Trait std::iter::DoubleEndedIterator 1.0.0
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[src]
pub trait DoubleEndedIterator: Iterator {
fn next_back(&mut self) -> Option<Self::Item>;
fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item>
where
P: FnMut(&Self::Item) -> bool,
{ ... }
}An iterator able to yield elements from both ends.
Something that implements DoubleEndedIterator has one extra capability
over something that implements Iterator: the ability to also take
Items from the back, as well as the front.
It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle.
In a similar fashion to the Iterator protocol, once a
DoubleEndedIterator returns None from a next_back(), calling it again
may or may not ever return Some again. next() and next_back() are
interchangeable for this purpose.
Examples
Basic usage:
let numbers = vec![1, 2, 3, 4, 5, 6]; let mut iter = numbers.iter(); assert_eq!(Some(&1), iter.next()); assert_eq!(Some(&6), iter.next_back()); assert_eq!(Some(&5), iter.next_back()); assert_eq!(Some(&2), iter.next()); assert_eq!(Some(&3), iter.next()); assert_eq!(Some(&4), iter.next()); assert_eq!(None, iter.next()); assert_eq!(None, iter.next_back());Run
Required Methods
fn next_back(&mut self) -> Option<Self::Item>
Removes and returns an element from the end of the iterator.
Returns None when there are no more elements.
The trait-level docs contain more details.
Examples
Basic usage:
let numbers = vec![1, 2, 3, 4, 5, 6]; let mut iter = numbers.iter(); assert_eq!(Some(&1), iter.next()); assert_eq!(Some(&6), iter.next_back()); assert_eq!(Some(&5), iter.next_back()); assert_eq!(Some(&2), iter.next()); assert_eq!(Some(&3), iter.next()); assert_eq!(Some(&4), iter.next()); assert_eq!(None, iter.next()); assert_eq!(None, iter.next_back());Run
Provided Methods
fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,
P: FnMut(&Self::Item) -> bool,
Searches for an element of an iterator from the right that satisfies a predicate.
rfind() takes a closure that returns true or false. It applies
this closure to each element of the iterator, starting at the end, and if any
of them return true, then rfind() returns Some(element). If they all return
false, it returns None.
rfind() is short-circuiting; in other words, it will stop processing
as soon as the closure returns true.
Because rfind() takes a reference, and many iterators iterate over
references, this leads to a possibly confusing situation where the
argument is a double reference. You can see this effect in the
examples below, with &&x.
Examples
Basic usage:
#![feature(iter_rfind)] let a = [1, 2, 3]; assert_eq!(a.iter().rfind(|&&x| x == 2), Some(&2)); assert_eq!(a.iter().rfind(|&&x| x == 5), None);Run
Stopping at the first true:
#![feature(iter_rfind)] let a = [1, 2, 3]; let mut iter = a.iter(); assert_eq!(iter.rfind(|&&x| x == 2), Some(&2)); // we can still use `iter`, as there are more elements. assert_eq!(iter.next_back(), Some(&1));Run
Implementors
impl<'a> DoubleEndedIterator for SplitWhitespace<'a>impl<'a, T> DoubleEndedIterator for std::collections::btree_set::Range<'a, T>impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V>impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V>impl<'a, K, V> DoubleEndedIterator for std::collections::btree_map::Iter<'a, K, V> where
K: 'a,
V: 'a,impl<'a> DoubleEndedIterator for std::string::Drain<'a>impl<T> DoubleEndedIterator for std::collections::vec_deque::IntoIter<T>impl<'a, T> DoubleEndedIterator for std::collections::binary_heap::Drain<'a, T> where
T: 'a,impl<'a, T> DoubleEndedIterator for std::collections::linked_list::IterMut<'a, T>impl<'a, 'b> DoubleEndedIterator for std::string::Splice<'a, 'b>impl<T> DoubleEndedIterator for std::collections::binary_heap::IntoIter<T>impl<'a, T> DoubleEndedIterator for std::collections::vec_deque::IterMut<'a, T>impl<T> DoubleEndedIterator for std::vec::IntoIter<T>impl<'a, T> DoubleEndedIterator for std::collections::btree_set::Iter<'a, T>impl<'a, T> DoubleEndedIterator for std::collections::linked_list::Iter<'a, T>impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V>impl<'a, T> DoubleEndedIterator for std::collections::binary_heap::Iter<'a, T>impl<'a, I> DoubleEndedIterator for std::vec::Splice<'a, I> where
I: Iterator,impl<'a, T> DoubleEndedIterator for std::collections::vec_deque::Drain<'a, T> where
T: 'a,impl<'a, T> DoubleEndedIterator for std::vec::Drain<'a, T>impl<T> DoubleEndedIterator for std::collections::btree_set::IntoIter<T>impl<I> DoubleEndedIterator for Box<I> where
