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| <title>The MPL Reference Manual: or_</title> |
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| <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="./logical-operations.html" class="navigation-link">Logical Operations</a> / <a href="./or.html" class="navigation-link">or_</a></td> |
| </tr></table><div class="header-separator"></div> |
| <div class="section" id="or"> |
| <h1><a class="toc-backref" href="./logical-operations.html#id1551">or_</a></h1> |
| <div class="section" id="id1075"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename F1 |
| , typename F2 |
| <em>...</em> |
| , typename F<em>n</em> = <em>unspecified</em> |
| > |
| struct <a href="./or.html" class="identifier">or_</a> |
| { |
| typedef <em>unspecified</em> type; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id1076"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Returns the result of short-circuit <em>logical or</em> (<tt class="literal"><span class="pre">||</span></tt>) operation on its arguments.</p> |
| </div> |
| <div class="section" id="id1077"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/or.hpp" class="header">boost/mpl/or.hpp</a>> |
| #include <<a href="../../../../boost/mpl/logical.hpp" class="header">boost/mpl/logical.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id1078"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
| <table border="1" class="docutils table"> |
| <colgroup> |
| <col width="17%" /> |
| <col width="30%" /> |
| <col width="53%" /> |
| </colgroup> |
| <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">F1</span></tt>, <tt class="literal"><span class="pre">F2</span></tt>,... <tt class="literal"><span class="pre">Fn</span></tt></td> |
| <td>Nullary <a class="reference internal" href="./metafunction.html">Metafunction</a></td> |
| <td>Operation's arguments.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1079"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <p>For arbitrary nullary <a class="reference internal" href="./metafunction.html">Metafunction</a>s <tt class="literal"><span class="pre">f1</span></tt>, <tt class="literal"><span class="pre">f2</span></tt>,... <tt class="literal"><span class="pre">fn</span></tt>:</p> |
| <pre class="literal-block"> |
| typedef <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>>::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">Return type:</th><td class="field-body"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</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 <tt class="literal"><span class="pre"><a href="./bool.html" class="identifier">true_</a></span></tt> if either of <tt class="literal"><span class="pre">f1::type::value</span></tt>, <tt class="literal"><span class="pre">f2::type::value</span></tt>,... |
| <tt class="literal"><span class="pre">fn::type::value</span></tt> expressions evaluates to <tt class="literal"><span class="pre">true</span></tt>, and <tt class="literal"><span class="pre"><a href="./bool.html" class="identifier">false_</a></span></tt> otherwise; |
| guarantees left-to-right evaluation; the operands subsequent to the first |
| <tt class="literal"><span class="pre">f</span></tt><em>i</em> metafunction that evaluates to <tt class="literal"><span class="pre">true</span></tt> are not evaluated.</td> |
| </tr> |
| </tbody> |
| </table> |
| <!-- .......................................................................... --> |
| <pre class="literal-block"> |
| typedef <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>> 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">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> |
| <pre class="last literal-block"> |
| struct r : <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>>::type {}; |
| </pre> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1080"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| struct unknown; |
| |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">true_</a>,<a href="./bool.html" class="identifier">true_</a> > )); |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">false_</a>,<a href="./bool.html" class="identifier">true_</a> > )); |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">true_</a>,<a href="./bool.html" class="identifier">false_</a> > )); |
| <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">false_</a>,<a href="./bool.html" class="identifier">false_</a> > )); |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">true_</a>,unknown > )); // OK |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>< <a href="./bool.html" class="identifier">true_</a>,unknown,unknown > )); // OK too |
| </pre> |
| </div> |
| <div class="section" id="id1081"> |
| <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="./logical-operations.html">Logical Operations</a>, <a class="reference internal" href="./and.html">and_</a>, <a class="reference internal" href="./not.html">not_</a></p> |
| <!-- Metafunctions/Logical Operations//not_ |30 --> |
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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 |
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