| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/itertools-0.10.5/src/kmerge_impl.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>kmerge_impl.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../itertools/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../itertools/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><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="kw">use </span>std::iter::FusedIterator; |
| <span class="kw">use </span>std::mem::replace; |
| <span class="kw">use </span>std::fmt; |
| |
| <span class="doccomment">/// Head element and Tail iterator pair |
| /// |
| /// `PartialEq`, `Eq`, `PartialOrd` and `Ord` are implemented by comparing sequences based on |
| /// first items (which are guaranteed to exist). |
| /// |
| /// The meanings of `PartialOrd` and `Ord` are reversed so as to turn the heap used in |
| /// `KMerge` into a min-heap. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>HeadTail<I> |
| <span class="kw">where </span>I: Iterator |
| { |
| head: I::Item, |
| tail: I, |
| } |
| |
| <span class="kw">impl</span><I> HeadTail<I> |
| <span class="kw">where </span>I: Iterator |
| { |
| <span class="doccomment">/// Constructs a `HeadTail` from an `Iterator`. Returns `None` if the `Iterator` is empty. |
| </span><span class="kw">fn </span>new(<span class="kw-2">mut </span>it: I) -> <span class="prelude-ty">Option</span><HeadTail<I>> { |
| <span class="kw">let </span>head = it.next(); |
| head.map(|h| { |
| HeadTail { |
| head: h, |
| tail: it, |
| } |
| }) |
| } |
| |
| <span class="doccomment">/// Get the next element and update `head`, returning the old head in `Some`. |
| /// |
| /// Returns `None` when the tail is exhausted (only `head` then remains). |
| </span><span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><I::Item> { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(next) = <span class="self">self</span>.tail.next() { |
| <span class="prelude-val">Some</span>(replace(<span class="kw-2">&mut </span><span class="self">self</span>.head, next)) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="doccomment">/// Hints at the size of the sequence, same as the `Iterator` method. |
| </span><span class="kw">fn </span>size_hint(<span class="kw-2">&</span><span class="self">self</span>) -> (usize, <span class="prelude-ty">Option</span><usize>) { |
| size_hint::add_scalar(<span class="self">self</span>.tail.size_hint(), <span class="number">1</span>) |
| } |
| } |
| |
| <span class="kw">impl</span><I> Clone <span class="kw">for </span>HeadTail<I> |
| <span class="kw">where </span>I: Iterator + Clone, |
| I::Item: Clone |
| { |
| <span class="macro">clone_fields!</span>(head, tail); |
| } |
| |
| <span class="doccomment">/// Make `data` a heap (min-heap w.r.t the sorting). |
| </span><span class="kw">fn </span>heapify<T, S>(data: <span class="kw-2">&mut </span>[T], <span class="kw-2">mut </span>less_than: S) |
| <span class="kw">where </span>S: FnMut(<span class="kw-2">&</span>T, <span class="kw-2">&</span>T) -> bool |
| { |
| <span class="kw">for </span>i <span class="kw">in </span>(<span class="number">0</span>..data.len() / <span class="number">2</span>).rev() { |
| sift_down(data, i, <span class="kw-2">&mut </span>less_than); |
| } |
| } |
| |
| <span class="doccomment">/// Sift down element at `index` (`heap` is a min-heap wrt the ordering) |
| </span><span class="kw">fn </span>sift_down<T, S>(heap: <span class="kw-2">&mut </span>[T], index: usize, <span class="kw-2">mut </span>less_than: S) |
| <span class="kw">where </span>S: FnMut(<span class="kw-2">&</span>T, <span class="kw-2">&</span>T) -> bool |
| { |
| <span class="macro">debug_assert!</span>(index <= heap.len()); |
| <span class="kw">let </span><span class="kw-2">mut </span>pos = index; |
| <span class="kw">let </span><span class="kw-2">mut </span>child = <span class="number">2 </span>* pos + <span class="number">1</span>; |
