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Move rfold
logic into iter_rfold
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@ -393,6 +393,35 @@ impl<I, U> FlattenCompat<I, U>
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where
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where
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I: DoubleEndedIterator<Item: IntoIterator<IntoIter = U>>,
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I: DoubleEndedIterator<Item: IntoIterator<IntoIter = U>>,
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{
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{
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/// Folds the inner iterators into an accumulator by applying an operation, starting form the
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/// back.
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///
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/// Folds over the inner iterators, not over their elements. Is used by the `rfold` method.
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#[inline]
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fn iter_rfold<Acc, Fold>(self, mut acc: Acc, mut fold: Fold) -> Acc
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where
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Fold: FnMut(Acc, U) -> Acc,
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{
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#[inline]
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fn flatten<T: IntoIterator, Acc>(
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fold: &mut impl FnMut(Acc, T::IntoIter) -> Acc,
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) -> impl FnMut(Acc, T) -> Acc + '_ {
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move |acc, iter| fold(acc, iter.into_iter())
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}
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if let Some(iter) = self.backiter {
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acc = fold(acc, iter);
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}
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acc = self.iter.rfold(acc, flatten(&mut fold));
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if let Some(iter) = self.frontiter {
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acc = fold(acc, iter);
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}
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acc
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}
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/// Folds over the inner iterators in reverse order as long as the given function returns
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/// Folds over the inner iterators in reverse order as long as the given function returns
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/// successfully, always storing the most recent inner iterator in `self.backiter`.
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/// successfully, always storing the most recent inner iterator in `self.backiter`.
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///
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///
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@ -579,31 +608,18 @@ where
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}
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}
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#[inline]
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#[inline]
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fn rfold<Acc, Fold>(self, mut init: Acc, mut fold: Fold) -> Acc
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fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
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where
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where
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Fold: FnMut(Acc, Self::Item) -> Acc,
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Fold: FnMut(Acc, Self::Item) -> Acc,
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{
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{
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#[inline]
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#[inline]
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fn flatten<T: IntoIterator, Acc>(
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fn flatten<U: DoubleEndedIterator, Acc>(
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fold: &mut impl FnMut(Acc, T::Item) -> Acc,
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mut fold: impl FnMut(Acc, U::Item) -> Acc,
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) -> impl FnMut(Acc, T) -> Acc + '_
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) -> impl FnMut(Acc, U) -> Acc {
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where
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move |acc, iter| iter.rfold(acc, &mut fold)
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T::IntoIter: DoubleEndedIterator,
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{
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move |acc, x| x.into_iter().rfold(acc, &mut *fold)
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}
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}
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if let Some(back) = self.backiter {
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self.iter_rfold(init, flatten(fold))
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init = back.rfold(init, &mut fold);
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}
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init = self.iter.rfold(init, flatten(&mut fold));
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if let Some(front) = self.frontiter {
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init = front.rfold(init, &mut fold);
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}
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init
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}
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}
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#[inline]
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#[inline]
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