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<p class='location'>Trait ExactSizeIterator</p><div class="block items"><ul><li><a href="#provided-methods">Provided Methods</a></li><li><a href="#implementors">Implementors</a></li></ul></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>iter</a></p><script>window.sidebarCurrent = {name: 'ExactSizeIterator', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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<h1 class='fqn'><span class='in-band'>Trait <a href='../index.html'>std</a>::<wbr><a href='index.html'>iter</a>::<wbr><a class="trait" href=''>ExactSizeIterator</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>−</span>]
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</span><a class='srclink' href='../../src/core/iter/traits.rs.html#552-613' title='goto source code'>[src]</a></span></h1>
<pre class='rust trait'>pub trait ExactSizeIterator: <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> {
fn <a href='#method.len' class='fnname'>len</a>(&self) -> <a class="primitive" href="../primitive.usize.html">usize</a> { ... }
fn <a href='#method.is_empty' class='fnname'>is_empty</a>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a> { ... }
}</pre><div class='docblock'><p>An iterator that knows its exact length.</p>
<p>Many <a href="trait.Iterator.html"><code>Iterator</code></a>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.</p>
<p>When implementing an <code>ExactSizeIterator</code>, You must also implement
<a href="trait.Iterator.html"><code>Iterator</code></a>. When doing so, the implementation of <a href="trait.Iterator.html#method.size_hint"><code>size_hint</code></a> <em>must</em>
return the exact size of the iterator.</p>
<p>The <a href="#method.len"><code>len</code></a> 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.</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<p>Basic usage:</p>
<pre class="rust rust-example-rendered">
<span class="comment">// a finite range knows exactly how many times it will iterate</span>
<span class="kw">let</span> <span class="ident">five</span> <span class="op">=</span> <span class="number">0</span>..<span class="number">5</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">5</span>, <span class="ident">five</span>.<span class="ident">len</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0A%2F%2F%20a%20finite%20range%20knows%20exactly%20how%20many%20times%20it%20will%20iterate%0Alet%20five%20%3D%200..5%3B%0A%0Aassert_eq!(5%2C%20five.len())%3B%0A%7D">Run</a></pre>
<p>In the <a href="index.html">module level docs</a>, we implemented an <a href="trait.Iterator.html"><code>Iterator</code></a>,
<code>Counter</code>. Let's implement <code>ExactSizeIterator</code> for it as well:</p>
<pre class="rust rust-example-rendered">
<span class="kw">impl</span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">Counter</span> {
<span class="comment">// We can easily calculate the remaining number of iterations.</span>
<span class="kw">fn</span> <span class="ident">len</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="number">5</span> <span class="op">-</span> <span class="self">self</span>.<span class="ident">count</span>
}
}
<span class="comment">// And now we can use it!</span>
<span class="kw">let</span> <span class="ident">counter</span> <span class="op">=</span> <span class="ident">Counter</span>::<span class="ident">new</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">5</span>, <span class="ident">counter</span>.<span class="ident">len</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Astruct%20Counter%20%7B%0A%20%20%20%20count%3A%20usize%2C%0A%7D%0Aimpl%20Counter%20%7B%0A%20%20%20%20fn%20new()%20-%3E%20Counter%20%7B%0A%20%20%20%20%20%20%20%20Counter%20%7B%20count%3A%200%20%7D%0A%20%20%20%20%7D%0A%7D%0Aimpl%20Iterator%20for%20Counter%20%7B%0A%20%20%20%20type%20Item%20%3D%20usize%3B%0A%20%20%20%20fn%20next(%26mut%20self)%20-%3E%20Option%3Cusize%3E%20%7B%0A%20%20%20%20%20%20%20%20self.count%20%2B%3D%201%3B%0A%20%20%20%20%20%20%20%20if%20self.count%20%3C%206%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20Some(self.count)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20None%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0Aimpl%20ExactSizeIterator%20for%20Counter%20%7B%0A%20%20%20%20%2F%2F%20We%20can%20easily%20calculate%20the%20remaining%20number%20of%20iterations.%0A%20%20%20%20fn%20len(%26self)%20-%3E%20usize%20%7B%0A%20%20%20%20%20%20%20%205%20-%20self.count%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20And%20now%20we%20can%20use%20it!%0A%0Alet%20counter%20%3D%20Counter%3A%3Anew()%3B%0A%0Aassert_eq!(5%2C%20counter.len())%3B%0A%7D">Run</a></pre>
</div>
<h2 id='provided-methods'>Provided Methods</h2>
<div class='methods'>
<h3 id='method.len' class='method'><span id='len.v' class='invisible'><code>fn <a href='#method.len' class='fnname'>len</a>(&self) -> <a class="primitive" href="../primitive.usize.html">usize</a></code></span></h3><div class='docblock'><p>Returns the exact number of times the iterator will iterate.</p>
<p>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 <a href="trait.ExactSizeIterator.html">trait-level</a> docs for an
example.</p>
<p>This function has the same safety guarantees as the <a href="trait.Iterator.html#method.size_hint"><code>size_hint</code></a>
function.</p>
