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| 2 | <head> | |
| 3 | <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> | |
| 4 | <title>Finding the Next Representable Value in a Specific Direction (nextafter)</title> | |
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| 22 | <div class="spirit-nav"> | |
| 23 | <a accesskey="p" href="../next_float.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../next_float.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="float_next.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> | |
| 24 | </div> | |
| 25 | <div class="section"> | |
| 26 | <div class="titlepage"><div><div><h3 class="title"> | |
| 27 | <a name="math_toolkit.next_float.nextafter"></a><a class="link" href="nextafter.html" title="Finding the Next Representable Value in a Specific Direction (nextafter)">Finding the Next Representable | |
| 28 | Value in a Specific Direction (nextafter)</a> | |
| 29 | </h3></div></div></div> | |
| 30 | <h5> | |
| 31 | <a name="math_toolkit.next_float.nextafter.h0"></a> | |
| 32 | <span class="phrase"><a name="math_toolkit.next_float.nextafter.synopsis"></a></span><a class="link" href="nextafter.html#math_toolkit.next_float.nextafter.synopsis">Synopsis</a> | |
| 33 | </h5> | |
| 34 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">special_functions</span><span class="special">/</span><span class="identifier">next</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
| 35 | </pre> | |
| 36 | <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span> | |
| 37 | ||
| 38 | <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">FPT</span><span class="special">></span> | |
| 39 | <span class="identifier">FPT</span> <span class="identifier">nextafter</span><span class="special">(</span><span class="identifier">FPT</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">FPT</span> <span class="identifier">direction</span><span class="special">);</span> | |
| 40 | ||
| 41 | <span class="special">}}</span> <span class="comment">// namespaces</span> | |
| 42 | </pre> | |
| 43 | <h5> | |
| 44 | <a name="math_toolkit.next_float.nextafter.h1"></a> | |
| 45 | <span class="phrase"><a name="math_toolkit.next_float.nextafter.description_nextafter"></a></span><a class="link" href="nextafter.html#math_toolkit.next_float.nextafter.description_nextafter">Description | |
| 46 | - nextafter</a> | |
| 47 | </h5> | |
| 48 | <p> | |
| 49 | This is an implementation of the <code class="computeroutput"><span class="identifier">nextafter</span></code> | |
| 50 | function included in the C99 standard. (It is also effectively an implementation | |
| 51 | of the C99 <code class="computeroutput"><span class="identifier">nexttoward</span></code> legacy | |
| 52 | function which differs only having a <code class="computeroutput"><span class="keyword">long</span> | |
| 53 | <span class="keyword">double</span></code> direction, and can generally | |
| 54 | serve in its place if required). | |
| 55 | </p> | |
| 56 | <div class="note"><table border="0" summary="Note"> | |
| 57 | <tr> | |
| 58 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> | |
| 59 | <th align="left">Note</th> | |
| 60 | </tr> | |
| 61 | <tr><td align="left" valign="top"><p> | |
| 62 | The C99 functions must use suffixes f and l to distinguish <code class="computeroutput"><span class="keyword">float</span></code> and <code class="computeroutput"><span class="keyword">long</span> | |
| 63 | <span class="keyword">double</span></code> versions. C++ uses the template | |
| 64 | mechanism instead. | |
| 65 | </p></td></tr> | |
| 66 | </table></div> | |
| 67 | <p> | |
| 68 | Returns the next representable value after <span class="emphasis"><em>x</em></span> in the | |
| 69 | direction of <span class="emphasis"><em>y</em></span>. If <code class="computeroutput"><span class="identifier">x</span> | |
| 70 | <span class="special">==</span> <span class="identifier">y</span></code> | |
| 71 | then returns <span class="emphasis"><em>x</em></span>. If <span class="emphasis"><em>x</em></span> is non-finite | |
| 72 | then returns the result of a <a class="link" href="../error_handling.html#math_toolkit.error_handling.domain_error">domain_error</a>. | |
| 73 | If there is no such value in the direction of <span class="emphasis"><em>y</em></span> then | |
| 74 | returns an <a class="link" href="../error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a>. | |
| 75 | </p> | |
| 76 | <div class="warning"><table border="0" summary="Warning"> | |
