/*============================================================================= | |
Copyright (c) 2001-2006 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/detail/access.hpp> | |
#include <boost/type_traits/is_const.hpp> | |
#include <boost/type_traits/add_const.hpp> | |
#include <boost/mpl/eval_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 detail::cons_deref< | |
typename detail::cons_advance<Sequence, N::value>::type> | |
element; | |
typedef typename | |
mpl::eval_if< | |
is_const<Sequence> | |
, detail::cref_result<element> | |
, detail::ref_result<element> | |
>::type | |
type; | |
template <typename Cons, int N2> | |
static type | |
call(Cons& s, mpl::int_<N2>) | |
{ | |
return call(s.cdr, mpl::int_<N2-1>()); | |
} | |
template <typename Cons> | |
static type | |
call(Cons& s, mpl::int_<0>) | |
{ | |
return s.car; | |
} | |
static type | |
call(Sequence& s) | |
{ | |
return call(s, mpl::int_<N::value>()); | |
} | |
}; | |
}; | |
} | |
}} | |
#endif |