67 lines
2.7 KiB
XML
67 lines
2.7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
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"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
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<!--
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Copyright Douglas Gregor 2001-2004
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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-->
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<header name="boost/visit_each.hpp" last-revision="$Date: 2007-03-06 16:51:55 -0500 (Tue, 06 Mar 2007) $">
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<namespace name="boost">
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<function name="visit_each">
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<template>
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<template-type-parameter name="Visitor"/>
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<template-type-parameter name="T"/>
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</template>
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<type>void</type>
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<parameter name="visitor">
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<paramtype>const Visitor&</paramtype>
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</parameter>
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<parameter name="t">
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<paramtype>const T&</paramtype>
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</parameter>
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<parameter>
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<paramtype>int</paramtype>
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</parameter>
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<purpose>Allow limited exploration of class members.</purpose>
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<description>
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<para>The <functionname>visit_each</functionname> mechanism
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allows a visitor to be applied to every subobject in a given
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object. It was used by the Signals library to discover (now deprecated)
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<classname>signals::trackable</classname> objects within a
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function object, but other uses may surface if used
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universally (e.g., conservative garbage collection). To fit
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within the <functionname>visit_each</functionname> framework,
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a <functionname>visit_each</functionname> overload must be
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supplied for each object type. </para>
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</description>
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<effects><para><code>visitor(t)</code>, and for
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every subobject <code>x</code> of
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<code>t</code>:
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<itemizedlist>
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<listitem><para>If <code>x</code> is a reference, <code>visit_each(visitor, <functionname>ref</functionname>(x), 0)</code></para></listitem>
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<listitem><para>Otherwise, <code>visit_each(visitor, x, 0)</code></para></listitem>
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</itemizedlist>
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</para></effects>
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<notes><para>The third parameter is
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<code>long</code> for the fallback version
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of <functionname>visit_each</functionname> and the argument
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supplied to this third paramter must always be 0. The third
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parameter is an artifact of the widespread lack of proper
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function template ordering, and will be removed in the future.</para>
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<para>Library authors will be expected to add additional
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overloads that specialize the T argument for their classes, so
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that subobjects can be visited.</para>
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<para>Calls to visit_each are required to be unqualified, to
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enable argument-dependent lookup.</para></notes>
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</function>
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</namespace>
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</header>
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