| 77 | <tr> | |
| 78 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../doc/src/images/warning.png"></td> | |
| 79 | <th align="left">Warning</th> | |
| 80 | </tr> | |
| 81 | <tr><td align="left" valign="top"><p> | |
| 82 | The template parameter FTP must be a floating-point type. An integer type, | |
| 83 | for example, will produce an unhelpful error message. | |
| 84 | </p></td></tr> | |
| 85 | </table></div> | |
| 86 | <div class="tip"><table border="0" summary="Tip"> | |
| 87 | <tr> | |
| 88 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td> | |
| 89 | <th align="left">Tip</th> | |
| 90 | </tr> | |
| 91 | <tr><td align="left" valign="top"><p> | |
| 92 | Nearly always, you just want the next or prior representable value, so | |
| 93 | instead use <code class="computeroutput"><span class="identifier">float_next</span></code> | |
| 94 | or <code class="computeroutput"><span class="identifier">float_prior</span></code> below. | |
| 95 | </p></td></tr> | |
| 96 | </table></div> | |
| 97 | <h5> | |
| 98 | <a name="math_toolkit.next_float.nextafter.h2"></a> | |
| 99 | <span class="phrase"><a name="math_toolkit.next_float.nextafter.examples_nextafter"></a></span><a class="link" href="nextafter.html#math_toolkit.next_float.nextafter.examples_nextafter">Examples - | |
| 100 | nextafter</a> | |
| 101 | </h5> | |
| 102 | <p> | |
| 103 | The two representations using a 32-bit float either side of unity are: | |
| 104 | </p> | |
| 105 | <pre class="programlisting"><span class="identifier">The</span> <span class="identifier">nearest</span> <span class="special">(</span><span class="identifier">exact</span><span class="special">)</span> <span class="identifier">representation</span> <span class="identifier">of</span> <span class="number">1.F</span> <span class="identifier">is</span> <span class="number">1.00000000</span> | |
| 106 | <span class="identifier">nextafter</span><span class="special">(</span><span class="number">1.F</span><span class="special">,</span> <span class="number">999</span><span class="special">)</span> <span class="identifier">is</span> <span class="number">1.00000012</span> | |
| 107 | <span class="identifier">nextafter</span><span class="special">(</span><span class="number">1</span><span class="special">/</span><span class="identifier">f</span><span class="special">,</span> <span class="special">-</span><span class="number">999</span><span class="special">)</span> <span class="identifier">is</span> <span class="number">0.99999994</span> | |
| 108 | ||
| 109 | <span class="identifier">The</span> <span class="identifier">nearest</span> <span class="special">(</span><span class="keyword">not</span> <span class="identifier">exact</span><span class="special">)</span> <span class="identifier">representation</span> <span class="identifier">of</span> <span class="number">0.1F</span> <span class="identifier">is</span> <span class="number">0.100000001</span> | |
| 110 | <span class="identifier">nextafter</span><span class="special">(</span><span class="number">0.1F</span><span class="special">,</span> <span class="number">10</span><span class="special">)</span> <span class="identifier">is</span> <span class="number">0.100000009</span> | |
| 111 | <span class="identifier">nextafter</span><span class="special">(</span><span class="number">0.1F</span><span class="special">,</span> <span class="number">10</span><span class="special">)</span> <span class="identifier">is</span> <span class="number">0.099999994</span> | |
| 112 | </pre> | |
| 113 | </div> | |
| 114 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
| 115 | <td align="left"></td> | |
| 116 | <td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal, | |
| 117 | Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert | |
| 118 | Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani, | |
| 119 | Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p> | |
| 120 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 121 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
| 122 | </p> | |
| 123 | </div></td> | |
| 124 | </tr></table> | |
| 125 | <hr> | |
| 126 | <div class="spirit-nav"> | |
| 127 | <a accesskey="p" href="../next_float.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../next_float.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="float_next.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> | |
| 128 | </div> | |
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| 130 | </html> |