hana/fwd/erase_key.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::erase_key`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_FWD_ERASE_KEY_HPP
0011 #define BOOST_HANA_FWD_ERASE_KEY_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     // Note: This function is documented per datatype/concept only.
0019     //! @cond
0020     template <typename T, typename = void>
0021     struct erase_key_impl : erase_key_impl<T, when<true>> { };
0022     //! @endcond
0023
0024     struct erase_key_t {
0025         template <typename Set, typename ...Args>
0026         constexpr decltype(auto) operator()(Set&& set, Args&& ...args) const;
0027     };
0028
0029     BOOST_HANA_INLINE_VARIABLE constexpr erase_key_t erase_key{};
0030 }} // end namespace boost::hana
0031
0032 #endif // !BOOST_HANA_FWD_ERASE_KEY_HPP