metafunction.hpp 1.1 KB

1234567891011121314151617181920212223242526272829303132333435363738394041
  1. /*!
  2. @file
  3. Defines `boost::hana::Metafunction`.
  4. @copyright Louis Dionne 2013-2017
  5. Distributed under the Boost Software License, Version 1.0.
  6. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
  7. */
  8. #ifndef BOOST_HANA_CONCEPT_METAFUNCTION_HPP
  9. #define BOOST_HANA_CONCEPT_METAFUNCTION_HPP
  10. #include <boost/hana/fwd/concept/metafunction.hpp>
  11. #include <boost/hana/config.hpp>
  12. #include <boost/hana/core/tag_of.hpp>
  13. #include <boost/hana/detail/integral_constant.hpp>
  14. BOOST_HANA_NAMESPACE_BEGIN
  15. namespace detail {
  16. template <typename F, typename Tag = typename tag_of<F>::type>
  17. struct metafunction_dispatch
  18. : hana::integral_constant<bool,
  19. Metafunction<Tag>::value
  20. >
  21. { };
  22. template <typename F>
  23. struct metafunction_dispatch<F, F>
  24. : hana::integral_constant<bool, false>
  25. { };
  26. }
  27. template <typename F>
  28. struct Metafunction
  29. : detail::metafunction_dispatch<F>
  30. { };
  31. BOOST_HANA_NAMESPACE_END
  32. #endif // !BOOST_HANA_CONCEPT_METAFUNCTION_HPP