at_impl.hpp 1.1 KB

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