boost/fusion/support/tag_of.hpp
/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
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)
==============================================================================*/
#if !defined(FUSION_TAG_OF_09232005_0845)
#define FUSION_TAG_OF_09232005_0845
#include <boost/fusion/support/config.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/remove_const.hpp>
#include <boost/fusion/support/tag_of_fwd.hpp>
#include <boost/fusion/support/detail/is_mpl_sequence.hpp>
#include <boost/mpl/has_xxx.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/mpl/if.hpp>
#include <boost/config/no_tr1/utility.hpp>
namespace boost
{
template <typename T, std::size_t N>
class array; // forward
namespace tuples
{
struct null_type;
template <
class T0, class T1, class T2, class T3, class T4,
class T5, class T6, class T7, class T8, class T9
>
class tuple;
template <class Head, class Tail>
struct cons;
}
}
namespace boost { namespace fusion
{
struct non_fusion_tag;
struct mpl_sequence_tag;
namespace detail
{
BOOST_MPL_HAS_XXX_TRAIT_DEF(fusion_tag)
template<typename Sequence, typename Active=void>
struct tag_of_fallback
{
typedef non_fusion_tag type;
};
template <typename Sequence, typename Active>
struct tag_of_impl
: mpl::if_<fusion::detail::is_mpl_sequence<Sequence>,
mpl::identity<mpl_sequence_tag>,
mpl::identity<typename tag_of_fallback<Sequence>::type> >::type
{};
template <typename Sequence>
struct tag_of_impl<
Sequence
, typename boost::enable_if<detail::has_fusion_tag<Sequence> >::type>
{
typedef typename Sequence::fusion_tag type;
};
}
namespace traits
{
template <typename Sequence, typename Active>
struct tag_of
: boost::fusion::detail::tag_of_impl<Sequence, Active>
{};
}
namespace detail
{
template<typename T>
struct tag_of
: traits::tag_of<typename remove_const<T>::type>
{};
}
}}
#endif