preprocessor/seq/first_n.hpp

0001 # /* **************************************************************************
0002 #  *                                                                          *
0003 #  *     (C) Copyright Paul Mensonides 2002.
0004 #  *     Distributed under the Boost Software License, Version 1.0. (See
0005 #  *     accompanying file LICENSE_1_0.txt or copy at
0006 #  *     http://www.boost.org/LICENSE_1_0.txt)
0007 #  *                                                                          *
0008 #  ************************************************************************** */
0009 #
0010 # /* See http://www.boost.org for most recent version. */
0011 #
0012 # ifndef BOOST_PREPROCESSOR_SEQ_FIRST_N_HPP
0013 # define BOOST_PREPROCESSOR_SEQ_FIRST_N_HPP
0014 #
0015 # include <boost/preprocessor/config/config.hpp>
0016 # include <boost/preprocessor/control/if.hpp>
0017 # include <boost/preprocessor/seq/detail/split.hpp>
0018 # include <boost/preprocessor/tuple/eat.hpp>
0019 # include <boost/preprocessor/tuple/elem.hpp>
0020 #
0021 # /* BOOST_PP_SEQ_FIRST_N */
0022 #
0023 # if ~BOOST_PP_CONFIG_FLAGS() & BOOST_PP_CONFIG_EDG()
0024 #    define BOOST_PP_SEQ_FIRST_N(n, seq) BOOST_PP_IF(n, BOOST_PP_TUPLE_ELEM, BOOST_PP_TUPLE_EAT_3)(2, 0, BOOST_PP_SEQ_SPLIT(n, seq (nil)))
0025 # else
0026 #    define BOOST_PP_SEQ_FIRST_N(n, seq) BOOST_PP_SEQ_FIRST_N_I(n, seq)
0027 #    define BOOST_PP_SEQ_FIRST_N_I(n, seq) BOOST_PP_IF(n, BOOST_PP_TUPLE_ELEM, BOOST_PP_TUPLE_EAT_3)(2, 0, BOOST_PP_SEQ_SPLIT(n, seq (nil)))
0028 # endif
0029 #
0030 # endif