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Diffstat (limited to 'boost/hana/ext/boost/mpl/vector.hpp')
| -rw-r--r-- | boost/hana/ext/boost/mpl/vector.hpp | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/boost/hana/ext/boost/mpl/vector.hpp b/boost/hana/ext/boost/mpl/vector.hpp new file mode 100644 index 0000000000..59cac5dd2b --- /dev/null +++ b/boost/hana/ext/boost/mpl/vector.hpp @@ -0,0 +1,185 @@ +/*! +@file +Adapts `boost::mpl::vector` for use with Hana. + +@copyright Louis Dionne 2013-2016 +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_EXT_BOOST_MPL_VECTOR_HPP +#define BOOST_HANA_EXT_BOOST_MPL_VECTOR_HPP + +#include <boost/hana/concept/foldable.hpp> +#include <boost/hana/config.hpp> +#include <boost/hana/core/when.hpp> +#include <boost/hana/ext/boost/mpl/integral_c.hpp> +#include <boost/hana/fwd/at.hpp> +#include <boost/hana/fwd/core/to.hpp> +#include <boost/hana/fwd/core/tag_of.hpp> +#include <boost/hana/fwd/drop_front.hpp> +#include <boost/hana/fwd/equal.hpp> +#include <boost/hana/fwd/is_empty.hpp> +#include <boost/hana/fwd/less.hpp> +#include <boost/hana/integral_constant.hpp> +#include <boost/hana/length.hpp> +#include <boost/hana/type.hpp> +#include <boost/hana/unpack.hpp> + +#include <boost/mpl/at.hpp> +#include <boost/mpl/empty.hpp> +#include <boost/mpl/equal.hpp> +#include <boost/mpl/sequence_tag.hpp> +#include <boost/mpl/size.hpp> +#include <boost/mpl/vector.hpp> + +#include <cstddef> +#include <type_traits> +#include <utility> + + +#ifdef BOOST_HANA_DOXYGEN_INVOKED +namespace boost { namespace mpl { + //! @ingroup group-ext-mpl + //! Adapter for Boost.MPL vectors. + //! + //! + //! Modeled concepts + //! ---------------- + //! It is possible for MPL vectors to model a couple of concepts. + //! However, because they are only able to hold types, they lack + //! the generality required to model concepts like `Functor`, + //! `Sequence` and other related concepts. + //! + //! 1. `Comparable`\n + //! Two MPL vectors are equal if and only if they contain the same + //! number of types, and if all those types are equal. + //! @include example/ext/boost/mpl/vector/comparable.cpp + //! + //! 2. `Foldable`\n + //! Folding a MPL vector is equivalent to folding it as a `Sequence`. + //! @include example/ext/boost/mpl/vector/foldable.cpp + //! + //! 3. `Iterable`\n + //! Iterating over a MPL vector is just iterating over each of the + //! types it contains, as if it were a `Sequence`. + //! @include example/ext/boost/mpl/vector/iterable.cpp + //! + //! 4. `Searchable`\n + //! A MPL vector can be searched as if it were a tuple containing + //! `hana::type`s. + //! @include example/ext/boost/mpl/vector/searchable.cpp + //! + //! + //! Conversion from any `Foldable` + //! ------------------------------ + //! A MPL vector can be created from any `Foldable`. More precisely, + //! for a `Foldable` `xs` whose linearization is `[x1, ..., xn]`, + //! @code + //! to<ext::boost::mpl::vector_tag>(xs) == mpl::vector<t1, ..., tn> + //! @endcode + //! where `tk` is the type of `xk`, or the type contained in `xk` if + //! `xk` is a `hana::type`. + //! @warning + //! The limitations on the size of `mpl::vector`s are inherited by + //! this conversion utility, and hence trying to convert a `Foldable` + //! containing more than [BOOST_MPL_LIMIT_VECTOR_SIZE][1] elements + //! is an error. + //! @include example/ext/boost/mpl/vector/conversion.cpp + //! + //! [1]: http://www.boost.org/doc/libs/release/libs/mpl/doc/refmanual/limit-vector-size.html + template <typename ...T> + struct vector { }; +}} +#endif + + +BOOST_HANA_NAMESPACE_BEGIN + namespace ext { namespace boost { namespace mpl { + using vector_tag = ::boost::mpl::sequence_tag< ::boost::mpl::vector<>>::type; + }}} + + template <typename T> + struct tag_of<T, when< + std::is_same< + typename ::boost::mpl::sequence_tag<T>::type, + ::boost::mpl::sequence_tag< ::boost::mpl::vector<>>::type + >::value + >> { + using type = ext::boost::mpl::vector_tag; + }; + + ////////////////////////////////////////////////////////////////////////// + // Comparable + ////////////////////////////////////////////////////////////////////////// + template <> + struct equal_impl<ext::boost::mpl::vector_tag, ext::boost::mpl::vector_tag> { + template <typename Xs, typename Ys> + static constexpr auto apply(Xs const&, Ys const&) { + return typename ::boost::mpl::equal<Xs, Ys>::type{}; + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Foldable + ////////////////////////////////////////////////////////////////////////// + template <> + struct length_impl<ext::boost::mpl::vector_tag> { + template <typename Xs> + static constexpr auto apply(Xs const&) { + return hana::size_c< ::boost::mpl::size<Xs>::type::value>; + } + }; + + ////////////////////////////////////////////////////////////////////////// + // Iterable + ////////////////////////////////////////////////////////////////////////// + template <> + struct at_impl<ext::boost::mpl::vector_tag> { + template <typename Ts, typename N> + static constexpr auto apply(Ts const&, N const&) { + constexpr std::size_t n = N::value; + using T = typename ::boost::mpl::at_c<Ts, n>::type; + return hana::type_c<T>; + } + }; + + template <> + struct drop_front_impl<ext::boost::mpl::vector_tag> { + template <std::size_t n, typename Xs, std::size_t ...i> + static constexpr auto drop_front_helper(Xs const&, std::index_sequence<i...>) { + return boost::mpl::vector< + typename boost::mpl::at_c<Xs, n + i>::type... + >{}; + } + + template <typename Xs, typename N> + static constexpr auto apply(Xs const& xs, N const&) { + constexpr std::size_t n = N::value; + constexpr std::size_t len = decltype(hana::length(xs))::value; + return drop_front_helper<n>(xs, + std::make_index_sequence<(n < len ? len - n : 0)>{}); + } + }; + + template <> + struct is_empty_impl<ext::boost::mpl::vector_tag> { + template <typename xs> + static constexpr auto apply(xs) + { return typename ::boost::mpl::empty<xs>::type{}; } + }; + + ////////////////////////////////////////////////////////////////////////// + // Conversion from a Foldable + ////////////////////////////////////////////////////////////////////////// + template <typename F> + struct to_impl<ext::boost::mpl::vector_tag, F, when<hana::Foldable<F>::value>> { + template <typename Xs> + static constexpr auto apply(Xs const& xs) { + auto vector_type = hana::unpack(xs, hana::template_<boost::mpl::vector>); + return typename decltype(vector_type)::type{}; + } + }; +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_EXT_BOOST_MPL_VECTOR_HPP |