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/*!
@file
Forward declares `boost::hana::keys`.
Copyright Louis Dionne 2013-2022
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_FWD_KEYS_HPP
#define BOOST_HANA_FWD_KEYS_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
namespace boost { namespace hana {
// Note: This function is documented per datatype/concept only.
//! @cond
template <typename T, typename = void>
struct keys_impl : keys_impl<T, when<true>> { };
//! @endcond
struct keys_t {
template <typename Map>
constexpr auto operator()(Map&& map) const;
};
BOOST_HANA_INLINE_VARIABLE constexpr keys_t keys{};
//! Returns a `Sequence` containing the name of the members of
//! the data structure.
//! @ingroup group-Struct
//!
//! Given a `Struct` object, `keys` returns a `Sequence` containing the
//! name of all the members of the `Struct`, in the same order as they
//! appear in the `accessors` sequence.
//!
//!
//! Example
//! -------
//! @include example/struct/keys.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto keys = [](auto&& object) {
return implementation_defined;
};
#endif
}} // end namespace boost::hana
#endif // !BOOST_HANA_FWD_KEYS_HPP
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