vmd/tuple/push_front.hpp

0001
0002 //  (C) Copyright Edward Diener 2015
0003 //  Use, modification and distribution are subject to the Boost Software License,
0004 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0005 //  http://www.boost.org/LICENSE_1_0.txt).
0006
0007 #if !defined(BOOST_VMD_TUPLE_PUSH_FRONT_HPP)
0008 #define BOOST_VMD_TUPLE_PUSH_FRONT_HPP
0009
0010 #include <boost/vmd/detail/setup.hpp>
0011
0012 #if BOOST_PP_VARIADICS
0013
0014 #include <boost/preprocessor/control/iif.hpp>
0015 #include <boost/preprocessor/tuple/push_front.hpp>
0016 #include <boost/vmd/identity.hpp>
0017 #include <boost/vmd/is_empty.hpp>
0018
0019 /*
0020
0021   The succeeding comments in this file are in doxygen format.
0022
0023 */
0024
0025 /** \file
0026 */
0027
0028 /** \def BOOST_VMD_TUPLE_PUSH_FRONT(tuple,elem)
0029
0030     \brief inserts an element at the beginning of a tuple.
0031
0032     tuple = tuple to insert an element at. <br/>
0033     elem  = element to insert.
0034
0035     If the tuple is an empty tuple the result is a tuple with the single element.
0036     Otherwise the result is a tuple after inserting the element at the beginning.
0037 */
0038
0039 #define BOOST_VMD_TUPLE_PUSH_FRONT(tuple,elem) \
0040     BOOST_VMD_IDENTITY_RESULT \
0041         ( \
0042         BOOST_PP_IIF \
0043             ( \
0044             BOOST_VMD_IS_EMPTY(tuple), \
0045             BOOST_VMD_IDENTITY((elem)), \
0046             BOOST_PP_TUPLE_PUSH_FRONT \
0047             ) \
0048         (tuple,elem) \
0049         ) \
0050 /**/
0051
0052 #endif /* BOOST_PP_VARIADICS */
0053 #endif /* BOOST_VMD_TUPLE_PUSH_FRONT_HPP */