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 <span id="projectnumber">2.10.0</span>
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<div class="title">Functors</div> </div>
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<p>Functors are copyable types that define operator()().
<a href="#details">More...</a></p>
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Modules</h2></td></tr>
<tr class="memitem:group__slot"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__slot.html">Slots</a></td></tr>
<tr class="memdesc:group__slot"><td class="mdescLeft"> </td><td class="mdescRight">Slots are type-safe representations of callback methods and functions. <br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:group__mem__fun"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__mem__fun.html">mem_fun()</a></td></tr>
<tr class="memdesc:group__mem__fun"><td class="mdescLeft"> </td><td class="mdescRight"><a class="el" href="group__mem__fun.html#gadf6b6d22c503b439019f0a2e77352419" title="Creates a functor of type sigc::mem_functor0 which wraps a method. ">mem_fun()</a> Creates a functor from a pointer to a method. <br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:group__ptr__fun"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="group__ptr__fun.html">ptr_fun()</a></td></tr>
<tr class="memdesc:group__ptr__fun"><td class="mdescLeft"> </td><td class="mdescRight"><a class="el" href="group__ptr__fun.html#ga9c80de72f656fb05e81fda622dddc863" title="Creates a functor of type sigc::pointer_functor0 which wraps an existing non-member function...">ptr_fun()</a> is used to convert a pointer to a function to a functor. <br /></td></tr>
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Classes</h2></td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classsigc_1_1can__deduce__result__type__with__decltype.html">sigc::can_deduce_result_type_with_decltype< T_functor ></a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Helper class, to determine if decltype() can deduce the result type of a functor. <a href="classsigc_1_1can__deduce__result__type__with__decltype.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structsigc_1_1functor__base.html">sigc::functor_base</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A hint to the compiler. <a href="structsigc_1_1functor__base.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structsigc_1_1functor__trait.html">sigc::functor_trait< T_functor, I_derives_functor_base, I_can_use_decltype ></a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Trait that specifies the return type of any type. <a href="structsigc_1_1functor__trait.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structsigc_1_1visitor.html">sigc::visitor< T_functor ></a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight"><a class="el" href="structsigc_1_1visitor.html#a9fe5d6be845e622a99a0db5d3621d4b3">sigc::visitor<T_functor>::do_visit_each()</a> performs a functor on each of the targets of a functor. <a href="structsigc_1_1visitor.html#details">More...</a><br /></td></tr>
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Macros</h2></td></tr>
<tr class="memitem:ga7a6f5575dc0b0ea896889c782721f6be"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__sigcfunctors.html#ga7a6f5575dc0b0ea896889c782721f6be">SIGC_FUNCTOR_TRAIT</a>(T_functor, T_return)</td></tr>
<tr class="memdesc:ga7a6f5575dc0b0ea896889c782721f6be"><td class="mdescLeft"> </td><td class="mdescRight">Helper macro, if you want to mix user-defined and third party functors with libsigc++. <a href="#ga7a6f5575dc0b0ea896889c782721f6be">More...</a><br /></td></tr>
<tr class="separator:ga7a6f5575dc0b0ea896889c782721f6be"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gadf1ba3cacb09cc5c3c3e399836ec6e50"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__sigcfunctors.html#gadf1ba3cacb09cc5c3c3e399836ec6e50">SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE</a></td></tr>
<tr class="memdesc:gadf1ba3cacb09cc5c3c3e399836ec6e50"><td class="mdescLeft"> </td><td class="mdescRight">Helper macro, if you want to mix user-defined and third party functors with libsigc++. <a href="#gadf1ba3cacb09cc5c3c3e399836ec6e50">More...</a><br /></td></tr>
<tr class="separator:gadf1ba3cacb09cc5c3c3e399836ec6e50"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga93b6ee8815d90adccfdceed72bcda577"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__sigcfunctors.html#ga93b6ee8815d90adccfdceed72bcda577">SIGC_FUNCTORS_HAVE_RESULT_TYPE</a></td></tr>
