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139 lines
6.4 KiB
HTML
139 lines
6.4 KiB
HTML
4 years ago
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>isgreater (LIBM)</title>
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<body lang="en">
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<a name="isgreater"></a>
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<div class="header">
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<p>
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Next: <a href="fpclassify.html#fpclassify" accesskey="n" rel="next">fpclassify</a>, Previous: <a href="infinity.html#infinity" accesskey="p" rel="prev">infinity</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="isgreater_002c-isgreaterequal_002c-isless_002c-islessequal_002c-islessgreater_002c-and-isunordered_002d_002d_002dcomparison-macros"></a>
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<h3 class="section">1.31 <code>isgreater</code>, <code>isgreaterequal</code>, <code>isless</code>, <code>islessequal</code>, <code>islessgreater</code>, and <code>isunordered</code>—comparison macros</h3>
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<a name="index-isgreater"></a>
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<a name="index-isgreaterequal"></a>
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<a name="index-isless"></a>
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<a name="index-islessequal"></a>
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<a name="index-islessgreater"></a>
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<a name="index-isunordered"></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 isgreater(real-floating <var>x</var>, real-floating <var>y</var>);
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int isgreaterequal(real-floating <var>x</var>, real-floating <var>y</var>);
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int isless(real-floating <var>x</var>, real-floating <var>y</var>);
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int islessequal(real-floating <var>x</var>, real-floating <var>y</var>);
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int islessgreater(real-floating <var>x</var>, real-floating <var>y</var>);
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int isunordered(real-floating <var>x</var>, real-floating <var>y</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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<code>isgreater</code>, <code>isgreaterequal</code>, <code>isless</code>, <code>islessequal</code>,
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<code>islessgreater</code>, and <code>isunordered</code> are macros defined for use in
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comparing floating-point numbers without raising any floating-point
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exceptions.
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</p>
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<p>The relational operators (i.e. <, >, <=, and >=) support the usual mathematical
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relationships between numeric values. For any ordered pair of numeric
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values exactly one of the relationships–less, greater, and equal–is
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true. Relational operators may raise the "invalid" floating-point
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exception when argument values are NaNs. For a NaN and a numeric value, or
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for two NaNs, just the unordered relationship is true (i.e., if one or both
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of the arguments a NaN, the relationship is called unordered). The specified
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macros are quiet (non floating-point exception raising) versions of the
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relational operators, and other comparison macros that facilitate writing
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efficient code that accounts for NaNs without suffering the "invalid"
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floating-point exception. In the synopses shown, "real-floating" indicates
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that the argument is an expression of real floating type.
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</p>
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<p>Please note that saying that the macros do not raise floating-point
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exceptions, it is referring to the function that they are performing. It
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is certainly possible to give them an expression which causes an exception.
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For example:
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</p><dl compact="compact">
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<dt><code>NaN < 1.0</code></dt>
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<dd><p>causes an "invalid" exception,
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</p></dd>
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<dt><code>isless(NaN, 1.0)</code></dt>
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<dd><p>does not, and
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</p></dd>
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<dt><code>isless(NaN*0., 1.0)</code></dt>
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<dd><p>causes an exception due to the "NaN*0.", but not from the
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resultant reduced comparison of isless(NaN, 1.0).
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</p></dd>
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</dl>
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<br>
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<p><strong>Returns</strong><br>
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No floating-point exceptions are raised for any of the macros.<br>
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The <code>isgreater</code> macro returns the value of (x) > (y).<br>
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The <code>isgreaterequal</code> macro returns the value of (x) >= (y).<br>
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The <code>isless</code> macro returns the value of (x) < (y).<br>
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The <code>islessequal</code> macro returns the value of (x) <= (y).<br>
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The <code>islessgreater</code> macro returns the value of (x) < (y) || (x) > (y).<br>
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The <code>isunordered</code> macro returns 1 if either of its arguments is NaN and 0 otherwise.
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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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<hr>
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<div class="header">
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<p>
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Next: <a href="fpclassify.html#fpclassify" accesskey="n" rel="next">fpclassify</a>, Previous: <a href="infinity.html#infinity" accesskey="p" rel="prev">infinity</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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</body>
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</html>
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