I: DoubleEndedIterator + ?Sized,impl<'a, K, V> DoubleEndedIterator for std::collections::btree_map::IterMut<'a, K, V> where
K: 'a,
V: 'a,impl<'a, T> DoubleEndedIterator for std::collections::vec_deque::Iter<'a, T>impl<T> DoubleEndedIterator for std::collections::linked_list::IntoIter<T>impl<K, V> DoubleEndedIterator for std::collections::btree_map::IntoIter<K, V>impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V>impl<'a, K, V> DoubleEndedIterator for std::collections::btree_map::Range<'a, K, V>impl<A, B> DoubleEndedIterator for Zip<A, B> where
A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator,impl<A> DoubleEndedIterator for Repeat<A> where
A: Clone,impl<'a, P> DoubleEndedIterator for MatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<I> DoubleEndedIterator for Fuse<I> where
I: DoubleEndedIterator,impl<I> DoubleEndedIterator for Enumerate<I> where
I: ExactSizeIterator + DoubleEndedIterator,impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
P: FnMut(&T) -> bool,impl<A> DoubleEndedIterator for std::option::IntoIter<A>impl<'a, A> DoubleEndedIterator for std::option::Iter<'a, A>impl<'a> DoubleEndedIterator for Bytes<'a>impl<'a, A> DoubleEndedIterator for std::option::IterMut<'a, A>impl<'a, T, P> DoubleEndedIterator for std::slice::Split<'a, T, P> where
P: FnMut(&T) -> bool,impl<'a, P> DoubleEndedIterator for Matches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<'a, T> DoubleEndedIterator for std::slice::IterMut<'a, T>impl<I> DoubleEndedIterator for Fuse<I> where
I: DoubleEndedIterator + FusedIterator,impl<'a, T, P> DoubleEndedIterator for std::slice::RSplit<'a, T, P> where
P: FnMut(&T) -> bool,impl<I, F> DoubleEndedIterator for Inspect<I, F> where
F: FnMut(&<I as Iterator>::Item) -> (),
I: DoubleEndedIterator,impl<'a, P> DoubleEndedIterator for RMatchIndices<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<'a, T> DoubleEndedIterator for Chunks<'a, T>impl<I> DoubleEndedIterator for Skip<I> where
I: DoubleEndedIterator + ExactSizeIterator,impl<I, U, F> DoubleEndedIterator for FlatMap<I, U, F> where
F: FnMut(<I as Iterator>::Item) -> U,
I: DoubleEndedIterator,
U: IntoIterator,
<U as IntoIterator>::IntoIter: DoubleEndedIterator,impl<I> DoubleEndedIterator for Rev<I> where
I: DoubleEndedIterator,impl<A> DoubleEndedIterator for std::ops::Range<A> where
A: Step,impl<'a, P> DoubleEndedIterator for SplitTerminator<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<T> DoubleEndedIterator for Empty<T>impl<'a, T> DoubleEndedIterator for std::result::IterMut<'a, T>impl<T> DoubleEndedIterator for std::result::IntoIter<T>impl<'a> DoubleEndedIterator for Lines<'a>impl<'a, P> DoubleEndedIterator for RSplitTerminator<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<'a, I, T> DoubleEndedIterator for Cloned<I> where
I: DoubleEndedIterator<Item = &'a T>,
T: 'a + Clone,impl<'a, T> DoubleEndedIterator for std::result::Iter<'a, T>impl<I, P> DoubleEndedIterator for Filter<I, P> where
I: DoubleEndedIterator,
P: FnMut(&<I as Iterator>::Item) -> bool,impl<'a> DoubleEndedIterator for CharIndices<'a>impl<'a> DoubleEndedIterator for LinesAny<'a>impl<A> DoubleEndedIterator for RangeInclusive<A> where
A: Step,impl<'a, P> DoubleEndedIterator for std::str::Split<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<'a, P> DoubleEndedIterator for RMatches<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<B, I, F> DoubleEndedIterator for FilterMap<I, F> where
F: FnMut(<I as Iterator>::Item) -> Option<B>,
I: DoubleEndedIterator,impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T>impl<'a, T> DoubleEndedIterator for Windows<'a, T>impl<'a, I> DoubleEndedIterator for &'a mut I where
I: DoubleEndedIterator + ?Sized,impl<'a> DoubleEndedIterator for Chars<'a>impl<'a, P> DoubleEndedIterator for std::str::RSplit<'a, P> where
P: Pattern<'a>,
<P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
P: FnMut(&T) -> bool,impl<'a, T> DoubleEndedIterator for std::slice::Iter<'a, T>impl<B, I, F> DoubleEndedIterator for Map<I, F> where
F: FnMut(<I as Iterator>::Item) -> B,
I: DoubleEndedIterator,impl<T> DoubleEndedIterator for Once<T>impl<A, B> DoubleEndedIterator for Chain<A, B> where
A: DoubleEndedIterator,
B: DoubleEndedIterator<Item = <A as Iterator>::Item>,impl DoubleEndedIterator for EscapeDefaultimpl DoubleEndedIterator for Argsimpl DoubleEndedIterator for ArgsOsimpl<'a> DoubleEndedIterator for std::path::Iter<'a>impl<'a> DoubleEndedIterator for Components<'a>