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- <title>The MPL Reference Manual: Numeric Metafunction</title>
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- <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> <a href="./trivial-metafunction.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tag-dispatched-metafunction.html" class="navigation-link">Back</a> <a href="./trivial-metafunction.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./metafunctions-concepts.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
- <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>
- </tr></table><div class="header-separator"></div>
- <div class="section" id="numeric-metafunction">
- <h1><a class="toc-backref" href="./metafunctions-concepts.html#id1517">Numeric Metafunction</a></h1>
- <div class="section" id="id847">
- <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
- <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
- a built-in infrastructure for easy implementation of mixed-type operations.</p>
- </div>
- <div class="section" id="id848">
- <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
- <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">op</span></tt> is a placeholder token for the actual
- <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
- arbitrary numeric types.</p>
- <table border="1" class="docutils table">
- <colgroup>
- <col width="46%" />
- <col width="25%" />
- <col width="29%" />
- </colgroup>
- <thead valign="bottom">
- <tr><th class="head">Expression</th>
- <th class="head">Type</th>
- <th class="head">Complexity</th>
- </tr>
- </thead>
- <tbody valign="top">
- <tr><td><tt class="literal"><span class="pre">op_tag<x>::type</span></tt></td>
- <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
- <td>Amortized constant time.</td>
- </tr>
- <tr><td><pre class="first last literal-block">
- op_impl<
- op_tag<x>::type
- , op_tag<y>::type
- >::<a href="./apply.html" class="identifier">apply</a><x,y>::type
- </pre>
- </td>
- <td>Any type</td>
- <td>Unspecified.</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre">op<</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">>::type</span></tt></td>
- <td>Any type</td>
- <td>Unspecified.</td>
- </tr>
- </tbody>
- </table>
- </div>
- <div class="section" id="id849">
- <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
- <pre class="literal-block">
- typedef op_tag<x>::type tag;
- </pre>
- <table class="docutils field-list" frame="void" rules="none">
- <col class="field-name" />
- <col class="field-body" />
- <tbody valign="top">
- <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>.
- <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>
- </tr>
- </tbody>
- </table>
- <!-- .......................................................................... -->
- <pre class="literal-block">
- typedef op_impl<
- op_tag<x>::type
- , op_tag<y>::type
- >::<a href="./apply.html" class="identifier">apply</a><x,y>::type r;
- </pre>
- <table class="docutils field-list" frame="void" rules="none">
- <col class="field-name" />
- <col class="field-body" />
- <tbody valign="top">
- <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>
- and <tt class="literal"><span class="pre">y</span></tt>.</td>
- </tr>
- </tbody>
- </table>
- <!-- .......................................................................... -->
- <pre class="literal-block">
- typedef op<<em>x</em><sub>1</sub>,<em>x</em><sub>2</sub>,... <em>x</em><sub>n</sub>>::type r;
- </pre>
- <table class="docutils field-list" frame="void" rules="none">
- <col class="field-name" />
- <col class="field-body" />
- <tbody valign="top">
- <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>
- </tr>
- </tbody>
- </table>
- </div>
- <div class="section" id="id850">
- <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 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 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,c2> r1;
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real<r1>::value, ==, 0 );
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag<r1>::value, ==, 0 );
- typedef <a href="./plus.html" class="identifier">plus</a><c1,c1> r2;
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real<r2>::value, ==, 10 );
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag<r2>::value, ==, -2 );
- typedef <a href="./plus.html" class="identifier">plus</a><c2,c2> r3;
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( real<r3>::value, ==, -10 );
- <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( imag<r3>::value, ==, 2 );
- </pre>
- </div>
- <div class="section" id="id851">
- <h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
- <ul class="simple">
- <li><a class="reference internal" href="./plus.html">plus</a></li>
- <li><a class="reference internal" href="./minus.html">minus</a></li>
- <li><a class="reference internal" href="./times.html">times</a></li>
- <li><a class="reference internal" href="./divides.html">divides</a></li>
- </ul>
- </div>
- <div class="section" id="id852">
- <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
- <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>
- <!-- Metafunctions/Concepts//Trivial Metafunction |70 -->
- </div>
- </div>
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- <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div>
- Distributed under the Boost Software License, Version 1.0. (See accompanying
- 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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