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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_numeric_math_fpclassify skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading">fpclassify</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 fpclassify(arg) /* implementation defined */</span></span></div>
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<td><span class="t-mark-rev t-since-c99">(C99 &#36215;)</span></td>
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<p>&#24402;&#31867;&#28014;&#28857;&#20540; <code>arg</code> &#21040;&#19979;&#21015;&#31867;&#21035;&#20013;&#65306;&#38646;&#12289;&#38750;&#27491;&#35268;&#12289;&#27491;&#35268;&#12289;&#26080;&#31351;&#22823;&#12289; NaN &#25110;&#23454;&#29616;&#23450;&#20041;&#31867;&#21035;&#12290;&#35813;&#23439;&#36820;&#22238;&#25972;&#25968;&#20540;&#12290;</p>
<p>&#24573;&#30053; <span class="t-lc"><a href="c-types-limits-FLT_EVAL_METHOD.html">FLT_EVAL_METHOD</a></span> &#65306;&#21363;&#20351;&#20197;&#22810;&#20110;&#21442;&#25968;&#31867;&#22411;&#30340;&#33539;&#22260;&#21644;&#31934;&#24230;&#23545;&#23427;&#27714;&#20540;&#65292;&#39318;&#20808;&#20173;&#23558;&#23427;&#36716;&#25442;&#21040;&#20854;&#35821;&#20041;&#31867;&#22411;&#65292;&#28982;&#21518;&#20998;&#31867;&#22522;&#20110;&#35813;&#31867;&#22411;&#65306;&#27491;&#35268;&#30340; <code>long double</code> &#20540;&#21487;&#33021;&#22312;&#36716;&#25442;&#21040; <code>double</code> &#26102;&#21464;&#20026;&#38750;&#27491;&#35268;&#65292;&#32780;&#22312;&#36716;&#25442;&#21040; <code>float</code> &#26102;&#21464;&#20026;&#38646;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
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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>&#25351;&#26126; <code>arg</code> &#31867;&#21035;&#30340; <span class="t-lc"><a href="c-numeric-math-FP_categories.html">FP_INFINITE</a></span> &#12289; <span class="t-lc"><a href="c-numeric-math-FP_categories.html">FP_NAN</a></span> &#12289; <span class="t-lc"><a href="c-numeric-math-FP_categories.html">FP_NORMAL</a></span> &#12289; <span class="t-lc"><a href="c-numeric-math-FP_categories.html">FP_SUBNORMAL</a></span> &#12289; <span class="t-lc"><a href="c-numeric-math-FP_categories.html">FP_ZERO</a></span> &#25110;&#23454;&#29616;&#23450;&#20041;&#31867;&#22411;&#20043;&#19968;&#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>
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<div class="c source-c">
<pre class="de1"><span class="co2">#include &lt;stdio.h&gt;</span>
<span class="co2">#include &lt;math.h&gt;</span>
<span class="co2">#include &lt;float.h&gt;</span>
<span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>show_classification<span class="br0">(</span><span class="kw4">double</span> x<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">switch</span><span class="br0">(</span>fpclassify<span class="br0">(</span>x<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">case</span> <a href="c-numeric-math-FP_categories.html"><span class="kw712">FP_INFINITE</span></a><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;Inf&quot;</span><span class="sy4">;</span>
<span class="kw1">case</span> <a href="c-numeric-math-FP_categories.html"><span class="kw713">FP_NAN</span></a><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;NaN&quot;</span><span class="sy4">;</span>
<span class="kw1">case</span> <a href="c-numeric-math-FP_categories.html"><span class="kw714">FP_NORMAL</span></a><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;normal&quot;</span><span class="sy4">;</span>
<span class="kw1">case</span> <a href="c-numeric-math-FP_categories.html"><span class="kw715">FP_SUBNORMAL</span></a><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;subnormal&quot;</span><span class="sy4">;</span>
<span class="kw1">case</span> <a href="c-numeric-math-FP_categories.html"><span class="kw716">FP_ZERO</span></a><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;zero&quot;</span><span class="sy4">;</span>
<span class="kw1">default</span><span class="sy4">:</span> <span class="kw1">return</span> <span class="st0">&quot;unknown&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</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;1.0/0.0 is %s<span class="es1">\n</span>&quot;</span>, show_classification<span class="br0">(</span><span class="nu0">1</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;0.0/0.0 is %s<span class="es1">\n</span>&quot;</span>, show_classification<span class="br0">(</span><span class="nu16">0.0</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;DBL_MIN/2 is %s<span class="es1">\n</span>&quot;</span>, show_classification<span class="br0">(</span><a href="c-types-limits.html"><span class="kw375">DBL_MIN</span></a><span class="sy2">/</span><span class="nu0">2</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;-0.0 is %s<span class="es1">\n</span>&quot;</span>, show_classification<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;1.0 is %s<span class="es1">\n</span>&quot;</span>, show_classification<span class="br0">(</span><span class="nu16">1.0</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">1.0/0.0 is Inf
0.0/0.0 is NaN
DBL_MIN/2 is subnormal
-0.0 is zero
1.0 is normal</pre></div>
</div>
</div>
<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>
</ul>
<dl>
<dd>
<ul>
<li>7.12.3.1 The fpclassify macro (p: 235)</li>
</ul>
</dd>
</dl>
<div class="t-ref-std-c99">
<ul>
<li>C99 &#26631;&#20934;&#65288;ISO/IEC 9899:1999&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>7.12.3.1 The fpclassify macro (p: 216)</li>
</ul>
</dd>
</dl>
</div>
<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-isfinite.html"><span class="t-lines"><span>isfinite</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
</div>
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<td>&#26816;&#26597;&#32473;&#23450;&#25968;&#26159;&#21542;&#20855;&#26377;&#26377;&#38480;&#20540;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-numeric-math-isinf.html"><span class="t-lines"><span>isinf</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597;&#32473;&#23450;&#25968;&#26159;&#21542;&#26159;&#26080;&#31351;&#22823;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-numeric-math-isnan.html"><span class="t-lines"><span>isnan</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597;&#32473;&#23450;&#25968;&#26159;&#21542;&#20026; NaN<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-numeric-math-isnormal.html"><span class="t-lines"><span>isnormal</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597;&#32473;&#23450;&#25968;&#26159;&#21542;&#27491;&#35268;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div class="visualClear"></div>
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