130 lines
4.4 KiB
HTML
130 lines
4.4 KiB
HTML
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<head>
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<title>The GNU Fortran Compiler: ISNAN</title>
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Intrinsic-Procedures.html#Intrinsic-Procedures" rel="up" title="Intrinsic Procedures">
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<link href="ISHFTC.html#ISHFTC" rel="prev" title="ISHFTC">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="ISNAN"></a>
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<div class="header">
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<p>
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Next: <a href="ITIME.html#ITIME" accesskey="n" rel="next">ITIME</a>, Previous: <a href="ISHFTC.html#ISHFTC" accesskey="p" rel="prev">ISHFTC</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="ISNAN-_002d_002d_002d-Test-for-a-NaN"></a>
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<h3 class="section">9.152 <code>ISNAN</code> — Test for a NaN</h3>
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<a name="index-ISNAN"></a>
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<a name="index-IEEE_002c-ISNAN"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p><code>ISNAN</code> tests whether a floating-point value is an IEEE
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Not-a-Number (NaN).
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</p></dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>GNU extension
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</p>
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</dd>
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<dt><em>Class</em>:</dt>
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<dd><p>Elemental function
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><p><code>ISNAN(X)</code>
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</p>
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</dd>
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<dt><em>Arguments</em>:</dt>
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<dd><table>
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<tr><td width="15%"><var>X</var></td><td width="70%">Variable of the type <code>REAL</code>.</td></tr>
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</table>
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</dd>
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<dt><em>Return value</em>:</dt>
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<dd><p>Returns a default-kind <code>LOGICAL</code>. The returned value is <code>TRUE</code>
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if <var>X</var> is a NaN and <code>FALSE</code> otherwise.
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</p>
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</dd>
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<dt><em>Example</em>:</dt>
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<dd><div class="smallexample">
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<pre class="smallexample">program test_nan
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implicit none
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real :: x
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x = -1.0
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x = sqrt(x)
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if (isnan(x)) stop '"x" is a NaN'
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end program test_nan
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</pre></div>
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</dd>
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</dl>
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