1<?xml version="1.0" encoding="utf-8" ?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 6<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> 7<title>The MPL Reference Manual: or_</title> 8<link rel="stylesheet" href="../style.css" type="text/css" /> 9</head> 10<body class="docframe refmanual"> 11<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./and.html" class="navigation-link">Prev</a> <a href="./not.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./and.html" class="navigation-link">Back</a> <a href="./not.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./logical-operations.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> 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="./logical-operations.html" class="navigation-link">Logical Operations</a> / <a href="./or.html" class="navigation-link">or_</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="or"> 15<h1><a class="toc-backref" href="./logical-operations.html#id1551">or_</a></h1> 16<div class="section" id="id1075"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19template< 20 typename F1 21 , typename F2 22 <em>...</em> 23 , typename F<em>n</em> = <em>unspecified</em> 24 > 25struct <a href="./or.html" class="identifier">or_</a> 26{ 27 typedef <em>unspecified</em> type; 28}; 29</pre> 30</div> 31<div class="section" id="id1076"> 32<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 33<p>Returns the result of short-circuit <em>logical or</em> (<tt class="literal"><span class="pre">||</span></tt>) operation on its arguments.</p> 34</div> 35<div class="section" id="id1077"> 36<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 37<pre class="literal-block"> 38#include <<a href="../../../../boost/mpl/or.hpp" class="header">boost/mpl/or.hpp</a>> 39#include <<a href="../../../../boost/mpl/logical.hpp" class="header">boost/mpl/logical.hpp</a>> 40</pre> 41</div> 42<div class="section" id="id1078"> 43<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 44<table border="1" class="docutils table"> 45<colgroup> 46<col width="17%" /> 47<col width="30%" /> 48<col width="53%" /> 49</colgroup> 50<thead valign="bottom"> 51<tr><th class="head">Parameter</th> 52<th class="head">Requirement</th> 53<th class="head">Description</th> 54</tr> 55</thead> 56<tbody valign="top"> 57<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> 58<td>Nullary <a class="reference internal" href="./metafunction.html">Metafunction</a></td> 59<td>Operation's arguments.</td> 60</tr> 61</tbody> 62</table> 63</div> 64<div class="section" id="id1079"> 65<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 66<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> 67<pre class="literal-block"> 68typedef <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>>::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 class="reference internal" href="./integral-constant.html">Integral Constant</a>.</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 <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>,... 77<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; 78guarantees left-to-right evaluation; the operands subsequent to the first 79<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> 80</tr> 81</tbody> 82</table> 83<!-- .......................................................................... --> 84<pre class="literal-block"> 85typedef <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>> r; 86</pre> 87<table class="docutils field-list" frame="void" rules="none"> 88<col class="field-name" /> 89<col class="field-body" /> 90<tbody valign="top"> 91<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> 92</td> 93</tr> 94<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 95<pre class="last literal-block"> 96struct r : <a href="./or.html" class="identifier">or_</a><f1,f2,<em>...</em>,f<em>n</em>>::type {}; 97</pre> 98</td> 99</tr> 100</tbody> 101</table> 102</div> 103<div class="section" id="id1080"> 104<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 105<pre class="literal-block"> 106struct unknown; 107 108<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> > )); 109<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> > )); 110<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> > )); 111<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> > )); 112<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 113<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 114</pre> 115</div> 116<div class="section" id="id1081"> 117<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 118<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> 119<!-- Metafunctions/Logical Operations//not_ |30 --> 120</div> 121</div> 122 123<div class="footer-separator"></div> 124<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./and.html" class="navigation-link">Prev</a> <a href="./not.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./and.html" class="navigation-link">Back</a> <a href="./not.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./logical-operations.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> 125<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 126Distributed under the Boost Software License, Version 1.0. (See accompanying 127file 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> 128</html> 129