<!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 to the Rust file `libcore/num/dec2flt/num.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>num.rs.html -- source</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><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[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='../../../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../../../settings.html"><img src="../../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
<span id="2"> 2</span>
<span id="3"> 3</span>
<span id="4"> 4</span>
<span id="5"> 5</span>
<span id="6"> 6</span>
<span id="7"> 7</span>
<span id="8"> 8</span>
<span id="9"> 9</span>
<span id="10">10</span>
<span id="11">11</span>
<span id="12">12</span>
<span id="13">13</span>
<span id="14">14</span>
<span id="15">15</span>
<span id="16">16</span>
<span id="17">17</span>
<span id="18">18</span>
<span id="19">19</span>
<span id="20">20</span>
<span id="21">21</span>
<span id="22">22</span>
<span id="23">23</span>
<span id="24">24</span>
<span id="25">25</span>
<span id="26">26</span>
<span id="27">27</span>
<span id="28">28</span>
<span id="29">29</span>
<span id="30">30</span>
<span id="31">31</span>
<span id="32">32</span>
<span id="33">33</span>
<span id="34">34</span>
<span id="35">35</span>
<span id="36">36</span>
<span id="37">37</span>
<span id="38">38</span>
<span id="39">39</span>
<span id="40">40</span>
<span id="41">41</span>
<span id="42">42</span>
<span id="43">43</span>
<span id="44">44</span>
<span id="45">45</span>
<span id="46">46</span>
<span id="47">47</span>
<span id="48">48</span>
<span id="49">49</span>
<span id="50">50</span>
<span id="51">51</span>
<span id="52">52</span>
<span id="53">53</span>
<span id="54">54</span>
<span id="55">55</span>
<span id="56">56</span>
<span id="57">57</span>
<span id="58">58</span>
<span id="59">59</span>
<span id="60">60</span>
<span id="61">61</span>
<span id="62">62</span>
<span id="63">63</span>
<span id="64">64</span>
<span id="65">65</span>
<span id="66">66</span>
<span id="67">67</span>
<span id="68">68</span>
<span id="69">69</span>
<span id="70">70</span>
<span id="71">71</span>
<span id="72">72</span>
<span id="73">73</span>
<span id="74">74</span>
<span id="75">75</span>
<span id="76">76</span>
<span id="77">77</span>
<span id="78">78</span>
<span id="79">79</span>
<span id="80">80</span>
<span id="81">81</span>
<span id="82">82</span>
<span id="83">83</span>
<span id="84">84</span>
<span id="85">85</span>
<span id="86">86</span>
<span id="87">87</span>
<span id="88">88</span>
<span id="89">89</span>
<span id="90">90</span>
<span id="91">91</span>
<span id="92">92</span>
<span id="93">93</span>
</pre><pre class="rust ">
<span class="comment">// Copyright 2015 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! Utility functions for bignums that don't make too much sense to turn into methods.</span>
<span class="comment">// FIXME This module's name is a bit unfortunate, since other modules also import `core::num`.</span>
<span class="kw">use</span> <span class="ident">cmp</span>::<span class="ident">Ordering</span>::{<span class="self">self</span>, <span class="ident">Less</span>, <span class="ident">Equal</span>, <span class="ident">Greater</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="ident">num</span>::<span class="ident">bignum</span>::<span class="ident">Big32x40</span> <span class="kw">as</span> <span class="ident">Big</span>;
<span class="doccomment">/// Test whether truncating all bits less significant than `ones_place` introduces</span>
<span class="doccomment">/// a relative error less, equal, or greater than 0.5 ULP.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">compare_with_half_ulp</span>(<span class="ident">f</span>: <span class="kw-2">&</span><span class="ident">Big</span>, <span class="ident">ones_place</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">Ordering</span> {
<span class="kw">if</span> <span class="ident">ones_place</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="ident">Less</span>;
}
<span class="kw">let</span> <span class="ident">half_bit</span> <span class="op">=</span> <span class="ident">ones_place</span> <span class="op">-</span> <span class="number">1</span>;
<span class="kw">if</span> <span class="ident">f</span>.<span class="ident">get_bit</span>(<span class="ident">half_bit</span>) <span class="op">==</span> <span class="number">0</span> {
<span class="comment">// < 0.5 ULP</span>
<span class="kw">return</span> <span class="ident">Less</span>;
}
<span class="comment">// If all remaining bits are zero, it's = 0.5 ULP, otherwise > 0.5</span>
<span class="comment">// If there are no more bits (half_bit == 0), the below also correctly returns Equal.</span>
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">half_bit</span> {
<span class="kw">if</span> <span class="ident">f</span>.<span class="ident">get_bit</span>(<span class="ident">i</span>) <span class="op">==</span> <span class="number">1</span> {
<span class="kw">return</span> <span class="ident">Greater</span>;
}
}
<span class="ident">Equal</span>
}
<span class="doccomment">/// Convert an ASCII string containing only decimal digits to a `u64`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Does not perform checks for overflow or invalid characters, so if the caller is not careful,</span>
<span class="doccomment">/// the result is bogus and can panic (though it won't be `unsafe`). Additionally, empty strings</span>
