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  25 <div class="refentry">
  26 <a name="boost.function"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Class template function</span></h2>
  29 <p>boost::function &#8212; A generalized function pointer that can be used for
  30     callbacks or wrapping function objects.</p>
  31 </div>
  32 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  33 <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="../function/reference.html#header.boost.function_hpp" title="Header &lt;boost/function.hpp&gt;">boost/function.hpp</a>&gt;
  34
  35 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">&gt;</span>
  36 <span class="keyword">class</span> <a class="link" href="function.html" title="Class template function">function</a> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&lt;</span><span class="identifier">R</span><span class="special">,</span> <span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="identifier">TN</span><span class="special">&gt;</span> <span class="special">{</span>
  37 <span class="keyword">public</span><span class="special">:</span>
  38   <span class="comment">// types</span>
  39   <span class="keyword">typedef</span> <span class="identifier">R</span>  <a name="boost.function.result_type"></a><span class="identifier">result_type</span><span class="special">;</span>
  40   <span class="keyword">typedef</span> <span class="identifier">T1</span> <a name="boost.function.argument_type"></a><span class="identifier">argument_type</span><span class="special">;</span>         <span class="comment">// If N == 1</span>
  41   <span class="keyword">typedef</span> <span class="identifier">T1</span> <a name="boost.function.first_argument_type"></a><span class="identifier">first_argument_type</span><span class="special">;</span>   <span class="comment">// If N == 2</span>
  42   <span class="keyword">typedef</span> <span class="identifier">T2</span> <a name="boost.function.second_argument_type"></a><span class="identifier">second_argument_type</span><span class="special">;</span>  <span class="comment">// If N == 2</span>
  43   <span class="keyword">typedef</span> <span class="identifier">T1</span> <a name="boost.function.arg1_type"></a><span class="identifier">arg1_type</span><span class="special">;</span>
  44   <span class="keyword">typedef</span> <span class="identifier">T2</span> <a name="boost.function.arg2_type"></a><span class="identifier">arg2_type</span><span class="special">;</span>
  45      .
  46      .
  47      .
  48   <span class="keyword">typedef</span> <span class="identifier">TN</span> <a name="boost.function.argN_type"></a><span class="identifier">argN_type</span><span class="special">;</span>
  49
  50   <span class="comment">// static constants</span>
  51   <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">arity</span> = <span class="identifier">N</span><span class="special">;</span>
  52
  53   <span class="comment">// member classes/structs/unions</span>
  54
  55   <span class="comment">// <a class="link" href="../lambda.html" title="Chapter&#160;16.&#160;Boost.Lambda">Lambda</a> library support</span>
  56   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Args<span class="special">&gt;</span>
  57   <span class="keyword">struct</span> <a class="link" href="function/sig.html" title="Struct template sig">sig</a> <span class="special">{</span>
  58     <span class="comment">// types</span>
  59     <span class="keyword">typedef</span> <span class="identifier">result_type</span> <a class="link" href="function/sig.html#boost.function.sig.type"><span class="identifier">type</span></a><span class="special">;</span>
  60   <span class="special">}</span><span class="special">;</span>
  61
  62   <span class="comment">// <a class="link" href="function.html#boost.functionconstruct-copy-destruct">construct/copy/destruct</a></span>
  63   <a class="link" href="function.html#idp75737696-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  64   <a class="link" href="function.html#idp39655760-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  65   <a class="link" href="function.html#idp106826448-bb"><span class="identifier">function</span></a><span class="special">(</span><a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
  66   <a class="link" href="function.html#idp110867712-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  67   <a class="link" href="function.html#idp42720176-bb"><span class="identifier">function</span></a><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
  68   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> F<span class="special">&gt;</span> <a class="link" href="function.html#idp40296688-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="identifier">F</span><span class="special">)</span><span class="special">;</span>
  69   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> F<span class="special">,</span> <span class="keyword">typename</span> Allocator<span class="special">&gt;</span> <a class="link" href="function.html#idp40994480-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="identifier">F</span><span class="special">,</span> <span class="identifier">Allocator</span><span class="special">)</span><span class="special">;</span>
  70   function&amp; <a class="link" href="function.html#idp69909120-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  71   function&amp; <a class="link" href="function.html#idp37708288-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
