<!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="API documentation for the Rust `eq` fn in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, eq"><title>std::ptr::eq - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize1.35.0.css"><link rel="stylesheet" type="text/css" href="../../rustdoc1.35.0.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark1.35.0.css"><link rel="stylesheet" type="text/css" href="../../light1.35.0.css" id="themeStyle"><script src="../../storage1.35.0.js"></script><noscript><link rel="stylesheet" href="../../noscript1.35.0.css"></noscript><link rel="shortcut icon" href="../../favicon1.35.0.ico"><style type="text/css">#crate-search{background-image:url("../../down-arrow1.35.0.svg");}</style></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../std/index.html'><img src='../../rust-logo1.35.0.png' alt='logo' width='100'></a><div class="sidebar-elems"><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>ptr</a></p><script>window.sidebarCurrent = {name: 'eq', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush1.35.0.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme1.35.0.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../../settings.html"><img src="../../wheel1.35.0.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span class='since' title='Stable since Rust version 1.17.0'>1.17.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../src/core/ptr.rs.html#2551-2553' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='../index.html'>std</a>::<wbr><a href='index.html'>ptr</a>::<wbr><a class="fn" href=''>eq</a></span></h1><pre class='rust fn'>pub fn eq<T>(a: <a class="primitive" href="../primitive.pointer.html">*const T</a>, b: <a class="primitive" href="../primitive.pointer.html">*const T</a>) -> <a class="primitive" href="../primitive.bool.html">bool</a> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></pre><div class='docblock'><p>Compares raw pointers for equality.</p>
<p>This is the same as using the <code>==</code> operator, but less generic:
the arguments have to be <code>*const T</code> raw pointers,
not anything that implements <code>PartialEq</code>.</p>
<p>This can be used to compare <code>&T</code> references (which coerce to <code>*const T</code> implicitly)
by their address rather than comparing the values they point to
(which is what the <code>PartialEq for &T</code> implementation does).</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ptr</span>;
<span class="kw">let</span> <span class="ident">five</span> <span class="op">=</span> <span class="number">5</span>;
<span class="kw">let</span> <span class="ident">other_five</span> <span class="op">=</span> <span class="number">5</span>;
<span class="kw">let</span> <span class="ident">five_ref</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">five</span>;
<span class="kw">let</span> <span class="ident">same_five_ref</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">five</span>;
<span class="kw">let</span> <span class="ident">other_five_ref</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">other_five</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">five_ref</span> <span class="op">==</span> <span class="ident">same_five_ref</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">ptr</span>::<span class="ident">eq</span>(<span class="ident">five_ref</span>, <span class="ident">same_five_ref</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">five_ref</span> <span class="op">==</span> <span class="ident">other_five_ref</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">ptr</span>::<span class="ident">eq</span>(<span class="ident">five_ref</span>, <span class="ident">other_five_ref</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Aptr%3B%0A%0Alet%20five%20%3D%205%3B%0Alet%20other_five%20%3D%205%3B%0Alet%20five_ref%20%3D%20%26five%3B%0Alet%20same_five_ref%20%3D%20%26five%3B%0Alet%20other_five_ref%20%3D%20%26other_five%3B%0A%0Aassert!(five_ref%20%3D%3D%20same_five_ref)%3B%0Aassert!(ptr%3A%3Aeq(five_ref%2C%20same_five_ref))%3B%0A%0Aassert!(five_ref%20%3D%3D%20other_five_ref)%3B%0Aassert!(!ptr%3A%3Aeq(five_ref%2C%20other_five_ref))%3B%0A%7D">Run</a></pre></div>
<p>Slices are also compared by their length (fat pointers):</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(<span class="kw-2">&</span><span class="ident">a</span>[..<span class="number">3</span>], <span class="kw-2">&</span><span class="ident">a</span>[..<span class="number">3</span>]));
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(<span class="kw-2">&</span><span class="ident">a</span>[..<span class="number">2</span>], <span class="kw-2">&</span><span class="ident">a</span>[..<span class="number">3</span>]));
