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  26 <a name="boost.contract.public_f_idm45123869691040"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Function template public_function</span></h2>
  29 <p>boost::contract::public_function &#8212; Program contracts for void public functions overrides (virtual or not). </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.public_function_hpp" title="Header &lt;boost/contract/public_function.hpp&gt;">boost/contract/public_function.hpp</a>&gt;
  33
  34 </span>
  35 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Override<span class="special">,</span> <span class="keyword">typename</span> F<span class="special">,</span> <span class="keyword">typename</span> Class<span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> Args<span class="special">&gt;</span>
  36   <a class="link" href="specify__idm45123870039968.html" title="Class template specify_precondition_old_postcondition_except">specify_precondition_old_postcondition_except</a>
  37   <span class="identifier">public_function</span><span class="special">(</span><a class="link" href="virtual_.html" title="Class virtual_">virtual_</a> <span class="special">*</span> v<span class="special">,</span> <span class="identifier">F</span> f<span class="special">,</span> <span class="identifier">Class</span> <span class="special">*</span> obj<span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;</span><span class="special">...</span> args<span class="special">)</span><span class="special">;</span></pre></div>
  38 <div class="refsect1">
  39 <a name="idm45751726934896"></a><h2>Description</h2>
  40 <p>This is used to specify preconditions, postconditions, exception guarantees, old value copies at body, and check class invariants for public function overrides (virtual or not) that return <code class="computeroutput">void:</code> </p>
  41 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span>
  42     <span class="preprocessor">#define</span> <span class="identifier">BASES</span> <span class="keyword">private</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">constructor_precondition</span><span class="special">&lt;</span><span class="identifier">u</span><span class="special">&gt;</span><span class="special">,</span> \
  43             <span class="keyword">public</span> <span class="identifier">b</span><span class="special">,</span> <span class="keyword">private</span> <span class="identifier">w</span>
  44     <span class="special">:</span> <span class="identifier">BASES</span>
  45 <span class="special">{</span>
  46     <span class="keyword">friend</span> <span class="keyword">class</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">access</span><span class="special">;</span>
  47
  48     <span class="keyword">typedef</span> <span class="identifier">BOOST_CONTRACT_BASE_TYPES</span><span class="special">(</span><span class="identifier">BASES</span><span class="special">)</span> <span class="identifier">base_types</span><span class="special">;</span>
  49     <span class="preprocessor">#undef</span> <span class="identifier">BASES</span>
  50
  51     <span class="keyword">void</span> <span class="identifier">invariant</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">{</span> <span class="comment">// Optional (as for static and volatile).</span>
  52         <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  53         <span class="special">...</span>
  54     <span class="special">}</span>
  55
  56     <span class="identifier">BOOST_CONTRACT_OVERRIDES</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
  57
  58 <span class="keyword">public</span><span class="special">:</span>
  59     <span class="comment">// Override from `b::f`.</span>
  60     <span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">t_1</span> <span class="identifier">a_1</span><span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="identifier">t_n</span> <span class="identifier">a_n</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">virtual_</span><span class="special">*</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">0</span><span class="special">)</span> <span class="special">{</span>
  61         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">old_ptr</span><span class="special">&lt;</span><span class="identifier">old_type</span><span class="special">&gt;</span> <span class="identifier">old_var</span><span class="special">;</span>
  62         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">check</span> <span class="identifier">c</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">public_function</span><span class="special">&lt;</span>
  63                 <span class="identifier">override_f</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">v</span><span class="special">,</span> <span class="special">&amp;</span><span class="identifier">u</span><span class="special">::</span><span class="identifier">f</span><span class="special">,</span> <span class="keyword">this</span><span class="special">,</span> <span class="identifier">a_1</span><span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="identifier">a_n</span><span class="special">)</span>
  64             <span class="special">.</span><span class="identifier">precondition</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  65                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  66                 <span class="special">...</span>
  67             <span class="special">}</span><span class="special">)</span>
  68             <span class="special">.</span><span class="identifier">old</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  69                 <span class="identifier">old_var</span> <span class="special">=</span> <span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">v</span><span class="special">,</span> <span class="identifier">old_expr</span><span class="special">)</span><span class="special">;</span>
  70                 <span class="special">...</span>
  71             <span class="special">}</span><span class="special">)</span>
  72             <span class="special">.</span><span class="identifier">postcondition</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  73                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  74                 <span class="special">...</span>
  75             <span class="special">}</span><span class="special">)</span>
  76             <span class="special">.</span><span class="identifier">except</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  77                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  78                 <span class="special">...</span>
  79             <span class="special">}</span><span class="special">)</span>
  80         <span class="special">;</span>
