generics

src/main.rs

@@ -9,28 +9,28 @@ fn main() {
 }
 
 #[derive(Debug)]
-pub struct List {
+pub struct List<T> {
-    head: Link,
+    head: Link<T>,
 }
 
 #[derive(Debug)]
-enum Link {
+enum Link<T> {
     Empty,
-    More(Box<Node>),
+    More(Box<Node<T>>),
 }
 
 #[derive(Debug)]
-struct Node {
+struct Node<T> {
-    elem: i32,
+    elem: T,
-    next: Link,
+    next: Link<T>,
 }
 
-impl List {
+impl <T> List<T> {
     pub fn new() -> Self {
         Self { head: Link::Empty }
     }
 
-    pub fn push(&mut self, elem: i32) {
+    pub fn push(&mut self, elem: T) {
         let new_node = Node {
             elem: elem,
             next: std::mem::replace(&mut self.head, Link::Empty),
@@ -38,7 +38,7 @@ impl List {
         self.head = Link::More(Box::new(new_node));
     }
 
-    pub fn pop(&mut self) -> Option<i32> {
+    pub fn pop(&mut self) -> Option<T> {
         match std::mem::replace(&mut self.head, Link::Empty) {
             Link::Empty => None,
             Link::More(node) => {