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

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   7 <title>The MPL Reference Manual: numeric_cast</title>
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  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="./miscellaneous.html" class="navigation-link">Miscellaneous</a> / <a href="./numeric-cast.html" class="navigation-link">numeric_cast</a></td>
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  14 <div class="section" id="numeric-cast">
  15 <h1><a class="toc-backref" href="./miscellaneous.html#id1568">numeric_cast</a></h1>
  16 <div class="section" id="id1181">
  17 <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18 <pre class="literal-block">
  19 template&lt;
  20       typename SourceTag
  21     , typename TargetTag
  22     &gt;
  23 struct <a href="./numeric-cast.html" class="identifier">numeric_cast</a>;
  24 </pre>
  25 </div>
  26 <div class="section" id="id1182">
  27 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  28 <p>Each <tt class="literal"><span class="pre"><a href="./numeric-cast.html" class="identifier">numeric_cast</a></span></tt> specialization is a user-specialized unary <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>
  29 providing a conversion between two numeric types.</p>
  30 </div>
  31 <div class="section" id="id1183">
  32 <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
  33 <pre class="literal-block">
  34 #include &lt;<a href="../../../../boost/mpl/numeric_cast.hpp" class="header">boost/mpl/numeric_cast.hpp</a>&gt;
  35 </pre>
  36 </div>
  37 <div class="section" id="id1184">
  38 <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
  39 <table border="1" class="docutils table">
  40 <colgroup>
  41 <col width="17%" />
  42 <col width="30%" />
  43 <col width="53%" />
  44 </colgroup>
  45 <thead valign="bottom">
  46 <tr><th class="head">Parameter</th>
  47 <th class="head">Requirement</th>
  48 <th class="head">Description</th>
  49 </tr>
  50 </thead>
  51 <tbody valign="top">
  52 <tr><td><tt class="literal"><span class="pre">SourceTag</span></tt></td>
  53 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  54 <td>A tag for the conversion's source type.</td>
  55 </tr>
  56 <tr><td><tt class="literal"><span class="pre">TargetTag</span></tt></td>
  57 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  58 <td>A tag for the conversion's destination type.</td>
  59 </tr>
  60 </tbody>
  61 </table>
  62 </div>
  63 <div class="section" id="id1185">
  64 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  65 <p>If <tt class="literal"><span class="pre">x</span></tt> and <tt class="literal"><span class="pre">y</span></tt> are two numeric types, <tt class="literal"><span class="pre">x</span></tt> is convertible to <tt class="literal"><span class="pre">y</span></tt>, and
  66 <tt class="literal"><span class="pre">x_tag</span></tt> and <tt class="literal"><span class="pre">y_tag</span></tt> are the types' corresponding <a class="reference internal" href="./integral-constant.html">Integral Constant</a> tags:</p>
  67 <pre class="literal-block">
  68 typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>&lt; <a href="./numeric-cast.html" class="identifier">numeric_cast</a>&lt;x_tag,y_tag&gt;,x &gt;::type  r;
  69 </pre>
  70 <table class="docutils field-list" frame="void" rules="none">
  71 <col class="field-name" />
  72 <col class="field-body" />
  73 <tbody valign="top">
  74 <tr class="field"><th class="field-name">Return type:</th><td class="field-body">A type.</td>
  75 </tr>
  76 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">r</span></tt> is a value of <tt class="literal"><span class="pre">x</span></tt> converted to the type of <tt class="literal"><span class="pre">y</span></tt>.</td>
  77 </tr>
  78 </tbody>
  79 </table>
  80 </div>
  81 <div class="section" id="id1186">
  82 <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
  83 <p>Unspecified.</p>
  84 </div>
  85 <div class="section" id="id1187">
  86 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
  87 <pre class="literal-block">
  88 struct complex_tag : <a href="./int.html" class="identifier">int_</a>&lt;10&gt; {};
  89
  90 template&lt; typename Re, typename Im &gt; struct complex
  91 {
  92     typedef complex_tag tag;
  93     typedef complex type;
  94     typedef Re real;
  95     typedef Im imag;
  96 };
  97
  98 template&lt; typename C &gt; struct real : C::real {};
  99 template&lt; typename C &gt; struct imag : C::imag {};
 100
 101 namespace boost { namespace mpl {
 102
 103 template&lt;&gt; struct <a href="./numeric-cast.html" class="identifier">numeric_cast</a>&lt; integral_c_tag,complex_tag &gt;
 104 {
 105     template&lt; typename N &gt; struct <a href="./apply.html" class="identifier">apply</a>
 106         : complex&lt; N, <a href="./integral-c.html" class="identifier">integral_c</a>&lt; typename N::<a href="./value-type.html" class="identifier">value_type</a>, 0 &gt; &gt;
 107     {
 108     };
 109 };
 110
 111 template&lt;&gt;
 112 struct plus_impl&lt; complex_tag,complex_tag &gt;
 113 {
 114     template&lt; typename N1, typename N2 &gt; struct <a href="./apply.html" class="identifier">apply</a>
 115         : complex&lt;
 116               <a href="./plus.html" class="identifier">plus</a>&lt; typename N1::real, typename N2::real &gt;
 117             , <a href="./plus.html" class="identifier">plus</a>&lt; typename N1::imag, typename N2::imag &gt;
 118             &gt;
 119     {
 120     };
 121 };
 122
 123 }}
 124
 125 typedef <a href="./int.html" class="identifier">int_</a>&lt;2&gt; i;
 126 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;
 127 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;
 128
 129 typedef <a href="./plus.html" class="identifier">plus</a>&lt;c1,i&gt; r4;
 130 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real&lt;r4&gt;::value, ==, 7 );
 131 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag&lt;r4&gt;::value, ==, -1 );
 132
 133 typedef <a href="./plus.html" class="identifier">plus</a>&lt;i,c2&gt; r5;
 134 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real&lt;r5&gt;::value, ==, -3 );
 135 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag&lt;r5&gt;::value, ==, 1 );
 136 </pre>
 137 </div>
 138 <div class="section" id="id1188">
 139 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 140 <p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./numeric-metafunction.html">Numeric Metafunction</a>, <a class="reference internal" href="./plus.html">plus</a>, <a class="reference internal" href="./minus.html">minus</a>, <a class="reference internal" href="./times.html">times</a></p>
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