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Diffstat (limited to 'boost/hana/keys.hpp')
-rw-r--r-- | boost/hana/keys.hpp | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/boost/hana/keys.hpp b/boost/hana/keys.hpp new file mode 100644 index 0000000000..d6d521b7e2 --- /dev/null +++ b/boost/hana/keys.hpp @@ -0,0 +1,48 @@ +/*! +@file +Defines `boost::hana::keys`. + +@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_KEYS_HPP +#define BOOST_HANA_KEYS_HPP + +#include <boost/hana/fwd/keys.hpp> + +#include <boost/hana/accessors.hpp> +#include <boost/hana/concept/struct.hpp> +#include <boost/hana/config.hpp> +#include <boost/hana/core/dispatch.hpp> +#include <boost/hana/first.hpp> +#include <boost/hana/transform.hpp> + + +BOOST_HANA_NAMESPACE_BEGIN + //! @cond + template <typename Map> + constexpr auto keys_t::operator()(Map&& map) const { + return keys_impl<typename hana::tag_of<Map>::type>::apply( + static_cast<Map&&>(map) + ); + } + //! @endcond + + template <typename T, bool condition> + struct keys_impl<T, when<condition>> : default_ { + template <typename ...Args> + static constexpr auto apply(Args&& ...) = delete; + }; + + template <typename S> + struct keys_impl<S, when<hana::Struct<S>::value>> { + template <typename Object> + static constexpr auto apply(Object const&) { + return hana::transform(hana::accessors<S>(), hana::first); + } + }; +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_KEYS_HPP |