| <span class="comment">// Require the right child to be present |
| // This allows to find the index of the smallest child without a branch |
| // that wouldn't be predicted if present |
| </span><span class="kw">while </span>child + <span class="number">1 </span>< heap.len() { |
| <span class="comment">// pick the smaller of the two children |
| // use arithmetic to avoid an unpredictable branch |
| </span>child += less_than(<span class="kw-2">&</span>heap[child+<span class="number">1</span>], <span class="kw-2">&</span>heap[child]) <span class="kw">as </span>usize; |
| |
| <span class="comment">// sift down is done if we are already in order |
| </span><span class="kw">if </span>!less_than(<span class="kw-2">&</span>heap[child], <span class="kw-2">&</span>heap[pos]) { |
| <span class="kw">return</span>; |
| } |
| heap.swap(pos, child); |
| pos = child; |
| child = <span class="number">2 </span>* pos + <span class="number">1</span>; |
| } |
| <span class="comment">// Check if the last (left) child was an only child |
| // if it is then it has to be compared with the parent |
| </span><span class="kw">if </span>child + <span class="number">1 </span>== heap.len() && less_than(<span class="kw-2">&</span>heap[child], <span class="kw-2">&</span>heap[pos]) { |
| heap.swap(pos, child); |
| } |
| } |
| |
| <span class="doccomment">/// An iterator adaptor that merges an abitrary number of base iterators in ascending order. |
| /// If all base iterators are sorted (ascending), the result is sorted. |
| /// |
| /// Iterator element type is `I::Item`. |
| /// |
| /// See [`.kmerge()`](crate::Itertools::kmerge) for more information. |
| </span><span class="kw">pub type </span>KMerge<I> = KMergeBy<I, KMergeByLt>; |
| |
| <span class="kw">pub trait </span>KMergePredicate<T> { |
| <span class="kw">fn </span>kmerge_pred(<span class="kw-2">&mut </span><span class="self">self</span>, a: <span class="kw-2">&</span>T, b: <span class="kw-2">&</span>T) -> bool; |
| } |
| |
| <span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub struct </span>KMergeByLt; |
| |
| <span class="kw">impl</span><T: PartialOrd> KMergePredicate<T> <span class="kw">for </span>KMergeByLt { |
| <span class="kw">fn </span>kmerge_pred(<span class="kw-2">&mut </span><span class="self">self</span>, a: <span class="kw-2">&</span>T, b: <span class="kw-2">&</span>T) -> bool { |
| a < b |
| } |
| } |
| |
| <span class="kw">impl</span><T, F: FnMut(<span class="kw-2">&</span>T, <span class="kw-2">&</span>T)->bool> KMergePredicate<T> <span class="kw">for </span>F { |
| <span class="kw">fn </span>kmerge_pred(<span class="kw-2">&mut </span><span class="self">self</span>, a: <span class="kw-2">&</span>T, b: <span class="kw-2">&</span>T) -> bool { |
| <span class="self">self</span>(a, b) |
| } |
| } |
| |
| <span class="doccomment">/// Create an iterator that merges elements of the contained iterators using |
| /// the ordering function. |
| /// |
| /// [`IntoIterator`] enabled version of [`Itertools::kmerge`]. |
| /// |
| /// ``` |
| /// use itertools::kmerge; |
| /// |
| /// for elt in kmerge(vec![vec![0, 2, 4], vec![1, 3, 5], vec![6, 7]]) { |
| /// /* loop body */ |
| /// } |
| /// ``` |
| </span><span class="kw">pub fn </span>kmerge<I>(iterable: I) -> KMerge<<I::Item <span class="kw">as </span>IntoIterator>::IntoIter> |
| <span class="kw">where </span>I: IntoIterator, |
| I::Item: IntoIterator, |
| <<I <span class="kw">as </span>IntoIterator>::Item <span class="kw">as </span>IntoIterator>::Item: PartialOrd |
| { |
| kmerge_by(iterable, KMergeByLt) |
| } |
| |
| <span class="doccomment">/// An iterator adaptor that merges an abitrary number of base iterators |
| /// according to an ordering function. |
| /// |
| /// Iterator element type is `I::Item`. |
| /// |
| /// See [`.kmerge_by()`](crate::Itertools::kmerge_by) for more |
