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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="API documentation for the Rust `AsPrimitive` trait in crate `num_traits`."><meta name="keywords" content="rust, rustlang, rust-lang, AsPrimitive"><title>num_traits::cast::AsPrimitive - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="shortcut icon" href="../../favicon.ico"><style type="text/css">#crate-search{background-image:url("../../down-arrow.svg");}</style></head><body class="rustdoc trait"><!--[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">&#9776;</div><a href='../../num_traits/index.html'><div class='logo-container'><img src='../../rust-logo.png' alt='logo'></div></a><p class='location'>Trait AsPrimitive</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.as_">as_</a></div><a class="sidebar-title" href="#foreign-impls">Implementations on Foreign Types</a><div class="sidebar-links"><a href="#impl-AsPrimitive%3Cchar%3E-for-char">char</a><a href="#impl-AsPrimitive%3Cchar%3E-for-u8">u8</a><a href="#impl-AsPrimitive%3Cf32%3E-for-f32">f32</a><a href="#impl-AsPrimitive%3Cf32%3E-for-f64">f64</a><a href="#impl-AsPrimitive%3Cf32%3E-for-i128">i128</a><a href="#impl-AsPrimitive%3Cf32%3E-for-i16">i16</a><a href="#impl-AsPrimitive%3Cf32%3E-for-i32">i32</a><a href="#impl-AsPrimitive%3Cf32%3E-for-i64">i64</a><a href="#impl-AsPrimitive%3Cf32%3E-for-i8">i8</a><a href="#impl-AsPrimitive%3Cf32%3E-for-isize">isize</a><a href="#impl-AsPrimitive%3Cf32%3E-for-u128">u128</a><a href="#impl-AsPrimitive%3Cf32%3E-for-u16">u16</a><a href="#impl-AsPrimitive%3Cf32%3E-for-u32">u32</a><a href="#impl-AsPrimitive%3Cf32%3E-for-u64">u64</a><a href="#impl-AsPrimitive%3Cf32%3E-for-u8">u8</a><a href="#impl-AsPrimitive%3Cf32%3E-for-usize">usize</a><a href="#impl-AsPrimitive%3Cf64%3E-for-f32">f32</a><a href="#impl-AsPrimitive%3Cf64%3E-for-f64">f64</a><a href="#impl-AsPrimitive%3Cf64%3E-for-i128">i128</a><a href="#impl-AsPrimitive%3Cf64%3E-for-i16">i16</a><a href="#impl-AsPrimitive%3Cf64%3E-for-i32">i32</a><a href="#impl-AsPrimitive%3Cf64%3E-for-i64">i64</a><a href="#impl-AsPrimitive%3Cf64%3E-for-i8">i8</a><a href="#impl-AsPrimitive%3Cf64%3E-for-isize">isize</a><a href="#impl-AsPrimitive%3Cf64%3E-for-u128">u128</a><a href="#impl-AsPrimitive%3Cf64%3E-for-u16">u16</a><a href="#impl-AsPrimitive%3Cf64%3E-for-u32">u32</a><a href="#impl-AsPrimitive%3Cf64%3E-for-u64">u64</a><a href="#impl-AsPrimitive%3Cf64%3E-for-u8">u8</a><a href="#impl-AsPrimitive%3Cf64%3E-for-usize">usize</a><a href="#impl-AsPrimitive%3Ci128%3E-for-bool">bool</a><a href="#impl-AsPrimitive%3Ci128%3E-for-char">char</a><a href="#impl-AsPrimitive%3Ci128%3E-for-f32">f32</a><a href="#impl-AsPrimitive%3Ci128%3E-for-f64">f64</a><a href="#impl-AsPrimitive%3Ci128%3E-for-i128">i128</a><a href="#impl-AsPrimitive%3Ci128%3E-for-i16">i16</a><a href="#impl-AsPrimitive%3Ci128%3E-for-i32">i32</a><a href="#impl-AsPrimitive%3Ci128%3E-for-i64">i64</a><a href="#impl-AsPrimitive%3Ci128%3E-for-i8">i8</a><a href="#impl-AsPrimitive%3Ci128%3E-for-isize">isize</a><a href="#impl-AsPrimitive%3Ci128%3E-for-u128">u128</a><a href="#impl-AsPrimitive%3Ci128%3E-for-u16">u16</a><a href="#impl-AsPrimitive%3Ci128%3E-for-u32">u32</a><a href="#impl-AsPrimitive%3Ci128%3E-for-u64">u64</a><a href="#impl-AsPrimitive%3Ci128%3E-for-u8">u8</a><a href="#impl-AsPrimitive%3Ci128%3E-for-usize">usize</a><a href="#impl-AsPrimitive%3Ci16%3
fn <a href='#tymethod.as_' class='fnname'>as_</a>(self) -&gt; T;
}</pre></div><div class='docblock'><p>A generic interface for casting between machine scalars with the
<code>as</code> operator, which admits narrowing and precision loss.
