]>
Commit | Line | Data |
---|---|---|
7c673cae FG |
1 | /*! |
2 | @file | |
3 | Defines `boost::hana::minus`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
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_MINUS_HPP | |
11 | #define BOOST_HANA_MINUS_HPP | |
12 | ||
13 | #include <boost/hana/fwd/minus.hpp> | |
14 | ||
15 | #include <boost/hana/concept/constant.hpp> | |
16 | #include <boost/hana/concept/group.hpp> | |
17 | #include <boost/hana/config.hpp> | |
18 | #include <boost/hana/core/common.hpp> | |
19 | #include <boost/hana/core/to.hpp> | |
20 | #include <boost/hana/core/dispatch.hpp> | |
21 | #include <boost/hana/detail/canonical_constant.hpp> | |
22 | #include <boost/hana/detail/has_common_embedding.hpp> | |
23 | #include <boost/hana/fwd/negate.hpp> | |
24 | #include <boost/hana/plus.hpp> | |
25 | #include <boost/hana/value.hpp> | |
26 | ||
27 | #include <type_traits> | |
28 | ||
29 | ||
30 | BOOST_HANA_NAMESPACE_BEGIN | |
31 | //! @cond | |
32 | template <typename X, typename Y> | |
33 | constexpr decltype(auto) minus_t::operator()(X&& x, Y&& y) const { | |
34 | using T = typename hana::tag_of<X>::type; | |
35 | using U = typename hana::tag_of<Y>::type; | |
36 | using Minus = BOOST_HANA_DISPATCH_IF(decltype(minus_impl<T, U>{}), | |
37 | hana::Group<T>::value && | |
38 | hana::Group<U>::value | |
39 | ); | |
40 | ||
41 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
42 | static_assert(hana::Group<T>::value, | |
43 | "hana::minus(x, y) requires 'x' to be in a Group"); | |
44 | ||
45 | static_assert(hana::Group<U>::value, | |
46 | "hana::minus(x, y) requires 'y' to be in a Group"); | |
47 | #endif | |
48 | ||
49 | return Minus::apply(static_cast<X&&>(x), static_cast<Y&&>(y)); | |
50 | } | |
51 | //! @endcond | |
52 | ||
53 | template <typename T, typename U, bool condition> | |
54 | struct minus_impl<T, U, when<condition>> : default_ { | |
55 | template <typename ...Args> | |
56 | static constexpr auto apply(Args&& ...) = delete; | |
57 | }; | |
58 | ||
59 | template <typename T, bool condition> | |
60 | struct minus_impl<T, T, when<condition>> : default_ { | |
61 | template <typename X, typename Y> | |
62 | static constexpr decltype(auto) apply(X&& x, Y&& y) { | |
63 | return hana::plus(static_cast<X&&>(x), | |
64 | hana::negate(static_cast<Y&&>(y))); | |
65 | } | |
66 | }; | |
67 | ||
68 | // Cross-type overload | |
69 | template <typename T, typename U> | |
70 | struct minus_impl<T, U, when< | |
71 | detail::has_nontrivial_common_embedding<Group, T, U>::value | |
72 | >> { | |
73 | using C = typename common<T, U>::type; | |
74 | template <typename X, typename Y> | |
75 | static constexpr decltype(auto) apply(X&& x, Y&& y) { | |
76 | return hana::minus(hana::to<C>(static_cast<X&&>(x)), | |
77 | hana::to<C>(static_cast<Y&&>(y))); | |
78 | } | |
79 | }; | |
80 | ||
81 | ////////////////////////////////////////////////////////////////////////// | |
82 | // Model for arithmetic data types | |
83 | ////////////////////////////////////////////////////////////////////////// | |
84 | template <typename T> | |
85 | struct minus_impl<T, T, when<std::is_arithmetic<T>::value && | |
86 | !std::is_same<bool, T>::value>> { | |
87 | template <typename X, typename Y> | |
88 | static constexpr decltype(auto) apply(X&& x, Y&& y) | |
89 | { return static_cast<X&&>(x) - static_cast<Y&&>(y); } | |
90 | }; | |
91 | ||
92 | ////////////////////////////////////////////////////////////////////////// | |
93 | // Model for Constants over a Group | |
94 | ////////////////////////////////////////////////////////////////////////// | |
95 | namespace detail { | |
96 | template <typename C, typename X, typename Y> | |
97 | struct constant_from_minus { | |
98 | static constexpr auto value = hana::minus(hana::value<X>(), hana::value<Y>()); | |
99 | using hana_tag = detail::CanonicalConstant<typename C::value_type>; | |
100 | }; | |
101 | } | |
102 | ||
103 | template <typename C> | |
104 | struct minus_impl<C, C, when< | |
105 | hana::Constant<C>::value && | |
106 | Group<typename C::value_type>::value | |
107 | >> { | |
108 | template <typename X, typename Y> | |
109 | static constexpr decltype(auto) apply(X const&, Y const&) | |
110 | { return hana::to<C>(detail::constant_from_minus<C, X, Y>{}); } | |
111 | }; | |
112 | BOOST_HANA_NAMESPACE_END | |
113 | ||
114 | #endif // !BOOST_HANA_MINUS_HPP |