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  26 <a name="boost.contract.call_if__idm45395000042848"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Struct template call_if_statement&lt;true, Then, ThenResult&gt;</span></h2>
  29 <p>boost::contract::call_if_statement&lt;true, Then, ThenResult&gt; &#8212; Template specialization to handle static predicates that are <code class="computeroutput">true</code> for then-branch functor template calls that do not return void (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><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Then<span class="special">,</span> <span class="keyword">typename</span> ThenResult<span class="special">&gt;</span>
  35 <span class="keyword">struct</span> <a class="link" href="call_if__idm45395000042848.html" title="Struct template call_if_statement&lt;true, Then, ThenResult&gt;">call_if_statement</a><span class="special">&lt;</span><span class="keyword">true</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">ThenResult</span><span class="special">&gt;</span> <span class="special">{</span>
  36   <span class="comment">// <a class="link" href="call_if__idm45395000042848.html#boost.contract.call_if__idm45395000042848construct-copy-destruct">construct/copy/destruct</a></span>
  37   <span class="keyword">explicit</span> <a class="link" href="call_if__idm45395000042848.html#idm45395000007120-bb"><span class="identifier">call_if_statement</span></a><span class="special">(</span><span class="identifier">Then</span><span class="special">)</span><span class="special">;</span>
  38
  39   <span class="comment">// <a class="link" href="call_if__idm45395000042848.html#idm45395000033040-bb">public member functions</a></span>
  40   <a class="link" href="call_if__idm45395000042848.html#idm45395000032480-bb"><span class="keyword">operator</span> <span class="identifier">ThenResult</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  41   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Else<span class="special">&gt;</span> <span class="identifier">ThenResult</span> <a class="link" href="call_if__idm45395000042848.html#idm45395000030976-bb"><span class="identifier">else_</span></a><span class="special">(</span><span class="identifier">Else</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  42   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">bool</span> ElseIfPred<span class="special">,</span> <span class="keyword">typename</span> ElseIfThen<span class="special">&gt;</span>
  43     <a class="link" href="call_if_statement.html" title="Struct template call_if_statement">call_if_statement</a><span class="special">&lt;</span> <span class="keyword">true</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">ThenResult</span> <span class="special">&gt;</span>
  44     <a class="link" href="call_if__idm45395000042848.html#idm45395000024480-bb"><span class="identifier">else_if_c</span></a><span class="special">(</span><span class="identifier">ElseIfThen</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  45   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> ElseIfPred<span class="special">,</span> <span class="keyword">typename</span> ElseIfThen<span class="special">&gt;</span>
  46     <a class="link" href="call_if_statement.html" title="Struct template call_if_statement">call_if_statement</a><span class="special">&lt;</span> <span class="keyword">true</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">ThenResult</span> <span class="special">&gt;</span>
  47     <a class="link" href="call_if__idm45395000042848.html#idm45395000015744-bb"><span class="identifier">else_if</span></a><span class="special">(</span><span class="identifier">ElseIfThen</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  48 <span class="special">}</span><span class="special">;</span></pre></div>
  49 <div class="refsect1">
  50 <a name="idm45707997968256"></a><h2>Description</h2>
  51 <p>Usually this class template is instantiated only via the return value of  <code class="computeroutput"><a class="link" href="call_if.html" title="Function template call_if">boost::contract::call_if</a></code> and <code class="computeroutput"><a class="link" href="call_if_c.html" title="Function template call_if_c">boost::contract::call_if_c</a></code>.</p>
  52 <p><span class="bold"><strong>See Also:</strong></span></p>
  53 <p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.assertion_requirements__templates_" title="Assertion Requirements (Templates)">
  54         Assertion Requirements</a></p>
  55 <p>
  56 </p>
  57 <p>
  58
  59 </p>
  60 <div class="refsect2">
  61 <a name="idm45707997962800"></a><h3>Template Parameters</h3>
  62 <div class="orderedlist"><ol class="orderedlist" type="1">
  63 <li class="listitem">
  64 <pre class="literallayout"><span class="keyword">typename</span> Then</pre>
  65 <p>Type of functor template to call when the static predicate is <code class="computeroutput">true</code> (as it is for this template specialization). </p>
  66 </li>
  67 <li class="listitem">
  68 <pre class="literallayout"><span class="keyword">typename</span> ThenResult</pre>
  69 <p>Non-void return type of the then-branch functor template call. </p>
