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