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/*=============================================================================
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_AT_IMPL_07172005_0726)
#define FUSION_AT_IMPL_07172005_0726
#include <boost/fusion/support/config.hpp>
#include <boost/fusion/support/detail/access.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/type_traits/add_const.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/bool.hpp>
namespace boost { namespace fusion
{
namespace detail
{
template <typename Cons>
struct cons_deref
{
typedef typename Cons::car_type type;
};
template <typename Cons, int I>
struct cons_advance
{
typedef typename
cons_advance<Cons, I-1>::type::cdr_type
type;
};
template <typename Cons>
struct cons_advance<Cons, 0>
{
typedef Cons type;
};
template <typename Cons>
struct cons_advance<Cons, 1>
{
typedef typename Cons::cdr_type type;
};
template <typename Cons>
struct cons_advance<Cons, 2>
{
#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
typedef typename Cons::cdr_type::cdr_type type;
#else
typedef typename Cons::cdr_type _a;
typedef typename _a::cdr_type type;
#endif
};
template <typename Cons>
struct cons_advance<Cons, 3>
{
#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
typedef typename Cons::cdr_type::cdr_type::cdr_type type;
#else
typedef typename Cons::cdr_type _a;
typedef typename _a::cdr_type _b;
typedef typename _b::cdr_type type;
#endif
};
template <typename Cons>
struct cons_advance<Cons, 4>
{
#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
typedef typename Cons::cdr_type::cdr_type::cdr_type::cdr_type type;
#else
typedef typename Cons::cdr_type _a;
typedef typename _a::cdr_type _b;
typedef typename _b::cdr_type _c;
typedef typename _c::cdr_type type;
#endif
};
}
struct cons_tag;
namespace extension
{
template <typename Tag>
struct at_impl;
template <>
struct at_impl<cons_tag>
{
template <typename Sequence, typename N>
struct apply
{
typedef typename detail::cons_deref<
typename detail::cons_advance<Sequence, N::value>::type>::type
element;
typedef typename
mpl::if_<
is_const<Sequence>
, typename detail::cref_result<element>::type
, typename detail::ref_result<element>::type
>::type
type;
template <typename Cons, int N2>
BOOST_FUSION_GPU_ENABLED
static type
call(Cons& s, mpl::int_<N2>)
{
return call(s.cdr, mpl::int_<N2-1>());
}
template <typename Cons>
BOOST_FUSION_GPU_ENABLED
static type
call(Cons& s, mpl::int_<0>)
{
return s.car;
}
BOOST_FUSION_GPU_ENABLED
static type
call(Sequence& s)
{
return call(s, mpl::int_<N::value>());
}
};
};
}
}}
#endif
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