  72   function&amp; <a class="link" href="function.html#idp38571792-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  73   function&amp; <a class="link" href="function.html#idp105085072-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
  74   <a class="link" href="function.html#idp45860512-bb"><span class="special">~</span><span class="identifier">function</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  75
  76   <span class="comment">// <a class="link" href="function.html#idp108302096-bb">modifiers</a></span>
  77   <span class="keyword">void</span> <a class="link" href="function.html#idp108302656-bb"><span class="identifier">swap</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  78   <span class="keyword">void</span> <a class="link" href="function.html#idp72870112-bb"><span class="identifier">clear</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  79
  80   <span class="comment">// <a class="link" href="function.html#idp99731696-bb">capacity</a></span>
  81   <span class="keyword">bool</span> <a class="link" href="function.html#idp39557232-bb"><span class="identifier">empty</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  82   <a class="link" href="function.html#idp41154480-bb"><span class="keyword">operator</span> <span class="identifier">safe_bool</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  83   <span class="keyword">bool</span> <a class="link" href="function.html#idp76193136-bb"><span class="keyword">operator</span><span class="special">!</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  84
  85   <span class="comment">// <a class="link" href="function.html#idp69032368-bb">target access</a></span>
  86   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="identifier">Functor</span><span class="special">*</span> <a class="link" href="function.html#idp113597808-bb"><span class="identifier">target</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  87   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">*</span> <a class="link" href="function.html#idp37917680-bb"><span class="identifier">target</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  88   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="keyword">bool</span> <a class="link" href="function.html#idp44257488-bb"><span class="identifier">contains</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  89   <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span><span class="special">&amp;</span> <a class="link" href="function.html#idp46276608-bb"><span class="identifier">target_type</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  90
  91   <span class="comment">// <a class="link" href="function.html#idp55139648-bb">invocation</a></span>
  92   <span class="identifier">result_type</span> <a class="link" href="function.html#idp55140176-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">arg1_type</span><span class="special">,</span> <span class="identifier">arg2_type</span><span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="identifier">argN_type</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  93 <span class="special">}</span><span class="special">;</span>
  94
  95 <span class="comment">// <a class="link" href="function.html#idp111166064-bb">specialized algorithms</a></span>
  96 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">&gt;</span>
  97   <span class="keyword">void</span> <a class="link" href="function.html#boost.function.swap_idp76190448"><span class="identifier">swap</span></a><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  98
  99 <span class="comment">// <a class="link" href="function.html#idp48579440-bb">comparison operators</a></span>
 100 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 101   <span class="keyword">bool</span> <a class="link" href="function.html#idp113383552-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Functor</span><span class="special">)</span><span class="special">;</span>
 102 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 103   <span class="keyword">bool</span> <a class="link" href="function.html#idp95785712-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><span class="identifier">Functor</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 104 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 105   <span class="keyword">bool</span> <a class="link" href="function.html#idp37641488-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span><span class="special">)</span><span class="special">;</span>
 106 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 107   <span class="keyword">bool</span> <a class="link" href="function.html#idp105237024-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span>reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 108 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">&gt;</span>
 109   <span class="keyword">void</span> <a class="link" href="function.html#idp69032896-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature1</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature2</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 110 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 111   <span class="keyword">bool</span> <a class="link" href="function.html#idp47556672-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Functor</span><span class="special">)</span><span class="special">;</span>
 112 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 113   <span class="keyword">bool</span> <a class="link" href="function.html#idp101036032-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><span class="identifier">Functor</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 114 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 115   <span class="keyword">bool</span> <a class="link" href="function.html#idp54996816-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span><span class="special">)</span><span class="special">;</span>
