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| <div class="section" id="numeric-cast"> |
| <h1><a class="toc-backref" href="./miscellaneous.html#id1568">numeric_cast</a></h1> |
| <div class="section" id="id1181"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename SourceTag |
| , typename TargetTag |
| > |
| struct <a href="./numeric-cast.html" class="identifier">numeric_cast</a>; |
| </pre> |
| </div> |
| <div class="section" id="id1182"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <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> |
| providing a conversion between two numeric types.</p> |
| </div> |
| <div class="section" id="id1183"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/numeric_cast.hpp" class="header">boost/mpl/numeric_cast.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id1184"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
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| <col width="53%" /> |
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| <thead valign="bottom"> |
| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">SourceTag</span></tt></td> |
| <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td> |
| <td>A tag for the conversion's source type.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">TargetTag</span></tt></td> |
| <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td> |
| <td>A tag for the conversion's destination type.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1185"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <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 |
| <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> |
| <pre class="literal-block"> |
| typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>< <a href="./numeric-cast.html" class="identifier">numeric_cast</a><x_tag,y_tag>,x >::type r; |
| </pre> |
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| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Return type:</th><td class="field-body">A type.</td> |
| </tr> |
| <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> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1186"> |
| <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> |
| <p>Unspecified.</p> |
| </div> |
| <div class="section" id="id1187"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| struct complex_tag : <a href="./int.html" class="identifier">int_</a><10> {}; |
| |
| template< typename Re, typename Im > struct complex |
| { |
| typedef complex_tag tag; |
| typedef complex type; |
| typedef Re real; |
| typedef Im imag; |
| }; |
| |
| template< typename C > struct real : C::real {}; |
| template< typename C > struct imag : C::imag {}; |
| |
| namespace boost { namespace mpl { |
| |
| template<> struct <a href="./numeric-cast.html" class="identifier">numeric_cast</a>< integral_c_tag,complex_tag > |
| { |
| template< typename N > struct <a href="./apply.html" class="identifier">apply</a> |
| : complex< N, <a href="./integral-c.html" class="identifier">integral_c</a>< typename N::<a href="./value-type.html" class="identifier">value_type</a>, 0 > > |
| { |
| }; |
| }; |
| |
| template<> |
| struct plus_impl< complex_tag,complex_tag > |
| { |
| template< typename N1, typename N2 > struct <a href="./apply.html" class="identifier">apply</a> |
| : complex< |
| <a href="./plus.html" class="identifier">plus</a>< typename N1::real, typename N2::real > |
| , <a href="./plus.html" class="identifier">plus</a>< typename N1::imag, typename N2::imag > |
| > |
| { |
| }; |
| }; |
| |
| }} |
| |
| typedef <a href="./int.html" class="identifier">int_</a><2> i; |
| typedef complex< <a href="./int.html" class="identifier">int_</a><5>, <a href="./int.html" class="identifier">int_</a><-1> > c1; |
| typedef complex< <a href="./int.html" class="identifier">int_</a><-5>, <a href="./int.html" class="identifier">int_</a><1> > c2; |
| |
| typedef <a href="./plus.html" class="identifier">plus</a><c1,i> r4; |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real<r4>::value, ==, 7 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag<r4>::value, ==, -1 ); |
| |
| typedef <a href="./plus.html" class="identifier">plus</a><i,c2> r5; |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real<r5>::value, ==, -3 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag<r5>::value, ==, 1 ); |
| </pre> |
| </div> |
| <div class="section" id="id1188"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <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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