1<?xml version="1.0" encoding="utf-8"?> 2<!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" 3 "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd"> 4<!-- 5Copyright Douglas Gregor 2001-2004 6 7Distributed under the Boost Software License, Version 1.0. (See accompanying 8file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 9--> 10<header name="boost/visit_each.hpp" last-revision="$Date: 2007-03-06 16:51:55 -0500 (Tue, 06 Mar 2007) $"> 11 <namespace name="boost"> 12 <function name="visit_each"> 13 <template> 14 <template-type-parameter name="Visitor"/> 15 <template-type-parameter name="T"/> 16 </template> 17 <type>void</type> 18 <parameter name="visitor"> 19 <paramtype>const Visitor&</paramtype> 20 </parameter> 21 <parameter name="t"> 22 <paramtype>const T&</paramtype> 23 </parameter> 24 <parameter> 25 <paramtype>int</paramtype> 26 </parameter> 27 28 <purpose>Allow limited exploration of class members.</purpose> 29 30 <description> 31 <para>The <functionname>visit_each</functionname> mechanism 32 allows a visitor to be applied to every subobject in a given 33 object. It was used by the Signals library to discover (now deprecated) 34 <classname>signals::trackable</classname> objects within a 35 function object, but other uses may surface if used 36 universally (e.g., conservative garbage collection). To fit 37 within the <functionname>visit_each</functionname> framework, 38 a <functionname>visit_each</functionname> overload must be 39 supplied for each object type. </para> 40 </description> 41 42 <effects><para><code>visitor(t)</code>, and for 43 every subobject <code>x</code> of 44 <code>t</code>: 45 <itemizedlist> 46 <listitem><para>If <code>x</code> is a reference, <code>visit_each(visitor, <functionname>ref</functionname>(x), 0)</code></para></listitem> 47 <listitem><para>Otherwise, <code>visit_each(visitor, x, 0)</code></para></listitem> 48 </itemizedlist> 49 </para></effects> 50 51 <notes><para>The third parameter is 52 <code>long</code> for the fallback version 53 of <functionname>visit_each</functionname> and the argument 54 supplied to this third paramter must always be 0. The third 55 parameter is an artifact of the widespread lack of proper 56 function template ordering, and will be removed in the future.</para> 57 58 <para>Library authors will be expected to add additional 59 overloads that specialize the T argument for their classes, so 60 that subobjects can be visited.</para> 61 62 <para>Calls to visit_each are required to be unqualified, to 63 enable argument-dependent lookup.</para></notes> 64 </function> 65 </namespace> 66</header> 67