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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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