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  26 <a name="boost.contract.public_f_idm45123869661408"></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 non-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> VirtualResult<span class="special">,</span> <span class="keyword">typename</span> F<span class="special">,</span>
  36          <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>
  37   <a class="link" href="specify__idm45123870039968.html" title="Class template specify_precondition_old_postcondition_except">specify_precondition_old_postcondition_except</a><span class="special">&lt;</span> <span class="identifier">VirtualResult</span> <span class="special">&gt;</span>
  38   <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">VirtualResult</span> <span class="special">&amp;</span> r<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>
  39                   <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>
  40 <div class="refsect1">
  41 <a name="idm45751726751296"></a><h2>Description</h2>
  42 <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 do not return <code class="computeroutput">void:</code> </p>
  43 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span>
  44     <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> \
  45             <span class="keyword">public</span> <span class="identifier">b</span><span class="special">,</span> <span class="keyword">private</span> <span class="identifier">w</span>
  46     <span class="special">:</span> <span class="identifier">BASES</span>
  47 <span class="special">{</span>
  48     <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>
  49
  50     <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>
  51     <span class="preprocessor">#undef</span> <span class="identifier">BASES</span>
  52
  53     <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>
  54         <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  55         <span class="special">...</span>
  56     <span class="special">}</span>
  57
  58     <span class="identifier">BOOST_CONTRACT_OVERRIDES</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
  59
  60 <span class="keyword">public</span><span class="special">:</span>
  61     <span class="comment">// Override from `b::f`.</span>
  62     <span class="identifier">t</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>
  63         <span class="identifier">t</span> <span class="identifier">result</span><span class="special">;</span>
  64         <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>
  65         <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>
  66                 <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="identifier">result</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>
  67             <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>
  68                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  69                 <span class="special">...</span>
  70             <span class="special">}</span><span class="special">)</span>
  71             <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>
  72                 <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>
  73                 <span class="special">...</span>
  74             <span class="special">}</span><span class="special">)</span>
  75             <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="identifier">t</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">result</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  76                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  77                 <span class="special">...</span>
  78             <span class="special">}</span><span class="special">)</span>
  79             <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>
  80                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  81                 <span class="special">...</span>
  82             <span class="special">}</span><span class="special">)</span>
  83         <span class="special">;</span>
  84
  85         <span class="special">...</span> <span class="comment">// Function body (use `return result = return_expr`).</span>
  86     <span class="special">}</span>
  87
  88     <span class="special">...</span>
  89 <span class="special">}</span><span class="special">;</span>
  90 </pre>
  91 <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>
  92 <p><span class="bold"><strong>See Also:</strong></span></p>
  93 <p> <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.public_function_overrides__subcontracting_" title="Public Function Overrides (Subcontracting)">
  94         Public Function Overrides</a></p>
  95 <p>
  96 </p>
  97 <p>
  98
  99
 100
 101 </p>
 102 <div class="variablelist"><table border="0" class="variablelist compact">
 103 <colgroup>
 104 <col align="left" valign="top">
 105 <col>
 106 </colgroup>
 107 <tbody>
 108 <tr>
 109 <td><p><span class="term">Parameters:</span></p></td>
 110 <td><div class="variablelist"><table border="0" class="variablelist compact">
 111 <colgroup>
 112 <col align="left" valign="top">
 113 <col>
 114 </colgroup>
 115 <tbody>
 116 <tr>
 117 <td><p><span class="term"><code class="computeroutput">args</code></span></p></td>
 118 <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>
 119 </tr>
 120 <tr>
 121 <td><p><span class="term"><code class="computeroutput">f</code></span></p></td>
 122 <td><p>A pointer to the enclosing public function override declaring the contract. </p></td>
 123 </tr>
 124 <tr>
 125 <td><p><span class="term"><code class="computeroutput">obj</code></span></p></td>
 126 <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">
 127             Volatile Public Functions</a>). </p></td>
 128 </tr>
 129 <tr>
 130 <td><p><span class="term"><code class="computeroutput">r</code></span></p></td>
 131 <td><p>A reference to the return value of the enclosing public function override declaring the contract. This is usually a local variable declared by the enclosing public function override just before the contract, but programmers must set it to the actual value being returned by the function at each <code class="computeroutput">return</code> statement. </p></td>
 132 </tr>
 133 <tr>
 134 <td><p><span class="term"><code class="computeroutput">v</code></span></p></td>
 135 <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>
 136 </tr>
 137 </tbody>
 138 </table></div></td>
 139 </tr>
 140 <tr>
 141 <td><p><span class="term">Template Parameters:</span></p></td>
 142 <td><div class="variablelist"><table border="0" class="variablelist compact">
 143 <colgroup>
 144 <col align="left" valign="top">
 145 <col>
 146 </colgroup>
 147 <tbody>
 148 <tr>
 149 <td><p><span class="term"><code class="computeroutput">Args</code></span></p></td>
 150 <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>
 151 </tr>
 152 <tr>
 153 <td><p><span class="term"><code class="computeroutput">Class</code></span></p></td>
 154 <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>
 155 </tr>
 156 <tr>
 157 <td><p><span class="term"><code class="computeroutput">F</code></span></p></td>
 158 <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">
 159             Function Overloads</a>.) </p></td>
 160 </tr>
 161 <tr>
 162 <td><p><span class="term"><code class="computeroutput">Override</code></span></p></td>
 163 <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>
 164 </tr>
 165 <tr>
 166 <td><p><span class="term"><code class="computeroutput">VirtualResult</code></span></p></td>
 167 <td><p>This type must be the same as, or compatible with, the return type of the enclosing public function override declaring the contract (this library might not be able to generate a compile-time error if these types mismatch, but in general that will cause run-time errors or undefined behaviour). Alternatively, <code class="computeroutput">boost::optional&lt;<span class="emphasis"><em>return-type</em></span>&gt;</code> can also be used (see  <a class="link" href="../../boost_contract/advanced.html#boost_contract.advanced.optional_return_values" title="Optional Return Values">
 168                         Optional Return Values</a>). (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.) </p></td>
 169 </tr>
 170 </tbody>
 171 </table></div></td>
 172 </tr>
 173 <tr>
 174 <td><p><span class="term">Returns:</span></p></td>
 175 <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>
 176 </tr>
 177 </tbody>
 178 </table></div>
 179 </div>
 180 </div>
 181 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 182 <td align="left"></td>
 183 <td align="right"><div class="copyright-footer">Copyright &#169; 2008-2018 Lorenzo Caminiti<p>
 184         Distributed under the Boost Software License, Version 1.0 (see accompanying
 185         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>)
 186       </p>
 187 </div></td>
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