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<h1 id="firstHeading" class="firstHeading">signbit</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="c.html">c</a>&lrm; | <a href="c-numeric.html">numeric</a>&lrm; | <a href="c-numeric-math.html">math</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code>&lt;math.h&gt;</code></div>
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<div><span class="mw-geshi c source-c"><span class="co2">#define signbit(arg) /* implementation defined */</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-c99">(C99 &#36215;)</span></td>
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<p>&#30830;&#23450;&#32473;&#23450;&#30340;&#28014;&#28857;&#25968; <code>arg</code> &#26159;&#21542;&#20026;&#36127;&#12290;&#35813;&#23439;&#36820;&#22238;&#25972;&#25968;&#20540;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>arg</td>
<td>-</td>
<td>&#28014;&#28857;&#20540;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#33509;<code>arg</code>&#20026;&#36127;&#65292;&#21017;&#36820;&#22238;&#38750;&#38646;&#25972;&#25968;&#20540;&#65292;&#21542;&#21017;&#36820;&#22238;<span class="t-c"><span class="mw-geshi c source-c">&#8203;<span class="nu0">0</span>&#8203;</span></span>&#12290;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">&#27880;&#24847;</span></h3>
<p>&#27492;&#23439;&#26816;&#27979;&#38646;&#12289;&#26080;&#31351;&#22823;&#21644; NaN &#30340;&#31526;&#21495;&#12290; signbit &#26159;&#26816;&#39564; NaN &#31526;&#21495;&#30340;&#21807;&#20108;&#21487;&#31227;&#26893;&#26041;&#24335;&#65292;&#21478;&#19968;&#26041;&#24335;&#26159; <span class="t-lc"><a href="c-numeric-math-copysign.html">copysign</a></span> &#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;stdio.h&gt;</span>
<span class="co2">#include &lt;math.h&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;signbit(+0.0) = %d<span class="es1">\n</span>&quot;</span>, signbit<span class="br0">(</span><span class="sy2">+</span><span class="nu16">0.0</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;signbit(-0.0) = %d<span class="es1">\n</span>&quot;</span>, signbit<span class="br0">(</span><span class="sy2">-</span><span class="nu16">0.0</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">signbit(+0.0) = 0
signbit(-0.0) = 128</pre></div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">&#24341;&#29992;</span></h3>
<div class="t-ref-std-11">
<ul>
<li>C11 &#26631;&#20934;&#65288;ISO/IEC 9899:2011&#65289;&#65306;</li>
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<li>7.12.3.6 The signbit macro (p: 237)</li>
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<li>C99 &#26631;&#20934;&#65288;ISO/IEC 9899:1999&#65289;&#65306;</li>
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<li>7.12.3.6 The signbit macro (p: 218)</li>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="c-numeric-math-fabs.html"><span class="t-lines"><span>fabs</span><span>fabsf</span><span>fabsl</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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<td>&#35745;&#31639;&#28014;&#28857;&#20540;&#30340;&#32477;&#23545;&#20540;&#65288; <span class="mjax" style="display:none">\(\small{|x|}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">|x|</span> &#65289;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="c-numeric-math-copysign.html"><span class="t-lines"><span>copysign</span><span>copysignf</span><span>copysignl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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<td>&#20174;&#19968;&#20010;&#32473;&#23450;&#20540;&#30340;&#32477;&#23545;&#20540;&#21644;&#21478;&#19968;&#20010;&#32473;&#23450;&#20540;&#30340;&#31526;&#21495;&#20135;&#29983;&#20540;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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