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<a name="boost.logic.tribool"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Class tribool</span></h2>
<p>boost::logic::tribool — A 3-state boolean type. </p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../tribool/reference.html#header.boost.logic.tribool_hpp" title="Header <boost/logic/tribool.hpp>">boost/logic/tribool.hpp</a>>
</span>
<span class="keyword">class</span> <a class="link" href="tribool.html" title="Class tribool">tribool</a> <span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">enum</span> <a class="link" href="tribool/value_t.html" title="Type value_t">value_t</a><span class="special">;</span>
<span class="comment">// <a class="link" href="tribool.html#boost.logic.triboolconstruct-copy-destruct">construct/copy/destruct</a></span>
<a class="link" href="tribool.html#idm45506993961424-bb"><span class="identifier">tribool</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
<a class="link" href="tribool.html#idm45506993962912-bb"><span class="identifier">tribool</span></a><span class="special">(</span><span class="keyword">bool</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
<a class="link" href="tribool.html#idm45507159480208-bb"><span class="identifier">tribool</span></a><span class="special">(</span><span class="identifier">indeterminate_keyword_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
<span class="comment">// <a class="link" href="tribool.html#idm45507103514832-bb">public member functions</a></span>
<span class="identifier">BOOST_CONSTEXPR</span> <a class="link" href="tribool.html#idm45506887866112-bb"><span class="keyword">operator</span> <span class="identifier">safe_bool</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
<span class="comment">// public data members</span>
<span class="keyword">enum</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">logic</span><span class="special">::</span><span class="identifier">tribool</span><span class="special">::</span><span class="identifier">value_t</span> <span class="identifier">value</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idm45555085520464"></a><h2>Description</h2>
<p>3-state boolean values are either true, false, or indeterminate. </p>
<div class="refsect2">
<a name="idm45555085519712"></a><h3>
<a name="boost.logic.triboolconstruct-copy-destruct"></a><code class="computeroutput">tribool</code>
public
construct/copy/destruct</h3>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<pre class="literallayout"><a name="idm45506993961424-bb"></a><span class="identifier">tribool</span><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
<p>Construct a new 3-state boolean value with the value 'false'.</p>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Throws:</span></p></td>
<td>Will not throw.</td>
</tr></tbody>
</table></div>
</li>
<li class="listitem">
<pre class="literallayout"><a name="idm45506993962912-bb"></a><span class="identifier">tribool</span><span class="special">(</span><span class="keyword">bool</span> initial_value<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
<p>Construct a new 3-state boolean value with the given boolean value, which may be <code class="computeroutput">true</code> or <code class="computeroutput">false</code>.</p>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Throws:</span></p></td>
<td>Will not throw.</td>
</tr></tbody>
</table></div>
</li>
<li class="listitem">
<pre class="literallayout"><a name="idm45507159480208-bb"></a><span class="identifier">tribool</span><span class="special">(</span><span class="identifier">indeterminate_keyword_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
<p>Construct a new 3-state boolean value with an indeterminate value.</p>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Throws:</span></p></td>
<td>Will not throw.</td>
</tr></tbody>
</table></div>
</li>
</ol></div>
</div>
<div class="refsect2">
<a name="idm45555085495760"></a><h3>
<a name="idm45507103514832-bb"></a><code class="computeroutput">tribool</code> public member functions</h3>
<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
<pre class="literallayout"><span class="identifier">BOOST_CONSTEXPR</span> <a name="idm45506887866112-bb"></a><span class="keyword">operator</span> <span class="identifier">safe_bool</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
<p>Use a 3-state boolean in a boolean context. Will evaluate true in a boolean context only when the 3-state boolean is definitely true.</p>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">Returns:</span></p></td>
<td><p>true if the 3-state boolean is true, false otherwise </p></td>
</tr>
<tr>
<td><p><span class="term">Throws:</span></p></td>
<td>Will not throw.</td>
</tr>
</tbody>
</table></div>
</li></ol></div>
</div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright © 2002-2004 Douglas Gregor<p>Use, modification and distribution is subject to the Boost
Software License, Version 1.0. (See accompanying file
<code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</p>
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