Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 1 | use std::iter::FusedIterator; |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 2 | |
| 3 | /// An iterator that produces *n* repetitions of an element. |
| 4 | /// |
Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 5 | /// See [`repeat_n()`](crate::repeat_n) for more information. |
Jakub Kotur | a425e55 | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 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`. |
| 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 | |
| 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 | |
| 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] |
| 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 | {} |
Joel Galenson | b593e25 | 2021-06-21 13:15:57 -0700 | [diff] [blame] | 56 | |
| 57 | impl<A> FusedIterator for RepeatN<A> |
| 58 | where A: Clone |
| 59 | {} |