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25<div class="refentry" lang="en">
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="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="emphasis"><em>  // Function type R (T1, T2, ..., TN)</em></span>
34         <span class="bold"><strong>typename</strong></span> Allocator = std::allocator&lt;<span class="bold"><strong>void</strong></span>&gt; &gt; 
35<span class="bold"><strong>class</strong></span> function : <span class="bold"><strong>public</strong></span> <a href="functionN.html" title="Class template functionN">functionN</a>&lt;R, T1, T2, ..., TN, Allocator&gt; {
36<span class="bold"><strong>public</strong></span>:
37  <span class="emphasis"><em>// types</em></span>
38  <span class="bold"><strong>typedef</strong></span> R         result_type;         
39  <span class="bold"><strong>typedef</strong></span> Allocator allocator_type;      
40  <span class="bold"><strong>typedef</strong></span> T1        argument_type;         <span class="emphasis"><em>// If N == 1</em></span>
41  <span class="bold"><strong>typedef</strong></span> T1        first_argument_type;   <span class="emphasis"><em>// If N == 2</em></span>
42  <span class="bold"><strong>typedef</strong></span> T2        second_argument_type;  <span class="emphasis"><em>// If N == 2</em></span>
43  <span class="bold"><strong>typedef</strong></span> T1        arg1_type;           
44  <span class="bold"><strong>typedef</strong></span> T2        arg2_type;           
45     .
46     .
47     .
48  <span class="bold"><strong>typedef</strong></span> TN        argN_type;           
49
50  <span class="emphasis"><em>// static constants</em></span>
51  <span class="bold"><strong>static</strong></span> <span class="bold"><strong>const</strong></span> <span class="bold"><strong>int</strong></span> arity = N;
52
53  <span class="emphasis"><em>// <a href="../lambda.html" title="Chapter 8. Boost.Lambda">Lambda</a> library support</em></span>
54  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Args&gt; 
55  <span class="bold"><strong>struct</strong></span> sig {
56    <span class="emphasis"><em>// types</em></span>
57    <span class="bold"><strong>typedef</strong></span> result_type type;
58  };
59
60  <span class="emphasis"><em>// <a href="function.html#boost.functionconstruct-copy-destruct">construct/copy/destruct</a></em></span>
61  <a href="function.html#id626791-bb">function</a>();
62  <a href="function.html#id684614-bb">function</a>(<span class="bold"><strong>const</strong></span> <a href="functionN.html" title="Class template functionN">functionN</a>&amp;);
63  <a href="function.html#id788052-bb">function</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp;);
64  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> F&gt; <a href="function.html#id929357-bb">function</a>(F);
65  function&amp; <a href="function.html#id647080-bb"><span class="bold"><strong>operator</strong></span>=</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp;);
66  function&amp; <a href="function.html#id648333-bb"><span class="bold"><strong>operator</strong></span>=</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp;);
67  <a href="function.html#id870861-bb">~function</a>();
68
69  <span class="emphasis"><em>// <a href="function.html#id972428-bb">modifiers</a></em></span>
70  <span class="type"><span class="bold"><strong>void</strong></span></span> <a href="function.html#id972432-bb">swap</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp;);
71  <span class="type"><span class="bold"><strong>void</strong></span></span> <a href="function.html#id970240-bb">clear</a>();
72
73  <span class="emphasis"><em>// <a href="function.html#id835069-bb">capacity</a></em></span>
74  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id835072-bb">empty</a>() <span class="bold"><strong>const</strong></span>;
75  <a href="function.html#id967814-bb"><span class="bold"><strong>operator</strong></span> safe_bool</a>() <span class="bold"><strong>const</strong></span>;
76  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id753517-bb"><span class="bold"><strong>operator</strong></span>!</a>() <span class="bold"><strong>const</strong></span>;
77
78  <span class="emphasis"><em>// <a href="function.html#id697895-bb">target access</a></em></span>
79  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type">Functor*</span> <a href="function.html#id803790-bb">target</a>();
80  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type"><span class="bold"><strong>const</strong></span> Functor*</span> <a href="function.html#id697875-bb">target</a>() <span class="bold"><strong>const</strong></span>;
