ceph/src/boost/libs/mpl/doc/refmanual/numeric-metafunction.html

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   7 <title>The MPL Reference Manual: Numeric Metafunction</title>
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  11 <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./tag-dispatched-metafunction.html" class="navigation-link">Prev</a>&nbsp;<a href="./trivial-metafunction.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./tag-dispatched-metafunction.html" class="navigation-link">Back</a>&nbsp;<a href="./trivial-metafunction.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunctions-concepts.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
  12 <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./metafunctions-concepts.html" class="navigation-link">Concepts</a> / <a href="./numeric-metafunction.html" class="navigation-link">Numeric Metafunction</a></td>
  13 </tr></table><div class="header-separator"></div>
  14 <div class="section" id="numeric-metafunction">
  15 <h1><a class="toc-backref" href="./metafunctions-concepts.html#id1517">Numeric Metafunction</a></h1>
  16 <div class="section" id="id847">
  17 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  18 <p>A <a class="reference internal" href="./numeric-metafunction.html">Numeric Metafunction</a> is a <a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a> that provides
  19 a built-in infrastructure for easy implementation of mixed-type operations.</p>
  20 </div>
  21 <div class="section" id="id848">
  22 <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
  23 <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">op</span></tt> is a placeholder token for the actual
  24 <a class="reference internal" href="./numeric-metafunction.html">Numeric Metafunction</a>'s name, and <tt class="literal"><span class="pre">x</span></tt>, <tt class="literal"><span class="pre">y</span></tt> and <em>x</em><sub>1</sub>,<em>x</em><sub>2</sub>,... <em>x</em><sub>n</sub> are
  25 arbitrary numeric types.</p>
  26 <table border="1" class="docutils table">
  27 <colgroup>
  28 <col width="46%" />
  29 <col width="25%" />
  30 <col width="29%" />
  31 </colgroup>
  32 <thead valign="bottom">
  33 <tr><th class="head">Expression</th>
  34 <th class="head">Type</th>
  35 <th class="head">Complexity</th>
  36 </tr>
  37 </thead>
  38 <tbody valign="top">
  39 <tr><td><tt class="literal"><span class="pre">op_tag&lt;x&gt;::type</span></tt></td>
  40 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  41 <td>Amortized constant time.</td>
  42 </tr>
  43 <tr><td><pre class="first last literal-block">
  44 op_impl&lt;
  45      op_tag&lt;x&gt;::type
  46    , op_tag&lt;y&gt;::type
  47    &gt;::<a href="./apply.html" class="identifier">apply</a>&lt;x,y&gt;::type
  48 </pre>
  49 </td>
  50 <td>Any type</td>
  51 <td>Unspecified.</td>
  52 </tr>
  53 <tr><td><tt class="literal"><span class="pre">op&lt;</span></tt><em>x</em><sub>1</sub>,<em>x</em><sub>2</sub>,... <em>x</em><sub>n</sub><tt class="literal"><span class="pre">&gt;::type</span></tt></td>
  54 <td>Any type</td>
  55 <td>Unspecified.</td>
  56 </tr>
  57 </tbody>
  58 </table>
  59 </div>
  60 <div class="section" id="id849">
  61 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  62 <pre class="literal-block">
  63 typedef op_tag&lt;x&gt;::type tag;
  64 </pre>
  65 <table class="docutils field-list" frame="void" rules="none">
  66 <col class="field-name" />
  67 <col class="field-body" />
  68 <tbody valign="top">
  69 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">tag</span></tt> is a tag type for <tt class="literal"><span class="pre">x</span></tt> for <tt class="literal"><span class="pre">op</span></tt>.
