diff options
Diffstat (limited to 'boost/hana/at_key.hpp')
| -rw-r--r-- | boost/hana/at_key.hpp | 38 |
1 files changed, 7 insertions, 31 deletions
diff --git a/boost/hana/at_key.hpp b/boost/hana/at_key.hpp index 74d45d6d56..e4f2e11255 100644 --- a/boost/hana/at_key.hpp +++ b/boost/hana/at_key.hpp @@ -3,6 +3,7 @@ Defines `boost::hana::at_key`. @copyright Louis Dionne 2013-2017 +@copyright Jason Rice 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) */ @@ -24,6 +25,7 @@ Distributed under the Boost Software License, Version 1.0. #include <boost/hana/find_if.hpp> #include <boost/hana/first.hpp> #include <boost/hana/functional/on.hpp> +#include <boost/hana/index_if.hpp> #include <boost/hana/length.hpp> #include <boost/hana/optional.hpp> #include <boost/hana/second.hpp> @@ -67,42 +69,16 @@ BOOST_HANA_NAMESPACE_BEGIN return hana::equal(t, u); } }; - - //! @todo This causes an awful duplication of code with `find_if`. - template <typename Xs, typename Pred, std::size_t i, std::size_t N, bool Done> - struct advance_until; - - template <typename Xs, typename Pred, std::size_t i, std::size_t N> - struct advance_until<Xs, Pred, i, N, false> - : advance_until<Xs, Pred, i + 1, N, static_cast<bool>(detail::decay<decltype( - std::declval<Pred>()(hana::at_c<i>(std::declval<Xs>())) - )>::type::value)> - { }; - - template <typename Xs, typename Pred, std::size_t N> - struct advance_until<Xs, Pred, N, N, false> { - template <typename Ys> - static constexpr auto apply(Ys&&) = delete; - }; - - template <typename Xs, typename Pred, std::size_t i, std::size_t N> - struct advance_until<Xs, Pred, i, N, true> { - template <typename Ys> - static constexpr decltype(auto) apply(Ys&& ys) { - return hana::at_c<i - 1>(static_cast<Ys&&>(ys)); - } - }; } template <typename S> struct at_key_impl<S, when<hana::Sequence<S>::value>> { template <typename Xs, typename Key> - static constexpr decltype(auto) apply(Xs&& xs, Key const&) { - constexpr std::size_t N = decltype(hana::length(xs))::value; - using Pred = at_key_detail::equal_to<Key>; - return at_key_detail::advance_until<Xs&&, Pred, 0, N, false>::apply( - static_cast<Xs&&>(xs) - ); + static constexpr decltype(auto) apply(Xs&& xs, Key const& key) { + using Result = decltype(hana::index_if( + static_cast<Xs&&>(xs), at_key_detail::equal_to<Key>{key})); + + return hana::at(static_cast<Xs&&>(xs), Result{}.value()); } }; |