  81
  82         <span class="special">...</span> <span class="comment">// Function body.</span>
  83     <span class="special">}</span>
  84
  85     <span class="special">...</span>
  86 <span class="special">}</span><span class="special">;</span>
  87 </pre>
  88 <p>A public function override should always call  <code class="computeroutput"><code class="computeroutput"><a class="link" href="public_f_idm45123869756752.html" title="Function template public_function">boost::contract::public_function</a></code></code> otherwise this library will not be able to correctly use it for subcontracting.</p>
  89 <p><span class="bold"><strong>See Also:</strong></span></p>
  90 <p> <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.public_function_overrides__subcontracting_" title="Public Function Overrides (Subcontracting)">
  91         Public Function Overrides</a></p>
  92 <p>
  93 </p>
  94 <p>
  95
  96
  97
  98 </p>
  99 <div class="variablelist"><table border="0" class="variablelist compact">
 100 <colgroup>
 101 <col align="left" valign="top">
 102 <col>
 103 </colgroup>
 104 <tbody>
 105 <tr>
 106 <td><p><span class="term">Parameters:</span></p></td>
 107 <td><div class="variablelist"><table border="0" class="variablelist compact">
 108 <colgroup>
 109 <col align="left" valign="top">
 110 <col>
 111 </colgroup>
 112 <tbody>
 113 <tr>
 114 <td><p><span class="term"><code class="computeroutput">args</code></span></p></td>
 115 <td><p>All arguments passed to the enclosing public function override declaring the contract (by reference and in the order they appear in the enclosing function declaration), but excluding the trailing argument <code class="computeroutput">v</code>.</p></td>
 116 </tr>
 117 <tr>
 118 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
 119 <td><p>A pointer to the enclosing public function override declaring the contract. </p></td>
 120 </tr>
 121 <tr>
 122 <td><p><span class="term"><code class="computeroutput">obj</code></span></p></td>
 123 <td><p>The object <code class="computeroutput">this</code> from the scope of the enclosing public function override declaring the contract. This object might be mutable, <code class="computeroutput">const</code>, <code class="computeroutput">volatile</code>, or <code class="computeroutput">const volatile</code> depending on the cv-qualifier of the enclosing function (volatile public functions will check volatile class invariants, see  <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.volatile_public_functions" title="Volatile Public Functions">
 124             Volatile Public Functions</a>). </p></td>
 125 </tr>
 126 <tr>
 127 <td><p><span class="term"><code class="computeroutput">v</code></span></p></td>
 128 <td><p>The trailing parameter of type  <code class="computeroutput"><code class="computeroutput"><a class="link" href="virtual_.html" title="Class virtual_">boost::contract::virtual_</a></code></code><code class="computeroutput">*</code> and default value <code class="computeroutput">0</code> from the enclosing public function override. </p></td>
 129 </tr>
 130 </tbody>
 131 </table></div></td>
 132 </tr>
 133 <tr>
 134 <td><p><span class="term">Template Parameters:</span></p></td>
 135 <td><div class="variablelist"><table border="0" class="variablelist compact">
 136 <colgroup>
 137 <col align="left" valign="top">
 138 <col>
 139 </colgroup>
 140 <tbody>
 141 <tr>
 142 <td><p><span class="term"><code class="computeroutput">Args</code></span></p></td>
 143 <td><p>The types of all parameters passed to the enclosing public function override declaring the contract, but excluding the trailing parameter type <code class="computeroutput"><code class="computeroutput"><a class="link" href="virtual_.html" title="Class virtual_">boost::contract::virtual_</a></code>*</code>. On compilers that do not support variadic templates, this library internally implements this function using preprocessor meta-programming (in this case, the maximum number of supported arguments is defined by  <code class="computeroutput"><code class="computeroutput"><a class="link" href="../../BOOST_CONTRACT_MAX_ARGS.html" title="Macro BOOST_CONTRACT_MAX_ARGS">BOOST_CONTRACT_MAX_ARGS</a></code></code>). (Usually these template parameters are automatically deduced by C++ and they do not need to be explicitly specified by programmers.)</p></td>
 144 </tr>
 145 <tr>
 146 <td><p><span class="term"><code class="computeroutput">Class</code></span></p></td>
 147 <td><p>The type of the class containing the virtual public function declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.) </p></td>
 148 </tr>
 149 <tr>
 150 <td><p><span class="term"><code class="computeroutput">F</code></span></p></td>
 151 <td><p>The function pointer type of the enclosing public function override declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers, but see  <a class="link" href="../../boost_contract/advanced.html#boost_contract.advanced.function_overloads" title="Function Overloads"> Function Overloads</a>.) </p></td>
 152 </tr>
 153 <tr>
 154 <td><p><span class="term"><code class="computeroutput">Override</code></span></p></td>
 155 <td><p>The type <code class="computeroutput">override_<span class="emphasis"><em>function-name</em></span></code> declared using the <code class="computeroutput"><code class="computeroutput"><a class="link" href="../../BOOST_CONTRACT_OVERRIDE.html" title="Macro BOOST_CONTRACT_OVERRIDE">BOOST_CONTRACT_OVERRIDE</a></code></code> or related macros. This template parameter must be explicitly specified (because there is no function argument from which it can be automatically deduced by C++). </p></td>
 156 </tr>
 157 </tbody>
 158 </table></div></td>
 159 </tr>
 160 <tr>
 161 <td><p><span class="term">Returns:</span></p></td>
 162 <td><p>The result of this function must be explicitly assigned to a variable of type <code class="computeroutput"><a class="link" href="check.html" title="Class check">boost::contract::check</a></code> declared locally just before the code of the public function body (otherwise this library will generate a run-time error, see  <code class="computeroutput"><a class="link" href="../../BOOST_CO_idm45123870548928.html" title="Macro BOOST_CONTRACT_ON_MISSING_CHECK_DECL">BOOST_CONTRACT_ON_MISSING_CHECK_DECL</a></code>). </p></td>
 163 </tr>
 164 </tbody>
 165 </table></div>
 166 </div>
 167 </div>
 168 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 169 <td align="left"></td>
 170 <td align="right"><div class="copyright-footer">Copyright &#169; 2008-2018 Lorenzo Caminiti<p>
 171         Distributed under the Boost Software License, Version 1.0 (see accompanying
 172         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>)
 173       </p>
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