105 lines
5.9 KiB
HTML
105 lines
5.9 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::ios_base::precision</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_ios_base_precision skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ios_base::</span>precision</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-ios_base.html">ios base</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">streamsize precision<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td class="t-dcl-nopad"></td>
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<div><span class="mw-geshi cpp source-cpp">streamsize precision<span class="br0">(</span> streamsize new_precision <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td></td>
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<p>管理 <span class="t-lc"><a href="cpp-locale-num_put-put.html">std::num_put::do_put</a></span> 所进行的浮点输出精度（即生成多少数位）。</p>
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<div class="t-li1"><span class="t-li">1)</span> 返回当前精度。</div>
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<div class="t-li1"><span class="t-li">2)</span> 设置精度为给定值。返回先前的精度。</div>
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<p><span class="t-lc"><a href="cpp-io-basic_ios-init.html">std::basic_ios::init</a></span> 所建立的默认精度为 6 。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>new_precision</td>
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<td>-</td>
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<td>新的精度设置</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>调用函数前的精度</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">const</span> <span class="kw4">double</span> d <span class="sy1">=</span> <span class="nu16">1.2345678901234</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"The default precision is "</span> <span class="sy1"><<</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">precision</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span><span class="es1">\n</span>"</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"With default precision d is "</span> <span class="sy1"><<</span> d <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">precision</span><span class="br0">(</span><span class="nu0">12</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"With high precision d is "</span> <span class="sy1"><<</span> d <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">The default precision is 6
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With default precision d is 1.23457
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With high precision d is 1.23456789012</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-ios_base-width.html"><span class="t-lines"><span>width</span></span></a></div>
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</div>
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</td>
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<td>管理域的宽度<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-manip-setprecision.html"><span class="t-lines"><span>setprecision</span></span></a></div>
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</div>
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</td>
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<td>更改浮点精度<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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<div class="visualClear"></div>
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