1.0.0[−][src]Trait competitive_hpp::prelude::__std_iter::ExactSizeIterator
An iterator that knows its exact length.
Many Iterator
s don't know how many times they will iterate, but some do.
If an iterator knows how many times it can iterate, providing access to
that information can be useful. For example, if you want to iterate
backwards, a good start is to know where the end is.
When implementing an ExactSizeIterator
, you must also implement
Iterator
. When doing so, the implementation of size_hint
must
return the exact size of the iterator.
The len
method has a default implementation, so you usually shouldn't
implement it. However, you may be able to provide a more performant
implementation than the default, so overriding it in this case makes sense.
Examples
Basic usage:
// a finite range knows exactly how many times it will iterate let five = 0..5; assert_eq!(5, five.len());
In the module level docs, we implemented an Iterator
,
Counter
. Let's implement ExactSizeIterator
for it as well:
impl ExactSizeIterator for Counter { // We can easily calculate the remaining number of iterations. fn len(&self) -> usize { 5 - self.count } } // And now we can use it! let counter = Counter::new(); assert_eq!(5, counter.len());
Provided methods
fn len(&self) -> usize
Returns the exact length of the iterator.
The implementation ensures that the iterator will return exactly len()
more times a Some(T)
value, before returning None
.
This method has a default implementation, so you usually should not
implement it directly. However, if you can provide a more efficient
implementation, you can do so. See the trait-level docs for an
example.
This function has the same safety guarantees as the size_hint
function.
Examples
Basic usage:
// a finite range knows exactly how many times it will iterate let five = 0..5; assert_eq!(5, five.len());
fn is_empty(&self) -> bool
exact_size_is_empty
)Returns true
if the iterator is empty.
This method has a default implementation using self.len()
, so you
don't need to implement it yourself.
Examples
Basic usage:
#![feature(exact_size_is_empty)] let mut one_element = std::iter::once(0); assert!(!one_element.is_empty()); assert_eq!(one_element.next(), Some(0)); assert!(one_element.is_empty()); assert_eq!(one_element.next(), None);
Implementations on Foreign Types
impl ExactSizeIterator for Args
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impl ExactSizeIterator for ArgsOs
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl ExactSizeIterator for RangeInclusive<u16>
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impl ExactSizeIterator for EscapeUnicode
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impl<'_, T> ExactSizeIterator for RChunks<'_, T>
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impl<'_, T> ExactSizeIterator for Windows<'_, T>
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impl<'_, T> ExactSizeIterator for RChunksExactMut<'_, T>
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impl<'_, A> ExactSizeIterator for Iter<'_, A>
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impl<'_, T> ExactSizeIterator for ChunksMut<'_, T>
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impl ExactSizeIterator for Range<isize>
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impl ExactSizeIterator for RangeInclusive<i16>
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impl<const N: usize, T> ExactSizeIterator for IntoIter<T, N> where
[T; N]: LengthAtMost32,
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[T; N]: LengthAtMost32,
impl ExactSizeIterator for Range<i8>
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impl<A> ExactSizeIterator for IntoIter<A>
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impl ExactSizeIterator for EscapeDefault
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impl<'_, T> ExactSizeIterator for ChunksExact<'_, T>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl ExactSizeIterator for Range<u8>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl<'_, A> ExactSizeIterator for IterMut<'_, A>
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impl ExactSizeIterator for ToLowercase
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impl ExactSizeIterator for RangeInclusive<u8>
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impl ExactSizeIterator for EscapeDefault
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impl ExactSizeIterator for Range<i16>
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impl<T> ExactSizeIterator for IntoIter<T>
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impl<'_> ExactSizeIterator for Bytes<'_>
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impl ExactSizeIterator for Range<i32>
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impl ExactSizeIterator for Range<u16>
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impl<'_, T> ExactSizeIterator for ChunksExactMut<'_, T>
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impl ExactSizeIterator for EscapeDebug
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impl ExactSizeIterator for ToUppercase
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impl ExactSizeIterator for Range<u32>
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impl<'_, T> ExactSizeIterator for Chunks<'_, T>
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl ExactSizeIterator for Range<usize>
