From 34574e6b30d5f8fbefd47936474d52143645c995 Mon Sep 17 00:00:00 2001
From: Lukas Kalbertodt <lukas.kalbertodt@gmail.com>
Date: Wed, 16 Nov 2016 11:48:04 +0100
Subject: [PATCH] Add source code from the lecture

---
 materialien/tree.rs | 116 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100755 materialien/tree.rs

diff --git a/materialien/tree.rs b/materialien/tree.rs
new file mode 100755
index 0000000..f8107f9
--- /dev/null
+++ b/materialien/tree.rs
@@ -0,0 +1,116 @@
+/// Represents a tree.
+///
+/// Each internal node can have any number of children. Each node (internal
+/// and leaf) carries an `i32`.
+#[derive(Debug, Clone)]
+enum Tree {
+    Leaf(i32),
+    Internal {
+        children: Vec<Tree>,
+        data: i32,
+    },
+}
+
+impl Tree {
+    /// Determines if this tree is just a leaf node.
+    fn is_leaf(&self) -> bool {
+        match *self {
+            Tree::Leaf(_) => true,
+            _ => false,
+        }
+    }
+
+    /// Returns the value attached to this node.
+    fn data(&self) -> i32 {
+        match *self {
+            Tree::Leaf(data) => data,
+            Tree::Internal { data, .. } => data,
+        }
+    }
+
+
+    fn data_mut(&mut self) -> &mut i32 {
+        match *self {
+            Tree::Leaf(ref mut data) => data,
+            Tree::Internal { ref mut data, .. } => data,
+        }
+    }
+
+    /// Adds another tree as a child of this node.
+    fn add_child(&mut self, child: Tree) {
+        if let Tree::Leaf(data) = *self {
+            *self = Tree::Internal {
+                children: vec![],
+                data: data,
+            };
+        }
+
+        match *self {
+            Tree::Internal { ref mut children, .. } => {
+                children.push(child);
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    /// Adds another leaf node with the given value as child of this node.
+    fn add_leaf_child(&mut self, child_data: i32) {
+        self.add_child(Tree::Leaf(child_data));
+    }
+
+    /// If this node is internal, this function returns a slice of all
+    /// children.
+    fn children(&self) -> Option<&[Tree]> {
+        match *self {
+            Tree::Internal { ref children, .. } => Some(children),
+            _ => None,
+        }
+    }
+
+    /// If this node is internal, this function returns a mutable slice of all
+    /// children.
+    fn children_mut(&mut self) -> Option<&mut [Tree]> {
+        match *self {
+            Tree::Internal { ref mut children, .. } => Some(children),
+            _ => None,
+        }
+    }
+
+    /// Returns a string that contains the values of all nodes in preorder. The
+    /// values are separated by `separator`.
+    fn format_preorder(&self, separator: char) -> String {
+        match *self {
+            Tree::Leaf(data) => data.to_string(),
+            Tree::Internal { data, ref children } => {
+                let mut out = data.to_string();
+
+                for child in children {
+                    out.push(separator);
+                    out += &child.format_preorder(separator);
+                }
+
+                out
+            }
+        }
+    }
+}
+
+
+
+fn main() {
+    let a = Tree::Leaf(3);
+    let b = Tree::Leaf(7);
+    let mut root = Tree::Internal {
+        children: vec![a, b],
+        data: 99,
+    };
+
+    for child in root.children_mut().unwrap() {
+        child.add_leaf_child(123);
+        child.add_leaf_child(234);
+    }
+
+    println!("{:#?}", root);
+
+    println!("{}", root.format_preorder(','));
+}