Trait rhit::__std_iter::ExactSizeIterator 1.0.0[−][src]
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 Iterator::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
pub fn len(&self) -> usize
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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
Iterator::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());
pub fn is_empty(&self) -> bool
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exact_size_is_empty
)Returns true
if the iterator is empty.
This method has a default implementation using
ExactSizeIterator::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<'a> ExactSizeIterator for CommandArgs<'a>
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impl<'_, K, V> ExactSizeIterator for Values<'_, K, V>
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impl<K, V> ExactSizeIterator for IntoIter<K, V>
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impl ExactSizeIterator for Args
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impl<'_, K> ExactSizeIterator for Drain<'_, K>
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impl ExactSizeIterator for ArgsOs
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impl<K, V> ExactSizeIterator for IntoKeys<K, V>
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impl<'_, K, V> ExactSizeIterator for Iter<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for Keys<'_, K, V>
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impl<'_, K, V> ExactSizeIterator for Drain<'_, K, V>
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impl<'a> ExactSizeIterator for CommandEnvs<'a>
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impl<'_, K, V> ExactSizeIterator for ValuesMut<'_, K, V>
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impl<K> ExactSizeIterator for IntoIter<K>
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impl<K, V> ExactSizeIterator for IntoValues<K, V>
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impl<'_, K> ExactSizeIterator for Iter<'_, K>
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impl<'_, K, V> ExactSizeIterator for IterMut<'_, K, V>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl<'_, T, const N: usize> ExactSizeIterator for ArrayChunks<'_, T, N>
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impl ExactSizeIterator for RangeInclusive<i8>
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impl<T> ExactSizeIterator for IntoIter<T>
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impl ExactSizeIterator for ToUppercase
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impl ExactSizeIterator for Range<u32>
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impl ExactSizeIterator for EscapeDebug
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impl<'_, T> ExactSizeIterator for RChunksMut<'_, T>
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impl<'_, T> ExactSizeIterator for ChunksExact<'_, T>
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impl ExactSizeIterator for Range<u16>
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impl<'_, T> ExactSizeIterator for ChunksExactMut<'_, T>
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impl<'_, I> ExactSizeIterator for &'_ mut I where
I: ExactSizeIterator + ?Sized,
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I: ExactSizeIterator + ?Sized,
impl ExactSizeIterator for ToLowercase
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impl<'_, T, const N: usize> ExactSizeIterator for ArrayWindows<'_, T, N>
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impl<'_, T> ExactSizeIterator for ChunksMut<'_, T>
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impl ExactSizeIterator for Range<u8>
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impl ExactSizeIterator for RangeInclusive<i16>
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impl ExactSizeIterator for EscapeDefault
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impl<'_, T> ExactSizeIterator for Chunks<'_, T>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl ExactSizeIterator for EscapeDefault
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impl<'_, T> ExactSizeIterator for RChunksExactMut<'_, T>
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impl ExactSizeIterator for Range<i16>
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impl<'_, A> ExactSizeIterator for IterMut<'_, A>
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impl ExactSizeIterator for Range<i32>
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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> ExactSizeIterator for Iter<'_, A>
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impl<T, const N: usize> ExactSizeIterator for IntoIter<T, N>
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impl<'_> ExactSizeIterator for Bytes<'_>
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impl ExactSizeIterator for Range<i8>
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impl<'_, T> ExactSizeIterator for Windows<'_, T>
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impl ExactSizeIterator for RangeInclusive<u8>
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impl<'_, T, const N: usize> ExactSizeIterator for ArrayChunksMut<'_, T, N>
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impl<A> ExactSizeIterator for IntoIter<A>
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impl<'a, T> ExactSizeIterator for RChunksExact<'a, T>
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impl ExactSizeIterator for RangeInclusive<u16>
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impl ExactSizeIterator for EscapeUnicode
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impl ExactSizeIterator for Range<isize>
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impl<'_, T> ExactSizeIterator for RChunks<'_, T>
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl<I, A> ExactSizeIterator for Box<I, A> where
A: Allocator,
I: ExactSizeIterator + ?Sized,
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A: Allocator,
I: ExactSizeIterator + ?Sized,
impl<K, V> ExactSizeIterator for IntoIter<K, V>
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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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 Values<'_, K, V>
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impl<T> ExactSizeIterator for IntoIter<T>
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impl<T> ExactSizeIterator for IntoIter<T>
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impl<'_, K, V> ExactSizeIterator for Iter<'_, K, V>
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impl<'_, I, A> ExactSizeIterator for Splice<'_, I, A> where
A: Allocator,
I: Iterator,
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A: Allocator,
I: Iterator,
impl<T, A> ExactSizeIterator for IntoIter<T, A> where
A: Allocator,
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A: Allocator,
impl<'_, K, V> ExactSizeIterator for IterMut<'_, K, V>
