239 lines
6.0 KiB
Rust
239 lines
6.0 KiB
Rust
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//! # A Bad Safe Deque
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use std::rc::Rc;
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use std::cell::{Ref, RefCell, RefMut};
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pub struct List<T> {
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head: Link<T>,
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tail: Link<T>,
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}
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type Link<T> = Option<Rc<RefCell<Node<T>>>>;
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struct Node<T> {
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elem: T,
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next: Link<T>,
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prev: Link<T>,
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}
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pub struct IntoIter<T>(List<T>);
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impl<T> Node<T> {
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fn new(elem: T) -> Rc<RefCell<Self>> {
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Rc::new(RefCell::new(Node {
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elem,
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prev: None,
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next: None,
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}))
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}
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}
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impl<T> List<T> {
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pub fn new() -> Self {
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List {
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head: None,
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tail: None,
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}
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}
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pub fn push_front(&mut self, elem: T) {
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let new_head = Node::new(elem);
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match self.head.take() {
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Some(old_head) => {
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old_head.borrow_mut().prev = Some(new_head.clone());
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new_head.borrow_mut().next = Some(old_head);
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self.head = Some(new_head);
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}
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None => {
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self.tail = Some(new_head.clone());
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self.head = Some(new_head);
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}
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}
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}
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pub fn pop_front(&mut self) -> Option<T> {
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self.head.take().map(|old_head| {
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match old_head.borrow_mut().next.take() {
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Some(new_head) => {
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new_head.borrow_mut().prev.take();
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self.head = Some(new_head);
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}
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None => {
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self.tail.take();
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}
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}
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Rc::try_unwrap(old_head).ok().unwrap().into_inner().elem
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})
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}
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pub fn push_back(&mut self, elem: T) {
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let new_tail = Node::new(elem);
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match self.tail.take() {
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Some(old_tail) => {
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old_tail.borrow_mut().next = Some(new_tail.clone());
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new_tail.borrow_mut().prev = Some(old_tail);
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self.tail = Some(new_tail);
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}
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None => {
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self.head = Some(new_tail.clone());
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self.tail = Some(new_tail);
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}
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}
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}
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pub fn pop_back(&mut self) -> Option<T> {
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self.tail.take().map(|old_tail| {
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match old_tail.borrow_mut().prev.take() {
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Some(new_tail) => {
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new_tail.borrow_mut().next.take();
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self.tail = Some(new_tail);
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}
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None => {
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self.head.take();
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}
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}
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Rc::try_unwrap(old_tail).ok().unwrap().into_inner().elem
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})
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}
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pub fn peek_front(&self) -> Option<Ref<T>> {
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self.head.as_ref().map(|node| {
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Ref::map(node.borrow(), |node| &node.elem)
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})
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}
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pub fn peek_front_mut(&mut self) -> Option<RefMut<T>> {
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self.head.as_ref().map(|node| {
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RefMut::map(node.borrow_mut(), |node| &mut node.elem)
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})
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}
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pub fn peek_back(&self) -> Option<Ref<T>> {
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self.tail.as_ref().map(|node| {
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Ref::map(node.borrow(), |node| &node.elem)
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})
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}
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pub fn peek_back_mut(&mut self) -> Option<RefMut<T>> {
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self.tail.as_ref().map(|node| {
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RefMut::map(node.borrow_mut(), |node| &mut node.elem)
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})
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}
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pub fn into_iter(self) -> IntoIter<T> {
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IntoIter(self)
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}
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}
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impl<T> Drop for List<T> {
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fn drop(&mut self) {
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while self.pop_front().is_some() {}
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}
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}
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impl<T> Iterator for IntoIter<T> {
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type Item = T;
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fn next(&mut self) -> Option<T> {
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self.0.pop_front()
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}
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}
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impl<T> DoubleEndedIterator for IntoIter<T> {
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fn next_back(&mut self) -> Option<T> {
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self.0.pop_back()
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}
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}
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#[cfg(test)]
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mod test {
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use super::List;
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#[test]
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fn basics() {
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let mut list = List::new();
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// Check empty list behaves right
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assert_eq!(list.pop_front(), None);
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// Populate list
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list.push_front(1);
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list.push_front(2);
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list.push_front(3);
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// Check normal removal
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assert_eq!(list.pop_front(), Some(3));
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assert_eq!(list.pop_front(), Some(2));
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// Push some more just to make sure nothing's corrupted
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list.push_front(4);
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list.push_front(5);
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// Check normal removal
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assert_eq!(list.pop_front(), Some(5));
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assert_eq!(list.pop_front(), Some(4));
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// Check exhaustion
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assert_eq!(list.pop_front(), Some(1));
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assert_eq!(list.pop_front(), None);
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// ---- back -----
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// Check empty list behaves right
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assert_eq!(list.pop_front(), None);
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// Populate list
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list.push_back(1);
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list.push_back(2);
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list.push_back(3);
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// Check normal removal
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assert_eq!(list.pop_back(), Some(3));
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assert_eq!(list.pop_back(), Some(2));
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// Push some more just to make sure nothing's corrupted
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list.push_back(4);
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list.push_back(5);
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// Check normal removal
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assert_eq!(list.pop_back(), Some(5));
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assert_eq!(list.pop_back(), Some(4));
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// Check exhaustion
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assert_eq!(list.pop_back(), Some(1));
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assert_eq!(list.pop_back(), None);
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}
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#[test]
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fn peek() {
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let mut list = List::new();
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assert!(list.peek_front().is_none());
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assert!(list.peek_back().is_none());
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assert!(list.peek_front_mut().is_none());
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assert!(list.peek_back_mut().is_none());
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list.push_front(1);
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list.push_front(2);
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list.push_front(3);
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assert_eq!(&*list.peek_front().unwrap(), &3);
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assert_eq!(&mut *list.peek_front_mut().unwrap(), &mut 3);
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assert_eq!(&*list.peek_back().unwrap(), &1);
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assert_eq!(&mut *list.peek_back_mut().unwrap(), &mut 1);
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}
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#[test]
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fn into_iter() {
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let mut list = List::new();
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list.push_front(1);
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list.push_front(2);
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list.push_front(3);
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let mut iter = list.into_iter();
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assert_eq!(iter.next(), Some(3));
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assert_eq!(iter.next_back(), Some(1));
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assert_eq!(iter.next(), Some(2));
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assert_eq!(iter.next_back(), None);
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assert_eq!(iter.next(), None);
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}
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}
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