monoid.hpp 977 B

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  1. /*!
  2. @file
  3. Defines `boost::hana::Monoid`.
  4. Copyright Louis Dionne 2013-2022
  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_MONOID_HPP
  9. #define BOOST_HANA_CONCEPT_MONOID_HPP
  10. #include <boost/hana/fwd/concept/monoid.hpp>
  11. #include <boost/hana/config.hpp>
  12. #include <boost/hana/core/default.hpp>
  13. #include <boost/hana/core/tag_of.hpp>
  14. #include <boost/hana/detail/integral_constant.hpp>
  15. #include <boost/hana/plus.hpp>
  16. #include <boost/hana/zero.hpp>
  17. namespace boost { namespace hana {
  18. template <typename M>
  19. struct Monoid
  20. : hana::integral_constant<bool,
  21. !is_default<zero_impl<typename tag_of<M>::type>>::value &&
  22. !is_default<plus_impl<typename tag_of<M>::type,
  23. typename tag_of<M>::type>>::value
  24. >
  25. { };
  26. }} // end namespace boost::hana
  27. #endif // !BOOST_HANA_CONCEPT_MONOID_HPP