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impl<K, V> ExactSizeIterator for IntoKeys<K, V>
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impl<K, V> ExactSizeIterator for IntoValues<K, V>
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impl<'_, T, A> ExactSizeIterator for Drain<'_, T, A> where
A: Allocator,
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A: Allocator,
impl<T> ExactSizeIterator for IntoIter<T>
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl<T> ExactSizeIterator for IntoIterSorted<T> where
T: Ord,
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T: Ord,
impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl<'_, K, V> ExactSizeIterator for ValuesMut<'_, K, V>
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impl<'_, T> ExactSizeIterator for DrainSorted<'_, T> where
T: Ord,
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T: Ord,
impl<'_, K, V> ExactSizeIterator for Keys<'_, K, V>
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impl<'_, T> ExactSizeIterator for Drain<'_, T>
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impl<'_, T> ExactSizeIterator for Iter<'_, T>
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impl<'_, T> ExactSizeIterator for IterMut<'_, T>
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impl<A> ExactSizeIterator for IntoIter<A> where
A: Array,
A: Array,
impl<'a, T> ExactSizeIterator for Drain<'a, T> where
T: Array,
T: Array,
impl<'r> ExactSizeIterator for CaptureNames<'r>
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impl<'r> ExactSizeIterator for CaptureNames<'r>
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impl<T> ExactSizeIterator for CachedIntoIter<T> where
T: Send,
T: Send,
impl<T> ExactSizeIterator for IntoIter<T> where
T: Send,
T: Send,
impl<'_, T> ExactSizeIterator for IterMut<'_, T> where
T: Send,
T: Send,
impl<'a, T> ExactSizeIterator for CachedIterMut<'a, T> where
T: 'a + Send,
Loading content...T: 'a + Send,
Implementors
impl<'_> ExactSizeIterator for Chain<'_>
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impl<'a, I, T> ExactSizeIterator for Cloned<I> where
T: 'a + Clone,
I: ExactSizeIterator<Item = &'a T>,
1.1.0[src]
T: 'a + Clone,
I: ExactSizeIterator<Item = &'a T>,
impl<'a, I, T> ExactSizeIterator for Copied<I> where
T: 'a + Copy,
I: ExactSizeIterator<Item = &'a T>,
1.36.0[src]
T: 'a + Copy,
I: ExactSizeIterator<Item = &'a T>,
impl<A> ExactSizeIterator for RepeatN<A> where
A: Clone,
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A: Clone,
impl<A> ExactSizeIterator for rhit::Zip<(A,)> where
A: ExactSizeIterator,
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A: ExactSizeIterator,
impl<A, B> ExactSizeIterator for rhit::__std_iter::Zip<A, B> where
A: ExactSizeIterator,
B: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B> ExactSizeIterator for rhit::Zip<(A, B)> where
A: ExactSizeIterator,
B: ExactSizeIterator,
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A: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C> ExactSizeIterator for rhit::Zip<(A, B, C)> where
C: ExactSizeIterator,
A: ExactSizeIterator,
B: ExactSizeIterator,
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C: ExactSizeIterator,
A: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C, D> ExactSizeIterator for rhit::Zip<(A, B, C, D)> where
C: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
B: ExactSizeIterator,
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C: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C, D, E> ExactSizeIterator for rhit::Zip<(A, B, C, D, E)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
B: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C, D, E, F> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
B: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C, D, E, F, G> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G, H)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
H: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H, I> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G, H, I)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
H: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H, I, J> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G, H, I, J)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H, I, J, K> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G, H, I, J, K)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
K: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
K: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, B, C, D, E, F, G, H, I, J, K, L> ExactSizeIterator for rhit::Zip<(A, B, C, D, E, F, G, H, I, J, K, L)> where
C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
K: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
L: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
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C: ExactSizeIterator,
E: ExactSizeIterator,
A: ExactSizeIterator,
D: ExactSizeIterator,
K: ExactSizeIterator,
I: ExactSizeIterator,
F: ExactSizeIterator,
G: ExactSizeIterator,
L: ExactSizeIterator,
B: ExactSizeIterator,
J: ExactSizeIterator,
H: ExactSizeIterator,
impl<A, F> ExactSizeIterator for OnceWith<F> where
F: FnOnce() -> A,
1.43.0[src]
F: FnOnce() -> A,
impl<B, I, F> ExactSizeIterator for Map<I, F> where
I: ExactSizeIterator,
F: FnMut(<I as Iterator>::Item) -> B,
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I: ExactSizeIterator,
F: FnMut(<I as Iterator>::Item) -> B,
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,
1.28.0[src]
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 PeekNth<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
I: ExactSizeIterator,
F: FnMut(&<I as Iterator>::Item),
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I: ExactSizeIterator,
F: FnMut(&<I as Iterator>::Item),
impl<I, F> ExactSizeIterator for PadUsing<I, F> where
I: ExactSizeIterator,
F: FnMut(usize) -> <I as Iterator>::Item,
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I: ExactSizeIterator,
F: FnMut(usize) -> <I as Iterator>::Item,
impl<I, F> ExactSizeIterator for Update<I, F> where
I: ExactSizeIterator,
F: FnMut(&mut <I as Iterator>::Item),
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I: ExactSizeIterator,
F: FnMut(&mut <I as Iterator>::Item),
impl<I, J> ExactSizeIterator for ZipEq<I, J> where
I: ExactSizeIterator,
J: ExactSizeIterator,
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I: ExactSizeIterator,
J: ExactSizeIterator,
impl<L, R> ExactSizeIterator for Either<L, R> where
R: ExactSizeIterator<Item = <L as Iterator>::Item>,
L: ExactSizeIterator,
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R: ExactSizeIterator<Item = <L as Iterator>::Item>,
L: ExactSizeIterator,
impl<T> ExactSizeIterator for Empty<T>
1.2.0[src]
impl<T> ExactSizeIterator for Once<T>
1.2.0[src]
impl<T> ExactSizeIterator for TupleBuffer<T> where
T: HomogeneousTuple,
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T: HomogeneousTuple,
impl<T, U> ExactSizeIterator for ZipLongest<T, U> where
T: ExactSizeIterator,
U: ExactSizeIterator,
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T: ExactSizeIterator,
U: ExactSizeIterator,