boost/hana/less_equal.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::less_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_LESS_EQUAL_HPP
0011 #define BOOST_HANA_LESS_EQUAL_HPP
0012
0013 #include <boost/hana/fwd/less_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/has_common_embedding.hpp>
0021 #include <boost/hana/detail/nested_than.hpp> // required by fwd decl
0022 #include <boost/hana/less.hpp>
0023 #include <boost/hana/not.hpp>
0024
0025 #include <type_traits>
0026
0027
0028 namespace boost { namespace hana {
0029     //! @cond
0030     template <typename X, typename Y>
0031     constexpr auto less_equal_t::operator()(X&& x, Y&& y) const {
0032         using T = typename hana::tag_of<X>::type;
0033         using U = typename hana::tag_of<Y>::type;
0034         using LessEqual = BOOST_HANA_DISPATCH_IF(
0035             decltype(less_equal_impl<T, U>{}),
0036             hana::Orderable<T>::value &&
0037             hana::Orderable<U>::value
0038         );
0039
0040     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0041         static_assert(hana::Orderable<T>::value,
0042         "hana::less_equal(x, y) requires 'x' to be Orderable");
0043
0044         static_assert(hana::Orderable<U>::value,
0045         "hana::less_equal(x, y) requires 'y' to be Orderable");
0046     #endif
0047
0048         return LessEqual::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
0049     }
0050     //! @endcond
0051
0052     template <typename T, typename U, bool condition>
0053     struct less_equal_impl<T, U, when<condition>> : default_ {
0054         template <typename X, typename Y>
0055         static constexpr decltype(auto) apply(X&& x, Y&& y) {
0056             return hana::not_(hana::less(static_cast<Y&&>(y),
0057                                          static_cast<X&&>(x)));
0058         }
0059     };
0060
0061     // Cross-type overload
0062     template <typename T, typename U>
0063     struct less_equal_impl<T, U, when<
0064         detail::has_nontrivial_common_embedding<Orderable, T, U>::value
0065     >> {
0066         using C = typename hana::common<T, U>::type;
0067         template <typename X, typename Y>
0068         static constexpr decltype(auto) apply(X&& x, Y&& y) {
0069             return hana::less_equal(hana::to<C>(static_cast<X&&>(x)),
0070                                     hana::to<C>(static_cast<Y&&>(y)));
0071         }
0072     };
0073 }} // end namespace boost::hana
0074
0075 #endif // !BOOST_HANA_LESS_EQUAL_HPP