From 4ed4c4edf8aca30e83c9239fe89e9aac8a9c4bda Mon Sep 17 00:00:00 2001
From: Jason Staten <jason.staten@domo.com>
Date: Tue, 26 Jun 2018 20:15:09 -0600
Subject: [PATCH] linked lists

---
 src/lib.rs       |   2 +
 src/linked.rs    |  81 ++++++++++++++++++++++++++++++++++++
 src/linked_im.rs | 104 +++++++++++++++++++++++++++++++++++++++++++++++
 src/search.rs    |   1 +
 src/tree.rs      |   1 +
 src/vec_basic.rs |   1 +
 6 files changed, 190 insertions(+)
 create mode 100644 src/linked.rs
 create mode 100644 src/linked_im.rs

diff --git a/src/lib.rs b/src/lib.rs
index 758e2b4..a72ce42 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,8 @@
 #![feature(test)]
 extern crate test;
 
+mod linked;
+mod linked_im;
 mod search;
 mod tree;
 mod vec_basic;
diff --git a/src/linked.rs b/src/linked.rs
new file mode 100644
index 0000000..9ff1b43
--- /dev/null
+++ b/src/linked.rs
@@ -0,0 +1,81 @@
+use std::iter::FromIterator;
+use std::mem;
+
+#[allow(unused)]
+#[derive(Debug, PartialEq)]
+enum Node<T> {
+    Cons(T, Box<Node<T>>),
+    Nil,
+}
+
+impl<T> Node<T> {
+    fn iter(self) -> Iter<T> {
+        Iter { node: self }
+    }
+}
+
+impl<'a, T> FromIterator<T> for Node<T> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+        let mut output = Node::Nil;
+
+        for x in iter {
+            output = Node::Cons(x, Box::new(output));
+        }
+
+        output
+    }
+}
+
+struct Iter<T> {
+    node: Node<T>,
+}
+
+impl<T> Iterator for Iter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let old_node = mem::replace(&mut self.node, Node::Nil);
+
+        match old_node {
+            Node::Cons(head, tail) => {
+                self.node = *tail;
+                Some(head)
+            }
+            Node::Nil => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use self::Node::*;
+    use super::*;
+
+    #[test]
+    fn test_can_construct() {
+        if let Cons(head, tail) = Cons("home", Box::new(Nil)) {
+            assert_eq!(head, "home");
+            assert_eq!(tail, Box::new(Nil));
+        } else {
+            assert!(false, "Not a Cons")
+        }
+    }
+
+    #[test]
+    fn test_from_iter() {
+        let expected = Cons(1, Box::new(Cons(2, Box::new(Cons(3, Box::new(Nil))))));
+
+        let result = Node::from_iter(vec![3, 2, 1]);
+        assert_eq!(result, expected);
+    }
+
+    #[test]
+    fn test_iterate() {
+        let list = Cons(1, Box::new(Cons(2, Box::new(Cons(3, Box::new(Nil))))));
+        let i = list.iter();
+        let result: Vec<i32> = i.collect();
+        let expected = vec![1, 2, 3];
+
+        assert_eq!(result, expected);
+    }
+}
diff --git a/src/linked_im.rs b/src/linked_im.rs
new file mode 100644
index 0000000..bd9c0a1
--- /dev/null
+++ b/src/linked_im.rs
@@ -0,0 +1,104 @@
+use std::iter::FromIterator;
+use std::rc::Rc;
+
+type Link<T> = Option<Rc<Node<T>>>;
+
+struct Node<T> {
+    value: T,
+    next: Link<T>,
+}
+
+struct LinkedList<T> {
+    head: Link<T>,
+}
+
+impl<T> LinkedList<T> {
+    fn new() -> LinkedList<T> {
+        LinkedList { head: Option::None }
+    }
+
+    fn append(self, el: T) -> LinkedList<T> {
+        LinkedList {
+            head: Option::Some(Rc::new(Node {
+                value: el,
+                next: self.head,
+            })),
+        }
+    }
+
+    fn head(&self) -> Option<&T> {
+        self.head.as_ref().map(|node| &node.value)
+    }
+
+    fn tail(&self) -> LinkedList<T> {
+        LinkedList {
+            head: self.head.as_ref().and_then(|node| node.next.clone()),
+        }
+    }
+}
+
+impl<'a, T> FromIterator<T> for LinkedList<T> {
+    fn from_iter<I: IntoIterator<Item = T>>(source: I) -> Self {
+        source
+            .into_iter()
+            .fold(LinkedList::new(), LinkedList::append)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::LinkedList;
+    use std::iter::FromIterator;
+
+    #[test]
+    fn test_append() {
+        let list = LinkedList::<u32> { head: Option::None };
+        let appended = list.append(42);
+        match appended.head {
+            Option::Some(node) => assert_eq!((*node).value, 42),
+            _ => assert!(false, "was not Some"),
+        }
+    }
+
+    #[test]
+    fn test_append_str() {
+        let list = LinkedList::<&str> { head: Option::None };
+        let appended = list.append("one").append("two").append("three");
+        match appended.head {
+            Option::Some(node) => assert_eq!((*node).value, "three"),
+            _ => assert!(false, "was not Some"),
+        }
+    }
+
+    #[test]
+    fn test_head() {
+        let list = LinkedList::<&str> { head: Option::None };
+        let appended = list.append("one").append("two").append("three");
+        match appended.head() {
+            Option::Some(val) => assert_eq!(val, &"three"),
+            _ => assert!(false, "was not Some"),
+        }
+    }
+
+    #[test]
+    fn test_tail() {
+        let list = LinkedList::<&str> { head: Option::None };
+        let appended = list.append("one").append("two").append("three");
+        match appended.tail().head() {
+            Option::Some(val) => assert_eq!(val, &"two"),
+            _ => assert!(false, "was not Some"),
+        }
+    }
+
+    #[test]
+    fn test_from_iter() {
+        let list = LinkedList::from_iter(vec![1, 2, 3]);
+        let h1 = list.head().unwrap().clone();
+        let h2 = list.tail().head().unwrap().clone();
+        let h3 = list.tail().tail().head().unwrap().clone();
+
+        assert_eq!(h1, 3);
+        assert_eq!(h2, 2);
+        assert_eq!(h3, 1);
+    }
+}
diff --git a/src/search.rs b/src/search.rs
index 5638e17..c8013e1 100644
--- a/src/search.rs
+++ b/src/search.rs
@@ -1,3 +1,4 @@
+#![allow(unused)]
 #[allow(unused_imports)]
 extern crate test;
 use test::Bencher;
diff --git a/src/tree.rs b/src/tree.rs
index d8a02c1..e95a1c6 100644
--- a/src/tree.rs
+++ b/src/tree.rs
@@ -1,3 +1,4 @@
+#![allow(unused)]
 #[derive(Debug)]
 struct Node<'a>(&'a str, Vec<Node<'a>>);
 
diff --git a/src/vec_basic.rs b/src/vec_basic.rs
index d383627..c88b79d 100644
--- a/src/vec_basic.rs
+++ b/src/vec_basic.rs
@@ -1,3 +1,4 @@
+#![allow(unused)]
 #[allow(unused_imports)]
 extern crate test;
 use test::Bencher;