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list-at optimization

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[SVN r47643]
This commit is contained in:
Joel de Guzman
2008-07-20 23:14:15 +00:00
parent 8506cd8be6
commit af0e42f13e
1 changed files with 69 additions and 16 deletions
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85
include/boost/fusion/container/list/detail/at_impl.hpp
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@ -1,7 +1,7 @@
/*=============================================================================
Copyright (c) 2001-2006 Joel de Guzman
Distributed under the Boost Software License, Version 1.0. (See accompanying
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)
@ -15,6 +15,71 @@
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
@ -26,22 +91,10 @@ namespace boost { namespace fusion
struct at_impl<cons_tag>
{
template <typename Sequence, typename N>
struct apply
struct apply
{
typedef typename
mpl::eval_if<
is_const<Sequence>
, add_const<typename Sequence::cdr_type>
, mpl::identity<typename Sequence::cdr_type>
>::type
cdr_type;
typedef typename
mpl::eval_if<
mpl::bool_<N::value == 0>
, mpl::identity<typename Sequence::car_type>
, apply<cdr_type, mpl::int_<N::value-1> >
>
typedef detail::cons_deref<
typename detail::cons_advance<Sequence, N::value>::type>
element;
typedef typename