| use crate::iter::{FusedIterator, TrustedLen}; |
| use crate::ops::Try; |
| |
| /// A double-ended iterator with the direction inverted. |
| /// |
| /// This `struct` is created by the [`rev`] method on [`Iterator`]. See its |
| /// documentation for more. |
| /// |
| /// [`rev`]: Iterator::rev |
| /// [`Iterator`]: trait.Iterator.html |
| #[derive(Clone, Debug)] |
| #[must_use = "iterators are lazy and do nothing unless consumed"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub struct Rev<T> { |
| iter: T, |
| } |
| |
| impl<T> Rev<T> { |
| pub(in crate::iter) fn new(iter: T) -> Rev<T> { |
| Rev { iter } |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<I> Iterator for Rev<I> |
| where |
| I: DoubleEndedIterator, |
| { |
| type Item = <I as Iterator>::Item; |
| |
| #[inline] |
| fn next(&mut self) -> Option<<I as Iterator>::Item> { |
| self.iter.next_back() |
| } |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.iter.size_hint() |
| } |
| |
| #[inline] |
| fn advance_by(&mut self, n: usize) -> Result<(), usize> { |
| self.iter.advance_back_by(n) |
| } |
| |
| #[inline] |
| fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item> { |
| self.iter.nth_back(n) |
| } |
| |
| fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R |
| where |
| Self: Sized, |
| F: FnMut(B, Self::Item) -> R, |
| R: Try<Output = B>, |
| { |
| self.iter.try_rfold(init, f) |
| } |
| |
| fn fold<Acc, F>(self, init: Acc, f: F) -> Acc |
| where |
| F: FnMut(Acc, Self::Item) -> Acc, |
| { |
| self.iter.rfold(init, f) |
| } |
| |
| #[inline] |
| fn find<P>(&mut self, predicate: P) -> Option<Self::Item> |
| where |
| P: FnMut(&Self::Item) -> bool, |
| { |
| self.iter.rfind(predicate) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<I> DoubleEndedIterator for Rev<I> |
| where |
| I: DoubleEndedIterator, |
| { |
| #[inline] |
| fn next_back(&mut self) -> Option<<I as Iterator>::Item> { |
| self.iter.next() |
| } |
| |
| #[inline] |
| fn advance_back_by(&mut self, n: usize) -> Result<(), usize> { |
| self.iter.advance_by(n) |
| } |
| |
| #[inline] |
| fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item> { |
| self.iter.nth(n) |
| } |
| |
| fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R |
| where |
| Self: Sized, |
| F: FnMut(B, Self::Item) -> R, |
| R: Try<Output = B>, |
| { |
| self.iter.try_fold(init, f) |
| } |
| |
| fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc |
| where |
| F: FnMut(Acc, Self::Item) -> Acc, |
| { |
| self.iter.fold(init, f) |
| } |
| |
| fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> |
| where |
| P: FnMut(&Self::Item) -> bool, |
| { |
| self.iter.find(predicate) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<I> ExactSizeIterator for Rev<I> |
| where |
| I: ExactSizeIterator + DoubleEndedIterator, |
| { |
| fn len(&self) -> usize { |
| self.iter.len() |
| } |
| |
| fn is_empty(&self) -> bool { |
| self.iter.is_empty() |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<I> FusedIterator for Rev<I> where I: FusedIterator + DoubleEndedIterator {} |
| |
| #[unstable(feature = "trusted_len", issue = "37572")] |
| unsafe impl<I> TrustedLen for Rev<I> where I: TrustedLen + DoubleEndedIterator {} |