 116 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 117   <span class="keyword">bool</span> <a class="link" href="function.html#idp110874944-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span>reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 118 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">&gt;</span>
 119   <span class="keyword">void</span> <a class="link" href="function.html#idp99861584-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature1</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature2</span><span class="special">&gt;</span><span class="special">&amp;</span><span class="special">)</span><span class="special">;</span></pre></div>
 120 <div class="refsect1">
 121 <a name="idp210007408"></a><h2>Description</h2>
 122 <p>Class template <a class="link" href="function.html" title="Class template function">function</a> is a thin
 123       wrapper around the numbered class templates <a class="link" href="functionN.html" title="Class template functionN">function0</a>, <a class="link" href="functionN.html" title="Class template functionN">function1</a>, etc. It accepts a
 124       function type with N arguments and will will derive from
 125       <a class="link" href="functionN.html" title="Class template functionN">functionN</a> instantiated with the arguments
 126       it receives.</p>
 127 <p>The semantics of all operations in class template
 128       <a class="link" href="function.html" title="Class template function">function</a> are equivalent to that of the
 129       underlying <a class="link" href="functionN.html" title="Class template functionN">functionN</a> object, although
 130       additional member functions are required to allow proper copy
 131       construction and copy assignment of function objects.</p>
 132 <div class="refsect2">
 133 <a name="idp210014112"></a><h3>Template Parameters</h3>
 134 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
 135 <pre class="literallayout"><span class="keyword">typename</span> Signature</pre>
 136 <p></p>
 137 </li></ol></div>
 138 </div>
 139 <div class="refsect2">
 140 <a name="idp210016976"></a><h3>
 141 <a name="boost.functionconstruct-copy-destruct"></a><code class="computeroutput">function</code>
 142         public
 143        construct/copy/destruct</h3>
 144 <div class="orderedlist"><ol class="orderedlist" type="1">
 145 <li class="listitem">
 146 <pre class="literallayout"><a name="idp75737696-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>
 147 <div class="variablelist"><table border="0" class="variablelist compact">
 148 <colgroup>
 149 <col align="left" valign="top">
 150 <col>
 151 </colgroup>
 152 <tbody>
 153 <tr>
 154 <td><p><span class="term">Postconditions:</span></p></td>
 155 <td><code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code></td>
 156 </tr>
 157 <tr>
 158 <td><p><span class="term">Throws:</span></p></td>
 159 <td>Will not throw.</td>
 160 </tr>
 161 </tbody>
 162 </table></div>
 163 </li>
 164 <li class="listitem">
 165 <pre class="literallayout"><a name="idp39655760-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 166 <div class="variablelist"><table border="0" class="variablelist compact">
 167 <colgroup>
 168 <col align="left" valign="top">
 169 <col>
 170 </colgroup>
 171 <tbody>
 172 <tr>
 173 <td><p><span class="term">Postconditions:</span></p></td>
 174 <td>Contains a copy of the <code class="computeroutput">f</code>'s target, if it has one, or is empty if <code class="computeroutput">f.<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>.</td>
 175 </tr>
 176 <tr>
 177 <td><p><span class="term">Throws:</span></p></td>
 178 <td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td>
 179 </tr>
 180 </tbody>
 181 </table></div>
 182 </li>
 183 <li class="listitem">
 184 <pre class="literallayout"><a name="idp106826448-bb"></a><span class="identifier">function</span><span class="special">(</span><a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 185 <div class="variablelist"><table border="0" class="variablelist compact">
 186 <colgroup>
 187 <col align="left" valign="top">
 188 <col>
 189 </colgroup>
 190 <tbody>
 191 <tr>
 192 <td><p><span class="term">Requires:</span></p></td>
 193 <td>C++11 compatible compiler.</td>
 194 </tr>
 195 <tr>
 196 <td><p><span class="term">Postconditions:</span></p></td>
 197 <td>Moves the value from <code class="computeroutput">f</code> to <code class="computeroutput">*this</code>. If the argument has its function object allocated on the heap, its buffer will be assigned to <code class="computeroutput">*this</code> leaving argument empty.</td>
 198 </tr>
 199 <tr>
 200 <td><p><span class="term">Throws:</span></p></td>
 201 <td>Will not throw unless argument has its function object allocated not on the heap and copying the target of <code class="computeroutput">f</code> throws.</td>
 202 </tr>
 203 </tbody>
 204 </table></div>
 205 </li>
 206 <li class="listitem">
 207 <pre class="literallayout"><a name="idp110867712-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 208 <div class="variablelist"><table border="0" class="variablelist compact">
 209 <colgroup>
 210 <col align="left" valign="top">
 211 <col>
 212 </colgroup>
 213 <tbody>
 214 <tr>
 215 <td><p><span class="term">Postconditions:</span></p></td>