81  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id728918-bb">contains</a>(<span class="bold"><strong>const</strong></span> Functor&amp;) <span class="bold"><strong>const</strong></span>;
82  <span class="type"><span class="bold"><strong>const</strong></span> std::type_info&amp;</span> <a href="function.html#id927594-bb">target_type</a>() <span class="bold"><strong>const</strong></span>;
83
84  <span class="emphasis"><em>// <a href="function.html#id659523-bb">invocation</a></em></span>
85  <span class="type">result_type</span> <a href="function.html#id659526-bb"><span class="bold"><strong>operator</strong></span>()</a>(arg1_type, arg2_type, ..., argN_type) <span class="bold"><strong>const</strong></span>;
86};
87
88<span class="emphasis"><em>// <a href="function.html#id716667-bb">specialized algorithms</a></em></span>
89<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator&gt; 
90  <span class="type"><span class="bold"><strong>void</strong></span></span> <a href="function.html#id754994-bb">swap</a>(<a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;, <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;);
91
92<span class="emphasis"><em>// <a href="function.html#id758190-bb">comparison operators</a></em></span>
93<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
94  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id717925-bb"><span class="bold"><strong>operator</strong></span>==</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;, Functor);
95<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
96  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id786913-bb"><span class="bold"><strong>operator</strong></span>==</a>(Functor, <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;);
97<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
98  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id683534-bb"><span class="bold"><strong>operator</strong></span>==</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;,
99                  <a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;);
100<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
101  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id733745-bb"><span class="bold"><strong>operator</strong></span>==</a>(<a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;,
102                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;);
103<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature1, <span class="bold"><strong>typename</strong></span> Allocator1, <span class="bold"><strong>typename</strong></span> Signature2,
104         <span class="bold"><strong>typename</strong></span> Allocator2&gt; 
105  <span class="type"><span class="bold"><strong>void</strong></span></span> <a href="function.html#id768895-bb"><span class="bold"><strong>operator</strong></span>==</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature1, Allocator1&gt;&amp;,
106                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature2, Allocator2&gt;&amp;);
107<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
108  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id792627-bb"><span class="bold"><strong>operator</strong></span>!=</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;, Functor);
109<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
110  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id897105-bb"><span class="bold"><strong>operator</strong></span>!=</a>(Functor, <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;);
111<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
112  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id827204-bb"><span class="bold"><strong>operator</strong></span>!=</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;,
113                  <a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;);
114<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
115  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a href="function.html#id730783-bb"><span class="bold"><strong>operator</strong></span>!=</a>(<a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;,
116                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp;);
117<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature1, <span class="bold"><strong>typename</strong></span> Allocator1, <span class="bold"><strong>typename</strong></span> Signature2,
118         <span class="bold"><strong>typename</strong></span> Allocator2&gt; 