<span class="doccomment">/// are treated as zero. This function exists because</span>
<span class="doccomment">///</span>
<span class="doccomment">/// 1. using `FromStr` on `&[u8]` requires `from_utf8_unchecked`, which is bad, and</span>
<span class="doccomment">/// 2. piecing together the results of `integral.parse()` and `fractional.parse()` is</span>
<span class="doccomment">/// more complicated than this entire function.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">from_str_unchecked</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>(<span class="ident">bytes</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">u64</span> <span class="kw">where</span> <span class="ident">T</span> : <span class="ident">IntoIterator</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">u8</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> <span class="kw-2">&</span><span class="ident">c</span> <span class="kw">in</span> <span class="ident">bytes</span> {
<span class="ident">result</span> <span class="op">=</span> <span class="ident">result</span> <span class="op">*</span> <span class="number">10</span> <span class="op">+</span> (<span class="ident">c</span> <span class="op">-</span> <span class="string">b'0'</span>) <span class="kw">as</span> <span class="ident">u64</span>;
}
<span class="ident">result</span>
}
<span class="doccomment">/// Convert a string of ASCII digits into a bignum.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Like `from_str_unchecked`, this function relies on the parser to weed out non-digits.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">digits_to_big</span>(<span class="ident">integral</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">fractional</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>]) <span class="op">-></span> <span class="ident">Big</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">f</span> <span class="op">=</span> <span class="ident">Big</span>::<span class="ident">from_small</span>(<span class="number">0</span>);
<span class="kw">for</span> <span class="kw-2">&</span><span class="ident">c</span> <span class="kw">in</span> <span class="ident">integral</span>.<span class="ident">iter</span>().<span class="ident">chain</span>(<span class="ident">fractional</span>) {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> (<span class="ident">c</span> <span class="op">-</span> <span class="string">b'0'</span>) <span class="kw">as</span> <span class="ident">u32</span>;
<span class="ident">f</span>.<span class="ident">mul_small</span>(<span class="number">10</span>);
<span class="ident">f</span>.<span class="ident">add_small</span>(<span class="ident">n</span>);
}
<span class="ident">f</span>
}
<span class="doccomment">/// Unwraps a bignum into a 64 bit integer. Panics if the number is too large.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_u64</span>(<span class="ident">x</span>: <span class="kw-2">&</span><span class="ident">Big</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">bit_length</span>() <span class="op"><</span> <span class="number">64</span>);
<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">digits</span>();
<span class="kw">if</span> <span class="ident">d</span>.<span class="ident">len</span>() <span class="op"><</span> <span class="number">2</span> {
<span class="ident">d</span>[<span class="number">0</span>] <span class="kw">as</span> <span class="ident">u64</span>
} <span class="kw">else</span> {
(<span class="ident">d</span>[<span class="number">1</span>] <span class="kw">as</span> <span class="ident">u64</span>) <span class="op"><<</span> <span class="number">32</span> <span class="op">|</span> <span class="ident">d</span>[<span class="number">0</span>] <span class="kw">as</span> <span class="ident">u64</span>
}
}
<span class="doccomment">/// Extract a range of bits.</span>
<span class="doccomment">/// Index 0 is the least significant bit and the range is half-open as usual.</span>
<span class="doccomment">/// Panics if asked to extract more bits than fit into the return type.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_bits</span>(<span class="ident">x</span>: <span class="kw-2">&</span><span class="ident">Big</span>, <span class="ident">start</span>: <span class="ident">usize</span>, <span class="ident">end</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">end</span> <span class="op">-</span> <span class="ident">start</span> <span class="op"><=</span> <span class="number">64</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> (<span class="ident">start</span>..<span class="ident">end</span>).<span class="ident">rev</span>() {
<span class="ident">result</span> <span class="op">=</span> <span class="ident">result</span> <span class="op"><<</span> <span class="number">1</span> <span class="op">|</span> <span class="ident">x</span>.<span class="ident">get_bit</span>(<span class="ident">i</span>) <span class="kw">as</span> <span class="ident">u64</span>;
}
<span class="ident">result</span>
}
</pre>
</section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../../../";window.currentCrate = "core";</script><script src="../../../../aliases.js"></script><script src="../../../../main.js"></script><script defer src="../../../../search-index.js"></script></body></html>
distrib
>
Mageia
>
6
>
armv7hl
>
media
>
core-updates
>
by-pkgid
>
4e2dbb669434a7691662cb2f0ad38972
>
files
>
11574
