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| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Adapts `std::integral_constant` for use with Hana. | |
| 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_EXT_STD_INTEGRAL_CONSTANT_HPP | |
| 11 | #define BOOST_HANA_EXT_STD_INTEGRAL_CONSTANT_HPP | |
| 12 | ||
| 13 | #include <boost/hana/concept/integral_constant.hpp> | |
| 14 | #include <boost/hana/config.hpp> | |
| 15 | #include <boost/hana/core/when.hpp> | |
| 16 | #include <boost/hana/fwd/core/to.hpp> | |
| 17 | #include <boost/hana/fwd/core/tag_of.hpp> | |
| 18 | #include <boost/hana/fwd/integral_constant.hpp> | |
| 19 | ||
| 20 | #include <type_traits> | |
| 21 | ||
| 22 | ||
| 23 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
| 24 | namespace std { | |
| 25 | //! @ingroup group-ext-std | |
| 26 | //! Adapter for `std::integral_constant`s. | |
| 27 | //! | |
| 28 | //! Provided models | |
| 29 | //! --------------- | |
| 30 | //! 1. `Constant` and `IntegralConstant`\n | |
| 31 | //! A `std::integral_constant` is a model of the `IntegralConstant` and | |
| 32 | //! `Constant` concepts, just like `hana::integral_constant`s are. As a | |
| 33 | //! consequence, they are also implicitly a model of the concepts provided | |
| 34 | //! for all models of `Constant`. | |
| 35 | //! @include example/ext/std/integral_constant.cpp | |
| 36 | template <typename T, T v> | |
| 37 | struct integral_constant { }; | |
| 38 | } | |
| 39 | #endif | |
| 40 | ||
| 41 | ||
| 42 | BOOST_HANA_NAMESPACE_BEGIN | |
| 43 | namespace ext { namespace std { | |
| 44 | template <typename T> | |
| 45 | struct integral_constant_tag { using value_type = T; }; | |
| 46 | }} | |
| 47 | ||
| 48 | namespace detail { | |
| 49 | template <typename T, T v> | |
| 50 | constexpr bool | |
| 51 | is_std_integral_constant(std::integral_constant<T, v>*) | |
| 52 | { return true; } | |
| 53 | ||
| 54 | constexpr bool is_std_integral_constant(...) | |
| 55 | { return false; } | |
| 56 | ||
| 57 | ||
| 58 | template <typename T, T v> | |
| 59 | constexpr bool | |
| 60 | is_hana_integral_constant(hana::integral_constant<T, v>*) | |
| 61 | { return true; } | |
| 62 | ||
| 63 | constexpr bool is_hana_integral_constant(...) | |
| 64 | { return false; } | |
| 65 | } | |
| 66 | ||
| 67 | template <typename T> | |
| 68 | struct tag_of<T, when< | |
| 69 | detail::is_std_integral_constant((T*)0) && | |
| 70 | !detail::is_hana_integral_constant((T*)0) | |
| 71 | >> { | |
| 72 | using type = ext::std::integral_constant_tag< | |
| 73 | typename hana::tag_of<typename T::value_type>::type | |
| 74 | >; | |
| 75 | }; | |
| 76 | ||
| 77 | ////////////////////////////////////////////////////////////////////////// | |
| 78 | // Constant/IntegralConstant | |
| 79 | ////////////////////////////////////////////////////////////////////////// | |
| 80 | template <typename T> | |
| 81 | struct IntegralConstant<ext::std::integral_constant_tag<T>> { | |
| 82 | static constexpr bool value = true; | |
| 83 | }; | |
| 84 | ||
| 85 | template <typename T, typename C> | |
| 86 | struct to_impl<ext::std::integral_constant_tag<T>, C, when< | |
| 87 | hana::IntegralConstant<C>::value | |
| 88 | >> : embedding<is_embedded<typename C::value_type, T>::value> { | |
| 89 | template <typename N> | |
| 90 | static constexpr auto apply(N const&) { | |
| 91 | return std::integral_constant<T, N::value>{}; | |
| 92 | } | |
| 93 | }; | |
| 94 | BOOST_HANA_NAMESPACE_END | |
| 95 | ||
| 96 | #endif // !BOOST_HANA_EXT_STD_INTEGRAL_CONSTANT_HPP |