1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Function template call_if_c</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. 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20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="call_if__idm46268585815184.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.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="boost.contract.call_if_c"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Function template call_if_c</span></h2> 29<p>boost::contract::call_if_c — Select compilation and execution of functor template calls 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: <<a class="link" href="../../reference.html#header.boost.contract.call_if_hpp" title="Header <boost/contract/call_if.hpp>">boost/contract/call_if.hpp</a>> 33 34</span> 35<span class="keyword">template</span><span class="special"><</span><span class="keyword">bool</span> Pred<span class="special">,</span> <span class="keyword">typename</span> Then<span class="special">></span> 36 <a class="link" href="call_if_statement.html" title="Struct template call_if_statement">call_if_statement</a><span class="special"><</span> <span class="identifier">Pred</span><span class="special">,</span> <span class="identifier">Then</span> <span class="special">></span> <span class="identifier">call_if_c</span><span class="special">(</span><span class="identifier">Then</span> f<span class="special">)</span><span class="special">;</span></pre></div> 37<div class="refsect1"> 38<a name="idm45988680490720"></a><h2>Description</h2> 39<p>Create a call-if object with the specified then-branch functor template:</p> 40<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">call_if_c</span><span class="special"><</span><span class="identifier">Pred1</span><span class="special">></span><span class="special">(</span> 41 <span class="identifier">then_functor_template1</span> 42<span class="special">)</span><span class="special">.</span><span class="keyword">template</span> <span class="identifier">else_if_c</span><span class="special"><</span><span class="identifier">Pred2</span><span class="special">></span><span class="special">(</span> <span class="comment">// Optional.</span> 43 <span class="identifier">then_functor_template2</span> 44<span class="special">)</span> <span class="comment">// Optionally, other `else_if_c` or</span> 45<span class="special">...</span> <span class="comment">// `else_if`.</span> 46<span class="special">.</span><span class="identifier">else_</span><span class="special">(</span> <span class="comment">// Optional for `void` functors,</span> 47 <span class="identifier">else_functor_template</span> <span class="comment">// but required for non `void`.</span> 48<span class="special">)</span> 49</pre> 50<p>Optional functor templates for else-if-branches and the else-branch can be specified as needed (the else-branch function template is required if <code class="computeroutput">f</code> returns non-void).</p> 51<p><span class="bold"><strong>See Also:</strong></span></p> 52<p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.assertion_requirements__templates_" title="Assertion Requirements (Templates)"> 53 Assertion Requirements</a></p> 54<p> 55</p> 56<p> 57 58 59 60</p> 61<div class="variablelist"><table border="0" class="variablelist compact"> 62<colgroup> 63<col align="left" valign="top"> 64<col> 65</colgroup> 66<tbody> 67<tr> 68<td><p><span class="term">Parameters:</span></p></td> 69<td><div class="variablelist"><table border="0" class="variablelist compact"> 70<colgroup> 71<col align="left" valign="top"> 72<col> 73</colgroup> 74<tbody><tr> 75<td><p><span class="term"><code class="computeroutput">f</code></span></p></td> 76<td><p>Then-branch nullary 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>. The return type of other functor template calls specified for this call-if statement (else-branch, else-if-branches, etc.) must be the same as (or implicitly convertible to) the return type of then-branch functor call <code class="computeroutput">f()</code>.</p></td> 77</tr></tbody> 78</table></div></td> 79</tr> 80<tr> 81<td><p><span class="term">Template Parameters:</span></p></td> 82<td><div class="variablelist"><table border="0" class="variablelist compact"> 83<colgroup> 84<col align="left" valign="top"> 85<col> 86</colgroup> 87<tbody><tr> 88<td><p><span class="term"><code class="computeroutput">Pred</code></span></p></td> 89<td><p>Static boolean predicate selecting which functor template call to compile and execute.</p></td> 90</tr></tbody> 91</table></div></td> 92</tr> 93<tr> 94<td><p><span class="term">Returns:</span></p></td> 95<td><p>A call-if statement so else and else-if statements can be specified if needed. Eventually, this will be the return value of the one functor template call being compiled and executed (which could also be <code class="computeroutput">void</code>). </p></td> 96</tr> 97</tbody> 98</table></div> 99</div> 100</div> 101<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 102<td align="left"></td> 103<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p> 104 Distributed under the Boost Software License, Version 1.0 (see accompanying 105 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>) 106 </p> 107</div></td> 108</tr></table> 109<hr> 110<div class="spirit-nav"> 111<a accesskey="p" href="call_if__idm46268585815184.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.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 112</div> 113</body> 114</html> 115
