162 lines
6.4 KiB
HTML
162 lines
6.4 KiB
HTML
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<title>fdim</title>
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<basefont size="3"> <a name="fdim"></a> <a name="tag_03_145"></a><!-- fdim -->
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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_145_01"></a>NAME</h4>
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<blockquote>fdim, fdimf, fdiml - compute positive difference between two floating-point numbers</blockquote>
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<h4><a name="tag_03_145_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 fdim(double</tt> <i>x</i><tt>, double</tt> <i>y</i><tt>);<br>
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float fdimf(float</tt> <i>x</i><tt>, float</tt> <i>y</i><tt>);<br>
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long double fdiml(long double</tt> <i>x</i><tt>, long double</tt> <i>y</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_145_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 determine the positive difference between their arguments. If <i>x</i> is greater than <i>y</i>, <i>x</i>-
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<i>y</i> is returned. If <i>x</i> is less than or equal to <i>y</i>, +0 is returned.</p>
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<p>An application wishing to check for error situations should set <i>errno</i> to zero and call
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<i>feclearexcept</i>(FE_ALL_EXCEPT) before calling these functions. On return, if <i>errno</i> is non-zero or
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<i>fetestexcept</i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.</p>
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</blockquote>
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<h4><a name="tag_03_145_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, these functions shall return the positive difference value.</p>
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<p>If <i>x</i>- <i>y</i> is positive and overflows, a range error shall occur and <i>fdim</i>(), <i>fdimf</i>(), and <i>fdiml</i>()
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shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.</p>
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<p>If <i>x</i>- <i>y</i> is positive and underflows, a range error may occur, and either ( <i>x</i>- <i>y</i>) (if representable),
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<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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or 0.0 (if supported), <img src="../images/opt-end.gif" alt="[Option End]" border="0"> or an implementation-defined value
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shall be returned.</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> or <i>y</i> is NaN, a NaN shall be returned. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_145_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>fdim</i>() function shall fail if:</p>
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<dl compact>
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<dt>Range Error</dt>
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<dd>The result overflows.
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<p>If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then <i>errno</i> shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be
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raised.</p>
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</dd>
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</dl>
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<p>The <i>fdim</i>() function may fail if:</p>
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<dl compact>
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<dt>Range Error</dt>
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<dd>The result underflows.
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<p>If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then <i>errno</i> shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be
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raised.</p>
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</dd>
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</dl>
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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_145_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_145_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>On implementations supporting IEEE Std 754-1985, <i>x</i>- <i>y</i> cannot underflow, and hence the 0.0 return value
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is shaded as an extension for implementations supporting the XSI extension rather than an MX extension.</p>
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<p>On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of
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each other, but at least one of them must be non-zero.</p>
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</blockquote>
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<h4><a name="tag_03_145_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_145_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_145_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="feclearexcept.html"><i>feclearexcept</i>()</a> , <a href="fetestexcept.html"><i>fetestexcept</i>()</a> , <a href=
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"fmax.html"><i>fmax</i>()</a> , <a href="fmin.html"><i>fmin</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap04.html#tag_04_18">Section 4.18, Treatment of Error Conditions for
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Mathematical Functions</a>, <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_145_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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