Implementers of this trait AsPrimitive should behave like a primitive
numeric type (e.g. a newtype around another primitive), and the
intended conversion must never fail.</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">let</span> <span class="ident">three</span>: <span class="ident">i32</span> <span class="op">=</span> (<span class="number">3.14159265f32</span>).<span class="ident">as_</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">three</span>, <span class="number">3</span>);</pre></div>
<h1 id="safety" class="section-header"><a href="#safety">Safety</a></h1>
<p>Currently, some uses of the <code>as</code> operator are not entirely safe.
In particular, it is undefined behavior if:</p>
<ul>
<li>A truncated floating point value cannot fit in the target integer
type (<a href="https://github.com/rust-lang/rust/issues/10184">#10184</a>);</li>
</ul>
<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">u8</span> <span class="op">=</span> (<span class="number">1.04E+17</span>).<span class="ident">as_</span>(); <span class="comment">// UB</span></pre></div>
<ul>
<li>Or a floating point value does not fit in another floating
point type (<a href="https://github.com/rust-lang/rust/issues/15536">#15536</a>).</li>
</ul>
<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore">
<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">f32</span> <span class="op">=</span> (<span class="number">1e300f64</span>).<span class="ident">as_</span>(); <span class="comment">// UB</span></pre></div>
</div>
<h2 id='required-methods' class='small-section-header'>Required methods<a href='#required-methods' class='anchor'></a></h2><div class='methods'><h3 id='tymethod.as_' class='method'><code id='as_.v'>fn <a href='#tymethod.as_' class='fnname'>as_</a>(self) -&gt; T</code></h3><div class='docblock'><p>Convert a value to another, using the <code>as</code> operator.</p>
</div></div><span class='loading-content'>Loading content...</span>
<h2 id='foreign-impls' class='small-section-header'>Implementations on Foreign Types<a href='#foreign-impls' class='anchor'></a></h2><h3 id='impl-AsPrimitive%3Cchar%3E-for-u8' class='impl'><code class='in-band'>impl <a class="trait" href="../../num_traits/cast/trait.AsPrimitive.html" title="trait num_traits::cast::AsPrimitive">AsPrimitive</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.char.html">char</a>&gt; for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a></code><a href='#impl-AsPrimitive%3Cchar%3E-for-u8' class='anchor'></a><a class='srclink' href='../../src/num_traits/cast.rs.html#729-731' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.as_' class="method hidden"><code id='as_.v-1'>fn <a href='#method.as_' class='fnname'>as_</a>(self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.char.html">char</a></code><a class='srclink' href='../../src/num_traits/cast.rs.html#730' title='goto source code'>[src]</a></h4></div><h3 id='impl-AsPrimitive%3Cf32%3E-for-u8' class='impl'><code class='in-band'>impl <a class="trait" href="../../num_traits/cast/trait.AsPrimitive.html" title="trait num_traits::cast::AsPrimitive">AsPrimitive</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f32.html">f32</a>&gt; for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a></code><a href='#impl-AsPrimitive%3Cf32%3E-for-u8' class='anchor'></a><a class='srclink' href='../../src/num_traits/cast.rs.html#729-731' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.as_-1' class="method hidden"><code id='as_.v-2'>fn <a href='#method.as_' class='fnname'>as_</a>(self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f32.html">f32</a></code><a class='srclink' href='../../src/num_traits/cast.rs.html#730' title='goto source code'>[src]</a></h4></div><h3 id='impl-AsPrimitive%3Cf64%3E-for-u8' class='impl'><code class='in-band'>impl <a class="trait" href="../../num_traits/cast/trait.AsPrimitive.html" title="trait num_traits::cast::AsPrimitive">AsPrimitive</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a>&gt; for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a></code><a href='#impl-AsPrimitive%3Cf64%3E-for-u8' class='anchor'></a><a class='srclink' href='../../src/num_traits/cast.rs.html#729-731' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.as_-2' class="method hidden"><code id='as_.v-3'>fn <a href='#method.as_' class='fnname'>as_</a>(self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a></code><a class='srclink' href='../../src/num_traits/cast.rs.html#730' title='goto source code'>[src]</a></h4></div><h3 id='impl-AsPrimitive%3Cu8%3E-for-u8' class='impl'><code class='in-band'>impl <a class="trait" href="../../num_traits/cast/trait.AsPrimitive.html" title="trait num_traits::cast::AsPrimitive">AsPrimitive</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a>&gt; for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a></code><a href='#impl-AsPrimitive%3Cu8%3E-for-u8' class='anchor'></a><a class='srclink' href='../../src/num_traits/cast.rs.html#729-731' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.as_-3' class="method hidden"><code id='as_.v-4'>fn <a href='#method.as_' class='fnname'>as_</a>(self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a></code><a class='srclink' href='../../src/num_traits/cast.rs.html#730' title='goto source code'>[src]</a></h4></div><h3 id='impl-AsPrimitive%3Cu16%3E-for-u8' class='impl'><code class='in-band'>impl <a class="trait" href="../../num_traits/cast/trait.AsPrimitive.html" title="trait num_traits::cast::AsPrimitive">AsPrimiti
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