 216 <td>Contains a copy of the <code class="computeroutput">f</code>'s target, if it has one, or is empty if <code class="computeroutput">f.<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>.</td>
 217 </tr>
 218 <tr>
 219 <td><p><span class="term">Throws:</span></p></td>
 220 <td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td>
 221 </tr>
 222 </tbody>
 223 </table></div>
 224 </li>
 225 <li class="listitem">
 226 <pre class="literallayout"><a name="idp42720176-bb"></a><span class="identifier">function</span><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 227 <div class="variablelist"><table border="0" class="variablelist compact">
 228 <colgroup>
 229 <col align="left" valign="top">
 230 <col>
 231 </colgroup>
 232 <tbody>
 233 <tr>
 234 <td><p><span class="term">Requires:</span></p></td>
 235 <td>C++11 compatible compiler.</td>
 236 </tr>
 237 <tr>
 238 <td><p><span class="term">Postconditions:</span></p></td>
 239 <td>Moves the value from <code class="computeroutput">f</code> to <code class="computeroutput">*this</code>. If the argument has its function object allocated on the heap, its buffer will be assigned to <code class="computeroutput">*this</code> leaving argument empty.</td>
 240 </tr>
 241 <tr>
 242 <td><p><span class="term">Throws:</span></p></td>
 243 <td>Will not throw unless argument has its function object allocated not on the heap and copying the target of <code class="computeroutput">f</code> throws.</td>
 244 </tr>
 245 </tbody>
 246 </table></div>
 247 </li>
 248 <li class="listitem">
 249 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> F<span class="special">&gt;</span> <a name="idp40296688-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="identifier">F</span> f<span class="special">)</span><span class="special">;</span></pre>
 250 <div class="variablelist"><table border="0" class="variablelist compact">
 251 <colgroup>
 252 <col align="left" valign="top">
 253 <col>
 254 </colgroup>
 255 <tbody>
 256 <tr>
 257 <td><p><span class="term">Requires:</span></p></td>
 258 <td>F is a function object Callable from <code class="computeroutput">this</code>.</td>
 259 </tr>
 260 <tr>
 261 <td><p><span class="term">Postconditions:</span></p></td>
 262 <td>
 263 <code class="computeroutput">*this</code> targets a copy of <code class="computeroutput">f</code> if <code class="computeroutput">f</code> is nonempty, or <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code> if <code class="computeroutput">f</code> is empty.</td>
 264 </tr>
 265 </tbody>
 266 </table></div>
 267 </li>
 268 <li class="listitem">
 269 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> F<span class="special">,</span> <span class="keyword">typename</span> Allocator<span class="special">&gt;</span> <a name="idp40994480-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="identifier">F</span> f<span class="special">,</span> <span class="identifier">Allocator</span> alloc<span class="special">)</span><span class="special">;</span></pre>
 270 <div class="variablelist"><table border="0" class="variablelist compact">
 271 <colgroup>
 272 <col align="left" valign="top">
 273 <col>
 274 </colgroup>
 275 <tbody>
 276 <tr>
 277 <td><p><span class="term">Requires:</span></p></td>
 278 <td>F is a function object Callable from <code class="computeroutput">this</code>, Allocator is an allocator. The copy constructor and destructor of Allocator shall not throw.</td>
 279 </tr>
 280 <tr>
 281 <td><p><span class="term">Postconditions:</span></p></td>
 282 <td>
 283 <code class="computeroutput">*this</code> targets a copy of <code class="computeroutput">f</code> if <code class="computeroutput">f</code> is nonempty, or <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code> if <code class="computeroutput">f</code> is empty.</td>
 284 </tr>
 285 <tr>
 286 <td><p><span class="term">Effects:</span></p></td>
 287 <td>If memory allocation is required, the given allocator (or a copy of it) will be used to allocate that memory.</td>
 288 </tr>
 289 </tbody>
 290 </table></div>
 291 </li>
 292 <li class="listitem">
 293 <pre class="literallayout">function&amp; <a name="idp69909120-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 294 <div class="variablelist"><table border="0" class="variablelist compact">
 295 <colgroup>
 296 <col align="left" valign="top">
 297 <col>
 298 </colgroup>
 299 <tbody><tr>
 300 <td><p><span class="term">Postconditions:</span></p></td>
 301 <td>If copy construction does not throw, <code class="computeroutput">*this</code> targets a copy of <code class="computeroutput">f</code>'s target, if it has one, or is empty if <code class="computeroutput">f.<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>. If copy construction does throw, <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>.</td>
 302 </tr></tbody>
 303 </table></div>
 304 </li>
 305 <li class="listitem">
 306 <pre class="literallayout">function&amp; <a name="idp37708288-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><a class="link" href="functionN.html" title="Class template functionN">functionN</a><span class="special">&amp;&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 307 <div class="variablelist"><table border="0" class="variablelist compact">
 308 <colgroup>
 309 <col align="left" valign="top">
 310 <col>
 311 </colgroup>
 312 <tbody>
 313 <tr>
 314 <td><p><span class="term">Requires:</span></p></td>
 315 <td>C++11 compatible compiler.</td>
 316 </tr>
 317 <tr>
 318 <td><p><span class="term">Postconditions:</span></p></td>
