Add code

example_4/.gitignore

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+/target

example_4/Cargo.toml

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+[package]
+name = "example_4"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

example_4/src/main.rs

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+#[derive(Debug)]
+enum Tree<T> {
+    Empty,
+    Node(T, Box<Tree<T>>, Box<Tree<T>>),
+}
+
+fn main() {
+    let tree = Tree::Node(
+        42,
+        Box::new(Tree::Node(0, Box::new(Tree::Empty), Box::new(Tree::Empty))),
+        Box::new(Tree::Empty),
+    );
+
+    println!("{:?}", tree); // prints Node(42, Node(0, Empty, Empty), Empty)
+}