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</pre><pre class="rust"><code><span class="attribute">#![cfg(feature = <span class="string">&quot;use_alloc&quot;</span>)]
</span><span class="kw">use </span><span class="kw">crate</span>::size_hint;
<span class="kw">use </span><span class="kw">crate</span>::Itertools;
<span class="kw">use </span>alloc::vec::Vec;
<span class="attribute">#[derive(Clone)]
</span><span class="doccomment">/// An iterator adaptor that iterates over the cartesian product of
/// multiple iterators of type `I`.
///
/// An iterator element type is `Vec&lt;I&gt;`.
///
/// See [`.multi_cartesian_product()`](crate::Itertools::multi_cartesian_product)
/// for more information.
</span><span class="attribute">#[must_use = <span class="string">&quot;iterator adaptors are lazy and do nothing unless consumed&quot;</span>]
</span><span class="kw">pub struct </span>MultiProduct&lt;I&gt;(Vec&lt;MultiProductIter&lt;I&gt;&gt;)
<span class="kw">where </span>I: Iterator + Clone,
I::Item: Clone;
<span class="kw">impl</span>&lt;I&gt; std::fmt::Debug <span class="kw">for </span>MultiProduct&lt;I&gt;
<span class="kw">where
</span>I: Iterator + Clone + std::fmt::Debug,
I::Item: Clone + std::fmt::Debug,
{
<span class="macro">debug_fmt_fields!</span>(CoalesceBy, <span class="number">0</span>);
}
<span class="doccomment">/// Create a new cartesian product iterator over an arbitrary number
/// of iterators of the same type.
///
/// Iterator element is of type `Vec&lt;H::Item::Item&gt;`.
</span><span class="kw">pub fn </span>multi_cartesian_product&lt;H&gt;(iters: H) -&gt; MultiProduct&lt;&lt;H::Item <span class="kw">as </span>IntoIterator&gt;::IntoIter&gt;
<span class="kw">where </span>H: Iterator,
H::Item: IntoIterator,
&lt;H::Item <span class="kw">as </span>IntoIterator&gt;::IntoIter: Clone,
&lt;H::Item <span class="kw">as </span>IntoIterator&gt;::Item: Clone
{
MultiProduct(iters.map(|i| MultiProductIter::new(i.into_iter())).collect())
}
<span class="attribute">#[derive(Clone, Debug)]
</span><span class="doccomment">/// Holds the state of a single iterator within a `MultiProduct`.
</span><span class="kw">struct </span>MultiProductIter&lt;I&gt;
<span class="kw">where </span>I: Iterator + Clone,
I::Item: Clone
{
cur: <span class="prelude-ty">Option</span>&lt;I::Item&gt;,
iter: I,
iter_orig: I,
}
<span class="doccomment">/// Holds the current state during an iteration of a `MultiProduct`.
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">enum </span>MultiProductIterState {
StartOfIter,
MidIter { on_first_iter: bool },
}
<span class="kw">impl</span>&lt;I&gt; MultiProduct&lt;I&gt;
<span class="kw">where </span>I: Iterator + Clone,
I::Item: Clone
{
<span class="doccomment">/// Iterates the rightmost iterator, then recursively iterates iterators
/// to the left if necessary.
///
/// Returns true if the iteration succeeded, else false.
</span><span class="kw">fn </span>iterate_last(
multi_iters: <span class="kw-2">&amp;mut </span>[MultiProductIter&lt;I&gt;],
<span class="kw-2">mut </span>state: MultiProductIterState
) -&gt; bool {
<span class="kw">use </span><span class="self">self</span>::MultiProductIterState::<span class="kw-2">*</span>;
<span class="kw">if let </span><span class="prelude-val">Some</span>((last, rest)) = multi_iters.split_last_mut() {
<span class="kw">let </span>on_first_iter = <span class="kw">match </span>state {
StartOfIter =&gt; {
<span class="kw">let </span>on_first_iter = !last.in_progress();
state = MidIter { on_first_iter };
on_first_iter
},
MidIter { on_first_iter } =&gt; on_first_iter
};
<span class="kw">if </span>!on_first_iter {
last.iterate();
}
<span class="kw">if </span>last.in_progress() {
<span class="bool-val">true
</span>} <span class="kw">else if </span>MultiProduct::iterate_last(rest, state) {
last.reset();
last.iterate();
<span class="comment">// If iterator is None twice consecutively, then iterator is
// empty; whole product is empty.
</span>last.in_progress()
} <span class="kw">else </span>{
<span class="bool-val">false
</span>}
} <span class="kw">else </span>{
<span class="comment">// Reached end of iterator list. On initialisation, return true.
// At end of iteration (final iterator finishes), finish.
</span><span class="kw">match </span>state {
StartOfIter =&gt; <span class="bool-val">false</span>,
MidIter { on_first_iter } =&gt; on_first_iter
}
}
}
<span class="doccomment">/// Returns the unwrapped value of the next iteration.