 319 <td>Moves the value from <code class="computeroutput">f</code> to <code class="computeroutput">*this</code>. If the argument has its function object allocated on the heap, its buffer will be assigned to <code class="computeroutput">*this</code> leaving argument empty.</td>
 320 </tr>
 321 <tr>
 322 <td><p><span class="term">Throws:</span></p></td>
 323 <td>Will not throw unless argument has its function object allocated not on the heap and copying the target of <code class="computeroutput">f</code> throws.</td>
 324 </tr>
 325 </tbody>
 326 </table></div>
 327 </li>
 328 <li class="listitem">
 329 <pre class="literallayout">function&amp; <a name="idp38571792-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 330 <div class="variablelist"><table border="0" class="variablelist compact">
 331 <colgroup>
 332 <col align="left" valign="top">
 333 <col>
 334 </colgroup>
 335 <tbody>
 336 <tr>
 337 <td><p><span class="term">Postconditions:</span></p></td>
 338 <td>If copy construction of the target of <code class="computeroutput">f</code> does not throw, <code class="computeroutput">*this</code> targets a copy of <code class="computeroutput">f</code>'s target, if it has one, or is empty if <code class="computeroutput">f.<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>. </td>
 339 </tr>
 340 <tr>
 341 <td><p><span class="term">Throws:</span></p></td>
 342 <td>Will not throw when the target of <code class="computeroutput">f</code> is a stateless function object or a reference to the function object. If copy construction does throw, <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>.</td>
 343 </tr>
 344 </tbody>
 345 </table></div>
 346 </li>
 347 <li class="listitem">
 348 <pre class="literallayout">function&amp; <a name="idp105085072-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 349 <div class="variablelist"><table border="0" class="variablelist compact">
 350 <colgroup>
 351 <col align="left" valign="top">
 352 <col>
 353 </colgroup>
 354 <tbody>
 355 <tr>
 356 <td><p><span class="term">Requires:</span></p></td>
 357 <td>C++11 compatible compiler.</td>
 358 </tr>
 359 <tr>
 360 <td><p><span class="term">Postconditions:</span></p></td>
 361 <td>Moves the value from <code class="computeroutput">f</code> to <code class="computeroutput">*this</code>. If the argument has its function object allocated on the heap, its buffer will be assigned to <code class="computeroutput">*this</code> leaving argument empty.</td>
 362 </tr>
 363 <tr>
 364 <td><p><span class="term">Throws:</span></p></td>
 365 <td>Will not throw unless argument has its function object allocated not on the heap and copying the target of <code class="computeroutput">f</code> throws.</td>
 366 </tr>
 367 </tbody>
 368 </table></div>
 369 </li>
 370 <li class="listitem">
 371 <pre class="literallayout"><a name="idp45860512-bb"></a><span class="special">~</span><span class="identifier">function</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>
 372 <div class="variablelist"><table border="0" class="variablelist compact">
 373 <colgroup>
 374 <col align="left" valign="top">
 375 <col>
 376 </colgroup>
 377 <tbody><tr>
 378 <td><p><span class="term">Effects:</span></p></td>
 379 <td>If <code class="computeroutput">!this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>, destroys the target of <code class="computeroutput">this</code>.</td>
 380 </tr></tbody>
 381 </table></div>
 382 </li>
 383 </ol></div>
 384 </div>
 385 <div class="refsect2">
 386 <a name="idp210159696"></a><h3>
 387 <a name="idp108302096-bb"></a><code class="computeroutput">function</code> modifiers</h3>
 388 <div class="orderedlist"><ol class="orderedlist" type="1">
 389 <li class="listitem">
 390 <pre class="literallayout"><span class="keyword">void</span> <a name="idp108302656-bb"></a><span class="identifier">swap</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span></pre>
 391 <div class="variablelist"><table border="0" class="variablelist compact">
 392 <colgroup>
 393 <col align="left" valign="top">
 394 <col>
 395 </colgroup>
 396 <tbody><tr>
 397 <td><p><span class="term">Effects:</span></p></td>
 398 <td>Interchanges the targets of <code class="computeroutput">*this</code> and <code class="computeroutput">f</code>.</td>
 399 </tr></tbody>
 400 </table></div>
 401 </li>
 402 <li class="listitem">
 403 <pre class="literallayout"><span class="keyword">void</span> <a name="idp72870112-bb"></a><span class="identifier">clear</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>
 404 <div class="variablelist"><table border="0" class="variablelist compact">
 405 <colgroup>
 406 <col align="left" valign="top">
 407 <col>
 408 </colgroup>
 409 <tbody>
 410 <tr>
 411 <td><p><span class="term">Postconditions:</span></p></td>
 412 <td><code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code></td>
 413 </tr>
 414 <tr>
 415 <td><p><span class="term">Throws:</span></p></td>
 416 <td>Will not throw.</td>
 417 </tr>
 418 </tbody>
 419 </table></div>
 420 </li>
 421 </ol></div>
 422 </div>
 423 <div class="refsect2">
 424 <a name="idp210178832"></a><h3>
 425 <a name="idp99731696-bb"></a><code class="computeroutput">function</code> capacity</h3>
 426 <div class="orderedlist"><ol class="orderedlist" type="1">
 427 <li class="listitem">
 428 <pre class="literallayout"><span class="keyword">bool</span> <a name="idp39557232-bb"></a><span class="identifier">empty</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 429 <div class="variablelist"><table border="0" class="variablelist compact">
 430 <colgroup>
 431 <col align="left" valign="top">
 432 <col>
 433 </colgroup>
 434 <tbody>
 435 <tr>
 436 <td><p><span class="term">Returns:</span></p></td>
