<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Class template function</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../function/reference.html#header.boost.function_hpp" title="Header <boost/function.hpp>"> <link rel="prev" href="functionN/sig.html" title="Struct template sig"> <link rel="next" href="function/sig.html" title="Struct template sig"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> <td align="center"><a href="../../../index.html">Home</a></td> <td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="functionN/sig.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../function/reference.html#header.boost.function_hpp"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="function/sig.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="refentry"> <a name="boost.function"></a><div class="titlepage"></div> <div class="refnamediv"> <h2><span class="refentrytitle">Class template function</span></h2> <p>boost::function — A generalized function pointer that can be used for callbacks or wrapping function objects.</p> </div> <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../function/reference.html#header.boost.function_hpp" title="Header <boost/function.hpp>">boost/function.hpp</a>> </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="comment"> // Function type R (T1, T2, ..., TN)</span> <span class="special">></span> <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"><</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">></span> <span class="special">{</span> <span class="keyword">public</span><span class="special">:</span> <span class="comment">// types</span> <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> <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> <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> <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> <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> <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> . . . <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> <span class="comment">// static constants</span> <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> <span class="comment">// member classes/structs/unions</span> <span class="comment">// <a class="link" href="../lambda.html" title="Chapter 11. Boost.Lambda">Lambda</a> library support</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Args<span class="special">></span> <span class="keyword">struct</span> <a class="link" href="function/sig.html" title="Struct template sig">sig</a> <span class="special">{</span> <span class="comment">// types</span> <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> <span class="special">}</span><span class="special">;</span> <span class="comment">// <a class="link" href="function.html#boost.functionconstruct-copy-destruct">construct/copy/destruct</a></span> <a class="link" href="function.html#id441120-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <a class="link" href="function.html#id428304-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">&</span><span class="special">)</span><span class="special">;</span> <a class="link" href="function.html#id369401-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">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> F<span class="special">></span> <a class="link" href="function.html#id385735-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="identifier">F</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> F<span class="special">,</span> <span class="keyword">typename</span> Allocator<span class="special">></span> <a class="link" href="function.html#id394378-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> function& <a class="link" href="function.html#id409804-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">&</span><span class="special">)</span><span class="special">;</span> function& <a class="link" href="function.html#id405279-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">&</span><span class="special">)</span><span class="special">;</span> <a class="link" href="function.html#id406369-bb"><span class="special">~</span><span class="identifier">function</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="function.html#id355907-bb">modifiers</a></span> <span class="keyword">void</span> <a class="link" href="function.html#id467661-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">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">void</span> <a class="link" href="function.html#id340367-bb"><span class="identifier">clear</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="function.html#id326626-bb">capacity</a></span> <span class="keyword">bool</span> <a class="link" href="function.html#id588390-bb"><span class="identifier">empty</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <a class="link" href="function.html#id397968-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> <span class="keyword">bool</span> <a class="link" href="function.html#id590808-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> <span class="comment">// <a class="link" href="function.html#id393644-bb">target access</a></span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="identifier">Functor</span><span class="special">*</span> <a class="link" href="function.html#id369622-bb"><span class="identifier">target</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">*</span> <a class="link" href="function.html#id468508-bb"><span class="identifier">target</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id398784-bb"><span class="identifier">contains</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">&</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span><span class="special">&</span> <a class="link" href="function.html#id470209-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> <span class="comment">// <a class="link" href="function.html#id343431-bb">invocation</a></span> <span class="identifier">result_type</span> <a class="link" href="function.html#id343434-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> <span class="special">}</span><span class="special">;</span> <span class="comment">// <a class="link" href="function.html#id597680-bb">specialized algorithms</a></span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">></span> <span class="keyword">void</span> <a