libs/contract/doc/html/boost/contract/condition_if.html

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  28 <h2><span class="refentrytitle">Function template condition_if</span></h2>
  29 <p>boost::contract::condition_if &#8212; Select compilation and execution of a boolean functor template condition using a nullary boolean meta-function (not needed on C++17 compilers, use <code class="computeroutput">if constexpr</code> instead). </p>
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  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">typename</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</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="idm45707997558304"></a><h2>Description</h2>
  39 <p>This is equivalent to <code class="computeroutput">boost::contract::condition_if_c&lt;Pred::value&gt;(f, else_)</code>. Compile and execute the nullary boolean functor template call <code class="computeroutput">f()</code> if and only if the specified nullary boolean meta-function <code class="computeroutput">Pred::value</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><span class="bold"><strong>See Also:</strong></span></p>
  41 <p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.assertion_requirements__templates_" title="Assertion Requirements (Templates)">
  42         Assertion Requirements</a></p>
  43 <p>
  44 </p>
  45 <p>
  46
  47
  48
  49 </p>
  50 <div class="variablelist"><table border="0" class="variablelist compact">
  51 <colgroup>
  52 <col align="left" valign="top">
  53 <col>
  54 </colgroup>
  55 <tbody>
  56 <tr>
  57 <td><p><span class="term">Parameters:</span></p></td>
  58 <td><div class="variablelist"><table border="0" class="variablelist compact">
  59 <colgroup>
  60 <col align="left" valign="top">
  61 <col>
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  63 <tbody>
  64 <tr>
  65 <td><p><span class="term"><code class="computeroutput">else_</code></span></p></td>
  66 <td><p>Boolean value to return when <code class="computeroutput">Pred::value</code> is <code class="computeroutput">false</code> (instead of compiling and executing the functor template call <code class="computeroutput">f()</code>).</p></td>
  67 </tr>
  68 <tr>
  69 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
  70 <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::value</code> is <code class="computeroutput">true</code>. </p></td>
  71 </tr>
  72 </tbody>
  73 </table></div></td>
  74 </tr>
  75 <tr>
  76 <td><p><span class="term">Template Parameters:</span></p></td>
  77 <td><div class="variablelist"><table border="0" class="variablelist compact">
  78 <colgroup>
  79 <col align="left" valign="top">
  80 <col>
  81 </colgroup>
  82 <tbody><tr>
  83 <td><p><span class="term"><code class="computeroutput">Pred</code></span></p></td>
  84 <td><p>Nullary boolean meta-function selecting when the functor template call <code class="computeroutput">f()</code> should be compiled and executed.</p></td>
  85 </tr></tbody>
  86 </table></div></td>
  87 </tr>
  88 <tr>
  89 <td><p><span class="term">Returns:</span></p></td>
  90 <td><p>Boolean value returned by <code class="computeroutput">f()</code> if the static predicate <code class="computeroutput">Pred::value</code> is <code class="computeroutput">true</code>. Otherwise, trivially return <code class="computeroutput">else_</code>. </p></td>
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  98 <td align="right"><div class="copyright-footer">Copyright &#169; 2008-2019 Lorenzo Caminiti<p>
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