150 lines
5.3 KiB
HTML
150 lines
5.3 KiB
HTML
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<title>modf</title>
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<basefont size="3"> <a name="modf"></a> <a name="tag_03_380"></a><!-- modf -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_380_01"></a>NAME</h4>
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<blockquote>modf, modff, modfl - decompose a floating-point number</blockquote>
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<h4><a name="tag_03_380_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/math.h.html">math.h</a>><br>
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<br>
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double modf(double</tt> <i>x</i><tt>, double *</tt><i>iptr</i><tt>);<br>
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float modff(float</tt> <i>value</i><tt>, float *</tt><i>iptr</i><tt>);<br>
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long double modfl(long double</tt> <i>value</i><tt>, long double *</tt><i>iptr</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_380_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>These functions shall break the argument <i>x</i> into integral and fractional parts, each of which has the same sign as the
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argument. It stores the integral part as a <b>double</b> (for the <i>modf</i>() function), a <b>float</b> (for the <i>modff</i>()
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function), or a <b>long double</b> (for the <i>modfl</i>() function), in the object pointed to by <i>iptr</i>.</p>
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</blockquote>
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<h4><a name="tag_03_380_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, these functions shall return the signed fractional part of <i>x</i>.</p>
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<p><sup>[<a href="javascript:open_code('MX')">MX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> If
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<i>x</i> is NaN, a NaN shall be returned, and *<i>iptr</i> shall be set to a NaN.</p>
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<p>If <i>x</i> is ±Inf, ±0 shall be returned, and *<i>iptr</i> shall be set to ±Inf. <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_380_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_380_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_380_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <i>modf</i>() function computes the function result and *<i>iptr</i> such that:</p>
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<pre>
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<tt>a = modf(x, &iptr) ;
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x == a+*iptr ;
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</tt>
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</pre>
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<p>allowing for the usual floating-point inaccuracies.</p>
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</blockquote>
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<h4><a name="tag_03_380_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_380_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_380_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="frexp.html"><i>frexp</i>()</a> , <a href="isnan.html"><i>isnan</i>()</a> , <a href="ldexp.html"><i>ldexp</i>()</a> ,
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the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/math.h.html"><i><math.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_380_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
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</blockquote>
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<h4><a name="tag_03_380_12"></a>Issue 5</h4>
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<blockquote>
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<p>The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the
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APPLICATION USAGE section.</p>
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</blockquote>
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<h4><a name="tag_03_380_13"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>modff</i>() and <i>modfl</i>() functions are added for alignment with the ISO/IEC 9899:1999 standard.</p>
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<p>The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999
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standard.</p>
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<p>IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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