class="link" href="function.html#boost.function.swap_id597683"><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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">,</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="function.html#id361533-bb">comparison operators</a></span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id412300-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">,</span> <span class="identifier">Functor</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id383625-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id347188-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">,</span> <a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id399945-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">></span> <span class="keyword">void</span> <a class="link" href="function.html#id352446-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"><</span><span class="identifier">Signature1</span><span class="special">></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"><</span><span class="identifier">Signature2</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id324767-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">,</span> <span class="identifier">Functor</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id434579-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id441061-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">,</span> <a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a class="link" href="function.html#id323306-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">></span> <span class="keyword">void</span> <a class="link" href="function.html#id438683-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"><</span><span class="identifier">Signature1</span><span class="special">></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"><</span><span class="identifier">Signature2</span><span class="special">></span><span class="special">&</span><span class="special">)</span><span class="special">;</span></pre></div> <div class="refsect1"> <a name="id1280502"></a><h2>Description</h2> <p>Class template <a class="link" href="function.html" title="Class template function">function</a> is a thin 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 function type with N arguments and will will derive from <a class="link" href="functionN.html" title="Class template functionN">functionN</a> instantiated with the arguments it receives.</p> <p>The semantics of all operations in class template <a class="link" href="function.html" title="Class template function">function</a> are equivalent to that of the underlying <a class="link" href="functionN.html" title="Class template functionN">functionN</a> object, although additional member functions are required to allow proper copy construction and copy assignment of function objects.</p> <div class="refsect2"> <a name="id1280562"></a><h3> <a name="boost.functionconstruct-copy-destruct"></a><code class="computeroutput">function</code> public construct/copy/destruct</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><a name="id441120-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Postconditions:</span></p></td> <td><code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code></td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="id428304-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">&</span> f<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Postconditions:</span></p></td> <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#id588390-bb">empty</a>()</code>.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="id369401-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">&</span> f<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Postconditions:</span></p></td> <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#id588390-bb">empty</a>()</code>.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw unless copying the target of <code class="computeroutput">f</code> throws.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> F<span class="special">></span> <a name="id385735-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <td>F is a function object Callable from <code class="computeroutput">this</code>.</td> </tr> <tr> <td><p><span class="term">Postconditions:</span></p></td> <td> <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-><a class="link" href="function.html#id588390-bb">empty</a>()</code> if <code class="computeroutput">f</code> is empty.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> F<span class="special">,</span> <span class="keyword">typename</span> Allocator<span class="special">></span> <a name="id394378-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <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> </tr> <tr> <td><p><span class="term">Postconditions:</span></p></td> <td> <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-><a class="link" href="function.html#id588390-bb">empty</a>()</code> if <code class="computeroutput">f</code> is empty.</td> </tr> <tr> <td><p><span class="term">Effects:</span></p></td> <td>If memory allocation is required, the given allocator (or a copy of it) will be used to allocate that memory.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout">function& <a name="id409804-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">&</span> f<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term">Postconditions:</span></p></td> <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#id588390-bb">empty</a>()</code>. If copy construction does throw, <code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code>.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout">function& <a name="id405279-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">&</span> f<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Postconditions:</span></p></td> <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#id588390-bb">empty</a>()</code>. </td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <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-><a class="link" href="function.html#id588390-bb">empty</a>()</code>.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="id406369-bb"></a><span class="special">~</span><span class="identifier">function</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term">Effects:</span></p></td> <td>If <code class="computeroutput">!this-><a class="link" href="function.html#id588390-bb">empty</a>()</code>, destroys the target of <code class="computeroutput">this</code>.