1 use crate::iter::{FusedIterator, TrustedLen}; 2 use crate::ops::Try; 3 4 /// A double-ended iterator with the direction inverted. 5 /// 6 /// This `struct` is created by the [`rev`] method on [`Iterator`]. See its 7 /// documentation for more. 8 /// 9 /// [`rev`]: Iterator::rev 10 /// [`Iterator`]: trait.Iterator.html 11 #[derive(Clone, Debug)] 12 #[must_use = "iterators are lazy and do nothing unless consumed"] 13 #[stable(feature = "rust1", since = "1.0.0")] 14 pub struct Rev<T> { 15 iter: T, 16 } 17 18 impl<T> Rev<T> { new(iter: T) -> Rev<T>19 pub(in crate::iter) fn new(iter: T) -> Rev<T> { 20 Rev { iter } 21 } 22 } 23 24 #[stable(feature = "rust1", since = "1.0.0")] 25 impl<I> Iterator for Rev<I> 26 where 27 I: DoubleEndedIterator, 28 { 29 type Item = <I as Iterator>::Item; 30 31 #[inline] next(&mut self) -> Option<<I as Iterator>::Item>32 fn next(&mut self) -> Option<<I as Iterator>::Item> { 33 self.iter.next_back() 34 } 35 #[inline] size_hint(&self) -> (usize, Option<usize>)36 fn size_hint(&self) -> (usize, Option<usize>) { 37 self.iter.size_hint() 38 } 39 40 #[inline] advance_by(&mut self, n: usize) -> Result<(), usize>41 fn advance_by(&mut self, n: usize) -> Result<(), usize> { 42 self.iter.advance_back_by(n) 43 } 44 45 #[inline] nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>46 fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item> { 47 self.iter.nth_back(n) 48 } 49 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>,50 fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R 51 where 52 Self: Sized, 53 F: FnMut(B, Self::Item) -> R, 54 R: Try<Output = B>, 55 { 56 self.iter.try_rfold(init, f) 57 } 58 fold<Acc, F>(self, init: Acc, f: F) -> Acc where F: FnMut(Acc, Self::Item) -> Acc,59 fn fold<Acc, F>(self, init: Acc, f: F) -> Acc 60 where 61 F: FnMut(Acc, Self::Item) -> Acc, 62 { 63 self.iter.rfold(init, f) 64 } 65 66 #[inline] find<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool,67 fn find<P>(&mut self, predicate: P) -> Option<Self::Item> 68 where 69 P: FnMut(&Self::Item) -> bool, 70 { 71 self.iter.rfind(predicate) 72 } 73 } 74 75 #[stable(feature = "rust1", since = "1.0.0")] 76 impl<I> DoubleEndedIterator for Rev<I> 77 where 78 I: DoubleEndedIterator, 79 { 80 #[inline] next_back(&mut self) -> Option<<I as Iterator>::Item>81 fn next_back(&mut self) -> Option<<I as Iterator>::Item> { 82 self.iter.next() 83 } 84 85 #[inline] advance_back_by(&mut self, n: usize) -> Result<(), usize>86 fn advance_back_by(&mut self, n: usize) -> Result<(), usize> { 87 self.iter.advance_by(n) 88 } 89 90 #[inline] nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item>91 fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item> { 92 self.iter.nth(n) 93 } 94 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>,95 fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R 96 where 97 Self: Sized, 98 F: FnMut(B, Self::Item) -> R, 99 R: Try<Output = B>, 100 { 101 self.iter.try_fold(init, f) 102 } 103 rfold<Acc, F>(self, init: Acc, f: F) -> Acc where F: FnMut(Acc, Self::Item) -> Acc,104 fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc 105 where 106 F: FnMut(Acc, Self::Item) -> Acc, 107 { 108 self.iter.fold(init, f) 109 } 110 rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where P: FnMut(&Self::Item) -> bool,111 fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> 112 where 113 P: FnMut(&Self::Item) -> bool, 114 { 115 self.iter.find(predicate) 116 } 117 } 118 119 #[stable(feature = "rust1", since = "1.0.0")] 120 impl<I> ExactSizeIterator for Rev<I> 121 where 122 I: ExactSizeIterator + DoubleEndedIterator, 123 { len(&self) -> usize124 fn len(&self) -> usize { 125 self.iter.len() 126 } 127 is_empty(&self) -> bool128 fn is_empty(&self) -> bool { 129 self.iter.is_empty() 130 } 131 } 132 133 #[stable(feature = "fused", since = "1.26.0")] 134 impl<I> FusedIterator for Rev<I> where I: FusedIterator + DoubleEndedIterator {} 135 136 #[unstable(feature = "trusted_len", issue = "37572")] 137 unsafe impl<I> TrustedLen for Rev<I> where I: TrustedLen + DoubleEndedIterator {} 138