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28<h2><span class="refentrytitle">Function template condition_if_c</span></h2>
29<p>boost::contract::condition_if_c — Select compilation and execution of a boolean functor template condition using a static boolean predicate (not needed on C++17 compilers, use <code class="computeroutput">if constexpr</code> instead). </p>
30</div>
31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
32<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../reference.html#header.boost.contract.call_if_hpp" title="Header &lt;boost/contract/call_if.hpp&gt;">boost/contract/call_if.hpp</a>&gt;
33
34</span>
35<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">bool</span> Pred<span class="special">,</span> <span class="keyword">typename</span> Then<span class="special">&gt;</span>
36  <span class="keyword">bool</span> <span class="identifier">condition_if_c</span><span class="special">(</span><span class="identifier">Then</span> f<span class="special">,</span> <span class="keyword">bool</span> else_ <span class="special">=</span> <span class="keyword">true</span><span class="special">)</span><span class="special">;</span></pre></div>
37<div class="refsect1">
38<a name="idm45988680390848"></a><h2>Description</h2>
39<p>Compile and execute the nullary boolean functor template call <code class="computeroutput">f()</code> if and only if the specified static boolean predicate <code class="computeroutput">Pred</code> is <code class="computeroutput">true</code>, otherwise trivially return <code class="computeroutput">else_</code> (<code class="computeroutput">true</code> by default) at run-time.</p>
40<p>A call to <code class="computeroutput">boost::contract::condition_if_c&lt;Pred&gt;(f, else_)</code> is logically equivalent to <code class="computeroutput">boost::contract::call_if_c&lt;Pred&gt;(f, [] { return else_; })</code> (but its internal implementation is optimized and it does not actually use <code class="computeroutput">call_if_c</code>).</p>
41<p><span class="bold"><strong>See Also:</strong></span></p>
42<p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.assertion_requirements__templates_" title="Assertion Requirements (Templates)">
43        Assertion Requirements</a></p>
44<p>
45</p>
46<p>
47
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51</p>
52<div class="variablelist"><table border="0" class="variablelist compact">
53<colgroup>
54<col align="left" valign="top">
55<col>
56</colgroup>
57<tbody>
58<tr>
59<td><p><span class="term">Parameters:</span></p></td>
60<td><div class="variablelist"><table border="0" class="variablelist compact">
61<colgroup>
62<col align="left" valign="top">
63<col>
64</colgroup>
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67<td><p><span class="term"><code class="computeroutput">else_</code></span></p></td>
68<td><p>Boolean value to return when <code class="computeroutput">Pred</code> is <code class="computeroutput">false</code> (instead of compiling and executing the functor template call <code class="computeroutput">f()</code>).</p></td>
69</tr>
70<tr>
71<td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
72<td><p>Nullary boolean functor template. The functor template call <code class="computeroutput">f()</code> is compiled and executed if and only if <code class="computeroutput">Pred</code> is <code class="computeroutput">true</code>.</p></td>
73</tr>
74</tbody>
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76</tr>
77<tr>
78<td><p><span class="term">Template Parameters:</span></p></td>
79<td><div class="variablelist"><table border="0" class="variablelist compact">
80<colgroup>
81<col align="left" valign="top">
82<col>
83</colgroup>
84<tbody><tr>
85<td><p><span class="term"><code class="computeroutput">Pred</code></span></p></td>
86<td><p>Static boolean predicate selecting when the functor template call <code class="computeroutput">f()</code> should be compiled and executed. </p></td>
87</tr></tbody>
88</table></div></td>
89</tr>
90<tr>
91<td><p><span class="term">Returns:</span></p></td>
92<td><p>Boolean value returned by <code class="computeroutput">f()</code> if the static predicate <code class="computeroutput">Pred</code> is <code class="computeroutput">true</code>. Otherwise, trivially return <code class="computeroutput">else_</code>. </p></td>
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100<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p>
101        Distributed under the Boost Software License, Version 1.0 (see accompanying
102        file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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