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<h1 id="firstHeading" class="firstHeading">&#25968;&#23398;&#24120;&#25968;</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-numeric.html">numeric</a></span></div>
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
<h3><span class="mw-headline" id=".E5.B8.B8.E6.95.B0_.28C.2B.2B20_.E8.B5.B7.29">&#24120;&#25968; <span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc-header">
<td colspan="2">
<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-numbers.html">&lt;numbers&gt;</a></code></div>
</td>
</tr>
<tr class="t-dsc-header">
<td colspan="2">
<div>&#23450;&#20041;&#20110;&#21629;&#21517;&#31354;&#38388; <code>std::numbers</code></div>
</td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>e_v</span></span></div>
</div>
</td>
<td><a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/E_(mathematical_constant)">&#25968;&#23398;&#24120;&#25968; <span class="mjax" style="display:none">\(\small e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">e</span></a><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>log2e_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\log_{2}e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">log<span class="t-su t-su-b"><br />
2</span>e</span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>log10e_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\log_{10}e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">log<span class="t-su t-su-b"><br />
10</span>e</span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>pi_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\pi\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">&pi;</span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>inv_pi_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\frac1\pi\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"></span></span>
<table>
<tr>
<td>1</td>
</tr>
<tr>
<td>&pi;</td>
</tr>
</table>
<br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>inv_sqrtpi_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\frac1{\sqrt\pi}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"></span></span>
<table>
<tr>
<td>1</td>
</tr>
<tr>
<td><span class="t-mrad"><span>&radic;</span><span>&pi;</span></span></td>
</tr>
</table>
<br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>ln2_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\ln{2}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">ln 2</span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>ln10_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\ln{10}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">ln 10</span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>sqrt2_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\sqrt2\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mrad"><span>&radic;</span><span>2</span></span></span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>sqrt3_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\sqrt3\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mrad"><span>&radic;</span><span>3</span></span></span><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>inv_sqrt3_v</span></span></div>
</div>
</td>
<td><span class="mjax" style="display:none">\(\frac1{\sqrt3}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"></span></span>
<table>
<tr>
<td>1</td>
</tr>
<tr>
<td><span class="t-mrad"><span>&radic;</span><span>3</span></span></td>
</tr>
</table>
<br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>egamma_v</span></span></div>
</div>
</td>
<td><a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/Euler%E2%80%93Mascheroni_constant">&#27431;&#25289;-&#39532;&#27463;&#32599;&#23612;&#24120;&#25968;</a><br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span>phi_v</span></span></div>
</div>
</td>
<td><a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/Golden_ratio">&#40644;&#37329;&#27604; &Phi; &#24120;&#25968;</a> (<span class="mjax" style="display:none">\(\frac{1+\sqrt5}2\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"></span></span>
<table>
<tr>
<td>1 + <span class="t-mrad"><span>&radic;</span><span>5</span></span></td>
</tr>
<tr>
<td>2</td>
</tr>
</table>
)<br />
<span class="t-mark">(&#21464;&#37327;&#27169;&#26495;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> e</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> log2e</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">log2e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> log10e</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">log10e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> pi</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">pi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_pi</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">inv_pi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_sqrtpi</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">inv_sqrtpi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> ln2</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">ln2_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> ln10</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">ln10_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> sqrt2</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">sqrt2_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> sqrt3</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">sqrt3_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_sqrt3</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">inv_sqrt3_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> egamma</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">egamma_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> phi</span></span></div>
</div>
</td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp">phi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span><br />
<span class="t-mark">(&#24120;&#37327;)</span></td>
</tr>
</table>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#23454;&#20363;&#21270;&#25968;&#23398;&#24120;&#25968;&#21464;&#37327;&#27169;&#26495;&#30340;&#21021;&#31561;&#27169;&#26495;&#30340;&#31243;&#24207;&#20026;&#35884;&#26500;&#12290;</p>
<p>&#26631;&#20934;&#24211;&#23545;&#25152;&#26377;&#28014;&#28857;&#31867;&#22411;&#65288;&#21363; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span></span></span> &#12289; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> &#19982; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span></span></span> &#65289;&#29305;&#21270;&#25968;&#23398;&#24120;&#25968;&#21464;&#37327;&#27169;&#26495;&#12290;</p>