<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
<p>Basic usage:</p>
<pre class="rust rust-example-rendered">
<span class="comment">// a finite range knows exactly how many times it will iterate</span>
<span class="kw">let</span> <span class="ident">five</span> <span class="op">=</span> <span class="number">0</span>..<span class="number">5</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">5</span>, <span class="ident">five</span>.<span class="ident">len</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0A%2F%2F%20a%20finite%20range%20knows%20exactly%20how%20many%20times%20it%20will%20iterate%0Alet%20five%20%3D%200..5%3B%0A%0Aassert_eq!(5%2C%20five.len())%3B%0A%7D">Run</a></pre>
</div><h3 id='method.is_empty' class='method'><span id='is_empty.v' class='invisible'><code>fn <a href='#method.is_empty' class='fnname'>is_empty</a>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></h3><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>exact_size_is_empty </code><a href="https://github.com/rust-lang/rust/issues/35428">#35428</a>)</div></div><div class='docblock'><p>Returns whether the iterator is empty.</p>
<p>This method has a default implementation using <code>self.len()</code>, so you
don't need to implement it yourself.</p>
<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
<p>Basic usage:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#<span class="op">!</span>[<span class="ident">feature</span>(<span class="ident">exact_size_is_empty</span>)]</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">one_element</span> <span class="op">=</span> <span class="number">0</span>..<span class="number">1</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">one_element</span>.<span class="ident">is_empty</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">one_element</span>.<span class="ident">next</span>(), <span class="prelude-val">Some</span>(<span class="number">0</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">one_element</span>.<span class="ident">is_empty</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">one_element</span>.<span class="ident">next</span>(), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Bfeature(exact_size_is_empty)%5D%0A%0Afn%20main()%20%7B%0Alet%20mut%20one_element%20%3D%200..1%3B%0Aassert!(!one_element.is_empty())%3B%0A%0Aassert_eq!(one_element.next()%2C%20Some(0))%3B%0Aassert!(one_element.is_empty())%3B%0A%0Aassert_eq!(one_element.next()%2C%20None)%3B%0A%7D&version=nightly">Run</a></pre>
</div></div>
<h2 id='implementors'>Implementors</h2>
<ul class='item-list' id='implementors-list'>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/boxed/struct.Box.html" title="struct std::boxed::Box">Box</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></li>
<li><code>impl<T> ExactSizeIterator for std::vec::<a class="struct" href="../../std/vec/struct.IntoIter.html" title="struct std::vec::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::linked_list::<a class="struct" href="../../std/collections/linked_list/struct.IterMut.html" title="struct std::collections::linked_list::IterMut">IterMut</a><'a, T></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::vec_deque::<a class="struct" href="../../std/collections/vec_deque/struct.Iter.html" title="struct std::collections::vec_deque::Iter">Iter</a><'a, T></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.Iter.html" title="struct std::collections::btree_map::Iter">Iter</a><'a, K, V> <span class="where fmt-newline">where<br> K: 'a,<br> V: 'a, </span></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::vec::<a class="struct" href="../../std/vec/struct.Drain.html" title="struct std::vec::Drain">Drain</a><'a, T></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::vec_deque::<a class="struct" href="../../std/collections/vec_deque/struct.IterMut.html" title="struct std::collections::vec_deque::IterMut">IterMut</a><'a, T></code></li>
<li><code>impl<T> ExactSizeIterator for std::collections::vec_deque::<a class="struct" href="../../std/collections/vec_deque/struct.IntoIter.html" title="struct std::collections::vec_deque::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.IterMut.html" title="struct std::collections::btree_map::IterMut">IterMut</a><'a, K, V> <span class="where fmt-newline">where<br> K: 'a,<br> V: 'a, </span></code></li>
<li><code>impl<T> ExactSizeIterator for std::collections::binary_heap::<a class="struct" href="../../std/collections/binary_heap/struct.IntoIter.html" title="struct std::collections::binary_heap::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.ValuesMut.html" title="struct std::collections::btree_map::ValuesMut">ValuesMut</a><'a, K, V></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::btree_set::<a class="struct" href="../../std/collections/btree_set/struct.Iter.html" title="struct std::collections::btree_set::Iter">Iter</a><'a, T></code></li>
<li><code>impl<K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.IntoIter.html" title="struct std::collections::btree_map::IntoIter">IntoIter</a><K, V></code></li>
<li><code>impl<'a, I> ExactSizeIterator for <a class="struct" href="../../std/vec/struct.Splice.html" title="struct std::vec::Splice">Splice</a><'a, I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>, </span></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::vec_deque::<a class="struct" href="../../std/collections/vec_deque/struct.Drain.html" title="struct std::collections::vec_deque::Drain">Drain</a><'a, T> <span class="where fmt-newline">where<br> T: 'a, </span></code></li>
