bjoernager/rust
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- Simplify nth() by making use of the fact that the slice is evenly
  divisible by the chunk size, and calling next() instead of
  duplicating it
- Call next_back() in last(), they are equivalent
- Implement ExactSizeIterator::is_empty()
This commit is contained in:
Sebastian Dröge 2018-01-02 23:54:42 +02:00
parent e51a89a0ad
commit aa0c08a22c
1 changed files with 23 additions and 44 deletions
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65
src/libcore/slice/mod.rs
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@ -2448,30 +2448,16 @@ impl<'a, T> Iterator for ExactChunks<'a, T> {
self.v = &[];
None
} else {
let end = match start.checked_add(self.chunk_size) {
Some(sum) => cmp::min(self.v.len(), sum),
None => self.v.len(),
};
if end - start != self.chunk_size {
self.v = &[];
None
} else {
let nth = &self.v[start..end];
self.v = &self.v[end..];
Some(nth)
}
let (_, snd) = self.v.split_at(start);
self.v = snd;
assert!(self.v.len() == self.chunk_size);
self.next()
}
}
#[inline]
fn last(self) -> Option<Self::Item> {
if self.v.len() < self.chunk_size {
None
} else {
let start = self.v.len() - self.chunk_size;
Some(&self.v[start..])
}
fn last(mut self) -> Option<Self::Item> {
self.next_back()
}
}
@ -2490,7 +2476,11 @@ impl<'a, T> DoubleEndedIterator for ExactChunks<'a, T> {
}
#[unstable(feature = "exact_chunks", issue = "47115")]
impl<'a, T> ExactSizeIterator for ExactChunks<'a, T> {}
impl<'a, T> ExactSizeIterator for ExactChunks<'a, T> {
fn is_empty(&self) -> bool {
self.v.is_empty()
}
}
#[unstable(feature = "fused", issue = "35602")]
impl<'a, T> FusedIterator for ExactChunks<'a, T> {}
@ -2543,33 +2533,18 @@ impl<'a, T> Iterator for ExactChunksMut<'a, T> {
if start >= self.v.len() || overflow {
self.v = &mut [];
None
} else {
let end = match start.checked_add(self.chunk_size) {
Some(sum) => cmp::min(self.v.len(), sum),
None => self.v.len(),
};
if end - start != self.chunk_size {
self.v = &mut [];
None
} else {
let tmp = mem::replace(&mut self.v, &mut []);
let (head, tail) = tmp.split_at_mut(end);
let (_, nth) = head.split_at_mut(start);
self.v = tail;
Some(nth)
}
let (_, snd) = tmp.split_at_mut(start);
self.v = snd;
assert!(self.v.len() == self.chunk_size);
self.next()
}
}
#[inline]
fn last(self) -> Option<Self::Item> {
if self.v.len() < self.chunk_size {
None
} else {
let start = (self.v.len() - self.chunk_size) / self.chunk_size * self.chunk_size;
Some(&mut self.v[start..])
}
fn last(mut self) -> Option<Self::Item> {
self.next_back()
}
}
@ -2590,7 +2565,11 @@ impl<'a, T> DoubleEndedIterator for ExactChunksMut<'a, T> {
}
#[unstable(feature = "exact_chunks", issue = "47115")]
impl<'a, T> ExactSizeIterator for ExactChunksMut<'a, T> {}
impl<'a, T> ExactSizeIterator for ExactChunksMut<'a, T> {
fn is_empty(&self) -> bool {
self.v.is_empty()
}
}
#[unstable(feature = "fused", issue = "35602")]
impl<'a, T> FusedIterator for ExactChunksMut<'a, T> {}