<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Provides a macro to simplify operator overloading."><title>overload - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../static.files/rustdoc-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="overload"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.0 (aedd173a2 2024-03-17)"data-channel="1.77.0"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="../crates.js"></script><scriptdefersrc="../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../static.files/noscript-04d5337699b92874.css"></noscript><linkrel="alternate icon"type="image/png"href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc mod crate"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle"title="show sidebar"></button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../overload/index.html">overload</a><spanclass="version">0.1.1</span></h2></div><divclass="sidebar-elems"><ulclass="block">
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../overload/all.html"title="show sidebar"></a></div><inputclass="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"><divid="help-button"tabindex="-1"><ahref="../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Crate <aclass="mod"href="#">overload</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../src/overload/lib.rs.html#1-257">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Provides a macro to simplify operator overloading.</p>
<p>We can overload the addition of <code>Val</code>s like so:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((a: Val) + (b: Val) -> Val { Val { v: a.v + b.v } });</code></pre></div>
<p>The macro call above generates the following code:</p>
<divclass="example-wrap ignore"><ahref="#"class="tooltip"title="This example is not tested">ⓘ</a><preclass="rust rust-example-rendered"><code><spanclass="kw">impl </span>ops::Add<Val><spanclass="kw">for </span>Val {
<p>If we also wanted to overload addition for the borrowed type <code>&Val</code> we could write:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((a: <spanclass="kw-2">&</span>Val) + (b: <spanclass="kw-2">&</span>Val) -> Val { Val { v: a.v + b.v } });</code></pre></div>
<p>We might also want to overload addition between the owned and borrowed types:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((a: Val) + (b: <spanclass="kw-2">&</span>Val) -> Val { Val { v: a.v + b.v } });
<spanclass="macro">overload!</span>((a: <spanclass="kw-2">&</span>Val) + (b: Val) -> Val { Val { v: a.v + b.v } });</code></pre></div>
<p>Let’s see how we can write these combinations more concisely.</p>
<p>We can include a <code>?</code> in front of a type to indicate that it should stand in for both the owned and borrowed type.</p>
<p>To overload addition for all four combinations between <code>Val</code> and <code>&Val</code> we can therefore simply include a <code>?</code> in front of both types:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((a: <spanclass="question-mark">?</span>Val) + (b: <spanclass="question-mark">?</span>Val) -> Val { Val { v: a.v + b.v } });</code></pre></div>
<p>The macro call above generates the following code:</p>
<divclass="example-wrap ignore"><ahref="#"class="tooltip"title="This example is not tested">ⓘ</a><preclass="rust rust-example-rendered"><code><spanclass="kw">impl </span>ops::Add<Val><spanclass="kw">for </span>Val {
<p>The general syntax to overload a binary operator between types <code><a_type></code> and <code><b_type></code> is:</p>
<divclass="example-wrap ignore"><ahref="#"class="tooltip"title="This example is not tested">ⓘ</a><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((<a_ident>: <a_type>) <op> (<b_ident>: <b_type>) -><out_type> { <spanclass="comment">/*body*/ </span>});</code></pre></div>
<p>Inside the body you can use <code><a_ident></code> and <code><b_ident></code> freely to perform any computation.</p>
<p>The last line of the body needs to be an expression (i.e. no <code>;</code> at the end of the line) of type <code><out_type></code>.</p>
<p>The general syntax to overload an assignment operator between types <code><a_type></code> and <code><b_type></code> is:</p>
<divclass="example-wrap ignore"><ahref="#"class="tooltip"title="This example is not tested">ⓘ</a><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>((<a_ident>: <spanclass="kw-2">&mut </span><a_type>) <op> (<b_ident>: <b_type>) { <spanclass="comment">/*body*/ </span>});</code></pre></div>
<p>Inside the body you can use <code><a_ident></code> and <code><b_ident></code> freely to perform any computation and mutate <code><a_ident></code> as desired.</p>
<p>The general syntax to overload a unary operator for type <code><a_type></code> is:</p>
<divclass="example-wrap ignore"><ahref="#"class="tooltip"title="This example is not tested">ⓘ</a><preclass="rust rust-example-rendered"><code><spanclass="macro">overload!</span>(<op> (<a_ident>: <a_type>) -><out_type> { <spanclass="comment">/*body*/ </span>});</code></pre></div>
<p>Inside the body you can use <code><a_ident></code> freely to perform any computation.</p>
<p>The last line of the body needs to be an expression (i.e. no <code>;</code> at the end of the line) of type <code><out_type></code>.</p>
</div></details><h2id="macros"class="section-header">Macros<ahref="#macros"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="macro"href="macro.overload.html"title="macro overload::overload">overload</a></div><divclass="desc docblock-short">Overloads an operator. See the <ahref="index.html">module level documentation</a> for more information.</div></li></ul></section></div></main></body></html>