| /// information. |
| </span><span class="attribute">#[must_use = <span class="string">"iterator adaptors are lazy and do nothing unless consumed"</span>] |
| </span><span class="kw">pub struct </span>KMergeBy<I, F> |
| <span class="kw">where </span>I: Iterator, |
| { |
| heap: Vec<HeadTail<I>>, |
| less_than: F, |
| } |
| |
| <span class="kw">impl</span><I, F> fmt::Debug <span class="kw">for </span>KMergeBy<I, F> |
| <span class="kw">where </span>I: Iterator + fmt::Debug, |
| I::Item: fmt::Debug, |
| { |
| <span class="macro">debug_fmt_fields!</span>(KMergeBy, heap); |
| } |
| |
| <span class="doccomment">/// Create an iterator that merges elements of the contained iterators. |
| /// |
| /// [`IntoIterator`] enabled version of [`Itertools::kmerge_by`]. |
| </span><span class="kw">pub fn </span>kmerge_by<I, F>(iterable: I, <span class="kw-2">mut </span>less_than: F) |
| -> KMergeBy<<I::Item <span class="kw">as </span>IntoIterator>::IntoIter, F> |
| <span class="kw">where </span>I: IntoIterator, |
| I::Item: IntoIterator, |
| F: KMergePredicate<<<I <span class="kw">as </span>IntoIterator>::Item <span class="kw">as </span>IntoIterator>::Item>, |
| { |
| <span class="kw">let </span>iter = iterable.into_iter(); |
| <span class="kw">let </span>(lower, <span class="kw">_</span>) = iter.size_hint(); |
| <span class="kw">let </span><span class="kw-2">mut </span>heap: Vec<<span class="kw">_</span>> = Vec::with_capacity(lower); |
| heap.extend(iter.filter_map(|it| HeadTail::new(it.into_iter()))); |
| heapify(<span class="kw-2">&mut </span>heap, |a, b| less_than.kmerge_pred(<span class="kw-2">&</span>a.head, <span class="kw-2">&</span>b.head)); |
| KMergeBy { heap, less_than } |
| } |
| |
| <span class="kw">impl</span><I, F> Clone <span class="kw">for </span>KMergeBy<I, F> |
| <span class="kw">where </span>I: Iterator + Clone, |
| I::Item: Clone, |
| F: Clone, |
| { |
| <span class="macro">clone_fields!</span>(heap, less_than); |
| } |
| |
| <span class="kw">impl</span><I, F> Iterator <span class="kw">for </span>KMergeBy<I, F> |
| <span class="kw">where </span>I: Iterator, |
| F: KMergePredicate<I::Item> |
| { |
| <span class="kw">type </span>Item = I::Item; |
| |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Item> { |
| <span class="kw">if </span><span class="self">self</span>.heap.is_empty() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>result = <span class="kw">if let </span><span class="prelude-val">Some</span>(next) = <span class="self">self</span>.heap[<span class="number">0</span>].next() { |
| next |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.heap.swap_remove(<span class="number">0</span>).head |
| }; |
| <span class="kw">let </span>less_than = <span class="kw-2">&mut </span><span class="self">self</span>.less_than; |
| sift_down(<span class="kw-2">&mut </span><span class="self">self</span>.heap, <span class="number">0</span>, |a, b| less_than.kmerge_pred(<span class="kw-2">&</span>a.head, <span class="kw-2">&</span>b.head)); |
| <span class="prelude-val">Some</span>(result) |
| } |
| |
| <span class="kw">fn </span>size_hint(<span class="kw-2">&</span><span class="self">self</span>) -> (usize, <span class="prelude-ty">Option</span><usize>) { |
| <span class="attribute">#[allow(deprecated)] </span><span class="comment">//TODO: once msrv hits 1.51. replace `fold1` with `reduce` |
| </span><span class="self">self</span>.heap.iter() |
| .map(|i| i.size_hint()) |
| .fold1(size_hint::add) |
| .unwrap_or((<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>))) |
| } |
| } |
| |
| <span class="kw">impl</span><I, F> FusedIterator <span class="kw">for </span>KMergeBy<I, F> |
| <span class="kw">where </span>I: Iterator, |
| F: KMergePredicate<I::Item> |
| {} |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="itertools" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