 437 <td>
 438 <code class="computeroutput">false</code> if <code class="computeroutput">this</code> has a target, and <code class="computeroutput">true</code> otherwise.</td>
 439 </tr>
 440 <tr>
 441 <td><p><span class="term">Throws:</span></p></td>
 442 <td>Will not throw.</td>
 443 </tr>
 444 </tbody>
 445 </table></div>
 446 </li>
 447 <li class="listitem">
 448 <pre class="literallayout"><a name="idp41154480-bb"></a><span class="keyword">operator</span> <span class="identifier">safe_bool</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 449 <div class="variablelist"><table border="0" class="variablelist compact">
 450 <colgroup>
 451 <col align="left" valign="top">
 452 <col>
 453 </colgroup>
 454 <tbody>
 455 <tr>
 456 <td><p><span class="term">Returns:</span></p></td>
 457 <td>A <code class="computeroutput">safe_bool</code> that evaluates <code class="computeroutput">false</code> in a boolean context when <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>, and <code class="computeroutput">true</code> otherwise.</td>
 458 </tr>
 459 <tr>
 460 <td><p><span class="term">Throws:</span></p></td>
 461 <td>Will not throw.</td>
 462 </tr>
 463 </tbody>
 464 </table></div>
 465 </li>
 466 <li class="listitem">
 467 <pre class="literallayout"><span class="keyword">bool</span> <a name="idp76193136-bb"></a><span class="keyword">operator</span><span class="special">!</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 468 <div class="variablelist"><table border="0" class="variablelist compact">
 469 <colgroup>
 470 <col align="left" valign="top">
 471 <col>
 472 </colgroup>
 473 <tbody>
 474 <tr>
 475 <td><p><span class="term">Returns:</span></p></td>
 476 <td><code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code></td>
 477 </tr>
 478 <tr>
 479 <td><p><span class="term">Throws:</span></p></td>
 480 <td>Will not throw.</td>
 481 </tr>
 482 </tbody>
 483 </table></div>
 484 </li>
 485 </ol></div>
 486 </div>
 487 <div class="refsect2">
 488 <a name="idp210210176"></a><h3>
 489 <a name="idp69032368-bb"></a><code class="computeroutput">function</code> target access</h3>
 490 <div class="orderedlist"><ol class="orderedlist" type="1">
 491 <li class="listitem">
 492 <pre class="literallayout"><a name="idp113597248-bb"></a><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="identifier">Functor</span><span class="special">*</span> <a name="idp113597808-bb"></a><span class="identifier">target</span><span class="special">(</span><span class="special">)</span><span class="special">;</span>
 493 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">*</span> <a name="idp37917680-bb"></a><span class="identifier">target</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 494 <div class="variablelist"><table border="0" class="variablelist compact">
 495 <colgroup>
 496 <col align="left" valign="top">
 497 <col>
 498 </colgroup>
 499 <tbody>
 500 <tr>
 501 <td><p><span class="term">Returns:</span></p></td>
 502 <td>If <code class="computeroutput">this</code> stores a target of type
 503         <code class="computeroutput">Functor</code>, returns the address of the
 504         target. Otherwise, returns the NULL
 505         pointer.</td>
 506 </tr>
 507 <tr>
 508 <td><p><span class="term">Throws:</span></p></td>
 509 <td>Will not throw.</td>
 510 </tr>
 511 </tbody>
 512 </table></div>
 513 </li>
 514 <li class="listitem">
 515 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Functor<span class="special">&gt;</span> <span class="keyword">bool</span> <a name="idp44257488-bb"></a><span class="identifier">contains</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">&amp;</span> f<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 516 <div class="variablelist"><table border="0" class="variablelist compact">
 517 <colgroup>
 518 <col align="left" valign="top">
 519 <col>
 520 </colgroup>
 521 <tbody><tr>
 522 <td><p><span class="term">Returns:</span></p></td>
 523 <td>
 524 <code class="computeroutput">true</code> if <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp113597248-bb">target</a>&lt;Functor&gt;()</code> is non-NULL and <code class="computeroutput"><a class="link" href="function_equal.html" title="Function template function_equal">function_equal</a>(*(this-&gt;target&lt;Functor&gt;()), f)</code>
 525 </td>
 526 </tr></tbody>
 527 </table></div>
 528 </li>
 529 <li class="listitem">
 530 <pre class="literallayout"><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span><span class="special">&amp;</span> <a name="idp46276608-bb"></a><span class="identifier">target_type</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 531 <div class="variablelist"><table border="0" class="variablelist compact">
 532 <colgroup>
 533 <col align="left" valign="top">
 534 <col>
 535 </colgroup>
 536 <tbody>
 537 <tr>
 538 <td><p><span class="term">Returns:</span></p></td>
 539 <td>
 540 <code class="computeroutput">typeid</code> of the target function object, or <code class="computeroutput">typeid(void)</code> if <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>.</td>
 541 </tr>
 542 <tr>
 543 <td><p><span class="term">Throws:</span></p></td>
 544 <td>Will not throw.</td>
 545 </tr>
 546 </tbody>
 547 </table></div>
 548 </li>
 549 </ol></div>
 550 </div>
 551 <div class="refsect2">
 552 <a name="idp210258608"></a><h3>
 553 <a name="idp55139648-bb"></a><code class="computeroutput">function</code> invocation</h3>
 554 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
