rust-too-many-lists-book/src/second.rs

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2019-03-12 15:49:28 -04:00
pub struct List<T> {
head: Link<T>,
}
type Link<T> = Option<Box<Node<T>>>;
struct Node<T> {
elem: T,
next: Link<T>,
}
pub struct Iter<'a, T: 'a> {
next: Option<&'a Node<T>>,
}
pub struct IterMut<'a, T: 'a> {
next: Option<&'a mut Node<T>>,
}
pub struct IntoIter<T>(List<T>);
impl<T> List<T> {
pub fn new() -> Self {
List { head: None }
}
pub fn push(&mut self, elem: T) {
let new_node = Box::new(Node {
elem,
next: self.head.take(),
});
self.head = Some(new_node);
}
pub fn pop(&mut self) -> Option<T> {
self.head.take().map(|node| {
let node = *node;
self.head = node.next;
node.elem
})
}
pub fn peek(&self) -> Option<&T> {
self.head.as_ref().map(|node| {
&node.elem
})
}
pub fn peek_mut(&mut self) -> Option<&mut T> {
self.head.as_mut().map(|node| {
&mut node.elem
})
}
pub fn iter(&self) -> Iter<T> {
Iter { next: self.head.as_ref().map(|node| &**node) }
}
pub fn iter_mut(&mut self) -> IterMut<T> {
IterMut { next: self.head.as_mut().map(|node| &mut **node) }
}
pub fn into_iter(self) -> IntoIter<T> {
IntoIter(self)
}
}
impl<'a, T> Iterator for Iter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
self.next.map(|node| {
self.next = node.next.as_ref().map(|node| &**node);
&node.elem
})
}
}
impl<'a, T> Iterator for IterMut<'a, T> {
type Item = &'a mut T;
fn next(&mut self) -> Option<Self::Item> {
self.next.take().map(|node| {
self.next = node.next.as_mut().map(|node| &mut **node);
&mut node.elem
})
}
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
// access fields of a tuple struct numerically
self.0.pop()
}
}
impl<T> Drop for List<T> {
fn drop(&mut self) {
let mut cur_link = self.head.take();
while let Some(mut boxed_node) = cur_link {
cur_link = boxed_node.next.take();
}
}
}
#[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);
}
#[test]
fn peek() {
let mut list = List::new();
assert_eq!(list.peek(), None);
assert_eq!(list.peek_mut(), None);
list.push(1);
list.push(2);
list.push(3);
assert_eq!(list.peek(), Some(&3));
assert_eq!(list.peek_mut(), Some(&mut 3));
}
#[test]
fn iter() {
let mut list = List::new();
list.push(1);
list.push(2);
list.push(3);
let mut iter = list.iter();
assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), Some(&1));
}
#[test]
fn iter_mut() {
let mut list = List::new();
list.push(1);
list.push(2);
list.push(3);
let mut iter = list.iter_mut();
assert_eq!(iter.next(), Some(&mut 3));
assert_eq!(iter.next(), Some(&mut 2));
assert_eq!(iter.next(), Some(&mut 1));
}
#[test]
fn into_iter() {
let mut list = List::new();
list.push(1);
list.push(2);
list.push(3);
let mut iter = list.into_iter();
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), Some(1));
}
}