1 /*!
2 @file
3 Defines `boost::hana::less_equal`.
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_LESS_EQUAL_HPP
11 #define BOOST_HANA_LESS_EQUAL_HPP
12 
13 #include <boost/hana/fwd/less_equal.hpp>
14 
15 #include <boost/hana/concept/orderable.hpp>
16 #include <boost/hana/config.hpp>
17 #include <boost/hana/core/common.hpp>
18 #include <boost/hana/core/to.hpp>
19 #include <boost/hana/core/dispatch.hpp>
20 #include <boost/hana/detail/has_common_embedding.hpp>
21 #include <boost/hana/detail/nested_than.hpp> // required by fwd decl
22 #include <boost/hana/less.hpp>
23 #include <boost/hana/not.hpp>
24 
25 #include <type_traits>
26 
27 
28 BOOST_HANA_NAMESPACE_BEGIN
29     //! @cond
30     template <typename X, typename Y>
operator ()(X && x,Y && y) const31     constexpr auto less_equal_t::operator()(X&& x, Y&& y) const {
32         using T = typename hana::tag_of<X>::type;
33         using U = typename hana::tag_of<Y>::type;
34         using LessEqual = BOOST_HANA_DISPATCH_IF(
35             decltype(less_equal_impl<T, U>{}),
36             hana::Orderable<T>::value &&
37             hana::Orderable<U>::value
38         );
39 
40     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
41         static_assert(hana::Orderable<T>::value,
42         "hana::less_equal(x, y) requires 'x' to be Orderable");
43 
44         static_assert(hana::Orderable<U>::value,
45         "hana::less_equal(x, y) requires 'y' to be Orderable");
46     #endif
47 
48         return LessEqual::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
49     }
50     //! @endcond
51 
52     template <typename T, typename U, bool condition>
53     struct less_equal_impl<T, U, when<condition>> : default_ {
54         template <typename X, typename Y>
applyless_equal_impl55         static constexpr decltype(auto) apply(X&& x, Y&& y) {
56             return hana::not_(hana::less(static_cast<Y&&>(y),
57                                          static_cast<X&&>(x)));
58         }
59     };
60 
61     // Cross-type overload
62     template <typename T, typename U>
63     struct less_equal_impl<T, U, when<
64         detail::has_nontrivial_common_embedding<Orderable, T, U>::value
65     >> {
66         using C = typename hana::common<T, U>::type;
67         template <typename X, typename Y>
applyless_equal_impl68         static constexpr decltype(auto) apply(X&& x, Y&& y) {
69             return hana::less_equal(hana::to<C>(static_cast<X&&>(x)),
70                                     hana::to<C>(static_cast<Y&&>(y)));
71         }
72     };
73 BOOST_HANA_NAMESPACE_END
74 
75 #endif // !BOOST_HANA_LESS_EQUAL_HPP
76