Generic Queue with Iterator

gistfile1.rs

use std::default::Default;

struct Q<T> {
  items : [T, ..10],
  count : uint
}

impl<T : Default + Copy> Q<T> {
  pub fn new() -> Box<Q<T>> {
    box Q {items: [Default::default(), ..10],
           count: 0}
  }

  pub fn empty(&self) -> bool {
    self.count == 0
  }

  pub fn enqueue<T>(&mut self, item : T) {
    self.items[self.count] = item;
    self.count += 1
  }

  pub fn iter<'r, T>(&'r self) -> Box<QCursor<'r, T>> {
    box QCursor {q: self, position: 0}
  }
}

struct QCursor<'r, T> {
  q : &'r Q<T>,
  position : uint
}

impl<'r, T> Iterator<T> for QCursor<'r, T> {
  fn next(&mut self) -> Option<T> {
    if self.position >= self.q.count {
      None
    } else {
      self.position += 1;
      Some(self.q.items[self.position - 1])
    }
  }
}

#[test]
fn test_empty() {
  let q = Q::<int>::new();

  assert!(q.empty());
}

#[test]
fn test_enqueue() {
  let mut q = Q::<int>::new();
  
  q.enqueue(99);
  assert!(!q.empty());
}

#[test]
fn test_iter() {
  let mut q = Q::<int>::new();

  q.enqueue(3);
  q.enqueue(2);
  q.enqueue(1);

  let mut count = 0;
  for item in q.iter() {
    count += 1;
  }
  assert!(count == 3);
}

pub fn main() {
  let mut q = Q::<int>::new();

  q.enqueue(3);
  q.enqueue(2);
  q.enqueue(1);

  for item in q.iter() {
    print!("Item is {:i}\n", item);
  }
}

rustc -o q_test --test q.rs
q.rs:68:3: 71:9 error: cannot determine a type for this expression: unconstrained type
q.rs:68 for item in q.iter() {
q.rs:69 count += 1;
q.rs:70 }
q.rs:71 assert!(count == 3);
q.rs:82:30: 82:34 error: cannot determine a type for this bounded type parameter: unconstrained type
q.rs:82 print!("Item is {:i}\n", item);
^~~~
note: in expansion of format_args!
:2:23: 2:75 note: expansion site
:1:1: 3:2 note: in expansion of print!
q.rs:82:5: 82:36 note: expansion site
make: *** [q_test] Error 101