vmd/seq/pop_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_SEQ_POP_FRONT_HPP)
0008 #define BOOST_VMD_SEQ_POP_FRONT_HPP
0009
0010 #include <boost/vmd/detail/setup.hpp>
0011
0012 #if BOOST_PP_VARIADICS
0013
0014 #include <boost/preprocessor/comparison/equal.hpp>
0015 #include <boost/preprocessor/control/iif.hpp>
0016 #include <boost/preprocessor/seq/pop_front.hpp>
0017 #include <boost/preprocessor/seq/size.hpp>
0018 #include <boost/vmd/empty.hpp>
0019
0020 /*
0021
0022   The succeeding comments in this file are in doxygen format.
0023
0024 */
0025
0026 /** \file
0027 */
0028
0029 /** \def BOOST_VMD_SEQ_POP_FRONT(seq)
0030
0031     \brief pops an element from the front of a seq.
0032
0033     seq = seq to pop an element from.
0034
0035     If the seq is an empty seq the result is undefined.
0036     If the seq is a single element the result is an empty seq.
0037     Otherwise the result is a seq after removing the first element.
0038 */
0039
0040 #define BOOST_VMD_SEQ_POP_FRONT(seq) \
0041     BOOST_PP_IIF \
0042         ( \
0043         BOOST_PP_EQUAL(BOOST_PP_SEQ_SIZE(seq),1), \
0044         BOOST_VMD_EMPTY, \
0045         BOOST_PP_SEQ_POP_FRONT \
0046         ) \
0047     (seq) \
0048 /**/
0049
0050 #endif /* BOOST_PP_VARIADICS */
0051 #endif /* BOOST_VMD_SEQ_POP_FRONT_HPP */