119  <span class="type"><span class="bold"><strong>void</strong></span></span> <a href="function.html#id732711-bb"><span class="bold"><strong>operator</strong></span>!=</a>(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature1, Allocator1&gt;&amp;,
120                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature2, Allocator2&gt;&amp;);</pre></div>
121<div class="refsect1" lang="en">
122<a name="id1212592"></a><h2>Description</h2>
123<p>Class template <a href="function.html" title="Class template function">function</a> is a thin
124      wrapper around the numbered class templates <a href="functionN.html" title="Class template functionN">function0</a>, <a href="functionN.html" title="Class template functionN">function1</a>, etc. It accepts a
125      function type with N arguments and will will derive from
126      <a href="functionN.html" title="Class template functionN">functionN</a> instantiated with the arguments
127      it receives.</p>
128<p>The semantics of all operations in class template
129      <a href="function.html" title="Class template function">function</a> are equivalent to that of the
130      underlying <a href="functionN.html" title="Class template functionN">functionN</a> object, although
131      additional member functions are required to allow proper copy
132      construction and copy assignment of function objects.</p>
133<div class="refsect2" lang="en">
134<a name="id1212651"></a><h3>
135<a name="boost.functionconstruct-copy-destruct"></a><code class="computeroutput">function</code> construct/copy/destruct</h3>
136<div class="orderedlist"><ol type="1">
137<li>
138<pre class="literallayout"><a name="id626791-bb"></a>function();</pre>
139<div class="variablelist"><table border="0">
140<col align="left" valign="top">
141<tbody>
142<tr>
143<td>
144<span class="term">Postconditions:</span></td>
145<td><code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code></td>
146</tr>
147<tr>
148<td>
149<span class="term">Throws:</span></td>
150<td>Will not throw.</td>
151</tr>
152</tbody>
153</table></div>
154</li>
155<li>
156<pre class="literallayout"><a name="id684614-bb"></a>function(<span class="bold"><strong>const</strong></span> <a href="functionN.html" title="Class template functionN">functionN</a>&amp; f);</pre>
157<div class="variablelist"><table border="0">
158<col align="left" valign="top">
159<tbody>
160<tr>
161<td>
162<span class="term">Postconditions:</span></td>
163<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 href="function.html#id835072-bb">empty</a>()</code>.</td>
164</tr>
165<tr>
166<td>
167<span class="term">Throws:</span></td>
168<td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td>
169</tr>
170</tbody>
171</table></div>
172</li>
173<li>
174<pre class="literallayout"><a name="id788052-bb"></a>function(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp; f);</pre>
175<div class="variablelist"><table border="0">
176<col align="left" valign="top">
177<tbody>
178<tr>
179<td>
180<span class="term">Postconditions:</span></td>
181<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 href="function.html#id835072-bb">empty</a>()</code>.</td>
182</tr>
183<tr>
184<td>
185<span class="term">Throws:</span></td>
186<td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td>
187</tr>
188</tbody>
189</table></div>
190</li>
191<li>
192<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> F&gt; <a name="id929357-bb"></a>function(F f);</pre>
193<div class="variablelist"><table border="0">
194<col align="left" valign="top">
195<tbody>
196<tr>
197<td>
198<span class="term">Requires:</span></td>
199<td>F is a function object Callable from <code class="computeroutput">this</code>.</td>
200</tr>
201<tr>
202<td>
203<span class="term">Postconditions:</span></td>
204<td>
205<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 href="function.html#id835072-bb">empty</a>()</code> if <code class="computeroutput">f</code> is empty.</td>
206</tr>
207</tbody>
208</table></div>
209</li>
210<li>
211<pre class="literallayout">function&amp; <a name="id647080-bb"></a><span class="bold"><strong>operator</strong></span>=(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp; f);</pre>
212<div class="variablelist"><table border="0">
213<col align="left" valign="top">
214<tbody><tr>
215<td>
216<span class="term">Postconditions:</span></td>
217<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 href="function.html#id835072-bb">empty</a>()</code>. If copy construction does throw, <code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code>.</td>
