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- /*!
- @file
- Defines `boost::hana::experimental::types`.
- @copyright Louis Dionne 2013-2017
- Distributed under the Boost Software License, Version 1.0.
- (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
- */
- #ifndef BOOST_HANA_EXPERIMENTAL_TYPES_HPP
- #define BOOST_HANA_EXPERIMENTAL_TYPES_HPP
- #include <boost/hana/bool.hpp>
- #include <boost/hana/concept/metafunction.hpp>
- #include <boost/hana/config.hpp>
- #include <boost/hana/detail/any_of.hpp>
- #include <boost/hana/detail/type_at.hpp>
- #include <boost/hana/fwd/at.hpp>
- #include <boost/hana/fwd/contains.hpp>
- #include <boost/hana/fwd/core/tag_of.hpp>
- #include <boost/hana/fwd/equal.hpp>
- #include <boost/hana/fwd/is_empty.hpp>
- #include <boost/hana/fwd/transform.hpp>
- #include <boost/hana/fwd/unpack.hpp>
- #include <boost/hana/type.hpp>
- #include <cstddef>
- #include <type_traits>
- #include <utility>
- BOOST_HANA_NAMESPACE_BEGIN
- namespace experimental {
- //! @ingroup group-experimental
- //! Container optimized for holding types.
- //!
- //! It is often useful to manipulate a sequence that contains types
- //! only, without any associated runtime value. This container allows
- //! storing and manipulating pure types in a much more compile-time
- //! efficient manner than using `hana::tuple`, which must assume that
- //! its contents might have runtime values.
- template <typename ...T>
- struct types;
- struct types_tag;
- template <typename ...T>
- struct types { };
- } // end namespace experimental
- template <typename ...T>
- struct tag_of<experimental::types<T...>> {
- using type = experimental::types_tag;
- };
- // Foldable
- template <>
- struct unpack_impl<hana::experimental::types_tag> {
- template <typename ...T, typename F, typename = typename std::enable_if<
- !hana::Metafunction<F>::value
- >::type>
- static constexpr decltype(auto) apply(hana::experimental::types<T...> const&, F&& f) {
- return static_cast<F&&>(f)(hana::type<T>{}...);
- }
- template <typename ...T, typename F, typename = typename std::enable_if<
- hana::Metafunction<F>::value
- >::type>
- static constexpr hana::type<typename F::template apply<T...>::type>
- apply(hana::experimental::types<T...> const&, F const&) { return {}; }
- };
- // Functor
- template <>
- struct transform_impl<hana::experimental::types_tag> {
- template <typename ...T, typename F, typename = typename std::enable_if<
- !hana::Metafunction<F>::value
- >::type>
- static constexpr auto apply(hana::experimental::types<T...> const&, F&& f)
- -> hana::experimental::types<typename decltype(+f(hana::type<T>{}))::type...>
- { return {}; }
- template <typename ...T, typename F, typename = typename std::enable_if<
- hana::Metafunction<F>::value
- >::type>
- static constexpr hana::experimental::types<typename F::template apply<T>::type...>
- apply(hana::experimental::types<T...> const&, F const&) { return {}; }
- };
- // Iterable
- template <>
- struct at_impl<hana::experimental::types_tag> {
- template <typename ...T, typename N>
- static constexpr auto
- apply(hana::experimental::types<T...> const&, N const&) {
- using Nth = typename detail::type_at<N::value, T...>::type;
- return hana::type<Nth>{};
- }
- };
- template <>
- struct is_empty_impl<hana::experimental::types_tag> {
- template <typename ...T>
- static constexpr hana::bool_<sizeof...(T) == 0>
- apply(hana::experimental::types<T...> const&)
- { return {}; }
- };
- template <>
- struct drop_front_impl<hana::experimental::types_tag> {
- template <std::size_t n, typename ...T, std::size_t ...i>
- static hana::experimental::types<typename detail::type_at<i + n, T...>::type...>
- helper(std::index_sequence<i...>);
- template <typename ...T, typename N>
- static constexpr auto
- apply(hana::experimental::types<T...> const&, N const&) {
- constexpr std::size_t n = N::value > sizeof...(T) ? sizeof...(T) : N::value;
- using Indices = std::make_index_sequence<sizeof...(T) - n>;
- return decltype(helper<n, T...>(Indices{})){};
- }
- };
- // Searchable
- template <>
- struct contains_impl<hana::experimental::types_tag> {
- template <typename U>
- struct is_same_as {
- template <typename T>
- struct apply {
- static constexpr bool value = std::is_same<U, T>::value;
- };
- };
- template <typename ...T, typename U>
- static constexpr auto apply(hana::experimental::types<T...> const&, U const&)
- -> hana::bool_<
- detail::any_of<is_same_as<typename U::type>::template apply, T...>::value
- >
- { return {}; }
- static constexpr hana::false_ apply(...) { return {}; }
- };
- // Comparable
- template <>
- struct equal_impl<hana::experimental::types_tag, hana::experimental::types_tag> {
- template <typename Types>
- static constexpr hana::true_ apply(Types const&, Types const&)
- { return {}; }
- template <typename Ts, typename Us>
- static constexpr hana::false_ apply(Ts const&, Us const&)
- { return {}; }
- };
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_EXPERIMENTAL_TYPES_HPP
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