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Reduce genericity in FlattenCompat

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This commit is contained in:
Josh Stone 2019-07-11 14:03:48 -07:00
parent 40ecbc7b7d
commit 9ef95ff4a6
1 changed files with 52 additions and 26 deletions
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78
src/libcore/iter/adapters/flatten.rs
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@ -229,7 +229,7 @@ where
if let elt@Some(_) = inner.next() { return elt }
}
match self.iter.next() {
None => return self.backiter.as_mut().and_then(|it| it.next()),
None => return self.backiter.as_mut()?.next(),
Some(inner) => self.frontiter = Some(inner.into_iter()),
}
}
@ -237,8 +237,8 @@ where
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (flo, fhi) = self.frontiter.as_ref().map_or((0, Some(0)), |it| it.size_hint());
let (blo, bhi) = self.backiter.as_ref().map_or((0, Some(0)), |it| it.size_hint());
let (flo, fhi) = self.frontiter.as_ref().map_or((0, Some(0)), U::size_hint);
let (blo, bhi) = self.backiter.as_ref().map_or((0, Some(0)), U::size_hint);
let lo = flo.saturating_add(blo);
match (self.iter.size_hint(), fhi, bhi) {
((0, Some(0)), Some(a), Some(b)) => (lo, a.checked_add(b)),
@ -250,20 +250,25 @@ where
fn try_fold<Acc, Fold, R>(&mut self, mut init: Acc, mut fold: Fold) -> R where
Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc>
{
#[inline]
fn flatten<'a, T: IntoIterator, Acc, R: Try<Ok = Acc>>(
frontiter: &'a mut Option<T::IntoIter>,
fold: &'a mut impl FnMut(Acc, T::Item) -> R,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, x| {
let mut mid = x.into_iter();
let r = mid.try_fold(acc, &mut *fold);
*frontiter = Some(mid);
r
}
}
if let Some(ref mut front) = self.frontiter {
init = front.try_fold(init, &mut fold)?;
}
self.frontiter = None;
{
let frontiter = &mut self.frontiter;
init = self.iter.try_fold(init, |acc, x| {
let mut mid = x.into_iter();
let r = mid.try_fold(acc, &mut fold);
*frontiter = Some(mid);
r
})?;
}
init = self.iter.try_fold(init, flatten(&mut self.frontiter, &mut fold))?;
self.frontiter = None;
if let Some(ref mut back) = self.backiter {
@ -275,13 +280,20 @@ where
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
fn fold<Acc, Fold>(self, init: Acc, ref mut fold: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
#[inline]
fn flatten<U: Iterator, Acc>(
fold: &mut impl FnMut(Acc, U::Item) -> Acc,
) -> impl FnMut(Acc, U) -> Acc + '_ {
move |acc, iter| iter.fold(acc, &mut *fold)
}
self.frontiter.into_iter()
.chain(self.iter.map(IntoIterator::into_iter))
.chain(self.backiter)
.fold(init, |acc, iter| iter.fold(acc, &mut fold))
.fold(init, flatten(fold))
}
}
@ -297,7 +309,7 @@ where
if let elt@Some(_) = inner.next_back() { return elt }
}
match self.iter.next_back() {
None => return self.frontiter.as_mut().and_then(|it| it.next_back()),
None => return self.frontiter.as_mut()?.next_back(),
next => self.backiter = next.map(IntoIterator::into_iter),
}
}
@ -307,20 +319,27 @@ where
fn try_rfold<Acc, Fold, R>(&mut self, mut init: Acc, mut fold: Fold) -> R where
Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc>
{
#[inline]
fn flatten<'a, T: IntoIterator, Acc, R: Try<Ok = Acc>>(
backiter: &'a mut Option<T::IntoIter>,
fold: &'a mut impl FnMut(Acc, T::Item) -> R,
) -> impl FnMut(Acc, T) -> R + 'a where
T::IntoIter: DoubleEndedIterator,
{
move |acc, x| {
let mut mid = x.into_iter();
let r = mid.try_rfold(acc, &mut *fold);
*backiter = Some(mid);
r
}
}
if let Some(ref mut back) = self.backiter {
init = back.try_rfold(init, &mut fold)?;
}
self.backiter = None;
{
let backiter = &mut self.backiter;
init = self.iter.try_rfold(init, |acc, x| {
let mut mid = x.into_iter();
let r = mid.try_rfold(acc, &mut fold);
*backiter = Some(mid);
r
})?;
}
init = self.iter.try_rfold(init, flatten(&mut self.backiter, &mut fold))?;
self.backiter = None;
if let Some(ref mut front) = self.frontiter {
@ -332,12 +351,19 @@ where
}
#[inline]
fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
fn rfold<Acc, Fold>(self, init: Acc, ref mut fold: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
#[inline]
fn flatten<U: DoubleEndedIterator, Acc>(
fold: &mut impl FnMut(Acc, U::Item) -> Acc,
) -> impl FnMut(Acc, U) -> Acc + '_ {
move |acc, iter| iter.rfold(acc, &mut *fold)
}
self.frontiter.into_iter()
.chain(self.iter.map(IntoIterator::into_iter))
.chain(self.backiter)
.rfold(init, |acc, iter| iter.rfold(acc, &mut fold))
.rfold(init, flatten(fold))
}
}