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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_DEDUCED_HPP_INCLUDED
- #define BOOST_TYPE_ERASURE_DEDUCED_HPP_INCLUDED
- #include <boost/mpl/eval_if.hpp>
- #include <boost/mpl/identity.hpp>
- #include <boost/mpl/set.hpp>
- #include <boost/mpl/empty.hpp>
- #include <boost/type_erasure/detail/get_placeholders.hpp>
- #include <boost/type_erasure/placeholder.hpp>
- namespace boost {
- namespace type_erasure {
- /**
- * A placeholder for an associated type. The type corresponding
- * to this placeholder is deduced by substituting placeholders
- * in the arguments of the metafunction and then evaluating it.
- *
- * When using @ref deduced in a template context, if it is possible for
- * Metafunction to contain no placeholders at all, use the nested type,
- * to automatically evaluate it early as needed.
- */
- template<class Metafunction>
- struct deduced : ::boost::type_erasure::placeholder
- {
- typedef typename ::boost::mpl::eval_if<
- ::boost::mpl::empty<
- typename ::boost::type_erasure::detail::get_placeholders<
- Metafunction,
- #ifndef BOOST_TYPE_ERASURE_USE_MP11
- ::boost::mpl::set0<>
- #else
- ::boost::mp11::mp_list<>
- #endif
- >::type
- >,
- Metafunction,
- ::boost::mpl::identity<
- ::boost::type_erasure::deduced<Metafunction>
- >
- >::type type;
- };
- }
- }
- #endif
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