</span><span class="kw">fn </span>curr_iterator(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; Vec&lt;I::Item&gt; {
<span class="self">self</span>.<span class="number">0</span>.iter().map(|multi_iter| {
multi_iter.cur.clone().unwrap()
}).collect()
}
<span class="doccomment">/// Returns true if iteration has started and has not yet finished; false
/// otherwise.
</span><span class="kw">fn </span>in_progress(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
<span class="kw">if let </span><span class="prelude-val">Some</span>(last) = <span class="self">self</span>.<span class="number">0</span>.last() {
last.in_progress()
} <span class="kw">else </span>{
<span class="bool-val">false
</span>}
}
}
<span class="kw">impl</span>&lt;I&gt; MultiProductIter&lt;I&gt;
<span class="kw">where </span>I: Iterator + Clone,
I::Item: Clone
{
<span class="kw">fn </span>new(iter: I) -&gt; <span class="self">Self </span>{
MultiProductIter {
cur: <span class="prelude-val">None</span>,
iter: iter.clone(),
iter_orig: iter
}
}
<span class="doccomment">/// Iterate the managed iterator.
</span><span class="kw">fn </span>iterate(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
<span class="self">self</span>.cur = <span class="self">self</span>.iter.next();
}
<span class="doccomment">/// Reset the managed iterator.
</span><span class="kw">fn </span>reset(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
<span class="self">self</span>.iter = <span class="self">self</span>.iter_orig.clone();
}
<span class="doccomment">/// Returns true if the current iterator has been started and has not yet
/// finished; false otherwise.
</span><span class="kw">fn </span>in_progress(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
<span class="self">self</span>.cur.is_some()
}
}
<span class="kw">impl</span>&lt;I&gt; Iterator <span class="kw">for </span>MultiProduct&lt;I&gt;
<span class="kw">where </span>I: Iterator + Clone,
I::Item: Clone
{
<span class="kw">type </span>Item = Vec&lt;I::Item&gt;;
<span class="kw">fn </span>next(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Item&gt; {
<span class="kw">if </span>MultiProduct::iterate_last(
<span class="kw-2">&amp;mut </span><span class="self">self</span>.<span class="number">0</span>,
MultiProductIterState::StartOfIter
) {
<span class="prelude-val">Some</span>(<span class="self">self</span>.curr_iterator())
} <span class="kw">else </span>{
<span class="prelude-val">None
</span>}
}
<span class="kw">fn </span>count(<span class="self">self</span>) -&gt; usize {
<span class="kw">if </span><span class="self">self</span>.<span class="number">0</span>.is_empty() {
<span class="kw">return </span><span class="number">0</span>;
}
<span class="kw">if </span>!<span class="self">self</span>.in_progress() {
<span class="kw">return </span><span class="self">self</span>.<span class="number">0</span>.into_iter().fold(<span class="number">1</span>, |acc, multi_iter| {
acc * multi_iter.iter.count()
});
}
<span class="self">self</span>.<span class="number">0</span>.into_iter().fold(
<span class="number">0</span>,
|acc, MultiProductIter { iter, iter_orig, cur: <span class="kw">_ </span>}| {
<span class="kw">let </span>total_count = iter_orig.count();
<span class="kw">let </span>cur_count = iter.count();
acc * total_count + cur_count
}
)
}
<span class="kw">fn </span>size_hint(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; (usize, <span class="prelude-ty">Option</span>&lt;usize&gt;) {
<span class="comment">// Not ExactSizeIterator because size may be larger than usize
</span><span class="kw">if </span><span class="self">self</span>.<span class="number">0</span>.is_empty() {
<span class="kw">return </span>(<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>));
}
<span class="kw">if </span>!<span class="self">self</span>.in_progress() {
<span class="kw">return </span><span class="self">self</span>.<span class="number">0</span>.iter().fold((<span class="number">1</span>, <span class="prelude-val">Some</span>(<span class="number">1</span>)), |acc, multi_iter| {
size_hint::mul(acc, multi_iter.iter.size_hint())
});
}
<span class="self">self</span>.<span class="number">0</span>.iter().fold(
(<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>)),
|acc, <span class="kw-2">&amp;</span>MultiProductIter { <span class="kw-2">ref </span>iter, <span class="kw-2">ref </span>iter_orig, cur: <span class="kw">_ </span>}| {
<span class="kw">let </span>cur_size = iter.size_hint();
<span class="kw">let </span>total_size = iter_orig.size_hint();
size_hint::add(size_hint::mul(acc, total_size), cur_size)
}
)
}
<span class="kw">fn </span>last(<span class="self">self</span>) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="self">Self</span>::Item&gt; {
<span class="kw">let </span>iter_count = <span class="self">self</span>.<span class="number">0</span>.len();
<span class="kw">let </span>lasts: <span class="self">Self</span>::Item = <span class="self">self</span>.<span class="number">0</span>.into_iter()
.map(|multi_iter| multi_iter.iter.last())
.while_some()
.collect();
<span class="kw">if </span>lasts.len() == iter_count {
<span class="prelude-val">Some</span>(lasts)
} <span class="kw">else </span>{
<span class="prelude-val">None
</span>}
}
}
</code></pre></div>
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