squash commit for nth_back on chunks exact

wip nth_back for chunks_exact

working nth_back for chunks exact

Signed-off-by: wizAmit <amitforfriends_dns@yahoo.com>
This commit is contained in:
@amit.chandra 2019-06-22 22:59:24 +05:30 committed by wizAmit
parent 4a365a29d6
commit 45832383af
2 changed files with 34 additions and 0 deletions

View File

@ -4453,6 +4453,21 @@ impl<'a, T> DoubleEndedIterator for ChunksExact<'a, T> {
Some(snd)
}
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
let len = self.len();
if n >= len {
self.v = &[];
None
} else {
let start = (len - 1 - n) * self.chunk_size;
let end = start + self.chunk_size;
let nth_back = &self.v[start..end];
self.v = &self.v[..start];
Some(nth_back)
}
}
}
#[stable(feature = "chunks_exact", since = "1.31.0")]

View File

@ -275,6 +275,25 @@ fn test_chunks_exact_nth() {
assert_eq!(c2.next(), None);
}
#[test]
fn test_chunks_exact_nth_back() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let mut c = v.chunks_exact(2);
assert_eq!(c.nth_back(1).unwrap(), &[2, 3]);
assert_eq!(c.next().unwrap(), &[0, 1]);
assert_eq!(c.next(), None);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let mut c2 = v2.chunks_exact(3);
assert_eq!(c2.nth_back(0).unwrap(), &[0, 1, 2]);
assert_eq!(c2.next(), None);
assert_eq!(c2.next_back(), None);
let v3: &[i32] = &[0, 1, 2, 3, 4];
let mut c3 = v3.chunks_exact(10);
assert_eq!(c3.nth_back(0), None);
}
#[test]
fn test_chunks_exact_last() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];