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(<span class="kw-2">&</span><span class="ident">a</span>[<span class="number">0</span>..<span class="number">2</span>], <span class="kw-2">&</span><span class="ident">a</span>[<span class="number">1</span>..<span class="number">3</span>]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20a%20%3D%20%5B1%2C%202%2C%203%5D%3B%0Aassert!(std%3A%3Aptr%3A%3Aeq(%26a%5B..3%5D%2C%20%26a%5B..3%5D))%3B%0Aassert!(!std%3A%3Aptr%3A%3Aeq(%26a%5B..2%5D%2C%20%26a%5B..3%5D))%3B%0Aassert!(!std%3A%3Aptr%3A%3Aeq(%26a%5B0..2%5D%2C%20%26a%5B1..3%5D))%3B%0A%7D">Run</a></pre></div>
<p>Traits are also compared by their implementation:</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">repr</span>(<span class="ident">transparent</span>)]</span>
<span class="kw">struct</span> <span class="ident">Wrapper</span> { <span class="ident">member</span>: <span class="ident">i32</span> }
<span class="kw">trait</span> <span class="ident">Trait</span> {}
<span class="kw">impl</span> <span class="ident">Trait</span> <span class="kw">for</span> <span class="ident">Wrapper</span> {}
<span class="kw">impl</span> <span class="ident">Trait</span> <span class="kw">for</span> <span class="ident">i32</span> {}
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">let</span> <span class="ident">wrapper</span> <span class="op">=</span> <span class="ident">Wrapper</span> { <span class="ident">member</span>: <span class="number">10</span> };
<span class="comment">// Pointers have equal addresses.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(
<span class="kw-2">&</span><span class="ident">wrapper</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Wrapper</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
<span class="kw-2">&</span><span class="ident">wrapper</span>.<span class="ident">member</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">i32</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>
));
<span class="comment">// Objects have equal addresses, but `Trait` has different implementations.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(
<span class="kw-2">&</span><span class="ident">wrapper</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span>,
<span class="kw-2">&</span><span class="ident">wrapper</span>.<span class="ident">member</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span>,
));
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(
<span class="kw-2">&</span><span class="ident">wrapper</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="kw">dyn</span> <span class="ident">Trait</span>,
<span class="kw-2">&</span><span class="ident">wrapper</span>.<span class="ident">member</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="kw">dyn</span> <span class="ident">Trait</span>,
));
<span class="comment">// Converting the reference to a `*const u8` compares by address.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">eq</span>(
<span class="kw-2">&</span><span class="ident">wrapper</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
<span class="kw-2">&</span><span class="ident">wrapper</span>.<span class="ident">member</span> <span class="kw">as</span> <span class="kw-2">&</span><span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="kw">dyn</span> <span class="ident">Trait</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
));
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23%5Brepr(transparent)%5D%0Astruct%20Wrapper%20%7B%20member%3A%20i32%20%7D%0A%0Atrait%20Trait%20%7B%7D%0Aimpl%20Trait%20for%20Wrapper%20%7B%7D%0Aimpl%20Trait%20for%20i32%20%7B%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20let%20wrapper%20%3D%20Wrapper%20%7B%20member%3A%2010%20%7D%3B%0A%0A%20%20%20%20%2F%2F%20Pointers%20have%20equal%20addresses.%0A%20%20%20%20assert!(std%3A%3Aptr%3A%3Aeq(%0A%20%20%20%20%20%20%20%20%26wrapper%20as%20*const%20Wrapper%20as%20*const%20u8%2C%0A%20%20%20%20%20%20%20%20%26wrapper.member%20as%20*const%20i32%20as%20*const%20u8%0A%20%20%20%20))%3B%0A%0A%20%20%20%20%2F%2F%20Objects%20have%20equal%20addresses%2C%20but%20%60Trait%60%20has%20different%20implementations.%0A%20%20%20%20assert!(!std%3A%3Aptr%3A%3Aeq(%0A%20%20%20%20%20%20%20%20%26wrapper%20as%20%26dyn%20Trait%2C%0A%20%20%20%20%20%20%20%20%26wrapper.member%20as%20%26dyn%20Trait%2C%0A%20%20%20%20))%3B%0A%20%20%20%20assert!(!std%3A%3Aptr%3A%3Aeq(%0A%20%20%20%20%20%20%20%20%26wrapper%20as%20%26dyn%20Trait%20as%20*const%20dyn%20Trait%2C%0A%20%20%20%20%20%20%20%20%26wrapper.member%20as%20%26dyn%20Trait%20as%20*const%20dyn%20Trait%2C%0A%20%20%20%20))%3B%0A%0A%20%20%20%20%2F%2F%20Converting%20the%20reference%20to%20a%20%60*const%20u8%60%20compares%20by%20address.%0A%20%20%20%20assert!(std%3A%3Aptr%3A%3Aeq(%0A%20%20%20%20%20%20%20%20%26wrapper%20as%20%26dyn%20Trait%20as%20*const%20dyn%20Trait%20as%20*const%20u8%2C%0A%20%20%20%20%20%20%20%20%26wrapper.member%20as%20%26dyn%20Trait%20as%20*const%20dyn%20Trait%20as%20*const%20u8%2C%0A%20%20%20%20))%3B%0A%7D">Run</a></pre></div>
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