<tr class="memdesc:ga93b6ee8815d90adccfdceed72bcda577"><td class="mdescLeft"> </td><td class="mdescRight">Helper macro, if you want to mix user-defined and third party functors with libsigc++. <a href="#ga93b6ee8815d90adccfdceed72bcda577">More...</a><br /></td></tr>
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Functions</h2></td></tr>
<tr class="memitem:ga64cb7832acc1e58efb5ffe0b4f5e9404"><td class="memTemplParams" colspan="2">template<class T_action , class T_functor > </td></tr>
<tr class="memitem:ga64cb7832acc1e58efb5ffe0b4f5e9404"><td class="memTemplItemLeft" align="right" valign="top">void </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404">sigc::visit_each</a> (const T_action& _A_action, const T_functor& _A_functor)</td></tr>
<tr class="memdesc:ga64cb7832acc1e58efb5ffe0b4f5e9404"><td class="mdescLeft"> </td><td class="mdescRight">This function performs a functor on each of the targets of a functor. <a href="#ga64cb7832acc1e58efb5ffe0b4f5e9404">More...</a><br /></td></tr>
<tr class="separator:ga64cb7832acc1e58efb5ffe0b4f5e9404"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gada222d975b87d64cfa7a7f29244ae587"><td class="memTemplParams" colspan="2">template<class T_type , class T_action , class T_functor > </td></tr>
<tr class="memitem:gada222d975b87d64cfa7a7f29244ae587"><td class="memTemplItemLeft" align="right" valign="top">void </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="group__sigcfunctors.html#gada222d975b87d64cfa7a7f29244ae587">sigc::visit_each_type</a> (const T_action& _A_action, const T_functor& _A_functor)</td></tr>
<tr class="memdesc:gada222d975b87d64cfa7a7f29244ae587"><td class="mdescLeft"> </td><td class="mdescRight">This function performs a functor on each of the targets of a functor limited to a restricted type. <a href="#gada222d975b87d64cfa7a7f29244ae587">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<p>Functors are copyable types that define operator()(). </p>
<p>Types that define operator()() overloads with different return types are referred to as multi-type functors. Multi-type functors are only partially supported in libsigc++.</p>
<p>Closures are functors that store all information needed to invoke a callback from operator()().</p>
<p>Adaptors are functors that alter the signature of a functor's operator()().</p>
<p>libsigc++ defines numerous functors, closures and adaptors. Since libsigc++ is a callback library, most functors are also closures. The documentation doesn't distinguish between functors and closures.</p>
<p>The basic functor types libsigc++ provides are created with <a class="el" href="group__ptr__fun.html#ga9c80de72f656fb05e81fda622dddc863" title="Creates a functor of type sigc::pointer_functor0 which wraps an existing non-member function...">ptr_fun()</a> and <a class="el" href="group__mem__fun.html#gadf6b6d22c503b439019f0a2e77352419" title="Creates a functor of type sigc::mem_functor0 which wraps a method. ">mem_fun()</a> and can be converted into slots implicitly. The set of adaptors that ships with libsigc++ is documented in the <a class="el" href="group__adaptors.html">Adaptors</a> module.</p>
<p>If you want to mix user-defined and third party functors with libsigc++, and you want them to be implicitly convertible into slots, libsigc++ must know the result type of your functors. There are different ways to achieve that.</p>
<ul>
<li>Derive your functors from <a class="el" href="structsigc_1_1functor__base.html" title="A hint to the compiler. ">sigc::functor_base</a> and place <code>typedef T_return result_type;</code> in the class definition.</li>
<li>Use the macro <a class="el" href="group__sigcfunctors.html#ga7a6f5575dc0b0ea896889c782721f6be" title="Helper macro, if you want to mix user-defined and third party functors with libsigc++. ">SIGC_FUNCTOR_TRAIT(T_functor,T_return)</a> in namespace sigc. Multi-type functors are only partly supported.</li>
<li>For functors not derived from <a class="el" href="structsigc_1_1functor__base.html" title="A hint to the compiler. ">sigc::functor_base</a>, and not specified with <a class="el" href="group__sigcfunctors.html#ga7a6f5575dc0b0ea896889c782721f6be" title="Helper macro, if you want to mix user-defined and third party functors with libsigc++. ">SIGC_FUNCTOR_TRAIT()</a>, libsigc++ tries to deduce the result type with the C++11 decltype() specifier. That attempt usually succeeds if the functor has a single operator()(), but it fails if operator()() is overloaded.</li>
<li>Use the macro <a class="el" href="group__sigcfunctors.html#ga93b6ee8815d90adccfdceed72bcda577" title="Helper macro, if you want to mix user-defined and third party functors with libsigc++. ">SIGC_FUNCTORS_HAVE_RESULT_TYPE</a>, if you want libsigc++ to assume that result_type is defined in all user-defined or third party functors, whose result type can't be deduced in any other way.</li>