  70 </li>
  71 </ol></div>
  72 </div>
  73 <div class="refsect2">
  74 <a name="idm45707997956816"></a><h3>
  75 <a name="boost.contract.call_if__idm45395000042848construct-copy-destruct"></a><code class="computeroutput">call_if_statement</code>
  76         public
  77        construct/copy/destruct</h3>
  78 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
  79 <pre class="literallayout"><span class="keyword">explicit</span> <a name="idm45395000007120-bb"></a><span class="identifier">call_if_statement</span><span class="special">(</span><span class="identifier">Then</span> f<span class="special">)</span><span class="special">;</span></pre>Construct this object with the then-branch functor template. <p>
  80 </p>
  81 <div class="variablelist"><table border="0" class="variablelist compact">
  82 <colgroup>
  83 <col align="left" valign="top">
  84 <col>
  85 </colgroup>
  86 <tbody><tr>
  87 <td><p><span class="term">Parameters:</span></p></td>
  88 <td><div class="variablelist"><table border="0" class="variablelist compact">
  89 <colgroup>
  90 <col align="left" valign="top">
  91 <col>
  92 </colgroup>
  93 <tbody><tr>
  94 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
  95 <td><p>Then-branch nullary functor template. The functor template call <code class="computeroutput">f()</code> is actually compiled and executed for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). The return type of <code class="computeroutput">f()</code> must be the same as (or implicitly convertible to) the <code class="computeroutput">ThenResult</code> type. </p></td>
  96 </tr></tbody>
  97 </table></div></td>
  98 </tr></tbody>
  99 </table></div>
 100 </li></ol></div>
 101 </div>
 102 <div class="refsect2">
 103 <a name="idm45707997943152"></a><h3>
 104 <a name="idm45395000033040-bb"></a><code class="computeroutput">call_if_statement</code> public member functions</h3>
 105 <div class="orderedlist"><ol class="orderedlist" type="1">
 106 <li class="listitem">
 107 <pre class="literallayout"><a name="idm45395000032480-bb"></a><span class="keyword">operator</span> <span class="identifier">ThenResult</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>This implicit type conversion returns a copy of the value returned by the call to the then-branch functor template. </li>
 108 <li class="listitem">
 109 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Else<span class="special">&gt;</span> <span class="identifier">ThenResult</span> <a name="idm45395000030976-bb"></a><span class="identifier">else_</span><span class="special">(</span><span class="identifier">Else</span> <span class="keyword">const</span> <span class="special">&amp;</span> f<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>Specify the else-branch functor template. <p>
 110
 111 </p>
 112 <div class="variablelist"><table border="0" class="variablelist compact">
 113 <colgroup>
 114 <col align="left" valign="top">
 115 <col>
 116 </colgroup>
 117 <tbody>
 118 <tr>
 119 <td><p><span class="term">Parameters:</span></p></td>
 120 <td><div class="variablelist"><table border="0" class="variablelist compact">
 121 <colgroup>
 122 <col align="left" valign="top">
 123 <col>
 124 </colgroup>
 125 <tbody><tr>
 126 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
 127 <td><p>Else-branch nullary functor template. The functor template call <code class="computeroutput">f()</code> is never compiled or executed for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). The return type of <code class="computeroutput">f()</code> must be the same as (or implicitly convertible to) the <code class="computeroutput">ThenResult</code> type.</p></td>
 128 </tr></tbody>
 129 </table></div></td>
 130 </tr>
 131 <tr>
 132 <td><p><span class="term">Returns:</span></p></td>
 133 <td><p>A copy of the value returned by the call to the then-branch functor template (because the else-branch functor template call is not executed). </p></td>
 134 </tr>
 135 </tbody>
 136 </table></div>
 137 </li>
 138 <li class="listitem">
 139 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">bool</span> ElseIfPred<span class="special">,</span> <span class="keyword">typename</span> ElseIfThen<span class="special">&gt;</span>
 140   <a class="link" href="call_if_statement.html" title="Struct template call_if_statement">call_if_statement</a><span class="special">&lt;</span> <span class="keyword">true</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">ThenResult</span> <span class="special">&gt;</span>
 141   <a name="idm45395000024480-bb"></a><span class="identifier">else_if_c</span><span class="special">(</span><span class="identifier">ElseIfThen</span> <span class="keyword">const</span> <span class="special">&amp;</span> f<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>Specify an else-if-branch functor template (using a static boolean predicate). <p>
 142
 143
 144 </p>
 145 <div class="variablelist"><table border="0" class="variablelist compact">
 146 <colgroup>
 147 <col align="left" valign="top">
 148 <col>
 149 </colgroup>
 150 <tbody>
 151 <tr>
 152 <td><p><span class="term">Parameters:</span></p></td>
