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1<?xml version="1.0" encoding="utf-8" ?>
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7<title>The MPL Reference Manual: or_</title>
8<link rel="stylesheet" href="../style.css" type="text/css" />
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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>&nbsp;<a href="./not.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./and.html" class="navigation-link">Back</a>&nbsp;<a href="./not.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./logical-operations.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</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#id477" name="or">or_</a></h1>
16<div class="section" id="or-synopsis">
17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
18<pre class="literal-block">
19template&lt; 
20      typename F1
21    , typename F2
22    <em>...</em>
23    , typename F<em>n</em> = <em>unspecified</em>
24    &gt;
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="or-description">
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="or-header">
36<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
37<pre class="literal-block">
38#include &lt;<a href="../../../../boost/mpl/or.hpp" class="header">boost/mpl/or.hpp</a>&gt;
39#include &lt;<a href="../../../../boost/mpl/logical.hpp" class="header">boost/mpl/logical.hpp</a>&gt;
40</pre>
41</div>
42<div class="section" id="or-parameters">
43<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
44<table border="1" class="table">
45<colgroup>
46<col width="17%" />
47<col width="30%" />
48<col width="53%" />
49</colgroup>
50<thead valign="bottom">
51<tr><th>Parameter</th>
52<th>Requirement</th>
53<th>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" 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="or-expression-semantics">
65<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
66<p>For arbitrary nullary <a class="reference" 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>&lt;f1,f2,<em>...</em>,f<em>n</em>&gt;::type r;
69</pre>
70<table class="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" 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">true_</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">false_</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>&lt;f1,f2,<em>...</em>,f<em>n</em>&gt; r;
86</pre>
87<table class="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"><a class="reference" href="./integral-constant.html">Integral Constant</a>.</td>
92</tr>
93<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
94<pre class="last literal-block">
95struct r : <a href="./or.html" class="identifier">or_</a>&lt;f1,f2,<em>...</em>,f<em>n</em>&gt;::type {};
96</pre>
97</td>
98</tr>
99</tbody>
100</table>
101</div>
102<div class="section" id="or-example">
103<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
104<pre class="literal-block">
105struct unknown;
106
107<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; true_,true_ &gt; ));
108<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; false_,true_ &gt; ));
109<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; true_,false_ &gt; ));
110<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; false_,false_ &gt; ));
111<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; true_,unknown &gt; )); // OK
112<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./or.html" class="identifier">or_</a>&lt; true_,unknown,unknown &gt; )); // OK too
113</pre>
114</div>
115<div class="section" id="or-see-also">
116<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
117<p><a class="reference" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./logical-operations.html">Logical Operations</a>, <a class="refentry reference" href="./and.html"><tt class="refentry literal"><span class="pre">and_</span></tt></a>, <a class="refentry reference" href="./not.html"><tt class="refentry literal"><span class="pre">not_</span></tt></a></p>
118<!-- modtime: November 10, 2004 04:36:44 +0000 -->
119<!-- Metafunctions/Logical Operations//not_ |30 -->
120</div>
121</div>
122
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