200, 255, 255),
+        Message::Quit
+    ];
+
+    for message in &messages {
+        message.call();
+    }
+}
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+// Hint: you can create enumerations that have different variants with different types
+// such as no data, anonymous structs, a single string, tuples, ...etc

exercises/enums/enums3.rs

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+// enums3.rs
+// Address all the TODOs to make the tests pass!
+
+enum Message {
+    // TODO: implement the message variant types based on their usage below
+}
+
+struct Point {
+    x: u8,
+    y: u8
+}
+
+struct State {
+    color: (u8, u8, u8),
+    position: Point,
+    quit: bool
+}
+
+impl State {
+    fn change_color(&mut self, color: (u8, u8, u8)) {
+        self.color = color;
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
+    fn echo(&self, s: String) {
+        println!("{}", s);
+    }
+
+    fn move_position(&mut self, p: Point) {
+        self.position = p;
+    }
+
+    fn process(&mut self, message: Message) {
+        // TODO: create a match expression to process the different message variants
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_match_message_call() {
+        let mut state = State{
+            quit: false,
+            position: Point{ x: 0, y: 0 },
+            color: (0, 0, 0)
+        };
+        state.process(Message::ChangeColor(255, 0, 255));
+        state.process(Message::Echo(String::from("hello world")));
+        state.process(Message::Move{ x: 10, y: 15 });
+        state.process(Message::Quit);
+
+        assert_eq!(state.color, (255, 0, 255));
+        assert_eq!(state.position.x, 10);
+        assert_eq!(state.position.y, 15);
+        assert_eq!(state.quit, true);
+    }
+
+}

info.toml

@@ -86,6 +86,20 @@ mode = "test"
 path = "exercises/structs/structs2.rs"
 mode = "test"
 
+# ENUMS
+
+[[exercises]]
+path = "exercises/enums/enums1.rs"
+mode = "compile"
+
+[[exercises]]
+path = "exercises/enums/enums2.rs"
+mode = "compile"
+
+[[exercises]]
+path = "exercises/enums/enums3.rs"
+mode = "test"
+
 # TESTS
 
 [[exercises]]