boost/hana/greater_equal.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::greater_equal`.
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_GREATER_EQUAL_HPP
0011 #define BOOST_HANA_GREATER_EQUAL_HPP
0012
0013 #include <boost/hana/fwd/greater_equal.hpp>
0014
0015 #include <boost/hana/concept/orderable.hpp>
0016 #include <boost/hana/config.hpp>
0017 #include <boost/hana/core/common.hpp>
0018 #include <boost/hana/core/to.hpp>
0019 #include <boost/hana/core/dispatch.hpp>
0020 #include <boost/hana/detail/concepts.hpp>
0021 #include <boost/hana/detail/has_common_embedding.hpp>
0022 #include <boost/hana/detail/nested_than.hpp> // required by fwd decl
0023 #include <boost/hana/if.hpp>
0024 #include <boost/hana/not.hpp>
0025
0026
0027 namespace boost { namespace hana {
0028     //! @cond
0029     template <typename X, typename Y>
0030     constexpr decltype(auto) greater_equal_t::operator()(X&& x, Y&& y) const {
0031         using T = typename hana::tag_of<X>::type;
0032         using U = typename hana::tag_of<Y>::type;
0033         using GreaterEqual = BOOST_HANA_DISPATCH_IF(
0034             decltype(greater_equal_impl<T, U>{}),
0035             hana::Orderable<T>::value &&
0036             hana::Orderable<U>::value
0037         );
0038
0039     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0040         static_assert(hana::Orderable<T>::value,
0041         "hana::greater_equal(x, y) requires 'x' to be Orderable");
0042
0043         static_assert(hana::Orderable<U>::value,
0044         "hana::greater_equal(x, y) requires 'y' to be Orderable");
0045     #endif
0046
0047         return GreaterEqual::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
0048     }
0049     //! @endcond
0050
0051     template <typename T, typename U, bool condition>
0052     struct greater_equal_impl<T, U, when<condition>> : default_ {
0053         template <typename X, typename Y>
0054         static constexpr decltype(auto) apply(X x, Y y) {
0055             return hana::not_(hana::less(static_cast<X&&>(x),
0056                                          static_cast<Y&&>(y)));
0057         }
0058     };
0059
0060     // Cross-type overload
0061     template <typename T, typename U>
0062     struct greater_equal_impl<T, U, when<
0063         detail::has_nontrivial_common_embedding<Orderable, T, U>::value
0064     >> {
0065         using C = typename hana::common<T, U>::type;
0066         template <typename X, typename Y>
0067         static constexpr decltype(auto) apply(X&& x, Y&& y) {
0068             return hana::greater_equal(hana::to<C>(static_cast<X&&>(x)),
0069                                        hana::to<C>(static_cast<Y&&>(y)));
0070         }
0071     };
0072 }} // end namespace boost::hana
0073
0074 #endif // !BOOST_HANA_GREATER_EQUAL_HPP