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Diffstat (limited to 'boost/hana/group.hpp')
| -rw-r--r-- | boost/hana/group.hpp | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/boost/hana/group.hpp b/boost/hana/group.hpp new file mode 100644 index 0000000000..66f005a347 --- /dev/null +++ b/boost/hana/group.hpp @@ -0,0 +1,157 @@ +/*! +@file +Defines `boost::hana::group`. + +@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_GROUP_HPP +#define BOOST_HANA_GROUP_HPP + +#include <boost/hana/fwd/group.hpp> + +#include <boost/hana/at.hpp> +#include <boost/hana/concept/sequence.hpp> +#include <boost/hana/config.hpp> +#include <boost/hana/core/dispatch.hpp> +#include <boost/hana/core/make.hpp> +#include <boost/hana/detail/algorithm.hpp> +#include <boost/hana/detail/array.hpp> +#include <boost/hana/detail/nested_by.hpp> // required by fwd decl +#include <boost/hana/equal.hpp> +#include <boost/hana/length.hpp> + +#include <cstddef> +#include <utility> + + +BOOST_HANA_NAMESPACE_BEGIN + //! @cond + template <typename Xs> + constexpr auto group_t::operator()(Xs&& xs) const { + using S = typename hana::tag_of<Xs>::type; + using Group = BOOST_HANA_DISPATCH_IF(group_impl<S>, + hana::Sequence<S>::value + ); + + #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS + static_assert(hana::Sequence<S>::value, + "hana::group(xs) requires 'xs' to be a Sequence"); + #endif + + return Group::apply(static_cast<Xs&&>(xs)); + } + + template <typename Xs, typename Predicate> + constexpr auto group_t::operator()(Xs&& xs, Predicate&& pred) const { + using S = typename hana::tag_of<Xs>::type; + using Group = BOOST_HANA_DISPATCH_IF(group_impl<S>, + hana::Sequence<S>::value + ); + + #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS + static_assert(hana::Sequence<S>::value, + "hana::group(xs, predicate) requires 'xs' to be a Sequence"); + #endif + + return Group::apply(static_cast<Xs&&>(xs), + static_cast<Predicate&&>(pred)); + } + //! @endcond + + namespace detail { + template <typename Xs, std::size_t ...i> + constexpr auto get_subsequence_(Xs&& xs, std::index_sequence<i...>) { + using S = typename hana::tag_of<Xs>::type; + return hana::make<S>(hana::at_c<i>(static_cast<Xs&&>(xs))...); + } + + template <std::size_t offset, typename Indices> + struct offset_by; + + template <std::size_t offset, std::size_t ...i> + struct offset_by<offset, std::index_sequence<i...>> { + using type = std::index_sequence<(offset + i)...>; + }; + + template <bool ...b> + struct group_indices { + static constexpr bool bs[] = {b...}; + static constexpr std::size_t n_groups = + detail::count(bs, bs + sizeof(bs), false) + 1; + + static constexpr auto compute_info() { + detail::array<std::size_t, n_groups> sizes{}, offsets{}; + for (std::size_t g = 0, i = 0, offset = 0; g < n_groups; ++g) { + offsets[g] = offset; + + sizes[g] = 1; + while (i < sizeof...(b) && bs[i++]) + ++sizes[g]; + + offset += sizes[g]; + } + return std::make_pair(offsets, sizes); + } + + static constexpr auto info = compute_info(); + static constexpr auto offsets = info.first; + static constexpr auto group_sizes = info.second; + + template <typename S, typename Xs, std::size_t ...i> + static constexpr auto finish(Xs&& xs, std::index_sequence<i...>) { + return hana::make<S>( + detail::get_subsequence_( + static_cast<Xs&&>(xs), + typename offset_by< + offsets[i], std::make_index_sequence<group_sizes[i]> + >::type{} + )... + ); + } + }; + } // end namespace detail + + template <typename S, bool condition> + struct group_impl<S, when<condition>> : default_ { + template <typename Xs, typename Pred, std::size_t ...i> + static constexpr auto + group_helper(Xs&& xs, Pred&& pred, std::index_sequence<0, i...>) { + using info = detail::group_indices<static_cast<bool>(decltype( + pred(hana::at_c<i - 1>(static_cast<Xs&&>(xs)), + hana::at_c<i>(static_cast<Xs&&>(xs))) + )::value)...>; + return info::template finish<S>(static_cast<Xs&&>(xs), + std::make_index_sequence<info::n_groups>{} + ); + } + + template <typename Xs, typename Pred> + static constexpr auto + group_helper(Xs&& xs, Pred&&, std::index_sequence<0>) { + return hana::make<S>(static_cast<Xs&&>(xs)); + } + + template <typename Xs, typename Pred> + static constexpr auto + group_helper(Xs&&, Pred&&, std::index_sequence<>) { + return hana::make<S>(); + } + + template <typename Xs, typename Pred> + static constexpr auto apply(Xs&& xs, Pred&& pred) { + constexpr std::size_t len = decltype(hana::length(xs))::value; + return group_helper(static_cast<Xs&&>(xs), + static_cast<Pred&&>(pred), + std::make_index_sequence<len>{}); + } + + template <typename Xs> + static constexpr auto apply(Xs&& xs) + { return group_impl::apply(static_cast<Xs&&>(xs), hana::equal); } + }; +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_GROUP_HPP |