</td> </tr></tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="id1281367"></a><h3> <a name="id355907-bb"></a><code class="computeroutput">function</code> modifiers</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><span class="keyword">void</span> <a name="id467661-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">&</span> f<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term">Effects:</span></p></td> <td>Interchanges the targets of <code class="computeroutput">*this</code> and <code class="computeroutput">f</code>.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="keyword">void</span> <a name="id340367-bb"></a><span class="identifier">clear</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Postconditions:</span></p></td> <td><code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code></td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="id1281524"></a><h3> <a name="id326626-bb"></a><code class="computeroutput">function</code> capacity</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><span class="keyword">bool</span> <a name="id588390-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td> <code class="computeroutput">false</code> if <code class="computeroutput">this</code> has a target, and <code class="computeroutput">true</code> otherwise.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="id397968-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td>A <code class="computeroutput">safe_bool</code> that evaluates <code class="computeroutput">false</code> in a boolean context when <code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code>, and <code class="computeroutput">true</code> otherwise.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="keyword">bool</span> <a name="id590808-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td><code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code></td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="id1281781"></a><h3> <a name="id393644-bb"></a><code class="computeroutput">function</code> target access</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><a name="id369619-bb"></a><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="identifier">Functor</span><span class="special">*</span> <a name="id369622-bb"></a><span class="identifier">target</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">*</span> <a name="id468508-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td>If <code class="computeroutput">this</code> stores a target of type <code class="computeroutput">Functor</code>, returns the address of the target. Otherwise, returns the NULL pointer.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id398784-bb"></a><span class="identifier">contains</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Functor</span><span class="special">&</span> f<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term">Returns:</span></p></td> <td> <code class="computeroutput">true</code> if <code class="computeroutput">this-><a class="link" href="function.html#id369619-bb">target</a><Functor>()</code> is non-NULL and <code class="computeroutput"><a class="link" href="function_equal.html" title="Function template function_equal">function_equal</a>(*(this->target<Functor>()), f)</code> </td> </tr></tbody> </table></div> </li> <li class="listitem"> <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">&</span> <a name="id470209-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td> <code class="computeroutput">typeid</code> of the target function object, or <code class="computeroutput">typeid(void)</code> if <code class="computeroutput">this-><a class="link" href="function.html#id588390-bb">empty</a>()</code>.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr> </tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="id1282179"></a><h3> <a name="id343431-bb"></a><code class="computeroutput">function</code> invocation</h3> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> <pre class="literallayout"><span class="identifier">result_type</span> <a name="id343434-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> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Effects:</span></p></td> <td> <code class="computeroutput">f(a1, a2, ..., aN)</code>, where <code class="computeroutput">f</code> is the target of <code class="computeroutput">*this</code>.</td> </tr> <tr> <td><p><span class="term">Returns:</span></p></td> <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> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td> <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-><a class="link" href="function.html#id588390-bb">empty</a>()</code>. Otherwise, may through any exception thrown by the target function <code class="computeroutput">f</code>.</td> </tr> </tbody> </table></div> </li></ol></div> </div> <div class="refsect2"> <a name="id1282504"></a><h3> <a name="id597680-bb"></a><code class="computeroutput">function</code> specialized algorithms</h3> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">></span> <span class="keyword">void</span> <a name="boost.function.swap_id597683"></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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f1<span class="special">,</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f2<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term">Effects:</span></p></td> <td><code class="computeroutput">f1.