<li><code>impl<T> ExactSizeIterator for std::collections::linked_list::<a class="struct" href="../../std/collections/linked_list/struct.IntoIter.html" title="struct std::collections::linked_list::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.Keys.html" title="struct std::collections::btree_map::Keys">Keys</a><'a, K, V></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::binary_heap::<a class="struct" href="../../std/collections/binary_heap/struct.Drain.html" title="struct std::collections::binary_heap::Drain">Drain</a><'a, T> <span class="where fmt-newline">where<br> T: 'a, </span></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::binary_heap::<a class="struct" href="../../std/collections/binary_heap/struct.Iter.html" title="struct std::collections::binary_heap::Iter">Iter</a><'a, T></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::btree_map::<a class="struct" href="../../std/collections/btree_map/struct.Values.html" title="struct std::collections::btree_map::Values">Values</a><'a, K, V></code></li>
<li><code>impl<T> ExactSizeIterator for std::collections::btree_set::<a class="struct" href="../../std/collections/btree_set/struct.IntoIter.html" title="struct std::collections::btree_set::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::collections::linked_list::<a class="struct" href="../../std/collections/linked_list/struct.Iter.html" title="struct std::collections::linked_list::Iter">Iter</a><'a, T></code></li>
<li><code>impl<T> ExactSizeIterator for std::result::<a class="struct" href="../../std/result/struct.IntoIter.html" title="struct std::result::IntoIter">IntoIter</a><T></code></li>
<li><code>impl<A> ExactSizeIterator for std::option::<a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><A></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::result::<a class="struct" href="../../std/result/struct.Iter.html" title="struct std::result::Iter">Iter</a><'a, T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/char/struct.EscapeDebug.html" title="struct std::char::EscapeDebug">EscapeDebug</a></code></li>
<li><code>impl<'a, I> ExactSizeIterator for &'a mut I <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Enumerate.html" title="struct std::iter::Enumerate">Enumerate</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<'a, I, T> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Cloned.html" title="struct std::iter::Cloned">Cloned</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a><Item = &'a T>,<br> T: 'a + <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a>, </span></code></li>
<li><code>impl<'a, T> ExactSizeIterator for <a class="struct" href="../../std/slice/struct.Chunks.html" title="struct std::slice::Chunks">Chunks</a><'a, T></code></li>
<li><code>impl<I, F> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Inspect.html" title="struct std::iter::Inspect">Inspect</a><I, F> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnMut.html" title="trait std::ops::FnMut">FnMut</a>(&<I as <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>>::<a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Item</a>) -> <a class="primitive" href="../primitive.tuple.html">()</a>,<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Take.html" title="struct std::iter::Take">Take</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<T> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Empty.html" title="struct std::iter::Empty">Empty</a><T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.u32.html">u32</a>></code></li>
<li><code>impl<'a, A> ExactSizeIterator for std::option::<a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></code></li>
<li><code>impl<A, B> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Zip.html" title="struct std::iter::Zip">Zip</a><A, B> <span class="where fmt-newline">where<br> A: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>,<br> B: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.u8.html">u8</a>></code></li>
<li><code>impl<'a, A> ExactSizeIterator for std::option::<a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></code></li>
<li><code>impl<'a> ExactSizeIterator for <a class="struct" href="../../std/str/struct.Bytes.html" title="struct std::str::Bytes">Bytes</a><'a></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.i32.html">i32</a>></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.usize.html">usize</a>></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.i8.html">i8</a>></code></li>
<li><code>impl ExactSizeIterator for std::char::<a class="struct" href="../../std/char/struct.EscapeDefault.html" title="struct std::char::EscapeDefault">EscapeDefault</a></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::result::<a class="struct" href="../../std/result/struct.IterMut.html" title="struct std::result::IterMut">IterMut</a><'a, T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.RangeInclusive.html" title="struct std::ops::RangeInclusive">RangeInclusive</a><<a class="primitive" href="../primitive.i16.html">i16</a>></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.i16.html">i16</a>></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.StepBy.html" title="struct std::iter::StepBy">StepBy</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Fuse.html" title="struct std::iter::Fuse">Fuse</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.u16.html">u16</a>></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Peekable.html" title="struct std::iter::Peekable">Peekable</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<T> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Once.html" title="struct std::iter::Once">Once</a><T></code></li>
