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92 lines
3.5 KiB
HTML
92 lines
3.5 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>signbit (LIBM)</title>
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<meta name="description" content="signbit (LIBM)">
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<meta name="keywords" content="signbit (LIBM)">
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<link href="Document-Index.html#Document-Index" rel="index" title="Document Index">
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Math.html#Math" rel="up" title="Math">
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<link href="sin.html#sin" rel="next" title="sin">
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</head>
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<body lang="en">
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<a name="signbit"></a>
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<div class="header">
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<p>
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Next: <a href="sin.html#sin" accesskey="n" rel="next">sin</a>, Previous: <a href="scalbn.html#scalbn" accesskey="p" rel="prev">scalbn</a>, Up: <a href="Math.html#Math" accesskey="u" rel="up">Math</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="signbit_002d_002d_002dDoes-floating_002dpoint-number-have-negative-sign_003f"></a>
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<h3 class="section">1.52 <code>signbit</code>—Does floating-point number have negative sign?</h3>
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<a name="index-signbit"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <math.h>
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int signbit(real-floating <var>x</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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The <code>signbit</code> macro determines whether the sign of its argument value is
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negative. The macro reports the sign of all values, including infinities,
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zeros, and NaNs. If zero is unsigned, it is treated as positive. As shown in
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the synopsis, the argument is "real-floating," meaning that any of the real
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floating-point types (float, double, etc.) may be given to it.
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</p>
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<p>Note that because of the possibilities of signed 0 and NaNs, the expression
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"<var>x</var> < 0.0" does not give the same result as <code>signbit</code> in all cases.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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The <code>signbit</code> macro returns a nonzero value if and only if the sign of its
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argument value is negative.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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C99, POSIX.
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</p>
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<br>
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</body>
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