218</tr></tbody>
219</table></div>
220</li>
221<li>
222<pre class="literallayout">function&amp; <a name="id648333-bb"></a><span class="bold"><strong>operator</strong></span>=(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp; f);</pre>
223<div class="variablelist"><table border="0">
224<col align="left" valign="top">
225<tbody>
226<tr>
227<td>
228<span class="term">Postconditions:</span></td>
229<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 href="function.html#id835072-bb">empty</a>()</code>. </td>
230</tr>
231<tr>
232<td>
233<span class="term">Throws:</span></td>
234<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 href="function.html#id835072-bb">empty</a>()</code>.</td>
235</tr>
236</tbody>
237</table></div>
238</li>
239<li>
240<pre class="literallayout"><a name="id870861-bb"></a>~function();</pre>
241<div class="variablelist"><table border="0">
242<col align="left" valign="top">
243<tbody><tr>
244<td>
245<span class="term">Effects:</span></td>
246<td>If <code class="computeroutput">!this-&gt;<a href="function.html#id835072-bb">empty</a>()</code>, destroys the target of <code class="computeroutput">this</code>.</td>
247</tr></tbody>
248</table></div>
249</li>
250</ol></div>
251</div>
252<div class="refsect2" lang="en">
253<a name="id1213160"></a><h3>
254<a name="id972428-bb"></a><code class="computeroutput">function</code> modifiers</h3>
255<div class="orderedlist"><ol type="1">
256<li>
257<pre class="literallayout"><span class="type"><span class="bold"><strong>void</strong></span></span> <a name="id972432-bb"></a>swap(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&amp; f);</pre>
258<div class="variablelist"><table border="0">
259<col align="left" valign="top">
260<tbody><tr>
261<td>
262<span class="term">Effects:</span></td>
263<td>Interchanges the targets of <code class="computeroutput">*this</code> and <code class="computeroutput">f</code>.</td>
264</tr></tbody>
265</table></div>
266</li>
267<li>
268<pre class="literallayout"><span class="type"><span class="bold"><strong>void</strong></span></span> <a name="id970240-bb"></a>clear();</pre>
269<div class="variablelist"><table border="0">
270<col align="left" valign="top">
271<tbody>
272<tr>
273<td>
274<span class="term">Postconditions:</span></td>
275<td><code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code></td>
276</tr>
277<tr>
278<td>
279<span class="term">Throws:</span></td>
280<td>Will not throw.</td>
281</tr>
282</tbody>
283</table></div>
284</li>
285</ol></div>
286</div>
287<div class="refsect2" lang="en">
288<a name="id1213282"></a><h3>
289<a name="id835069-bb"></a><code class="computeroutput">function</code> capacity</h3>
290<div class="orderedlist"><ol type="1">
291<li>
292<pre class="literallayout"><span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id835072-bb"></a>empty() <span class="bold"><strong>const</strong></span>;</pre>
293<div class="variablelist"><table border="0">
294<col align="left" valign="top">
295<tbody>
296<tr>
297<td>
298<span class="term">Returns:</span></td>
299<td>
300<code class="computeroutput">false</code> if <code class="computeroutput">this</code> has a target, and <code class="computeroutput">true</code> otherwise.</td>
301</tr>
302<tr>
303<td>
304<span class="term">Throws:</span></td>
305<td>Will not throw.</td>
306</tr>
307</tbody>
308</table></div>
309</li>
310<li>
311<pre class="literallayout"><a name="id967814-bb"></a><span class="bold"><strong>operator</strong></span> safe_bool() <span class="bold"><strong>const</strong></span>;</pre>
312<div class="variablelist"><table border="0">
313<col align="left" valign="top">
314<tbody>
315<tr>
316<td>
317<span class="term">Returns:</span></td>
318<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 href="function.html#id835072-bb">empty</a>()</code>, and <code class="computeroutput">true</code> otherwise.</td>
319</tr>
320<tr>
321<td>
322<span class="term">Throws:</span></td>
323<td>Will not throw.</td>
324</tr>
325</tbody>
326</table></div>
327</li>
328<li>
329<pre class="literallayout"><span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id753517-bb"></a><span class="bold"><strong>operator</strong></span>!() <span class="bold"><strong>const</strong></span>;</pre>
330<div class="variablelist"><table border="0">
331<col align="left" valign="top">
332<tbody>
333<tr>
334<td>
335<span class="term">Returns:</span></td>
336<td><code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code></td>
337</tr>
338<tr>
339<td>
340<span class="term">Throws:</span></td>
