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- // Boost.TypeErasure library
- //
- // Copyright 2011 Steven Watanabe
- //
- // Distributed under the Boost Software License Version 1.0. (See
- // accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- //
- // $Id$
- #ifndef BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED
- #define BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED
- namespace boost {
- namespace type_erasure {
- #ifndef BOOST_TYPE_ERASURE_DOXYGEN
- template<class Concept, class T>
- class any;
- template<class Concept, class T>
- class param;
- #endif
- /**
- * A metafunction returning the (const/reference qualified) placeholder
- * corresponding to an @ref any. It will also work for all bases
- * of @ref any, so it can be applied to the @c Base
- * parameter of @ref concept_interface.
- */
- template<class T>
- struct placeholder_of
- {
- #ifdef BOOST_TYPE_ERASURE_DOXYGEN
- typedef detail::unspecified type;
- #else
- typedef typename ::boost::type_erasure::placeholder_of<
- typename T::_boost_type_erasure_derived_type
- >::type type;
- #endif
- };
- /** INTERNAL ONLY */
- template<class Concept, class T>
- struct placeholder_of< ::boost::type_erasure::any<Concept, T> >
- {
- typedef T type;
- };
- /** INTERNAL ONLY */
- template<class Concept, class T>
- struct placeholder_of< ::boost::type_erasure::param<Concept, T> >
- {
- typedef T type;
- };
- #ifndef BOOST_NO_CXX11_TEMPLATE_ALIASES
- template<class T>
- using placeholder_of_t = typename ::boost::type_erasure::placeholder_of<T>::type;
- #endif
- }
- }
- #endif
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