 555 <pre class="literallayout"><span class="identifier">result_type</span> <a name="idp55140176-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">arg1_type</span> a1<span class="special">,</span> <span class="identifier">arg2_type</span> a2<span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="identifier">argN_type</span> aN<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 556 <div class="variablelist"><table border="0" class="variablelist compact">
 557 <colgroup>
 558 <col align="left" valign="top">
 559 <col>
 560 </colgroup>
 561 <tbody>
 562 <tr>
 563 <td><p><span class="term">Effects:</span></p></td>
 564 <td>
 565 <code class="computeroutput">f(a1, a2, ..., aN)</code>, where <code class="computeroutput">f</code> is the target of <code class="computeroutput">*this</code>.</td>
 566 </tr>
 567 <tr>
 568 <td><p><span class="term">Returns:</span></p></td>
 569 <td>if <code class="computeroutput">R</code> is <code class="computeroutput">void</code>, nothing is returned; otherwise, the return value of the call to <code class="computeroutput">f</code> is returned.</td>
 570 </tr>
 571 <tr>
 572 <td><p><span class="term">Throws:</span></p></td>
 573 <td>
 574 <code class="computeroutput"><a class="link" href="bad_function_call.html" title="Class bad_function_call">bad_function_call</a></code> if <code class="computeroutput">this-&gt;<a class="link" href="function.html#idp39557232-bb">empty</a>()</code>. Otherwise, may through any exception thrown by the target function <code class="computeroutput">f</code>.</td>
 575 </tr>
 576 </tbody>
 577 </table></div>
 578 </li></ol></div>
 579 </div>
 580 <div class="refsect2">
 581 <a name="idp210297584"></a><h3>
 582 <a name="idp111166064-bb"></a><code class="computeroutput">function</code> specialized algorithms</h3>
 583 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
 584 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">&gt;</span>
 585   <span class="keyword">void</span> <a name="boost.function.swap_idp76190448"></a><span class="identifier">swap</span><span class="special">(</span><a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f1<span class="special">,</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f2<span class="special">)</span><span class="special">;</span></pre>
 586 <div class="variablelist"><table border="0" class="variablelist compact">
 587 <colgroup>
 588 <col align="left" valign="top">
 589 <col>
 590 </colgroup>
 591 <tbody><tr>
 592 <td><p><span class="term">Effects:</span></p></td>
 593 <td><code class="computeroutput">f1.<a class="link" href="function.html#idp108302656-bb">swap</a>(f2)</code></td>
 594 </tr></tbody>
 595 </table></div>
 596 </li></ol></div>
 597 </div>
 598 <div class="refsect2">
 599 <a name="idp210316016"></a><h3>
 600 <a name="idp48579440-bb"></a><code class="computeroutput">function</code> comparison operators</h3>
 601 <div class="orderedlist"><ol class="orderedlist" type="1">
 602 <li class="listitem">
 603 <p><a name="boost.function.operator==_idp113382992"></a></p>
 604 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 605   <span class="keyword">bool</span> <a name="idp113383552-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">,</span> <span class="identifier">Functor</span> g<span class="special">)</span><span class="special">;</span>
 606 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 607   <span class="keyword">bool</span> <a name="idp95785712-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><span class="identifier">Functor</span> g<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span>
 608 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 609   <span class="keyword">bool</span> <a name="idp37641488-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">,</span> reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span> g<span class="special">)</span><span class="special">;</span>
 610 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 611   <span class="keyword">bool</span> <a name="idp105237024-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span>reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span> g<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span>
 612 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">&gt;</span>
 613   <span class="keyword">void</span> <a name="idp69032896-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature1</span><span class="special">&gt;</span><span class="special">&amp;</span> f1<span class="special">,</span>
 614                   <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature2</span><span class="special">&gt;</span><span class="special">&amp;</span> f2<span class="special">)</span><span class="special">;</span></pre>
 615 <div class="variablelist"><table border="0" class="variablelist compact">
 616 <colgroup>
 617 <col align="left" valign="top">
 618 <col>
 619 </colgroup>
 620 <tbody>
 621 <tr>
 622 <td><p><span class="term">Returns:</span></p></td>
 623 <td>True when <code class="computeroutput">f</code> stores an object of
 624         type <code class="computeroutput">Functor</code> and one of the following conditions applies:
 625           <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 626 <li class="listitem">
 627 <code class="computeroutput">g</code> is of type
 628             <code class="computeroutput">reference_wrapper&lt;Functor&gt;</code>
 629             and <code class="computeroutput">f.target&lt;Functor&gt;() == g.get_pointer()</code>.</li>
 630 <li class="listitem">
 631 <code class="computeroutput">g</code> is not of type
 632             <code class="computeroutput">reference_wrapper&lt;Functor&gt;</code>
