unused_skipper.hpp 1.7 KB

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  1. // Copyright (c) 2001-2011 Hartmut Kaiser
  2. //
  3. // Distributed under the Boost Software License, Version 1.0. (See accompanying
  4. // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  5. #if !defined(BOOST_SPIRIT_QI_UNUSED_SKIPPER_JUL_25_2009_0921AM)
  6. #define BOOST_SPIRIT_QI_UNUSED_SKIPPER_JUL_25_2009_0921AM
  7. #if defined(_MSC_VER)
  8. #pragma once
  9. #endif
  10. #include <boost/spirit/home/support/unused.hpp>
  11. #include <boost/mpl/bool.hpp>
  12. namespace boost { namespace spirit { namespace qi { namespace detail
  13. {
  14. template <typename Skipper>
  15. struct unused_skipper : unused_type
  16. {
  17. unused_skipper(Skipper const& skipper_)
  18. : skipper(skipper_) {}
  19. Skipper const& skipper;
  20. private:
  21. // silence MSVC warning C4512: assignment operator could not be generated
  22. unused_skipper& operator= (unused_skipper const&);
  23. };
  24. template <typename Skipper>
  25. struct is_unused_skipper
  26. : mpl::false_ {};
  27. template <typename Skipper>
  28. struct is_unused_skipper<unused_skipper<Skipper> >
  29. : mpl::true_ {};
  30. template <>
  31. struct is_unused_skipper<unused_type>
  32. : mpl::true_ {};
  33. // If a surrounding lexeme[] directive was specified, the current
  34. // skipper is of the type unused_skipper. In this case we
  35. // re-activate the skipper which was active before the skip[]
  36. // directive.
  37. template <typename Skipper>
  38. inline Skipper const&
  39. get_skipper(unused_skipper<Skipper> const& u)
  40. {
  41. return u.skipper;
  42. }
  43. // If no surrounding lexeme[] directive was specified we keep what we got.
  44. template <typename Skipper>
  45. inline Skipper const&
  46. get_skipper(Skipper const& u)
  47. {
  48. return u;
  49. }
  50. }}}}
  51. #endif