 153 <td><div class="variablelist"><table border="0" class="variablelist compact">
 154 <colgroup>
 155 <col align="left" valign="top">
 156 <col>
 157 </colgroup>
 158 <tbody><tr>
 159 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
 160 <td><p>Else-if-branch nullary functor template. The functor template call <code class="computeroutput">f()</code> is never compiled or executed for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). The return type of <code class="computeroutput">f()</code> must be the same as (or implicitly convertible to) the <code class="computeroutput">ThenResult</code> type.</p></td>
 161 </tr></tbody>
 162 </table></div></td>
 163 </tr>
 164 <tr>
 165 <td><p><span class="term">Template Parameters:</span></p></td>
 166 <td><div class="variablelist"><table border="0" class="variablelist compact">
 167 <colgroup>
 168 <col align="left" valign="top">
 169 <col>
 170 </colgroup>
 171 <tbody><tr>
 172 <td><p><span class="term"><code class="computeroutput">ElseIfPred</code></span></p></td>
 173 <td><p>Static boolean predicate selecting which functor template call to compile and execute.</p></td>
 174 </tr></tbody>
 175 </table></div></td>
 176 </tr>
 177 <tr>
 178 <td><p><span class="term">Returns:</span></p></td>
 179 <td><p>A call-if statement so the else statement and additional else-if statements can be specified if needed. Eventually, it will be the return value of the then-branch functor template call for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). </p></td>
 180 </tr>
 181 </tbody>
 182 </table></div>
 183 </li>
 184 <li class="listitem">
 185 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> ElseIfPred<span class="special">,</span> <span class="keyword">typename</span> ElseIfThen<span class="special">&gt;</span>
 186   <a class="link" href="call_if_statement.html" title="Struct template call_if_statement">call_if_statement</a><span class="special">&lt;</span> <span class="keyword">true</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">ThenResult</span> <span class="special">&gt;</span>
 187   <a name="idm45395000015744-bb"></a><span class="identifier">else_if</span><span class="special">(</span><span class="identifier">ElseIfThen</span> <span class="keyword">const</span> <span class="special">&amp;</span> f<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>Specify an else-if-branch functor template (using a nullary boolean meta-function). <p>
 188
 189
 190 </p>
 191 <div class="variablelist"><table border="0" class="variablelist compact">
 192 <colgroup>
 193 <col align="left" valign="top">
 194 <col>
 195 </colgroup>
 196 <tbody>
 197 <tr>
 198 <td><p><span class="term">Parameters:</span></p></td>
 199 <td><div class="variablelist"><table border="0" class="variablelist compact">
 200 <colgroup>
 201 <col align="left" valign="top">
 202 <col>
 203 </colgroup>
 204 <tbody><tr>
 205 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
 206 <td><p>Else-if-branch nullary functor template. The functor template call <code class="computeroutput">f()</code> is never compiled or executed for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). The return type of <code class="computeroutput">f()</code> must be the same as (or implicitly convertible to) the <code class="computeroutput">ThenResult</code> type.</p></td>
 207 </tr></tbody>
 208 </table></div></td>
 209 </tr>
 210 <tr>
 211 <td><p><span class="term">Template Parameters:</span></p></td>
 212 <td><div class="variablelist"><table border="0" class="variablelist compact">
 213 <colgroup>
 214 <col align="left" valign="top">
 215 <col>
 216 </colgroup>
 217 <tbody><tr>
 218 <td><p><span class="term"><code class="computeroutput">ElseIfPred</code></span></p></td>
 219 <td><p>Nullary boolean meta-function selecting which functor template call to compile and execute.</p></td>
 220 </tr></tbody>
 221 </table></div></td>
 222 </tr>
 223 <tr>
 224 <td><p><span class="term">Returns:</span></p></td>
 225 <td><p>A call-if statement so the else statement and additional else-if statements can be specified if needed. Eventually, it will be the return value of the then-branch functor template call for this template specialization (because the if-statement static predicate is <code class="computeroutput">true</code>). </p></td>
 226 </tr>
 227 </tbody>
 228 </table></div>
 229 </li>
 230 </ol></div>
 231 </div>
 232 </div>
 233 </div>
 234 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 235 <td align="left"></td>
 236 <td align="right"><div class="copyright-footer">Copyright &#169; 2008-2019 Lorenzo Caminiti<p>
 237         Distributed under the Boost Software License, Version 1.0 (see accompanying
 238         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>)
 239       </p>
 240 </div></td>
 241 </tr></table>
 242 <hr>
 243 <div class="spirit-nav">
 244 <a accesskey="p" href="call_if__idm45395000058976.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../reference.html#header.boost.contract.call_if_hpp"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="call_if__idm45395000002720.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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