 633             and <code class="computeroutput">function_equals(*(f.target&lt;Functor&gt;()), g)</code>.</li>
 634 </ul></div>
 635           </td>
 636 </tr>
 637 <tr>
 638 <td><p><span class="term">Notes:</span></p></td>
 639 <td>
 640 <code class="computeroutput"><a class="link" href="function.html" title="Class template function">function</a></code>
 641         objects are not
 642         EqualityComparable.</td>
 643 </tr>
 644 <tr>
 645 <td><p><span class="term">Rationale:</span></p></td>
 646 <td>The <code class="computeroutput">safe_bool</code> conversion
 647         opens a loophole whereby two <code class="computeroutput">function</code>
 648         instances can be compared via <code class="computeroutput">==</code>, although this
 649         is not feasible to implement. The undefined <code class="computeroutput">void
 650         operator==</code> closes the loophole and ensures a
 651         compile-time or link-time error.</td>
 652 </tr>
 653 </tbody>
 654 </table></div>
 655 </li>
 656 <li class="listitem">
 657 <p><a name="boost.function.operator!=_idp47556112"></a></p>
 658 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 659   <span class="keyword">bool</span> <a name="idp47556672-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">,</span> <span class="identifier">Functor</span> g<span class="special">)</span><span class="special">;</span>
 660 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 661   <span class="keyword">bool</span> <a name="idp101036032-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><span class="identifier">Functor</span> g<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span>
 662 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 663   <span class="keyword">bool</span> <a name="idp54996816-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">,</span> reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span> g<span class="special">)</span><span class="special">;</span>
 664 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">&gt;</span>
 665   <span class="keyword">bool</span> <a name="idp110874944-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span>reference_wrapper<span class="special">&lt;</span><span class="identifier">Functor</span><span class="special">&gt;</span> g<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature</span><span class="special">&gt;</span><span class="special">&amp;</span> f<span class="special">)</span><span class="special">;</span>
 666 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">&gt;</span>
 667   <span class="keyword">void</span> <a name="idp99861584-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature1</span><span class="special">&gt;</span><span class="special">&amp;</span> f1<span class="special">,</span>
 668                   <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special">&lt;</span><span class="identifier">Signature2</span><span class="special">&gt;</span><span class="special">&amp;</span> f2<span class="special">)</span><span class="special">;</span></pre>
 669 <div class="variablelist"><table border="0" class="variablelist compact">
 670 <colgroup>
 671 <col align="left" valign="top">
 672 <col>
 673 </colgroup>
 674 <tbody>
 675 <tr>
 676 <td><p><span class="term">Returns:</span></p></td>
 677 <td>True when <code class="computeroutput">f</code> does not store an
 678         object of type <code class="computeroutput">Functor</code> or it stores an object of
 679         type <code class="computeroutput">Functor</code> and one of the following conditions
 680         applies:
 681           <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 682 <li class="listitem">
 683 <code class="computeroutput">g</code> is of type
 684             <code class="computeroutput">reference_wrapper&lt;Functor&gt;</code>
 685             and <code class="computeroutput">f.target&lt;Functor&gt;() != g.get_pointer()</code>.</li>
 686 <li class="listitem">
 687 <code class="computeroutput">g</code> is not of type
 688             <code class="computeroutput">reference_wrapper&lt;Functor&gt;</code>
 689             and <code class="computeroutput">!function_equals(*(f.target&lt;Functor&gt;()), g)</code>.</li>
 690 </ul></div>
 691           </td>
 692 </tr>
 693 <tr>
 694 <td><p><span class="term">Notes:</span></p></td>
 695 <td>
 696 <code class="computeroutput"><a class="link" href="function.html" title="Class template function">function</a></code>
 697         objects are not
 698         EqualityComparable.</td>
 699 </tr>
 700 <tr>
 701 <td><p><span class="term">Rationale:</span></p></td>
 702 <td>The <code class="computeroutput">safe_bool</code> conversion
 703         opens a loophole whereby two <code class="computeroutput">function</code>
 704         instances can be compared via <code class="computeroutput">!=</code>, although this
 705         is not feasible to implement. The undefined <code class="computeroutput">void
 706         operator!=</code> closes the loophole and ensures a
 707         compile-time or link-time error.</td>
 708 </tr>
 709 </tbody>
 710 </table></div>
 711 </li>
 712 </ol></div>
 713 </div>
 714 </div>
 715 </div>
 716 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 717 <td align="left"></td>
 718 <td align="right"><div class="copyright-footer">Copyright &#169; 2001-2004 Douglas Gregor<p>Use, modification and distribution is subject to the Boost
 719     Software License, Version 1.0. (See accompanying file
 720     <code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</p>
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