From: joel_at_[hidden]
Date: 2008-07-20 19:14:15
Author: djowel
Date: 2008-07-20 19:14:15 EDT (Sun, 20 Jul 2008)
New Revision: 47643
URL: http://svn.boost.org/trac/boost/changeset/47643
Log:
list-at optimization
Text files modified:
trunk/boost/fusion/container/list/detail/at_impl.hpp | 85 ++++++++++++++++++++++++++++++++-------
1 files changed, 69 insertions(+), 16 deletions(-)
Modified: trunk/boost/fusion/container/list/detail/at_impl.hpp
==============================================================================
--- trunk/boost/fusion/container/list/detail/at_impl.hpp (original)
+++ trunk/boost/fusion/container/list/detail/at_impl.hpp 2008-07-20 19:14:15 EDT (Sun, 20 Jul 2008)
@@ -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 @@
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