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<!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="`Equivalent` and `Comparable` are traits for key comparison in maps."><title>equivalent - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-5bc39a1768837dd0.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="equivalent" data-themes="" data-resource-suffix="" data-rustdoc-version="1.77.1 (7cf61ebde 2024-03-27)" data-channel="1.77.1" data-search-js="search-dd67cee4cfa65049.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-4c98445ec4002617.js"></script><script defer src="../crates.js"></script><script defer src="../static.files/main-48f368f3872407c8.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-04d5337699b92874.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc mod crate"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../equivalent/index.html">equivalent</a><span class="version">1.0.1</span></h2></div><div class="sidebar-elems"><ul class="block">
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<li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#traits">Traits</a></li></ul></section></div></nav><div class="sidebar-resizer"></div>
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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../equivalent/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Crate <a class="mod" href="#">equivalent</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/equivalent/lib.rs.html#1-113">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><a href="trait.Equivalent.html" title="trait equivalent::Equivalent"><code>Equivalent</code></a> and <a href="trait.Comparable.html" title="trait equivalent::Comparable"><code>Comparable</code></a> are traits for key comparison in maps.</p>
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<p>These may be used in the implementation of maps where the lookup type <code>Q</code>
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may be different than the stored key type <code>K</code>.</p>
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<ul>
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<li><code>Q: Equivalent<K></code> checks for equality, similar to the <code>HashMap<K, V></code>
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constraint <code>K: Borrow<Q>, Q: Eq</code>.</li>
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<li><code>Q: Comparable<K></code> checks the ordering, similar to the <code>BTreeMap<K, V></code>
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constraint <code>K: Borrow<Q>, Q: Ord</code>.</li>
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</ul>
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<p>These traits are not used by the maps in the standard library, but they may
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add more flexibility in third-party map implementations, especially in
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situations where a strict <code>K: Borrow<Q></code> relationship is not available.</p>
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<h2 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>equivalent::<span class="kw-2">*</span>;
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<span class="kw">use </span>std::cmp::Ordering;
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<span class="kw">pub struct </span>Pair<A, B>(<span class="kw">pub </span>A, <span class="kw">pub </span>B);
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<span class="kw">impl</span><<span class="lifetime">'a</span>, A: <span class="question-mark">?</span>Sized, B: <span class="question-mark">?</span>Sized, C, D> Equivalent<(C, D)> <span class="kw">for </span>Pair<<span class="kw-2">&</span><span class="lifetime">'a </span>A, <span class="kw-2">&</span><span class="lifetime">'a </span>B>
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<span class="kw">where
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</span>A: Equivalent<C>,
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B: Equivalent<D>,
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{
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<span class="kw">fn </span>equivalent(<span class="kw-2">&</span><span class="self">self</span>, key: <span class="kw-2">&</span>(C, D)) -> bool {
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<span class="self">self</span>.<span class="number">0</span>.equivalent(<span class="kw-2">&</span>key.<span class="number">0</span>) && <span class="self">self</span>.<span class="number">1</span>.equivalent(<span class="kw-2">&</span>key.<span class="number">1</span>)
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}
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}
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<span class="kw">impl</span><<span class="lifetime">'a</span>, A: <span class="question-mark">?</span>Sized, B: <span class="question-mark">?</span>Sized, C, D> Comparable<(C, D)> <span class="kw">for </span>Pair<<span class="kw-2">&</span><span class="lifetime">'a </span>A, <span class="kw-2">&</span><span class="lifetime">'a </span>B>
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<span class="kw">where
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</span>A: Comparable<C>,
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B: Comparable<D>,
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{
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<span class="kw">fn </span>compare(<span class="kw-2">&</span><span class="self">self</span>, key: <span class="kw-2">&</span>(C, D)) -> Ordering {
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<span class="kw">match </span><span class="self">self</span>.<span class="number">0</span>.compare(<span class="kw-2">&</span>key.<span class="number">0</span>) {
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Ordering::Equal => <span class="self">self</span>.<span class="number">1</span>.compare(<span class="kw-2">&</span>key.<span class="number">1</span>),
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not_equal => not_equal,
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}
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}
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}
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<span class="kw">fn </span>main() {
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<span class="kw">let </span>key = (String::from(<span class="string">"foo"</span>), String::from(<span class="string">"bar"</span>));
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<span class="kw">let </span>q1 = Pair(<span class="string">"foo"</span>, <span class="string">"bar"</span>);
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<span class="kw">let </span>q2 = Pair(<span class="string">"boo"</span>, <span class="string">"bar"</span>);
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<span class="kw">let </span>q3 = Pair(<span class="string">"foo"</span>, <span class="string">"baz"</span>);
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<span class="macro">assert!</span>(q1.equivalent(<span class="kw-2">&</span>key));
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<span class="macro">assert!</span>(!q2.equivalent(<span class="kw-2">&</span>key));
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<span class="macro">assert!</span>(!q3.equivalent(<span class="kw-2">&</span>key));
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<span class="macro">assert_eq!</span>(q1.compare(<span class="kw-2">&</span>key), Ordering::Equal);
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<span class="macro">assert_eq!</span>(q2.compare(<span class="kw-2">&</span>key), Ordering::Less);
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<span class="macro">assert_eq!</span>(q3.compare(<span class="kw-2">&</span>key), Ordering::Greater);
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}</code></pre></div>
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</div></details><h2 id="traits" class="section-header">Traits<a href="#traits" class="anchor">§</a></h2><ul class="item-table"><li><div class="item-name"><a class="trait" href="trait.Comparable.html" title="trait equivalent::Comparable">Comparable</a></div><div class="desc docblock-short">Key ordering trait.</div></li><li><div class="item-name"><a class="trait" href="trait.Equivalent.html" title="trait equivalent::Equivalent">Equivalent</a></div><div class="desc docblock-short">Key equivalence trait.</div></li></ul></section></div></main></body></html> |