| /*============================================================================= |
| Copyright (c) 2001-2006 Joel de Guzman |
| Copyright (c) 2005-2006 Dan Marsden |
| |
| 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(BOOST_FUSION_VALUE_AT_IMPL_24122005_1917) |
| #define BOOST_FUSION_VALUE_AT_IMPL_24122005_1917 |
| |
| #include <boost/mpl/if.hpp> |
| #include <boost/static_assert.hpp> |
| |
| namespace boost { namespace fusion { |
| |
| struct std_pair_tag; |
| |
| namespace extension |
| { |
| template<typename T> |
| struct value_at_impl; |
| |
| template <> |
| struct value_at_impl<std_pair_tag> |
| { |
| template <typename Sequence, typename N> |
| struct apply |
| { |
| static int const n_value = N::value; |
| BOOST_STATIC_ASSERT((n_value >= 0 && n_value < 2)); |
| typedef typename |
| mpl::if_c< |
| (n_value == 0) |
| , typename Sequence::first_type |
| , typename Sequence::second_type |
| >::type |
| type; |
| }; |
| }; |
| } |
| }} |
| |
| #endif |