341<td>Will not throw.</td>
342</tr>
343</tbody>
344</table></div>
345</li>
346</ol></div>
347</div>
348<div class="refsect2" lang="en">
349<a name="id1213492"></a><h3>
350<a name="id697895-bb"></a><code class="computeroutput">function</code> target access</h3>
351<div class="orderedlist"><ol type="1">
352<li>
353<p><a name="id697899-bb"></a></p>
354<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type">Functor*</span> <a name="id803790-bb"></a>target();
355<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type"><span class="bold"><strong>const</strong></span> Functor*</span> <a name="id697875-bb"></a>target() <span class="bold"><strong>const</strong></span>;</pre>
356<div class="variablelist"><table border="0">
357<col align="left" valign="top">
358<tbody>
359<tr>
360<td>
361<span class="term">Returns:</span></td>
362<td>If <code class="computeroutput">this</code> stores a target of type
363        <code class="computeroutput">Functor</code>, returns the address of the
364        target. Otherwise, returns the NULL
365        pointer.</td>
366</tr>
367<tr>
368<td>
369<span class="term">Throws:</span></td>
370<td>Will not throw.</td>
371</tr>
372</tbody>
373</table></div>
374</li>
375<li>
376<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Functor&gt; <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id728918-bb"></a>contains(<span class="bold"><strong>const</strong></span> Functor&amp; f) <span class="bold"><strong>const</strong></span>;</pre>
377<div class="variablelist"><table border="0">
378<col align="left" valign="top">
379<tbody><tr>
380<td>
381<span class="term">Returns:</span></td>
382<td>
383<code class="computeroutput">true</code> if <code class="computeroutput">this-&gt;<a href="function.html#id697899-bb">target</a>&lt;Functor&gt;()</code> is non-NULL and <code class="computeroutput"><a href="function_equal.html" title="Function template function_equal">function_equal</a>(*(this-&gt;target&lt;Functor&gt;()), f)</code>
384</td>
385</tr></tbody>
386</table></div>
387</li>
388<li>
389<pre class="literallayout"><span class="type"><span class="bold"><strong>const</strong></span> std::type_info&amp;</span> <a name="id927594-bb"></a>target_type() <span class="bold"><strong>const</strong></span>;</pre>
390<div class="variablelist"><table border="0">
391<col align="left" valign="top">
392<tbody>
393<tr>
394<td>
395<span class="term">Returns:</span></td>
396<td>
397<code class="computeroutput">typeid</code> of the target function object, or <code class="computeroutput">typeid(void)</code> if <code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code>.</td>
398</tr>
399<tr>
400<td>
401<span class="term">Throws:</span></td>
402<td>Will not throw.</td>
403</tr>
404</tbody>
405</table></div>
406</li>
407</ol></div>
408</div>
409<div class="refsect2" lang="en">
410<a name="id1213759"></a><h3>
411<a name="id659523-bb"></a><code class="computeroutput">function</code> invocation</h3>
412<div class="orderedlist"><ol type="1"><li>
413<pre class="literallayout"><span class="type">result_type</span> <a name="id659526-bb"></a><span class="bold"><strong>operator</strong></span>()(arg1_type a1, arg2_type a2, ..., argN_type aN) <span class="bold"><strong>const</strong></span>;</pre>
414<div class="variablelist"><table border="0">
415<col align="left" valign="top">
416<tbody>
417<tr>
418<td>
419<span class="term">Effects:</span></td>
420<td>
421<code class="computeroutput">f(a1, a2, ..., aN)</code>, where <code class="computeroutput">f</code> is the target of <code class="computeroutput">*this</code>.</td>
422</tr>
423<tr>
424<td>
425<span class="term">Returns:</span></td>
426<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>
427</tr>
428<tr>
429<td>
430<span class="term">Throws:</span></td>
431<td>
432<code class="computeroutput"><a href="bad_function_call.html" title="Class bad_function_call">bad_function_call</a></code> if <code class="computeroutput">this-&gt;<a href="function.html#id835072-bb">empty</a>()</code>. Otherwise, may through any exception thrown by the target function <code class="computeroutput">f</code>.</td>
433</tr>
434</tbody>
435</table></div>
436</li></ol></div>
437</div>
438<div class="refsect2" lang="en">
439<a name="id1213893"></a><h3>
440<a name="id716667-bb"></a><code class="computeroutput">function</code> specialized algorithms</h3>
441<div class="orderedlist"><ol type="1"><li>
442<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator&gt; 
443  <span class="type"><span class="bold"><strong>void</strong></span></span> <a name="id754994-bb"></a>swap(<a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f1,