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impl<'a, T> ExactSizeIterator for RChunksExact<'a, T>
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impl<'_, T> ExactSizeIterator for RChunksMut<'_, T>
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impl ExactSizeIterator for RangeInclusive<i8>
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impl<'_, I> ExactSizeIterator for &'_ mut I where
I: ExactSizeIterator + ?Sized,
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I: ExactSizeIterator + ?Sized,
impl<'_, I> ExactSizeIterator for Splice<'_, I> where
I: Iterator,
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I: Iterator,
impl<I> ExactSizeIterator for Box<I> where
I: ExactSizeIterator + ?Sized,
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I: ExactSizeIterator + ?Sized,
impl<T> ExactSizeIterator for IntoIter<T>
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impl<'_, T> ExactSizeIterator for Drain<'_, T>
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impl<'_, K, V> ExactSizeIterator for Keys<'_, K, V>
impl<'_, K, V> ExactSizeIterator for IterMut<'_, K, V>
impl<'_, K, V> ExactSizeIterator for ValuesMut<'_, K, V>
impl<'_, K, V> ExactSizeIterator for Values<'_, K, V>
impl<K> ExactSizeIterator for IntoIter<K>
impl<'_, K, V> ExactSizeIterator for Drain<'_, K, V>
impl<'_, K> ExactSizeIterator for Drain<'_, K>
impl<'_, K, V> ExactSizeIterator for Iter<'_, K, V>
impl<'a, K> ExactSizeIterator for Iter<'a, K>
impl<K, V> ExactSizeIterator for IntoIter<K, V>
impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V>
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impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V>
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impl<K, V> ExactSizeIterator for IntoIter<K, V>
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impl<'a, K, V> ExactSizeIterator for ValuesMut<'a, K, V>
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impl<'a, K, V> ExactSizeIterator for Values<'a, K, V>
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impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V>
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impl<'a, T> ExactSizeIterator for Iter<'a, T>
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impl<T> ExactSizeIterator for IntoIter<T>
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Implementors
impl<'_, K> ExactSizeIterator for competitive_hpp::prelude::hash_set::Drain<'_, K>
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impl<'_, K> ExactSizeIterator for competitive_hpp::prelude::hash_set::Iter<'_, K>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::Iter<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::IterMut<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::Keys<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::Values<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::ValuesMut<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::Drain<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::Iter<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::IterMut<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::Keys<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::Values<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::ValuesMut<'_, K, V>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::binary_heap::Drain<'_, T>
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impl<'_, T> ExactSizeIterator for DrainSorted<'_, T> where
T: Ord,
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T: Ord,
impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::binary_heap::Iter<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::btree_set::Iter<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::linked_list::Iter<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::linked_list::IterMut<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::vec_deque::Drain<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::vec_deque::Iter<'_, T>
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impl<'_, T> ExactSizeIterator for competitive_hpp::prelude::vec_deque::IterMut<'_, T>
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impl<'a, I, T> ExactSizeIterator for Cloned<I> where
I: ExactSizeIterator<Item = &'a T>,
T: 'a + Clone,
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I: ExactSizeIterator<Item = &'a T>,
T: 'a + Clone,
impl<'a, I, T> ExactSizeIterator for Copied<I> where
I: ExactSizeIterator<Item = &'a T>,
T: 'a + Copy,
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I: ExactSizeIterator<Item = &'a T>,
T: 'a + Copy,
impl<A> ExactSizeIterator for RepeatN<A> where
A: Clone,
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A: Clone,
impl<A> ExactSizeIterator for competitive_hpp::prelude::Zip<(A,)> where
A: ExactSizeIterator,
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A: ExactSizeIterator,
impl<A, B> ExactSizeIterator for competitive_hpp::prelude::__std_iter::Zip<A, B> where
A: ExactSizeIterator,
B: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
impl<A, B, C, D> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C, D)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
impl<A, B, C, D, E> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C, D, E)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