  70 <tt class="literal"><span class="pre">tag::value</span></tt> is <tt class="literal"><span class="pre">x</span></tt>'s <em>conversion rank</em>.</td>
  71 </tr>
  72 </tbody>
  73 </table>
  74 <!-- .......................................................................... -->
  75 <pre class="literal-block">
  76 typedef op_impl&lt;
  77       op_tag&lt;x&gt;::type
  78     , op_tag&lt;y&gt;::type
  79     &gt;::<a href="./apply.html" class="identifier">apply</a>&lt;x,y&gt;::type r;
  80 </pre>
  81 <table class="docutils field-list" frame="void" rules="none">
  82 <col class="field-name" />
  83 <col class="field-body" />
  84 <tbody valign="top">
  85 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">r</span></tt> is the result of <tt class="literal"><span class="pre">op</span></tt> application on arguments <tt class="literal"><span class="pre">x</span></tt>
  86 and <tt class="literal"><span class="pre">y</span></tt>.</td>
  87 </tr>
  88 </tbody>
  89 </table>
  90 <!-- .......................................................................... -->
  91 <pre class="literal-block">
  92 typedef op&lt;<em>x</em><sub>1</sub>,<em>x</em><sub>2</sub>,... <em>x</em><sub>n</sub>&gt;::type r;
  93 </pre>
  94 <table class="docutils field-list" frame="void" rules="none">
  95 <col class="field-name" />
  96 <col class="field-body" />
  97 <tbody valign="top">
  98 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">r</span></tt> is the result of <tt class="literal"><span class="pre">op</span></tt> application on arguments <em>x</em><sub>1</sub>,<em>x</em><sub>2</sub>,... <em>x</em><sub>n</sub>.</td>
  99 </tr>
 100 </tbody>
 101 </table>
 102 </div>
 103 <div class="section" id="id850">
 104 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
 105 <pre class="literal-block">
 106 struct complex_tag : <a href="./int.html" class="identifier">int_</a>&lt;10&gt; {};
 107
 108 template&lt; typename Re, typename Im &gt; struct complex
 109 {
 110     typedef complex_tag tag;
 111     typedef complex type;
 112     typedef Re real;
 113     typedef Im imag;
 114 };
 115
 116 template&lt; typename C &gt; struct real : C::real {};
 117 template&lt; typename C &gt; struct imag : C::imag {};
 118
 119 namespace boost { namespace mpl {
 120
 121 template&lt;&gt;
 122 struct plus_impl&lt; complex_tag,complex_tag &gt;
 123 {
 124     template&lt; typename N1, typename N2 &gt; struct <a href="./apply.html" class="identifier">apply</a>
 125         : complex&lt;
 126               <a href="./plus.html" class="identifier">plus</a>&lt; typename N1::real, typename N2::real &gt;
 127             , <a href="./plus.html" class="identifier">plus</a>&lt; typename N1::imag, typename N2::imag &gt;
 128             &gt;
 129     {
 130     };
 131 };
 132
 133 }}
 134
 135 typedef complex&lt; <a href="./int.html" class="identifier">int_</a>&lt;5&gt;, <a href="./int.html" class="identifier">int_</a>&lt;-1&gt; &gt; c1;
 136 typedef complex&lt; <a href="./int.html" class="identifier">int_</a>&lt;-5&gt;, <a href="./int.html" class="identifier">int_</a>&lt;1&gt; &gt; c2;
 137
 138 typedef <a href="./plus.html" class="identifier">plus</a>&lt;c1,c2&gt; r1;
 139 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real&lt;r1&gt;::value, ==, 0 );
 140 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag&lt;r1&gt;::value, ==, 0 );
 141
 142 typedef <a href="./plus.html" class="identifier">plus</a>&lt;c1,c1&gt; r2;
 143 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real&lt;r2&gt;::value, ==, 10 );
 144 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag&lt;r2&gt;::value, ==, -2 );
 145
 146 typedef <a href="./plus.html" class="identifier">plus</a>&lt;c2,c2&gt; r3;
 147 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real&lt;r3&gt;::value, ==, -10 );
 148 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag&lt;r3&gt;::value, ==, 2 );
 149 </pre>
 150 </div>
 151 <div class="section" id="id851">
 152 <h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
 153 <ul class="simple">
 154 <li><a class="reference internal" href="./plus.html">plus</a></li>
 155 <li><a class="reference internal" href="./minus.html">minus</a></li>
 156 <li><a class="reference internal" href="./times.html">times</a></li>
 157 <li><a class="reference internal" href="./divides.html">divides</a></li>
 158 </ul>
 159 </div>
 160 <div class="section" id="id852">
 161 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 162 <p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a>, <a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./numeric-cast.html">numeric_cast</a></p>
 163 <!-- Metafunctions/Concepts//Trivial Metafunction |70 -->
 164 </div>
 165 </div>
 166
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 169 <td><div class="copyright-footer"><div class="copyright">Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams</div>
 170 Distributed under the Boost Software License, Version 1.0. (See accompanying
 171 file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body>
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