444            <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f2);</pre>
445<div class="variablelist"><table border="0">
446<col align="left" valign="top">
447<tbody><tr>
448<td>
449<span class="term">Effects:</span></td>
450<td><code class="computeroutput">f1.<a href="function.html#id972432-bb">swap</a>(f2)</code></td>
451</tr></tbody>
452</table></div>
453</li></ol></div>
454</div>
455<div class="refsect2" lang="en">
456<a name="id1213988"></a><h3>
457<a name="id758190-bb"></a><code class="computeroutput">function</code> comparison operators</h3>
458<div class="orderedlist"><ol type="1">
459<li>
460<p><a name="id717922-bb"></a></p>
461<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
462  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id717925-bb"></a><span class="bold"><strong>operator</strong></span>==(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f, Functor g);
463<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
464  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id786913-bb"></a><span class="bold"><strong>operator</strong></span>==(Functor g, <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f);
465<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
466  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id683534-bb"></a><span class="bold"><strong>operator</strong></span>==(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f,
467                  <a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt; g);
468<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
469  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id733745-bb"></a><span class="bold"><strong>operator</strong></span>==(<a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt; g,
470                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f);
471<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature1, <span class="bold"><strong>typename</strong></span> Allocator1, <span class="bold"><strong>typename</strong></span> Signature2,
472         <span class="bold"><strong>typename</strong></span> Allocator2&gt; 
473  <span class="type"><span class="bold"><strong>void</strong></span></span> <a name="id768895-bb"></a><span class="bold"><strong>operator</strong></span>==(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature1, Allocator1&gt;&amp; f1,
474                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature2, Allocator2&gt;&amp; f2);</pre>
475<div class="variablelist"><table border="0">
476<col align="left" valign="top">
477<tbody>
478<tr>
479<td>
480<span class="term">Returns:</span></td>
481<td>True when <code class="computeroutput">f</code> stores an object of
482        type <code class="computeroutput">Functor</code> and one of the following conditions applies:
483          <div class="itemizedlist"><ul type="disc">
484<li>
485<code class="computeroutput">g</code> is of type
486            <code class="computeroutput"><a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;</code>
487            and <code class="computeroutput">f.target&lt;Functor&gt;() == g.<a href="reference_wrapper.html#id623846-bb">get_pointer</a>()</code>.</li>
488<li>
489<code class="computeroutput">g</code> is not of type
490            <code class="computeroutput"><a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;</code>
491            and <code class="computeroutput">function_equals(*(f.target&lt;Functor&gt;()), g)</code>.</li>
492</ul></div>
493          </td>
494</tr>
495<tr>
496<td>
497<span class="term">Notes:</span></td>
498<td>
499<code class="computeroutput"><a href="function.html" title="Class template function">function</a></code>
500        objects are not
501        <a href="../EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</td>
502</tr>
503<tr>
504<td>
505<span class="term">Rationale:</span></td>
506<td>The <code class="computeroutput">safe_bool</code> conversion
507        opens a loophole whereby two <code class="computeroutput">function</code>
508        instances can be compared via <code class="computeroutput">==</code>, although this
509        is not feasible to implement. The undefined <code class="computeroutput">void
510        operator==</code> closes the loophole and ensures a
511        compile-time or link-time error.</td>
512</tr>
513</tbody>
514</table></div>
515</li>
516<li>
517<p><a name="id792623-bb"></a></p>
518<pre class="literallayout"><span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
