1 use std::iter::FusedIterator;
2
3 /// An iterator that produces *n* repetitions of an element.
4 ///
5 /// See [`repeat_n()`](crate::repeat_n) for more information.
6 #[must_use = "iterators are lazy and do nothing unless consumed"]
7 #[derive(Clone, Debug)]
8 pub struct RepeatN<A> {
9 elt: Option<A>,
10 n: usize,
11 }
12
13 /// Create an iterator that produces `n` repetitions of `element`.
repeat_n<A>(element: A, n: usize) -> RepeatN<A> where A: Clone,14 pub fn repeat_n<A>(element: A, n: usize) -> RepeatN<A>
15 where A: Clone,
16 {
17 if n == 0 {
18 RepeatN { elt: None, n, }
19 } else {
20 RepeatN { elt: Some(element), n, }
21 }
22 }
23
24 impl<A> Iterator for RepeatN<A>
25 where A: Clone
26 {
27 type Item = A;
28
next(&mut self) -> Option<Self::Item>29 fn next(&mut self) -> Option<Self::Item> {
30 if self.n > 1 {
31 self.n -= 1;
32 self.elt.as_ref().cloned()
33 } else {
34 self.n = 0;
35 self.elt.take()
36 }
37 }
38
size_hint(&self) -> (usize, Option<usize>)39 fn size_hint(&self) -> (usize, Option<usize>) {
40 (self.n, Some(self.n))
41 }
42 }
43
44 impl<A> DoubleEndedIterator for RepeatN<A>
45 where A: Clone
46 {
47 #[inline]
next_back(&mut self) -> Option<Self::Item>48 fn next_back(&mut self) -> Option<Self::Item> {
49 self.next()
50 }
51 }
52
53 impl<A> ExactSizeIterator for RepeatN<A>
54 where A: Clone
55 {}
56
57 impl<A> FusedIterator for RepeatN<A>
58 where A: Clone
59 {}
60