// (C) Copyright Edward Diener 2011-2015 // Use, modification and distribution are subject to 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). #if !defined(BOOST_VMD_IS_EMPTY_HPP) #define BOOST_VMD_IS_EMPTY_HPP #include <boost/vmd/detail/setup.hpp> #if BOOST_PP_VARIADICS #include <boost/preprocessor/punctuation/is_begin_parens.hpp> #include <boost/vmd/detail/is_empty.hpp> /* The succeeding comments in this file are in doxygen format. */ /** \file */ /** \def BOOST_VMD_IS_EMPTY(...) \brief Tests whether its input is empty or not. The macro checks to see if the input is empty or not. It returns 1 if the input is empty, else returns 0. The macro is a variadic macro taking any input. For the VC++8 compiler (VS2005) the macro takes a single parameter of input to check. The macro is not perfect, and can not be so. The problem area is if the input to be checked is a function-like macro name, in which case either a compiler error can result or a false result can occur. This macro is a replacement, using variadic macro support, for the undocumented macro BOOST_PP_IS_EMPTY in the Boost PP library. The code is taken from a posting by Paul Mensonides of a variadic version for BOOST_PP_IS_EMPTY, and changed in order to also support VC++. .... = variadic input, for VC++8 this must be a single parameter returns = 1 if the input is empty, 0 if it is not It is recommended to append BOOST_PP_EMPTY() to whatever input is being tested in order to avoid possible warning messages from some compilers about no parameters being passed to the macro when the input is truly empty. */ #if BOOST_VMD_MSVC_V8 #define BOOST_VMD_IS_EMPTY(sequence) \ BOOST_VMD_DETAIL_IS_EMPTY_IIF \ ( \ BOOST_PP_IS_BEGIN_PARENS \ ( \ sequence \ ) \ ) \ ( \ BOOST_VMD_DETAIL_IS_EMPTY_GEN_ZERO, \ BOOST_VMD_DETAIL_IS_EMPTY_PROCESS \ ) \ (sequence) \ /**/ #else #define BOOST_VMD_IS_EMPTY(...) \ BOOST_VMD_DETAIL_IS_EMPTY_IIF \ ( \ BOOST_PP_IS_BEGIN_PARENS \ ( \ __VA_ARGS__ \ ) \ ) \ ( \ BOOST_VMD_DETAIL_IS_EMPTY_GEN_ZERO, \ BOOST_VMD_DETAIL_IS_EMPTY_PROCESS \ ) \ (__VA_ARGS__) \ /**/ #endif /* BOOST_VMD_MSVC_V8 */ #endif /* BOOST_PP_VARIADICS */ #endif /* BOOST_VMD_IS_EMPTY_HPP */