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enums/README.md

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+# Enums
+
+Rust allows you to define types called "enums" which enumerate possible values.
+Enums are a feature in many languages, but their capabilities differ in each language. Rust’s enums are most similar to algebraic data types in functional languages, such as F#, OCaml, and Haskell.
+Useful in combination with enums is Rust's "pattern matching" facility, which makes it easy to run different code for different values of an enumeration.
+
+## Further information
+
+- [Enums](https://doc.rust-lang.org/book/ch06-00-enums.html)
+- [Pattern syntax](https://doc.rust-lang.org/book/ch18-03-pattern-syntax.html)

enums/enums1.rs

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+// enums1.rs
+//
+// No hints this time! ;)
+
+// I AM DONE
+
+#[derive(Debug)]
+enum Message {
+    // TODO: define a few types of messages as used below
+    Quit,
+    Echo,
+    Move,
+    ChangeColor,
+}
+
+fn main() {
+    println!("{:?}", Message::Quit);
+    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::Move);
+    println!("{:?}", Message::ChangeColor);
+}

enums/enums2.rs

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+// enums2.rs
+//
+// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM DONE
+
+#[derive(Debug)]
+enum Message {
+    // TODO: define the different variants used below
+    Move { x: u8, y: u8 },
+    Echo(String),
+    ChangeColor(u8, u8, u8),
+    Quit,
+}
+
+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();
+    }
+}

enums/enums3.rs

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+// enums3.rs
+//
+// Address all the TODOs to make the tests pass!
+//
+// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM DONE
+
+enum Message {
+    ChangeColor(u8, u8, u8),
+    Echo(String),
+    Move(Point),
+    Quit,
+}
+
+struct Point {
+    x: u8,
+    y: u8,
+}
+
+struct State {
+    color: (u8, u8, u8),
+    position: Point,
+    quit: bool,
+    message: String,
+}
+
+impl State {
+    fn change_color(&mut self, color: (u8, u8, u8)) {
+        self.color = color;
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
+    fn echo(&mut self, s: String) {
+        self.message = 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
+        // Remember: When passing a tuple as a function argument, you'll need
+        // extra parentheses: fn function((t, u, p, l, e))
+        match message {
+            Message::ChangeColor(red, green, blue) => self.change_color((red, green, blue)),
+            Message::Move(point) => self.move_position(point),
+            Message::Echo(string) => self.echo(string),
+            Message::Quit => self.quit(),
+        }
+    }
+}
+
+#[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),
+            message: "hello world".to_string(),
+        };
+        state.process(Message::ChangeColor(255, 0, 255));
+        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::Move(Point { 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);
+        assert_eq!(state.message, "Hello world!");
+    }
+}