</ul>
<p>If all these ways to deduce the result type fail, void is assumed.</p>
<p>With libsigc++ versions before 2.6, the macro <a class="el" href="group__sigcfunctors.html#gadf1ba3cacb09cc5c3c3e399836ec6e50" title="Helper macro, if you want to mix user-defined and third party functors with libsigc++. ">SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE</a> activated the test with decltype(). That macro is now unneccesary and deprecated. </p>
<h2 class="groupheader">Macro Definition Documentation</h2>
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<td class="memname">#define SIGC_FUNCTOR_TRAIT</td>
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<td class="paramtype"> </td>
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<p>Helper macro, if you want to mix user-defined and third party functors with libsigc++. </p>
<p>If you want to mix functors not derived from <a class="el" href="structsigc_1_1functor__base.html" title="A hint to the compiler. ">sigc::functor_base</a> with libsigc++, and these functors don't define <code>result_type</code>, use this macro inside namespace sigc to expose the return type of the functors like so: </p><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> namespace sigc {</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>  SIGC_FUNCTOR_TRAIT(first_functor_type, return_type_of_first_functor_type)</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>  SIGC_FUNCTOR_TRAIT(second_functor_type, return_type_of_second_functor_type)</div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>  ...</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> }</div>
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<td class="memname">#define SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE</td>
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<p>Helper macro, if you want to mix user-defined and third party functors with libsigc++. </p>
<p>If you want to mix functors not derived from <a class="el" href="structsigc_1_1functor__base.html" title="A hint to the compiler. ">sigc::functor_base</a> with libsigc++, and your compiler can deduce the result type of the functor with the C++11 keyword <code>decltype</code>, use this macro inside namespace sigc like so: </p><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> namespace sigc {</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>  SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> }</div>
</div><!-- fragment --><p>Functors with overloaded operator()() are not supported.</p>
<dl class="since_2_2_11"><dt><b><a class="el" href="since_2_2_11.html#_since_2_2_11000001">Since libsigc++ 2.2.11:</a></b></dt><dd></dd></dl>
<dl class="deprecated"><dt><b><a class="el" href="deprecated.html#_deprecated000069">Deprecated:</a></b></dt><dd>This macro does nothing. The test it activated in libsigc++ versions before 2.6, is now unconditionally activated.</dd></dl>
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<td class="memname">#define SIGC_FUNCTORS_HAVE_RESULT_TYPE</td>
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<p>Helper macro, if you want to mix user-defined and third party functors with libsigc++. </p>
<p>If you want to mix functors not derived from <a class="el" href="structsigc_1_1functor__base.html" title="A hint to the compiler. ">sigc::functor_base</a> with libsigc++, and these functors define <code>result_type</code>, use this macro inside namespace sigc like so: </p><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> namespace sigc { SIGC_FUNCTORS_HAVE_RESULT_TYPE }</div>
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<h2 class="groupheader">Function Documentation</h2>
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template <class T_action , class T_functor > </div>
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<td class="memname">void sigc::visit_each </td>
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<p>This function performs a functor on each of the targets of a functor. </p>
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template <class T_type , class T_action , class T_functor > </div>
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<td class="memname">void sigc::visit_each_type </td>
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<p>This function performs a functor on each of the targets of a functor limited to a restricted type. </p>
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