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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_RELAXED_HPP_INCLUDED
- #define BOOST_TYPE_ERASURE_RELAXED_HPP_INCLUDED
- #include <boost/mpl/vector.hpp>
- #include <boost/mpl/bool.hpp>
- #include <boost/mpl/is_sequence.hpp>
- #include <boost/mpl/find_if.hpp>
- #include <boost/mpl/not.hpp>
- #include <boost/mpl/end.hpp>
- #include <boost/type_traits/is_same.hpp>
- namespace boost {
- namespace type_erasure {
- template<class T>
- struct is_relaxed;
- namespace detail {
- template<class T>
- struct is_relaxed_impl :
- ::boost::mpl::not_<
- typename ::boost::is_same<
- typename ::boost::mpl::find_if<
- T,
- ::boost::type_erasure::is_relaxed< ::boost::mpl::_1>
- >::type,
- typename ::boost::mpl::end<T>::type
- >::type
- >::type
- {};
- }
- /**
- * This special concept enables various useful default behavior that
- * makes @ref any act like an ordinary object. By default @ref any
- * forwards all operations to the underlying type, and provides only
- * the operations that are specified in its @c Concept.
- *
- * In detail, @ref relaxed enables the following:
- * - A raw value can be assigned to an @ref any. This will replace
- * the value stored by the @ref any. (But note that if @ref assignable
- * is present, it takes priority.)
- * - assignment of @ref any uses the constructor if it can't
- * use @ref assignable (either because @ref assignable is missing,
- * or because the stored types do not match).
- * - default construction of @ref any is allowed and creates a null any.
- * - @ref equality_comparable "equality_comparable": If the types do not
- * match, it will return false.
- * - @ref less_than_comparable "less_than_comparable": If the types do not
- * match, the ordering will be according to
- * @c std::type_info::before.
- * - if the arguments to any other function do not match, it will throw
- * a @ref bad_function_call exception instead of having undefined
- * behavior.
- */
- struct relaxed : ::boost::mpl::vector0<> {};
- /**
- * A metafunction indicating whether @c Concept
- * includes @ref relaxed.
- */
- template<class Concept>
- struct is_relaxed :
- ::boost::mpl::eval_if< ::boost::mpl::is_sequence<Concept>,
- ::boost::type_erasure::detail::is_relaxed_impl<Concept>,
- ::boost::mpl::false_
- >::type
- {};
- /** INTERNAL ONLY */
- template<>
- struct is_relaxed< ::boost::type_erasure::relaxed> :
- ::boost::mpl::true_
- {};
- }
- }
- #endif
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