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</pre><pre class="rust">
<span class="kw">use</span> <span class="ident">Itertools</span>;
<span class="doccomment">/// Combine all an iterator's elements into one element by using `Extend`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `IntoIterator`-enabled version of `.concat()`</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This combinator will extend the first item with each of the rest of the</span>
<span class="doccomment">/// items of the iterator. If the iterator is empty, the default value of</span>
<span class="doccomment">/// `I::Item` is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use itertools::concat;</span>
<span class="doccomment">/// </span>
<span class="doccomment">/// let input = vec![vec![1], vec![2, 3], vec![4, 5, 6]];</span>
<span class="doccomment">/// assert_eq!(concat(input), vec![1, 2, 3, 4, 5, 6]);</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">concat</span><span class="op"><</span><span class="ident">I</span><span class="op">></span>(<span class="ident">iterable</span>: <span class="ident">I</span>) <span class="op">-</span><span class="op">></span> <span class="ident">I::Item</span>
<span class="kw">where</span> <span class="ident">I</span>: <span class="ident">IntoIterator</span>,
<span class="ident">I::Item</span>: <span class="ident">Extend</span><span class="op"><</span><span class="op"><</span><span class="op"><</span><span class="ident">I</span> <span class="kw">as</span> <span class="ident">IntoIterator</span><span class="op">></span><span class="ident">::Item</span> <span class="kw">as</span> <span class="ident">IntoIterator</span><span class="op">></span><span class="ident">::Item</span><span class="op">></span> <span class="op">+</span> <span class="ident">IntoIterator</span> <span class="op">+</span> <span class="ident">Default</span>
{
<span class="ident">iterable</span>.<span class="ident">into_iter</span>().<span class="ident">fold1</span>(<span class="op">|</span><span class="kw-2">mut</span> <span class="ident">a</span>, <span class="ident">b</span><span class="op">|</span> { <span class="ident">a</span>.<span class="ident">extend</span>(<span class="ident">b</span>); <span class="ident">a</span> }).<span class="ident">unwrap_or_else</span>(<span class="op">|</span><span class="op">|</span> <span class="op"><</span><span class="kw">_</span><span class="op">></span><span class="ident">::default</span>())
}
</pre></div>
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