59 lines
1.3 KiB
C++
59 lines
1.3 KiB
C++
// Boost.TypeErasure library
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//
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// Copyright 2011 Steven Watanabe
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//
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// Distributed under the Boost Software License Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// $Id: placeholder_of.hpp 80909 2012-10-08 21:59:50Z steven_watanabe $
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#ifndef BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED
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#define BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED
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namespace boost {
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namespace type_erasure {
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template<class Concept, class T>
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class any;
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template<class Concept, class T>
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class param;
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/**
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* A metafunction returning the (const/reference qualified) placeholder
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* corresponding to an @ref any. It will also work for all bases
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* of @ref any, so it can be applied to the @c Base
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* parameter of @ref concept_interface.
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*/
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template<class T>
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struct placeholder_of
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{
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#ifdef BOOST_TYPE_ERASURE_DOXYGEN
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typedef detail::unspecified type;
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#else
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typedef typename ::boost::type_erasure::placeholder_of<
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typename T::_boost_type_erasure_derived_type
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>::type type;
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#endif
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};
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/** INTERNAL ONLY */
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template<class Concept, class T>
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struct placeholder_of< ::boost::type_erasure::any<Concept, T> >
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{
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typedef T type;
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};
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/** INTERNAL ONLY */
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template<class Concept, class T>
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struct placeholder_of< ::boost::type_erasure::param<Concept, T> >
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{
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typedef T type;
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};
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}
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}
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#endif
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