impl<A, B, C, D, E, F> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C, D, E, F)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
impl<A, B, C, D, E, F, G> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C, D, E, F, G)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H> ExactSizeIterator for competitive_hpp::prelude::Zip<(A, B, C, D, E, F, G, H)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
H: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
C: ExactSizeIterator,
D: ExactSizeIterator,
E: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, F> ExactSizeIterator for OnceWith<F> where
F: FnOnce() -> A,
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F: FnOnce() -> A,
impl<B, I, F> ExactSizeIterator for Map<I, F> where
F: FnMut(<I as Iterator>::Item) -> B,
I: ExactSizeIterator,
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F: FnMut(<I as Iterator>::Item) -> B,
I: ExactSizeIterator,
impl<F> ExactSizeIterator for Linspace<F> where
Linspace<F>: Iterator,
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Linspace<F>: Iterator,
impl<I> ExactSizeIterator for Enumerate<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Fuse<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Peekable<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Rev<I> where
I: ExactSizeIterator + DoubleEndedIterator,
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I: ExactSizeIterator + DoubleEndedIterator,
impl<I> ExactSizeIterator for Skip<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for StepBy<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Take<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for ExactlyOneError<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for MultiPeek<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Step<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I> ExactSizeIterator for Tee<I> where
I: ExactSizeIterator,
<I as Iterator>::Item: Clone,
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I: ExactSizeIterator,
<I as Iterator>::Item: Clone,
impl<I> ExactSizeIterator for WithPosition<I> where
I: ExactSizeIterator,
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I: ExactSizeIterator,
impl<I, F> ExactSizeIterator for Inspect<I, F> where
F: FnMut(&<I as Iterator>::Item),
I: ExactSizeIterator,
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F: FnMut(&<I as Iterator>::Item),
I: ExactSizeIterator,
impl<I, F> ExactSizeIterator for PadUsing<I, F> where
F: FnMut(usize) -> <I as Iterator>::Item,
I: ExactSizeIterator,
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F: FnMut(usize) -> <I as Iterator>::Item,
I: ExactSizeIterator,
impl<I, F> ExactSizeIterator for Update<I, F> where
F: FnMut(&mut <I as Iterator>::Item),
I: ExactSizeIterator,
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F: FnMut(&mut <I as Iterator>::Item),
I: ExactSizeIterator,
impl<I, J> ExactSizeIterator for ZipEq<I, J> where
I: ExactSizeIterator,
J: ExactSizeIterator,
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I: ExactSizeIterator,
J: ExactSizeIterator,
impl<I, R> ExactSizeIterator for MapInto<I, R> where
I: ExactSizeIterator,
<I as Iterator>::Item: Into<R>,
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I: ExactSizeIterator,
<I as Iterator>::Item: Into<R>,
impl<I, S> ExactSizeIterator for Cumsum<I, S> where
I: Iterator,
S: Add<<I as Iterator>::Item, Output = S> + Zero + Clone,
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I: Iterator,
S: Add<<I as Iterator>::Item, Output = S> + Zero + Clone,
impl<K> ExactSizeIterator for competitive_hpp::prelude::hash_set::IntoIter<K>
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impl<K, V> ExactSizeIterator for competitive_hpp::prelude::btree_map::IntoIter<K, V>
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impl<K, V> ExactSizeIterator for competitive_hpp::prelude::hash_map::IntoIter<K, V>
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impl<L, R> ExactSizeIterator for Either<L, R> where
L: ExactSizeIterator,
R: ExactSizeIterator<Item = <L as Iterator>::Item>,
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L: ExactSizeIterator,
R: ExactSizeIterator<Item = <L as Iterator>::Item>,
impl<T> ExactSizeIterator for Empty<T>
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impl<T> ExactSizeIterator for Once<T>
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impl<T> ExactSizeIterator for competitive_hpp::prelude::binary_heap::IntoIter<T>
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impl<T> ExactSizeIterator for IntoIterSorted<T> where
T: Ord,
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T: Ord,
impl<T> ExactSizeIterator for competitive_hpp::prelude::btree_set::IntoIter<T>
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impl<T> ExactSizeIterator for competitive_hpp::prelude::linked_list::IntoIter<T>
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impl<T> ExactSizeIterator for TupleBuffer<T> where
T: HomogeneousTuple,
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T: HomogeneousTuple,
impl<T> ExactSizeIterator for competitive_hpp::prelude::vec_deque::IntoIter<T>
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impl<T, U> ExactSizeIterator for ZipLongest<T, U> where
T: ExactSizeIterator,
U: ExactSizeIterator,
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T: ExactSizeIterator,
U: ExactSizeIterator,