boost/preprocessor/tuple/elem.hpp
# /* Copyright (C) 2001 # * Housemarque Oy # * http://www.housemarque.com # * # * Distributed under the Boost Software License, Version 1.0. (See # * accompanying file LICENSE_1_0.txt or copy at # * http://www.boost.org/LICENSE_1_0.txt) # */ # # /* Revised by Paul Mensonides (2002-2011) */ # /* Revised by Edward Diener (2011,2014,2020) */ # # /* See http://www.boost.org for most recent version. */ # # ifndef BOOST_PREPROCESSOR_TUPLE_ELEM_HPP # define BOOST_PREPROCESSOR_TUPLE_ELEM_HPP # # include <boost/preprocessor/cat.hpp> # include <boost/preprocessor/config/config.hpp> # include <boost/preprocessor/facilities/expand.hpp> # include <boost/preprocessor/facilities/overload.hpp> # include <boost/preprocessor/tuple/rem.hpp> # include <boost/preprocessor/variadic/elem.hpp> # include <boost/preprocessor/tuple/detail/is_single_return.hpp> # # if BOOST_PP_VARIADICS_MSVC # define BOOST_PP_TUPLE_ELEM(...) BOOST_PP_TUPLE_ELEM_I(BOOST_PP_OVERLOAD(BOOST_PP_TUPLE_ELEM_O_, __VA_ARGS__), (__VA_ARGS__)) # define BOOST_PP_TUPLE_ELEM_I(m, args) BOOST_PP_TUPLE_ELEM_II(m, args) # define BOOST_PP_TUPLE_ELEM_II(m, args) BOOST_PP_CAT(m ## args,) /* Use BOOST_PP_REM_CAT if it is a single element tuple ( which might be empty ) else use BOOST_PP_REM. This fixes a VC++ problem with an empty tuple and BOOST_PP_TUPLE_ELEM functionality. See tuple_elem_bug_test.cxx. */ # define BOOST_PP_TUPLE_ELEM_O_2(n, tuple) \ BOOST_PP_VARIADIC_ELEM(n, BOOST_PP_EXPAND(BOOST_PP_TUPLE_IS_SINGLE_RETURN(BOOST_PP_REM_CAT,BOOST_PP_REM,tuple) tuple)) \ /**/ # else # define BOOST_PP_TUPLE_ELEM(...) BOOST_PP_OVERLOAD(BOOST_PP_TUPLE_ELEM_O_, __VA_ARGS__)(__VA_ARGS__) # define BOOST_PP_TUPLE_ELEM_O_2(n, tuple) BOOST_PP_VARIADIC_ELEM(n, BOOST_PP_REM tuple) # endif # define BOOST_PP_TUPLE_ELEM_O_3(size, n, tuple) BOOST_PP_TUPLE_ELEM_O_2(n, tuple) # # /* directly used elsewhere in Boost... */ # # define BOOST_PP_TUPLE_ELEM_1_0(a) a # # define BOOST_PP_TUPLE_ELEM_2_0(a, b) a # define BOOST_PP_TUPLE_ELEM_2_1(a, b) b # # define BOOST_PP_TUPLE_ELEM_3_0(a, b, c) a # define BOOST_PP_TUPLE_ELEM_3_1(a, b, c) b # define BOOST_PP_TUPLE_ELEM_3_2(a, b, c) c # # endif