519  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id792627-bb"></a><span class="bold"><strong>operator</strong></span>!=(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f, Functor g);
520<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
521  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id897105-bb"></a><span class="bold"><strong>operator</strong></span>!=(Functor g, <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f);
522<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
523  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id827204-bb"></a><span class="bold"><strong>operator</strong></span>!=(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f,
524                  <a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt; g);
525<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature, <span class="bold"><strong>typename</strong></span> Allocator, <span class="bold"><strong>typename</strong></span> Functor&gt; 
526  <span class="type"><span class="bold"><strong>bool</strong></span></span> <a name="id730783-bb"></a><span class="bold"><strong>operator</strong></span>!=(<a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt; g,
527                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature, Allocator&gt;&amp; f);
528<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> Signature1, <span class="bold"><strong>typename</strong></span> Allocator1, <span class="bold"><strong>typename</strong></span> Signature2,
529         <span class="bold"><strong>typename</strong></span> Allocator2&gt; 
530  <span class="type"><span class="bold"><strong>void</strong></span></span> <a name="id732711-bb"></a><span class="bold"><strong>operator</strong></span>!=(<span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature1, Allocator1&gt;&amp; f1,
531                  <span class="bold"><strong>const</strong></span> <a href="function.html" title="Class template function">function</a>&lt;Signature2, Allocator2&gt;&amp; f2);</pre>
532<div class="variablelist"><table border="0">
533<col align="left" valign="top">
534<tbody>
535<tr>
536<td>
537<span class="term">Returns:</span></td>
538<td>True when <code class="computeroutput">f</code> does not store an
539        object of type <code class="computeroutput">Functor</code> or it stores an object of
540        type <code class="computeroutput">Functor</code> and one of the following conditions
541        applies:
542          <div class="itemizedlist"><ul type="disc">
543<li>
544<code class="computeroutput">g</code> is of type
545            <code class="computeroutput"><a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;</code>
546            and <code class="computeroutput">f.target&lt;Functor&gt;() != g.<a href="reference_wrapper.html#id623846-bb">get_pointer</a>()</code>.</li>
547<li>
548<code class="computeroutput">g</code> is not of type
549            <code class="computeroutput"><a href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a>&lt;Functor&gt;</code>
550            and <code class="computeroutput">!function_equals(*(f.target&lt;Functor&gt;()), g)</code>.</li>
551</ul></div>
552          </td>
553</tr>
554<tr>
555<td>
556<span class="term">Notes:</span></td>
557<td>
558<code class="computeroutput"><a href="function.html" title="Class template function">function</a></code>
559        objects are not
560        <a href="../EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</td>
561</tr>
562<tr>
563<td>
564<span class="term">Rationale:</span></td>
565<td>The <code class="computeroutput">safe_bool</code> conversion
566        opens a loophole whereby two <code class="computeroutput">function</code>
567        instances can be compared via <code class="computeroutput">!=</code>, although this
568        is not feasible to implement. The undefined <code class="computeroutput">void
569        operator!=</code> closes the loophole and ensures a
570        compile-time or link-time error.</td>
571</tr>
572</tbody>
573</table></div>
574</li>
575</ol></div>
576</div>
577</div>
578</div>
579<table width="100%"><tr>
580<td align="left"></td>
581<td align="right"><small>Copyright © 2001-2004 Douglas Gregor</small></td>
582</tr></table>
583<hr>
584<div class="spirit-nav">
585<a accesskey="p" href="functionN.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../function/reference.html#header.boost.function.hpp"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="function_equal.html"><img src="../images/next.png" alt="Next"></a>
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