<p>&#31243;&#24207;&#21487;&#20197;&#37096;&#20998;&#25110;&#26174;&#24335;&#29305;&#21270;&#25968;&#23398;&#24120;&#25968;&#21464;&#37327;&#27169;&#26495;&#65292;&#21482;&#35201;&#35813;&#29305;&#21270;&#20381;&#36182;&#31243;&#24207;&#23450;&#20041;&#30340;&#31867;&#22411;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<div class="t-example-live-link"></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;cmath&gt;</span>
<span class="co2">#include &lt;iomanip&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;limits&gt;</span>
<span class="co2">#include &lt;numbers&gt;</span>
<span class="co2">#include &lt;string_view&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">numbers</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>
<span class="sy1">&lt;&lt;</span> <a href="cpp-numeric-math-pow.html"><span class="kw1332">std::<span class="me2">pow</span></span></a><span class="br0">(</span>e, ln2<span class="br0">)</span> <span class="sy2">/</span> <span class="nu0">2</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-numeric-math-pow.html"><span class="kw1332">std::<span class="me2">pow</span></span></a><span class="br0">(</span><a href="cpp-numeric-math-cosh.html"><span class="kw1341">std::<span class="me2">cosh</span></span></a><span class="br0">(</span>pi<span class="br0">)</span>, <span class="nu0">2</span><span class="br0">)</span> <span class="sy2">-</span> <a href="cpp-numeric-math-pow.html"><span class="kw1332">std::<span class="me2">pow</span></span></a><span class="br0">(</span><a href="cpp-numeric-math-sinh.html"><span class="kw1340">std::<span class="me2">sinh</span></span></a><span class="br0">(</span>pi<span class="br0">)</span>, <span class="nu0">2</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-numeric-math-sqrt.html"><span class="kw1329">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span>pi<span class="br0">)</span> <span class="sy2">*</span> inv_sqrtpi <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-numeric-math-pow.html"><span class="kw1332">std::<span class="me2">pow</span></span></a><span class="br0">(</span>sqrt2 <span class="sy2">*</span> sqrt3, <span class="nu0">2</span><span class="br0">)</span> <span class="sy2">/</span> <span class="nu0">6</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> sqrt3 <span class="sy2">*</span> inv_sqrt3 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> log2e <span class="sy2">*</span> ln2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> log10e <span class="sy2">*</span> ln10 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> pi <span class="sy2">*</span> inv_pi <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span>
<span class="sy1">&lt;&lt;</span> phi <span class="sy2">*</span> phi <span class="sy2">-</span> phi <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw4">auto</span> egamma_aprox <span class="sy1">=</span> <span class="br0">[</span><span class="br0">]</span> <span class="br0">{</span>
<span class="kw4">long</span> <span class="kw4">double</span> s <span class="sy1">=</span> <span class="nu0">0</span>, m <span class="sy1">=</span> <span class="nu16">2.0</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">unsigned</span> c <span class="sy1">=</span> <span class="nu0">2</span><span class="sy4">;</span> c <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">1</span><span class="st0">&#39;000&#39;</span><span class="nu8">000</span><span class="sy4">;</span> <span class="sy2">++</span>c, <span class="sy2">++</span>m<span class="br0">)</span> <span class="br0">{</span>
<span class="kw4">const</span> <span class="kw4">long</span> <span class="kw4">double</span> t <span class="sy1">=</span> <a href="cpp-numeric-special_math-riemann_zeta.html"><span class="kw1438">std::<span class="me2">riemann_zeta</span></span></a><span class="br0">(</span>m<span class="br0">)</span> <span class="sy2">/</span> m<span class="sy4">;</span>
<span class="br0">(</span>c <span class="sy3">&amp;</span> <span class="nu0">1</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">0</span> <span class="sy4">?</span> s <span class="sy2">+</span><span class="sy1">=</span> t <span class="sy4">:</span> s <span class="sy2">-</span><span class="sy1">=</span> t<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">return</span> s<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-fixed.html"><span class="kw1784">std::<span class="me2">fixed</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span>egamma_v<span class="sy1">&lt;</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">&gt;</span> <span class="sy2">-</span> egamma_aprox<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw4">constexpr</span> <a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a> &gamma; <span class="br0">{</span><span class="st0">&quot;0.577215664901532860606512090082402&quot;</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;&gamma; as egamma_v&lt;float&gt; = &quot;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-setprecision.html"><span class="kw1796">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="cpp-types-numeric_limits.html"><span class="kw344">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">float</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">float</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;&gamma; as egamma_v&lt;double&gt; = &quot;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-setprecision.html"><span class="kw1796">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="cpp-types-numeric_limits.html"><span class="kw344">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;&gamma; as egamma_v&lt;long double&gt; = &quot;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-setprecision.html"><span class="kw1796">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="cpp-types-numeric_limits.html"><span class="kw344">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;&gamma; with &quot;</span> <span class="sy1">&lt;&lt;</span> &gamma;.<span class="me1">length</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> <span class="nu0">1</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; digits precision = &quot;</span> <span class="sy1">&lt;&lt;</span> &gamma; <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<div class="text source-text">
<pre class="de1">1 1 1 1 1 1 1 1 1
0.000001
&gamma; as egamma_v&lt;float&gt; = 0.5772157
&gamma; as egamma_v&lt;double&gt; = 0.5772156649015329
&gamma; as egamma_v&lt;long double&gt; = 0.5772156649015328606
&gamma; with 34 digits precision = 0.577215664901532860606512090082402</pre></div>
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