The Final Code
好吧,6000字后,这里是我们写下的所有代码:
#![allow(unused)] fn main() { use std::mem; pub struct List { head: Link, } enum Link { Empty, More(Box<Node>), } struct Node { elem: i32, next: Link, } impl List { pub fn new() -> Self { List { head: Link::Empty } } pub fn push(&mut self, elem: i32) { let new_node = Box::new(Node { elem: elem, next: mem::replace(&mut self.head, Link::Empty), }); self.head = Link::More(new_node); } pub fn pop(&mut self) -> Option<i32> { match mem::replace(&mut self.head, Link::Empty) { Link::Empty => None, Link::More(node) => { self.head = node.next; Some(node.elem) } } } } impl Drop for List { fn drop(&mut self) { let mut cur_link = mem::replace(&mut self.head, Link::Empty); while let Link::More(mut boxed_node) = cur_link { cur_link = mem::replace(&mut boxed_node.next, Link::Empty); } } } #[cfg(test)] mod test { use super::List; #[test] fn basics() { let mut list = List::new(); // Check empty list behaves right assert_eq!(list.pop(), None); // Populate list list.push(1); list.push(2); list.push(3); // Check normal removal assert_eq!(list.pop(), Some(3)); assert_eq!(list.pop(), Some(2)); // Push some more just to make sure nothing's corrupted list.push(4); list.push(5); // Check normal removal assert_eq!(list.pop(), Some(5)); assert_eq!(list.pop(), Some(4)); // Check exhaustion assert_eq!(list.pop(), Some(1)); assert_eq!(list.pop(), None); } } }
天啊,80行,一半是测试!80行,其中一半是测试! 好吧,我说过这第一篇要花点时间的!