106 lines
2.1 KiB
Rust
106 lines
2.1 KiB
Rust
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use std::sync::Arc;
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pub struct List <T> {
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head: Link<T>,
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}
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type Link <T> = Option<Arc<Node<T>>>;
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struct Node <T> {
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value: T,
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next: Link<T>,
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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 { head: None }
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}
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pub fn prepend (&self, value: T) -> List<T> {
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List { head: Some(Arc::new(Node {
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value, next: self.head.clone()
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})) }
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}
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pub fn tail (&self) -> List<T> {
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List { head: self.head.as_ref().and_then(|node| node.next.clone()) }
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}
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pub fn head (&self) -> Option<&T> {
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self.head.as_ref().map(|node| &node.value)
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}
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pub fn iter (&self) -> Iter<T> {
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Iter { next: self.head.as_deref()}
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}
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}
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pub struct Iter <'a, T> {
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next: Option<&'a Node<T>>,
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}
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impl <'a, T> Iterator for Iter<'a, T> {
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type Item = &'a T;
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fn next (&mut self) -> Option<Self::Item> {
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self.next.map(|node| {
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self.next = node.next.as_deref();
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&node.value
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})
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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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let mut head = self.head.take();
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while let Some(node) = head {
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if let Ok(mut node) = Arc::try_unwrap(node) {
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head = node.next.take();
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} else {
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break;
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}
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}
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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 list = List::new();
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assert_eq!(list.head(), None);
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let list = list.prepend(1).prepend(2).prepend(3);
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assert_eq!(list.head(), Some(&3));
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let list = list.tail();
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assert_eq!(list.head(), Some(&2));
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let list = list.tail();
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assert_eq!(list.head(), Some(&1));
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let list = list.tail();
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assert_eq!(list.head(), None);
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// Make sure empty tail works
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let list = list.tail();
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assert_eq!(list.head(), None);
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}
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#[test]
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fn iter() {
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let list = List::new().prepend(1).prepend(2).prepend(3);
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let mut iter = list.iter();
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assert_eq!(iter.next(), Some(&3));
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assert_eq!(iter.next(), Some(&2));
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assert_eq!(iter.next(), Some(&1));
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}
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}
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