at_impl.hpp 1.2 KB

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  1. /*=============================================================================
  2. Copyright (c) 2001-2011 Joel de Guzman
  3. Copyright (c) 2005-2006 Dan Marsden
  4. Distributed under the Boost Software License, Version 1.0. (See accompanying
  5. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  6. ==============================================================================*/
  7. #if !defined(BOOST_FUSION_AT_IMPL_31122005_1642)
  8. #define BOOST_FUSION_AT_IMPL_31122005_1642
  9. #include <boost/fusion/support/config.hpp>
  10. #include <boost/mpl/at.hpp>
  11. namespace boost { namespace fusion
  12. {
  13. struct mpl_sequence_tag;
  14. namespace extension
  15. {
  16. template<typename Tag>
  17. struct at_impl;
  18. template <>
  19. struct at_impl<mpl_sequence_tag>
  20. {
  21. template <typename Sequence, typename N>
  22. struct apply
  23. {
  24. typedef typename mpl::at<Sequence, N>::type type;
  25. BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  26. static type
  27. call(Sequence)
  28. {
  29. return type();
  30. }
  31. };
  32. };
  33. }
  34. }}
  35. #endif