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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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