fusion/support/unused.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
0003     Copyright (c) 2018 Kohei Takahashi
0004
0005     Distributed under the Boost Software License, Version 1.0. (See accompanying
0006     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 ==============================================================================*/
0008 #if !defined(BOOST_FUSION_SUPPORT_UNUSED_20070305_1038)
0009 #define BOOST_FUSION_SUPPORT_UNUSED_20070305_1038
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <iosfwd>
0013
0014 #if defined(BOOST_MSVC)
0015 # pragma warning(push)
0016 # pragma warning(disable: 4522) // multiple assignment operators specified warning
0017 #endif
0018
0019 #define BOOST_FUSION_UNUSED_HAS_IO
0020
0021 namespace boost { namespace fusion
0022 {
0023     struct unused_type
0024     {
0025         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0026         BOOST_DEFAULTED_FUNCTION(
0027         unused_type() BOOST_FUSION_NOEXCEPT_ON_DEFAULTED,
0028         {
0029         })
0030
0031         template <typename T>
0032         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0033         unused_type(T const&) BOOST_NOEXCEPT
0034         {
0035         }
0036     };
0037
0038     BOOST_CONSTEXPR_OR_CONST unused_type unused = unused_type();
0039
0040     namespace detail
0041     {
0042         struct unused_only
0043         {
0044             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0045             unused_only(unused_type const&) BOOST_NOEXCEPT {}
0046         };
0047     }
0048
0049     BOOST_CONSTEXPR
0050     inline std::ostream& operator<<(std::ostream& out, detail::unused_only const&) BOOST_NOEXCEPT
0051     {
0052         return out;
0053     }
0054
0055     BOOST_CONSTEXPR
0056     inline std::istream& operator>>(std::istream& in, unused_type&) BOOST_NOEXCEPT
0057     {
0058         return in;
0059     }
0060 }}
0061
0062 #if defined(BOOST_MSVC)
0063 # pragma warning(pop)
0064 #endif
0065
0066 #endif