<a class="link" href="function.html#id467661-bb">swap</a>(f2)</code></td> </tr></tbody> </table></div> </li></ol></div> </div> <div class="refsect2"> <a name="id1282654"></a><h3> <a name="id361533-bb"></a><code class="computeroutput">function</code> comparison operators</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <p><a name="boost.function.operator==_id412297"></a></p> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id412300-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">,</span> <span class="identifier">Functor</span> g<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id383625-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id347188-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">,</span> <a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></span> g<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id399945-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">></span> <span class="keyword">void</span> <a name="id352446-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"><</span><span class="identifier">Signature1</span><span class="special">></span><span class="special">&</span> f1<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special"><</span><span class="identifier">Signature2</span><span class="special">></span><span class="special">&</span> f2<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td>True when <code class="computeroutput">f</code> stores an object of type <code class="computeroutput">Functor</code> and one of the following conditions applies: <div class="itemizedlist"><ul class="itemizedlist" type="disc"> <li class="listitem"> <code class="computeroutput">g</code> is of type <code class="computeroutput"><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><Functor></code> and <code class="computeroutput">f.target<Functor>() == g.<a class="link" href="reference_wrapper.html#id1139071-bb">get_pointer</a>()</code>.</li> <li class="listitem"> <code class="computeroutput">g</code> is not of type <code class="computeroutput"><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><Functor></code> and <code class="computeroutput">function_equals(*(f.target<Functor>()), g)</code>.</li> </ul></div> </td> </tr> <tr> <td><p><span class="term">Notes:</span></p></td> <td> <code class="computeroutput"><a class="link" href="function.html" title="Class template function">function</a></code> objects are not <a class="link" href="../EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</td> </tr> <tr> <td><p><span class="term">Rationale:</span></p></td> <td>The <code class="computeroutput">safe_bool</code> conversion opens a loophole whereby two <code class="computeroutput">function</code> instances can be compared via <code class="computeroutput">==</code>, although this is not feasible to implement. The undefined <code class="computeroutput">void operator==</code> closes the loophole and ensures a compile-time or link-time error.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <p><a name="boost.function.operator!=_id605881"></a></p> <pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id324767-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">,</span> <span class="identifier">Functor</span> g<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id434579-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id441061-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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">,</span> <a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></span> g<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature<span class="special">,</span> <span class="keyword">typename</span> Functor<span class="special">></span> <span class="keyword">bool</span> <a name="id323306-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span><span class="identifier">Functor</span><span class="special">></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"><</span><span class="identifier">Signature</span><span class="special">></span><span class="special">&</span> f<span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Signature1<span class="special">,</span> <span class="keyword">typename</span> Signature2<span class="special">></span> <span class="keyword">void</span> <a name="id438683-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"><</span><span class="identifier">Signature1</span><span class="special">></span><span class="special">&</span> f1<span class="special">,</span> <span class="keyword">const</span> <a class="link" href="function.html" title="Class template function">function</a><span class="special"><</span><span class="identifier">Signature2</span><span class="special">></span><span class="special">&</span> f2<span class="special">)</span><span class="special">;</span></pre> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term">Returns:</span></p></td> <td>True when <code class="computeroutput">f</code> does not store an object of type <code class="computeroutput">Functor</code> or it stores an object of type <code class="computeroutput">Functor</code> and one of the following conditions applies: <div class="itemizedlist"><ul class="itemizedlist" type="disc"> <li class="listitem"> <code class="computeroutput">g</code> is of type <code class="computeroutput"><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><Functor></code> and <code class="computeroutput">f.target<Functor>() != g.<a class="link" href="reference_wrapper.html#id1139071-bb">get_pointer</a>()</code>.</li> <li class="listitem"> <code class="computeroutput">g</code> is not of type <code class="computeroutput"><a class="link" href="reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><Functor></code> and <code class="computeroutput">!function_equals(*(f.target<Functor>()), g)</code>.</li> </ul></div> </td> </tr> <tr> <td><p><span class="term">Notes:</span></p></td> <td> <code class="computeroutput"><a class="link" href="function.html" title="Class template function">function</a></code> objects are not <a class="link" href="../EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</td> </tr> <tr> <td><p><span class="term">Rationale:</span></p></td> <td>The <code class="computeroutput">safe_bool</code> conversion opens a loophole whereby two <code class="computeroutput">function</code> instances can be compared via <code class="computeroutput">!=</code>, although this is not feasible to implement. The undefined <code class="computeroutput">void operator!=</code> closes the loophole and ensures a compile-time or link-time error.</td> </tr> </tbody> </table></div> </li> </ol></div> </div> </div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2001-2004 Douglas Gregor<p>Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file <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> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="functionN/sig.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../function/reference.html#header.boost.function_hpp"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="function/sig.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>