rt-lists 0.1.2

type Link<T> = Option<Box<Node<T>>>;

struct  Node<T> {
  elem: T,
  next: Link<T>
}

pub struct List<T> {
  head: Link<T>
}

pub struct IntoIter<T>(List<T>);

pub struct  Iter<'a, T> {
  next: Option<&'a Box<Node<T>>>,
}

pub struct IterMut<'a, T> {
  next: Option<&'a mut Node<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: elem,
      next: self.head.take(),
    });

    self.head = Some(new_node);
  }

  pub fn pop(&mut self) -> Option<T> {
    self.head.take().map(|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 into_iter(self) -> IntoIter<T> {
    IntoIter(self)
  }

  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_deref_mut() }
  }
}



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();
    }
  }
}

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<'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_deref_mut();
      &mut node.elem
    })
  }
}