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use std::collections::VecDeque;
pub struct Slide<T: Iterator<Item=A>, A> {
iter: T,
n: usize,
window: VecDeque<A>
}
impl<A: Clone, T: Iterator<Item=A>> Slide<T, A> {
fn push_window(&mut self) -> bool {
match self.iter.next() {
Some(x) => {
self.window.push_back(x);
true
},
None => false,
}
}
fn new(iter: T, n: usize) -> Slide<T, A> {
Slide {
iter: iter,
n: n,
window: VecDeque::with_capacity(n)
}
}
}
impl<A: Clone, T: Iterator<Item=A>> Iterator for Slide<T, A> {
type Item = VecDeque<A>;
fn next(&mut self) -> Option<VecDeque<A>> {
if self.n == 0 {
return None;
}
if self.window.len() == 0 {
while self.window.len() < self.n {
if !self.push_window() {
return None;
}
}
}
else {
self.window.pop_front();
if !self.push_window() {
return None;
}
}
Some(self.window.clone())
}
}
pub trait SlideIterator<T: Iterator<Item=A>, A> {
fn slide(self, n: usize) -> Slide<T, A>;
}
impl<A: Clone, T: IntoIterator<Item=A>> SlideIterator<T::IntoIter, A> for T {
fn slide(self, n: usize) -> Slide<T::IntoIter, A> {
Slide::new(self.into_iter(), n)
}
}
#[test]
fn test_slide() {
let mut slide_iter = vec![1i8, 2, 3, 4, 5].slide(3);
assert_eq!(slide_iter.next().unwrap(), &[1, 2, 3]);
assert_eq!(slide_iter.next().unwrap(), &[2, 3, 4]);
assert_eq!(slide_iter.next().unwrap(), &[3, 4, 5]);
assert!(slide_iter.next().is_none());
}
#[test]
fn test_slide_equal_window() {
let mut slide_iter = vec![1i8, 2, 3, 4, 5].slide(5);
assert_eq!(slide_iter.next().unwrap(), &[1, 2, 3, 4, 5]);
assert!(slide_iter.next().is_none());
}
#[test]
fn test_slide_zero_window() {
let mut slide_iter = vec![1i8, 2, 3, 4, 5].slide(0);
assert!(slide_iter.next().is_none());
}
#[test]
fn test_slide_overlong_window() {
let mut slide_iter = vec![1i8, 2, 3, 4, 5].slide(7);
assert!(slide_iter.next().is_none());
}