1 /*! 2 @file 3 Defines `boost::hana::Monoid`. 4 5 @copyright Louis Dionne 2013-2017 6 Distributed under the Boost Software License, Version 1.0. 7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) 8 */ 9 10 #ifndef BOOST_HANA_CONCEPT_MONOID_HPP 11 #define BOOST_HANA_CONCEPT_MONOID_HPP 12 13 #include <boost/hana/fwd/concept/monoid.hpp> 14 15 #include <boost/hana/config.hpp> 16 #include <boost/hana/core/default.hpp> 17 #include <boost/hana/core/tag_of.hpp> 18 #include <boost/hana/detail/integral_constant.hpp> 19 #include <boost/hana/plus.hpp> 20 #include <boost/hana/zero.hpp> 21 22 23 BOOST_HANA_NAMESPACE_BEGIN 24 template <typename M> 25 struct Monoid 26 : hana::integral_constant<bool, 27 !is_default<zero_impl<typename tag_of<M>::type>>::value && 28 !is_default<plus_impl<typename tag_of<M>::type, 29 typename tag_of<M>::type>>::value 30 > 31 { }; 32 BOOST_HANA_NAMESPACE_END 33 34 #endif // !BOOST_HANA_CONCEPT_MONOID_HPP 35