1 2 #ifndef BOOST_MPL_AUX_AT_IMPL_HPP_INCLUDED 3 #define BOOST_MPL_AUX_AT_IMPL_HPP_INCLUDED 4 5 // Copyright Aleksey Gurtovoy 2000-2004 6 // 7 // Distributed under the Boost Software License, Version 1.0. 8 // (See accompanying file LICENSE_1_0.txt or copy at 9 // http://www.boost.org/LICENSE_1_0.txt) 10 // 11 // See http://www.boost.org/libs/mpl for documentation. 12 13 // $Id$ 14 // $Date$ 15 // $Revision$ 16 17 #include <boost/mpl/begin_end.hpp> 18 #include <boost/mpl/advance.hpp> 19 #include <boost/mpl/deref.hpp> 20 #include <boost/mpl/aux_/traits_lambda_spec.hpp> 21 22 namespace boost { namespace mpl { 23 24 // default implementation; conrete sequences might override it by 25 // specializing either the 'at_impl' or the primary 'at' template 26 27 template< typename Tag > 28 struct at_impl 29 { 30 template< typename Sequence, typename N > struct apply 31 { 32 typedef typename advance< 33 typename begin<Sequence>::type 34 , N 35 >::type iter_; 36 37 typedef typename deref<iter_>::type type; 38 }; 39 }; 40 41 BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(2, at_impl) 42 43 }} 44 45 #endif // BOOST_MPL_AUX_AT_IMPL_HPP_INCLUDED 46