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wip nth_back on chunks

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Signed-off-by: wizAmit <amitforfriends_dns@yahoo.com>
This commit is contained in:
@amit.chandra 2019-04-26 19:53:18 +05:30 • committed by wizAmit
parent 2080b86566
commit 29a103daa9
2 changed files with 0 additions and 36 deletions
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17
src/libcore/slice/mod.rs
View file

@ -4178,23 +4178,6 @@ impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
Some(snd)
}
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
let (end, overflow) = self.v.len().overflowing_sub(n * self.chunk_size);
if overflow {
self.v = &mut [];
None
} else {
let start = match end.checked_sub(self.chunk_size) {
Some(res) => cmp::min(self.v.len(), res),
None => 0,
};
let nth_back = &self.v[start..end];
self.v = &self.v[..start];
Some(nth_back)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]

19
src/libcore/tests/slice.rs
View file

@ -134,25 +134,6 @@ fn test_chunks_nth() {
assert_eq!(c2.next(), None);
}
#[test]
fn test_chunks_nth_back() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let mut c = v.chunks(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(3);
assert_eq!(c2.nth_back(1).unwrap(), &[0, 1]);
assert_eq!(c2.next(), None);
assert_eq!(c2.next_back(), None);
let v3: &[i32] = &[0, 1, 2, 3, 4];
let mut c3 = v3.chunks(10);
assert_eq!(c3.nth_back(0).unwrap(), &[0, 1, 2, 3, 4]);
assert_eq!(c3.next(), None);
}
#[test]
fn test_chunks_last() {