hana/concept/monoid.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::Monoid`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_CONCEPT_MONOID_HPP
0011 #define BOOST_HANA_CONCEPT_MONOID_HPP
0012
0013 #include <boost/hana/fwd/concept/monoid.hpp>
0014
0015 #include <boost/hana/config.hpp>
0016 #include <boost/hana/core/default.hpp>
0017 #include <boost/hana/core/tag_of.hpp>
0018 #include <boost/hana/detail/integral_constant.hpp>
0019 #include <boost/hana/plus.hpp>
0020 #include <boost/hana/zero.hpp>
0021
0022
0023 namespace boost { namespace hana {
0024     template <typename M>
0025     struct Monoid
0026         : hana::integral_constant<bool,
0027             !is_default<zero_impl<typename tag_of<M>::type>>::value &&
0028             !is_default<plus_impl<typename tag_of<M>::type,
0029                                   typename tag_of<M>::type>>::value
0030         >
0031     { };
0032 }} // end namespace boost::hana
0033
0034 #endif // !BOOST_HANA_CONCEPT_MONOID_HPP