<li><code>impl<B, I, F> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Map.html" title="struct std::iter::Map">Map</a><I, F> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnMut.html" title="trait std::ops::FnMut">FnMut</a>(<I as <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>>::<a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Item</a>) -> B,<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Rev.html" title="struct std::iter::Rev">Rev</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a> + <a class="trait" href="../../std/iter/trait.DoubleEndedIterator.html" title="trait std::iter::DoubleEndedIterator">DoubleEndedIterator</a>, </span></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.RangeInclusive.html" title="struct std::ops::RangeInclusive">RangeInclusive</a><<a class="primitive" href="../primitive.i8.html">i8</a>></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::slice::<a class="struct" href="../../std/slice/struct.IterMut.html" title="struct std::slice::IterMut">IterMut</a><'a, T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/char/struct.EscapeUnicode.html" title="struct std::char::EscapeUnicode">EscapeUnicode</a></code></li>
<li><code>impl<'a, T> ExactSizeIterator for <a class="struct" href="../../std/slice/struct.Windows.html" title="struct std::slice::Windows">Windows</a><'a, T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.RangeInclusive.html" title="struct std::ops::RangeInclusive">RangeInclusive</a><<a class="primitive" href="../primitive.u8.html">u8</a>></code></li>
<li><code>impl<'a, T> ExactSizeIterator for std::slice::<a class="struct" href="../../std/slice/struct.Iter.html" title="struct std::slice::Iter">Iter</a><'a, T></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.Range.html" title="struct std::ops::Range">Range</a><<a class="primitive" href="../primitive.isize.html">isize</a>></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/ops/struct.RangeInclusive.html" title="struct std::ops::RangeInclusive">RangeInclusive</a><<a class="primitive" href="../primitive.u16.html">u16</a>></code></li>
<li><code>impl<'a, T> ExactSizeIterator for <a class="struct" href="../../std/slice/struct.ChunksMut.html" title="struct std::slice::ChunksMut">ChunksMut</a><'a, T></code></li>
<li><code>impl<I> ExactSizeIterator for <a class="struct" href="../../std/iter/struct.Skip.html" title="struct std::iter::Skip">Skip</a><I> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.ExactSizeIterator.html" title="trait std::iter::ExactSizeIterator">ExactSizeIterator</a>, </span></code></li>
<li><code>impl ExactSizeIterator for std::ascii::<a class="struct" href="../../std/ascii/struct.EscapeDefault.html" title="struct std::ascii::EscapeDefault">EscapeDefault</a></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.Iter.html" title="struct std::collections::hash_map::Iter">Iter</a><'a, K, V></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.IterMut.html" title="struct std::collections::hash_map::IterMut">IterMut</a><'a, K, V></code></li>
<li><code>impl<K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.IntoIter.html" title="struct std::collections::hash_map::IntoIter">IntoIter</a><K, V></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.Keys.html" title="struct std::collections::hash_map::Keys">Keys</a><'a, K, V></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.Values.html" title="struct std::collections::hash_map::Values">Values</a><'a, K, V></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.ValuesMut.html" title="struct std::collections::hash_map::ValuesMut">ValuesMut</a><'a, K, V></code></li>
<li><code>impl<'a, K, V> ExactSizeIterator for std::collections::hash_map::<a class="struct" href="../../std/collections/hash_map/struct.Drain.html" title="struct std::collections::hash_map::Drain">Drain</a><'a, K, V></code></li>
<li><code>impl<'a, K> ExactSizeIterator for std::collections::hash_set::<a class="struct" href="../../std/collections/hash_set/struct.Iter.html" title="struct std::collections::hash_set::Iter">Iter</a><'a, K></code></li>
<li><code>impl<K> ExactSizeIterator for std::collections::hash_set::<a class="struct" href="../../std/collections/hash_set/struct.IntoIter.html" title="struct std::collections::hash_set::IntoIter">IntoIter</a><K></code></li>
<li><code>impl<'a, K> ExactSizeIterator for std::collections::hash_set::<a class="struct" href="../../std/collections/hash_set/struct.Drain.html" title="struct std::collections::hash_set::Drain">Drain</a><'a, K></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/env/struct.Args.html" title="struct std::env::Args">Args</a></code></li>
<li><code>impl ExactSizeIterator for <a class="struct" href="../../std/env/struct.ArgsOs.html" title="struct std::env::ArgsOs">ArgsOs</a></code></li>
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